text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2015 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "main.h"
  
  #include "addrman.h"
  #include "alert.h"
  #include "arith_uint256.h"
  #include "chainparams.h"
  #include "checkpoints.h"
  #include "checkqueue.h"
  #include "consensus/consensus.h"
  #include "consensus/merkle.h"
  #include "consensus/validation.h"
  #include "hash.h"
  #include "init.h"
  #include "merkleblock.h"
  #include "net.h"
  #include "policy/policy.h"
  #include "pow.h"
  #include "primitives/block.h"
  #include "primitives/transaction.h"
  #include "script/script.h"
  #include "script/sigcache.h"
  #include "script/standard.h"
  #include "tinyformat.h"
  #include "txdb.h"
  #include "txmempool.h"
  #include "ui_interface.h"
  #include "undo.h"
  #include "util.h"
  #include "utilmoneystr.h"
  #include "utilstrencodings.h"
  #include "validationinterface.h"
  #include "versionbits.h"
  
  #include <sstream>
  
  #include <boost/algorithm/string/replace.hpp>
  #include <boost/filesystem.hpp>
  #include <boost/filesystem/fstream.hpp>
  #include <boost/math/distributions/poisson.hpp>
  #include <boost/thread.hpp>
  
  using namespace std;
  
  #if defined(NDEBUG)
  # error "Bitcoin cannot be compiled without assertions."
  #endif
  
  /**
   * Global state
   */
  
  CCriticalSection cs_main;
  
  BlockMap mapBlockIndex;
  CChain chainActive;
  CBlockIndex *pindexBestHeader = NULL;
  int64_t nTimeBestReceived = 0;
  CWaitableCriticalSection csBestBlock;
  CConditionVariable cvBlockChange;
  int nScriptCheckThreads = 0;
  bool fImporting = false;
  bool fReindex = false;
  bool fTxIndex = false;
  bool fHavePruned = false;
  bool fPruneMode = false;
  bool fIsBareMultisigStd = DEFAULT_PERMIT_BAREMULTISIG;
  bool fRequireStandard = true;
  unsigned int nBytesPerSigOp = DEFAULT_BYTES_PER_SIGOP;
  bool fCheckBlockIndex = false;
  bool fCheckpointsEnabled = DEFAULT_CHECKPOINTS_ENABLED;
  size_t nCoinCacheUsage = 5000 * 300;
  uint64_t nPruneTarget = 0;
  bool fAlerts = DEFAULT_ALERTS;
  bool fEnableReplacement = DEFAULT_ENABLE_REPLACEMENT;
  
  /** Fees smaller than this (in satoshi) are considered zero fee (for relaying, mining and transaction creation) */
  CFeeRate minRelayTxFee = CFeeRate(DEFAULT_MIN_RELAY_TX_FEE);
  
  CTxMemPool mempool(::minRelayTxFee);
  
  struct COrphanTx {
      CTransaction tx;
      NodeId fromPeer;
  };
  map<uint256, COrphanTx> mapOrphanTransactions GUARDED_BY(cs_main);;
  map<uint256, set<uint256> > mapOrphanTransactionsByPrev GUARDED_BY(cs_main);;
  void EraseOrphansFor(NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /**
   * Returns true if there are nRequired or more blocks of minVersion or above
   * in the last Consensus::Params::nMajorityWindow blocks, starting at pstart and going backwards.
   */
  static bool IsSuperMajority(int minVersion, const CBlockIndex* pstart, unsigned nRequired, const Consensus::Params& consensusParams);
  static void CheckBlockIndex(const Consensus::Params& consensusParams);
  
  /** Constant stuff for coinbase transactions we create: */
  CScript COINBASE_FLAGS;
  
  const string strMessageMagic = "Bitcoin Signed Message:\n";
  
  // Internal stuff
  namespace {
  
      struct CBlockIndexWorkComparator
      {
          bool operator()(CBlockIndex *pa, CBlockIndex *pb) const {
              // First sort by most total work, ...
              if (pa->nChainWork > pb->nChainWork) return false;
              if (pa->nChainWork < pb->nChainWork) return true;
  
              // ... then by earliest time received, ...
              if (pa->nSequenceId < pb->nSequenceId) return false;
              if (pa->nSequenceId > pb->nSequenceId) return true;
  
              // Use pointer address as tie breaker (should only happen with blocks
              // loaded from disk, as those all have id 0).
              if (pa < pb) return false;
              if (pa > pb) return true;
  
              // Identical blocks.
              return false;
          }
      };
  
      CBlockIndex *pindexBestInvalid;
  
      /**
       * The set of all CBlockIndex entries with BLOCK_VALID_TRANSACTIONS (for itself and all ancestors) and
       * as good as our current tip or better. Entries may be failed, though, and pruning nodes may be
       * missing the data for the block.
       */
      set<CBlockIndex*, CBlockIndexWorkComparator> setBlockIndexCandidates;
      /** Number of nodes with fSyncStarted. */
      int nSyncStarted = 0;
      /** All pairs A->B, where A (or one of its ancestors) misses transactions, but B has transactions.
       * Pruned nodes may have entries where B is missing data.
       */
      multimap<CBlockIndex*, CBlockIndex*> mapBlocksUnlinked;
  
      CCriticalSection cs_LastBlockFile;
      std::vector<CBlockFileInfo> vinfoBlockFile;
      int nLastBlockFile = 0;
      /** Global flag to indicate we should check to see if there are
       *  block/undo files that should be deleted.  Set on startup
       *  or if we allocate more file space when we're in prune mode
       */
      bool fCheckForPruning = false;
  
      /**
       * Every received block is assigned a unique and increasing identifier, so we
       * know which one to give priority in case of a fork.
       */
      CCriticalSection cs_nBlockSequenceId;
      /** Blocks loaded from disk are assigned id 0, so start the counter at 1. */
      uint32_t nBlockSequenceId = 1;
  
      /**
       * Sources of received blocks, saved to be able to send them reject
       * messages or ban them when processing happens afterwards. Protected by
       * cs_main.
       */
      map<uint256, NodeId> mapBlockSource;
  
      /**
       * Filter for transactions that were recently rejected by
       * AcceptToMemoryPool. These are not rerequested until the chain tip
       * changes, at which point the entire filter is reset. Protected by
       * cs_main.
       *
       * Without this filter we'd be re-requesting txs from each of our peers,
       * increasing bandwidth consumption considerably. For instance, with 100
       * peers, half of which relay a tx we don't accept, that might be a 50x
       * bandwidth increase. A flooding attacker attempting to roll-over the
       * filter using minimum-sized, 60byte, transactions might manage to send
       * 1000/sec if we have fast peers, so we pick 120,000 to give our peers a
       * two minute window to send invs to us.
       *
       * Decreasing the false positive rate is fairly cheap, so we pick one in a
       * million to make it highly unlikely for users to have issues with this
       * filter.
       *
       * Memory used: 1.7MB
       */
      boost::scoped_ptr<CRollingBloomFilter> recentRejects;
      uint256 hashRecentRejectsChainTip;
  
      /** Blocks that are in flight, and that are in the queue to be downloaded. Protected by cs_main. */
      struct QueuedBlock {
          uint256 hash;
          CBlockIndex* pindex;     //!< Optional.
          bool fValidatedHeaders;  //!< Whether this block has validated headers at the time of request.
      };
      map<uint256, pair<NodeId, list<QueuedBlock>::iterator> > mapBlocksInFlight;
  
      /** Number of preferable block download peers. */
      int nPreferredDownload = 0;
  
      /** Dirty block index entries. */
      set<CBlockIndex*> setDirtyBlockIndex;
  
      /** Dirty block file entries. */
      set<int> setDirtyFileInfo;
  
      /** Number of peers from which we're downloading blocks. */
      int nPeersWithValidatedDownloads = 0;
  } // anon namespace
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // Registration of network node signals.
  //
  
  namespace {
  
  struct CBlockReject {
      unsigned char chRejectCode;
      string strRejectReason;
      uint256 hashBlock;
  };
  
  /**
   * Maintain validation-specific state about nodes, protected by cs_main, instead
   * by CNode's own locks. This simplifies asynchronous operation, where
   * processing of incoming data is done after the ProcessMessage call returns,
   * and we're no longer holding the node's locks.
   */
  struct CNodeState {
      //! The peer's address
      CService address;
      //! Whether we have a fully established connection.
      bool fCurrentlyConnected;
      //! Accumulated misbehaviour score for this peer.
      int nMisbehavior;
      //! Whether this peer should be disconnected and banned (unless whitelisted).
      bool fShouldBan;
      //! String name of this peer (debugging/logging purposes).
      std::string name;
      //! List of asynchronously-determined block rejections to notify this peer about.
      std::vector<CBlockReject> rejects;
      //! The best known block we know this peer has announced.
      CBlockIndex *pindexBestKnownBlock;
      //! The hash of the last unknown block this peer has announced.
      uint256 hashLastUnknownBlock;
      //! The last full block we both have.
      CBlockIndex *pindexLastCommonBlock;
      //! The best header we have sent our peer.
      CBlockIndex *pindexBestHeaderSent;
      //! Whether we've started headers synchronization with this peer.
      bool fSyncStarted;
      //! Since when we're stalling block download progress (in microseconds), or 0.
      int64_t nStallingSince;
      list<QueuedBlock> vBlocksInFlight;
      //! When the first entry in vBlocksInFlight started downloading. Don't care when vBlocksInFlight is empty.
      int64_t nDownloadingSince;
      int nBlocksInFlight;
      int nBlocksInFlightValidHeaders;
      //! Whether we consider this a preferred download peer.
      bool fPreferredDownload;
      //! Whether this peer wants invs or headers (when possible) for block announcements.
      bool fPreferHeaders;
  
      CNodeState() {
          fCurrentlyConnected = false;
          nMisbehavior = 0;
          fShouldBan = false;
          pindexBestKnownBlock = NULL;
          hashLastUnknownBlock.SetNull();
          pindexLastCommonBlock = NULL;
          pindexBestHeaderSent = NULL;
          fSyncStarted = false;
          nStallingSince = 0;
          nDownloadingSince = 0;
          nBlocksInFlight = 0;
          nBlocksInFlightValidHeaders = 0;
          fPreferredDownload = false;
          fPreferHeaders = false;
      }
  };
  
  /** Map maintaining per-node state. Requires cs_main. */
  map<NodeId, CNodeState> mapNodeState;
  
  // Requires cs_main.
  CNodeState *State(NodeId pnode) {
      map<NodeId, CNodeState>::iterator it = mapNodeState.find(pnode);
      if (it == mapNodeState.end())
          return NULL;
      return &it->second;
  }
  
  int GetHeight()
  {
      LOCK(cs_main);
      return chainActive.Height();
  }
  
  void UpdatePreferredDownload(CNode* node, CNodeState* state)
  {
      nPreferredDownload -= state->fPreferredDownload;
  
      // Whether this node should be marked as a preferred download node.
      state->fPreferredDownload = (!node->fInbound || node->fWhitelisted) && !node->fOneShot && !node->fClient;
  
      nPreferredDownload += state->fPreferredDownload;
  }
  
  void InitializeNode(NodeId nodeid, const CNode *pnode) {
      LOCK(cs_main);
      CNodeState &state = mapNodeState.insert(std::make_pair(nodeid, CNodeState())).first->second;
      state.name = pnode->addrName;
      state.address = pnode->addr;
  }
  
  void FinalizeNode(NodeId nodeid) {
      LOCK(cs_main);
      CNodeState *state = State(nodeid);
  
      if (state->fSyncStarted)
          nSyncStarted--;
  
      if (state->nMisbehavior == 0 && state->fCurrentlyConnected) {
          AddressCurrentlyConnected(state->address);
      }
  
      BOOST_FOREACH(const QueuedBlock& entry, state->vBlocksInFlight) {
          mapBlocksInFlight.erase(entry.hash);
      }
      EraseOrphansFor(nodeid);
      nPreferredDownload -= state->fPreferredDownload;
      nPeersWithValidatedDownloads -= (state->nBlocksInFlightValidHeaders != 0);
      assert(nPeersWithValidatedDownloads >= 0);
  
      mapNodeState.erase(nodeid);
  
      if (mapNodeState.empty()) {
          // Do a consistency check after the last peer is removed.
          assert(mapBlocksInFlight.empty());
          assert(nPreferredDownload == 0);
          assert(nPeersWithValidatedDownloads == 0);
      }
  }
  
  // Requires cs_main.
  // Returns a bool indicating whether we requested this block.
  bool MarkBlockAsReceived(const uint256& hash) {
      map<uint256, pair<NodeId, list<QueuedBlock>::iterator> >::iterator itInFlight = mapBlocksInFlight.find(hash);
      if (itInFlight != mapBlocksInFlight.end()) {
          CNodeState *state = State(itInFlight->second.first);
          state->nBlocksInFlightValidHeaders -= itInFlight->second.second->fValidatedHeaders;
          if (state->nBlocksInFlightValidHeaders == 0 && itInFlight->second.second->fValidatedHeaders) {
              // Last validated block on the queue was received.
              nPeersWithValidatedDownloads--;
          }
          if (state->vBlocksInFlight.begin() == itInFlight->second.second) {
              // First block on the queue was received, update the start download time for the next one
              state->nDownloadingSince = std::max(state->nDownloadingSince, GetTimeMicros());
          }
          state->vBlocksInFlight.erase(itInFlight->second.second);
          state->nBlocksInFlight--;
          state->nStallingSince = 0;
          mapBlocksInFlight.erase(itInFlight);
          return true;
      }
      return false;
  }
  
  // Requires cs_main.
  void MarkBlockAsInFlight(NodeId nodeid, const uint256& hash, const Consensus::Params& consensusParams, CBlockIndex *pindex = NULL) {
      CNodeState *state = State(nodeid);
      assert(state != NULL);
  
      // Make sure it's not listed somewhere already.
      MarkBlockAsReceived(hash);
  
      QueuedBlock newentry = {hash, pindex, pindex != NULL};
      list<QueuedBlock>::iterator it = state->vBlocksInFlight.insert(state->vBlocksInFlight.end(), newentry);
      state->nBlocksInFlight++;
      state->nBlocksInFlightValidHeaders += newentry.fValidatedHeaders;
      if (state->nBlocksInFlight == 1) {
          // We're starting a block download (batch) from this peer.
          state->nDownloadingSince = GetTimeMicros();
      }
      if (state->nBlocksInFlightValidHeaders == 1 && pindex != NULL) {
          nPeersWithValidatedDownloads++;
      }
      mapBlocksInFlight[hash] = std::make_pair(nodeid, it);
  }
  
  /** Check whether the last unknown block a peer advertized is not yet known. */
  void ProcessBlockAvailability(NodeId nodeid) {
      CNodeState *state = State(nodeid);
      assert(state != NULL);
  
      if (!state->hashLastUnknownBlock.IsNull()) {
          BlockMap::iterator itOld = mapBlockIndex.find(state->hashLastUnknownBlock);
          if (itOld != mapBlockIndex.end() && itOld->second->nChainWork > 0) {
              if (state->pindexBestKnownBlock == NULL || itOld->second->nChainWork >= state->pindexBestKnownBlock->nChainWork)
                  state->pindexBestKnownBlock = itOld->second;
              state->hashLastUnknownBlock.SetNull();
          }
      }
  }
  
  /** Update tracking information about which blocks a peer is assumed to have. */
  void UpdateBlockAvailability(NodeId nodeid, const uint256 &hash) {
      CNodeState *state = State(nodeid);
      assert(state != NULL);
  
      ProcessBlockAvailability(nodeid);
  
      BlockMap::iterator it = mapBlockIndex.find(hash);
      if (it != mapBlockIndex.end() && it->second->nChainWork > 0) {
          // An actually better block was announced.
          if (state->pindexBestKnownBlock == NULL || it->second->nChainWork >= state->pindexBestKnownBlock->nChainWork)
              state->pindexBestKnownBlock = it->second;
      } else {
          // An unknown block was announced; just assume that the latest one is the best one.
          state->hashLastUnknownBlock = hash;
      }
  }
  
  // Requires cs_main
  bool CanDirectFetch(const Consensus::Params &consensusParams)
  {
      return chainActive.Tip()->GetBlockTime() > GetAdjustedTime() - consensusParams.nPowTargetSpacing * 20;
  }
  
  // Requires cs_main
  bool PeerHasHeader(CNodeState *state, CBlockIndex *pindex)
  {
      if (state->pindexBestKnownBlock && pindex == state->pindexBestKnownBlock->GetAncestor(pindex->nHeight))
          return true;
      if (state->pindexBestHeaderSent && pindex == state->pindexBestHeaderSent->GetAncestor(pindex->nHeight))
          return true;
      return false;
  }
  
  /** Find the last common ancestor two blocks have.
   *  Both pa and pb must be non-NULL. */
  CBlockIndex* LastCommonAncestor(CBlockIndex* pa, CBlockIndex* pb) {
      if (pa->nHeight > pb->nHeight) {
          pa = pa->GetAncestor(pb->nHeight);
      } else if (pb->nHeight > pa->nHeight) {
          pb = pb->GetAncestor(pa->nHeight);
      }
  
      while (pa != pb && pa && pb) {
          pa = pa->pprev;
          pb = pb->pprev;
      }
  
      // Eventually all chain branches meet at the genesis block.
      assert(pa == pb);
      return pa;
  }
  
  /** Update pindexLastCommonBlock and add not-in-flight missing successors to vBlocks, until it has
   *  at most count entries. */
  void FindNextBlocksToDownload(NodeId nodeid, unsigned int count, std::vector<CBlockIndex*>& vBlocks, NodeId& nodeStaller) {
      if (count == 0)
          return;
  
      vBlocks.reserve(vBlocks.size() + count);
      CNodeState *state = State(nodeid);
      assert(state != NULL);
  
      // Make sure pindexBestKnownBlock is up to date, we'll need it.
      ProcessBlockAvailability(nodeid);
  
      if (state->pindexBestKnownBlock == NULL || state->pindexBestKnownBlock->nChainWork < chainActive.Tip()->nChainWork) {
          // This peer has nothing interesting.
          return;
      }
  
      if (state->pindexLastCommonBlock == NULL) {
          // Bootstrap quickly by guessing a parent of our best tip is the forking point.
          // Guessing wrong in either direction is not a problem.
          state->pindexLastCommonBlock = chainActive[std::min(state->pindexBestKnownBlock->nHeight, chainActive.Height())];
      }
  
      // If the peer reorganized, our previous pindexLastCommonBlock may not be an ancestor
      // of its current tip anymore. Go back enough to fix that.
      state->pindexLastCommonBlock = LastCommonAncestor(state->pindexLastCommonBlock, state->pindexBestKnownBlock);
      if (state->pindexLastCommonBlock == state->pindexBestKnownBlock)
          return;
  
      std::vector<CBlockIndex*> vToFetch;
      CBlockIndex *pindexWalk = state->pindexLastCommonBlock;
      // Never fetch further than the best block we know the peer has, or more than BLOCK_DOWNLOAD_WINDOW + 1 beyond the last
      // linked block we have in common with this peer. The +1 is so we can detect stalling, namely if we would be able to
      // download that next block if the window were 1 larger.
      int nWindowEnd = state->pindexLastCommonBlock->nHeight + BLOCK_DOWNLOAD_WINDOW;
      int nMaxHeight = std::min<int>(state->pindexBestKnownBlock->nHeight, nWindowEnd + 1);
      NodeId waitingfor = -1;
      while (pindexWalk->nHeight < nMaxHeight) {
          // Read up to 128 (or more, if more blocks than that are needed) successors of pindexWalk (towards
          // pindexBestKnownBlock) into vToFetch. We fetch 128, because CBlockIndex::GetAncestor may be as expensive
          // as iterating over ~100 CBlockIndex* entries anyway.
          int nToFetch = std::min(nMaxHeight - pindexWalk->nHeight, std::max<int>(count - vBlocks.size(), 128));
          vToFetch.resize(nToFetch);
          pindexWalk = state->pindexBestKnownBlock->GetAncestor(pindexWalk->nHeight + nToFetch);
          vToFetch[nToFetch - 1] = pindexWalk;
          for (unsigned int i = nToFetch - 1; i > 0; i--) {
              vToFetch[i - 1] = vToFetch[i]->pprev;
          }
  
          // Iterate over those blocks in vToFetch (in forward direction), adding the ones that
          // are not yet downloaded and not in flight to vBlocks. In the mean time, update
          // pindexLastCommonBlock as long as all ancestors are already downloaded, or if it's
          // already part of our chain (and therefore don't need it even if pruned).
          BOOST_FOREACH(CBlockIndex* pindex, vToFetch) {
              if (!pindex->IsValid(BLOCK_VALID_TREE)) {
                  // We consider the chain that this peer is on invalid.
                  return;
              }
              if (pindex->nStatus & BLOCK_HAVE_DATA || chainActive.Contains(pindex)) {
                  if (pindex->nChainTx)
                      state->pindexLastCommonBlock = pindex;
              } else if (mapBlocksInFlight.count(pindex->GetBlockHash()) == 0) {
                  // The block is not already downloaded, and not yet in flight.
                  if (pindex->nHeight > nWindowEnd) {
                      // We reached the end of the window.
                      if (vBlocks.size() == 0 && waitingfor != nodeid) {
                          // We aren't able to fetch anything, but we would be if the download window was one larger.
                          nodeStaller = waitingfor;
                      }
                      return;
                  }
                  vBlocks.push_back(pindex);
                  if (vBlocks.size() == count) {
                      return;
                  }
              } else if (waitingfor == -1) {
                  // This is the first already-in-flight block.
                  waitingfor = mapBlocksInFlight[pindex->GetBlockHash()].first;
              }
          }
      }
  }
  
  } // anon namespace
  
  bool GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats) {
      LOCK(cs_main);
      CNodeState *state = State(nodeid);
      if (state == NULL)
          return false;
      stats.nMisbehavior = state->nMisbehavior;
      stats.nSyncHeight = state->pindexBestKnownBlock ? state->pindexBestKnownBlock->nHeight : -1;
      stats.nCommonHeight = state->pindexLastCommonBlock ? state->pindexLastCommonBlock->nHeight : -1;
      BOOST_FOREACH(const QueuedBlock& queue, state->vBlocksInFlight) {
          if (queue.pindex)
              stats.vHeightInFlight.push_back(queue.pindex->nHeight);
      }
      return true;
  }
  
  void RegisterNodeSignals(CNodeSignals& nodeSignals)
  {
      nodeSignals.GetHeight.connect(&GetHeight);
      nodeSignals.ProcessMessages.connect(&ProcessMessages);
      nodeSignals.SendMessages.connect(&SendMessages);
      nodeSignals.InitializeNode.connect(&InitializeNode);
      nodeSignals.FinalizeNode.connect(&FinalizeNode);
  }
  
  void UnregisterNodeSignals(CNodeSignals& nodeSignals)
  {
      nodeSignals.GetHeight.disconnect(&GetHeight);
      nodeSignals.ProcessMessages.disconnect(&ProcessMessages);
      nodeSignals.SendMessages.disconnect(&SendMessages);
      nodeSignals.InitializeNode.disconnect(&InitializeNode);
      nodeSignals.FinalizeNode.disconnect(&FinalizeNode);
  }
  
  CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator)
  {
      // Find the first block the caller has in the main chain
      BOOST_FOREACH(const uint256& hash, locator.vHave) {
          BlockMap::iterator mi = mapBlockIndex.find(hash);
          if (mi != mapBlockIndex.end())
          {
              CBlockIndex* pindex = (*mi).second;
              if (chain.Contains(pindex))
                  return pindex;
          }
      }
      return chain.Genesis();
  }
  
  CCoinsViewCache *pcoinsTip = NULL;
  CBlockTreeDB *pblocktree = NULL;
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // mapOrphanTransactions
  //
  
  bool AddOrphanTx(const CTransaction& tx, NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      uint256 hash = tx.GetHash();
      if (mapOrphanTransactions.count(hash))
          return false;
  
      // Ignore big transactions, to avoid a
      // send-big-orphans memory exhaustion attack. If a peer has a legitimate
      // large transaction with a missing parent then we assume
      // it will rebroadcast it later, after the parent transaction(s)
      // have been mined or received.
      // 10,000 orphans, each of which is at most 5,000 bytes big is
      // at most 500 megabytes of orphans:
      unsigned int sz = tx.GetSerializeSize(SER_NETWORK, CTransaction::CURRENT_VERSION);
      if (sz > 5000)
      {
          LogPrint("mempool", "ignoring large orphan tx (size: %u, hash: %s)\n", sz, hash.ToString());
          return false;
      }
  
      mapOrphanTransactions[hash].tx = tx;
      mapOrphanTransactions[hash].fromPeer = peer;
      BOOST_FOREACH(const CTxIn& txin, tx.vin)
          mapOrphanTransactionsByPrev[txin.prevout.hash].insert(hash);
  
      LogPrint("mempool", "stored orphan tx %s (mapsz %u prevsz %u)\n", hash.ToString(),
               mapOrphanTransactions.size(), mapOrphanTransactionsByPrev.size());
      return true;
  }
  
  void static EraseOrphanTx(uint256 hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.find(hash);
      if (it == mapOrphanTransactions.end())
          return;
      BOOST_FOREACH(const CTxIn& txin, it->second.tx.vin)
      {
          map<uint256, set<uint256> >::iterator itPrev = mapOrphanTransactionsByPrev.find(txin.prevout.hash);
          if (itPrev == mapOrphanTransactionsByPrev.end())
              continue;
          itPrev->second.erase(hash);
          if (itPrev->second.empty())
              mapOrphanTransactionsByPrev.erase(itPrev);
      }
      mapOrphanTransactions.erase(it);
  }
  
  void EraseOrphansFor(NodeId peer)
  {
      int nErased = 0;
      map<uint256, COrphanTx>::iterator iter = mapOrphanTransactions.begin();
      while (iter != mapOrphanTransactions.end())
      {
          map<uint256, COrphanTx>::iterator maybeErase = iter++; // increment to avoid iterator becoming invalid
          if (maybeErase->second.fromPeer == peer)
          {
              EraseOrphanTx(maybeErase->second.tx.GetHash());
              ++nErased;
          }
      }
      if (nErased > 0) LogPrint("mempool", "Erased %d orphan tx from peer %d\n", nErased, peer);
  }
  
  
  unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      unsigned int nEvicted = 0;
      while (mapOrphanTransactions.size() > nMaxOrphans)
      {
          // Evict a random orphan:
          uint256 randomhash = GetRandHash();
          map<uint256, COrphanTx>::iterator it = mapOrphanTransactions.lower_bound(randomhash);
          if (it == mapOrphanTransactions.end())
              it = mapOrphanTransactions.begin();
          EraseOrphanTx(it->first);
          ++nEvicted;
      }
      return nEvicted;
  }
  
  bool IsFinalTx(const CTransaction &tx, int nBlockHeight, int64_t nBlockTime)
  {
      if (tx.nLockTime == 0)
          return true;
      if ((int64_t)tx.nLockTime < ((int64_t)tx.nLockTime < LOCKTIME_THRESHOLD ? (int64_t)nBlockHeight : nBlockTime))
          return true;
      BOOST_FOREACH(const CTxIn& txin, tx.vin) {
          if (!(txin.nSequence == CTxIn::SEQUENCE_FINAL))
              return false;
      }
      return true;
  }
  
  bool CheckFinalTx(const CTransaction &tx, int flags)
  {
      AssertLockHeld(cs_main);
  
      // By convention a negative value for flags indicates that the
      // current network-enforced consensus rules should be used. In
      // a future soft-fork scenario that would mean checking which
      // rules would be enforced for the next block and setting the
      // appropriate flags. At the present time no soft-forks are
      // scheduled, so no flags are set.
      flags = std::max(flags, 0);
  
      // CheckFinalTx() uses chainActive.Height()+1 to evaluate
      // nLockTime because when IsFinalTx() is called within
      // CBlock::AcceptBlock(), the height of the block *being*
      // evaluated is what is used. Thus if we want to know if a
      // transaction can be part of the *next* block, we need to call
      // IsFinalTx() with one more than chainActive.Height().
      const int nBlockHeight = chainActive.Height() + 1;
  
      // BIP113 will require that time-locked transactions have nLockTime set to
      // less than the median time of the previous block they're contained in.
      // When the next block is created its previous block will be the current
      // chain tip, so we use that to calculate the median time passed to
      // IsFinalTx() if LOCKTIME_MEDIAN_TIME_PAST is set.
      const int64_t nBlockTime = (flags & LOCKTIME_MEDIAN_TIME_PAST)
                               ? chainActive.Tip()->GetMedianTimePast()
                               : GetAdjustedTime();
  
      return IsFinalTx(tx, nBlockHeight, nBlockTime);
  }
  
  /**
   * Calculates the block height and previous block's median time past at
   * which the transaction will be considered final in the context of BIP 68.
   * Also removes from the vector of input heights any entries which did not
   * correspond to sequence locked inputs as they do not affect the calculation.
   */
  static std::pair<int, int64_t> CalculateSequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeights, const CBlockIndex& block)
  {
      assert(prevHeights->size() == tx.vin.size());
  
      // Will be set to the equivalent height- and time-based nLockTime
      // values that would be necessary to satisfy all relative lock-
      // time constraints given our view of block chain history.
      // The semantics of nLockTime are the last invalid height/time, so
      // use -1 to have the effect of any height or time being valid.
      int nMinHeight = -1;
      int64_t nMinTime = -1;
  
      // tx.nVersion is signed integer so requires cast to unsigned otherwise
      // we would be doing a signed comparison and half the range of nVersion
      // wouldn't support BIP 68.
      bool fEnforceBIP68 = static_cast<uint32_t>(tx.nVersion) >= 2
                        && flags & LOCKTIME_VERIFY_SEQUENCE;
  
      // Do not enforce sequence numbers as a relative lock time
      // unless we have been instructed to
      if (!fEnforceBIP68) {
          return std::make_pair(nMinHeight, nMinTime);
      }
  
      for (size_t txinIndex = 0; txinIndex < tx.vin.size(); txinIndex++) {
          const CTxIn& txin = tx.vin[txinIndex];
  
          // Sequence numbers with the most significant bit set are not
          // treated as relative lock-times, nor are they given any
          // consensus-enforced meaning at this point.
          if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_DISABLE_FLAG) {
              // The height of this input is not relevant for sequence locks
              (*prevHeights)[txinIndex] = 0;
              continue;
          }
  
          int nCoinHeight = (*prevHeights)[txinIndex];
  
          if (txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_TYPE_FLAG) {
              int64_t nCoinTime = block.GetAncestor(std::max(nCoinHeight-1, 0))->GetMedianTimePast();
              // NOTE: Subtract 1 to maintain nLockTime semantics
              // BIP 68 relative lock times have the semantics of calculating
              // the first block or time at which the transaction would be
              // valid. When calculating the effective block time or height
              // for the entire transaction, we switch to using the
              // semantics of nLockTime which is the last invalid block
              // time or height.  Thus we subtract 1 from the calculated
              // time or height.
  
              // Time-based relative lock-times are measured from the
              // smallest allowed timestamp of the block containing the
              // txout being spent, which is the median time past of the
              // block prior.
              nMinTime = std::max(nMinTime, nCoinTime + (int64_t)((txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_MASK) << CTxIn::SEQUENCE_LOCKTIME_GRANULARITY) - 1);
          } else {
              nMinHeight = std::max(nMinHeight, nCoinHeight + (int)(txin.nSequence & CTxIn::SEQUENCE_LOCKTIME_MASK) - 1);
          }
      }
  
      return std::make_pair(nMinHeight, nMinTime);
  }
  
  static bool EvaluateSequenceLocks(const CBlockIndex& block, std::pair<int, int64_t> lockPair)
  {
      assert(block.pprev);
      int64_t nBlockTime = block.pprev->GetMedianTimePast();
      if (lockPair.first >= block.nHeight || lockPair.second >= nBlockTime)
          return false;
  
      return true;
  }
  
  bool SequenceLocks(const CTransaction &tx, int flags, std::vector<int>* prevHeights, const CBlockIndex& block)
  {
      return EvaluateSequenceLocks(block, CalculateSequenceLocks(tx, flags, prevHeights, block));
  }
  
  bool TestLockPointValidity(const LockPoints* lp)
  {
      AssertLockHeld(cs_main);
      assert(lp);
      // If there are relative lock times then the maxInputBlock will be set
      // If there are no relative lock times, the LockPoints don't depend on the chain
      if (lp->maxInputBlock) {
          // Check whether chainActive is an extension of the block at which the LockPoints
          // calculation was valid.  If not LockPoints are no longer valid
          if (!chainActive.Contains(lp->maxInputBlock)) {
              return false;
          }
      }
  
      // LockPoints still valid
      return true;
  }
  
  bool CheckSequenceLocks(const CTransaction &tx, int flags, LockPoints* lp, bool useExistingLockPoints)
  {
      AssertLockHeld(cs_main);
      AssertLockHeld(mempool.cs);
  
      CBlockIndex* tip = chainActive.Tip();
      CBlockIndex index;
      index.pprev = tip;
      // CheckSequenceLocks() uses chainActive.Height()+1 to evaluate
      // height based locks because when SequenceLocks() is called within
      // ConnectBlock(), the height of the block *being*
      // evaluated is what is used.
      // Thus if we want to know if a transaction can be part of the
      // *next* block, we need to use one more than chainActive.Height()
      index.nHeight = tip->nHeight + 1;
  
      std::pair<int, int64_t> lockPair;
      if (useExistingLockPoints) {
          assert(lp);
          lockPair.first = lp->height;
          lockPair.second = lp->time;
      }
      else {
          // pcoinsTip contains the UTXO set for chainActive.Tip()
          CCoinsViewMemPool viewMemPool(pcoinsTip, mempool);
          std::vector<int> prevheights;
          prevheights.resize(tx.vin.size());
          for (size_t txinIndex = 0; txinIndex < tx.vin.size(); txinIndex++) {
              const CTxIn& txin = tx.vin[txinIndex];
              CCoins coins;
              if (!viewMemPool.GetCoins(txin.prevout.hash, coins)) {
                  return error("%s: Missing input", __func__);
              }
              if (coins.nHeight == MEMPOOL_HEIGHT) {
                  // Assume all mempool transaction confirm in the next block
                  prevheights[txinIndex] = tip->nHeight + 1;
              } else {
                  prevheights[txinIndex] = coins.nHeight;
              }
          }
          lockPair = CalculateSequenceLocks(tx, flags, &prevheights, index);
          if (lp) {
              lp->height = lockPair.first;
              lp->time = lockPair.second;
              // Also store the hash of the block with the highest height of
              // all the blocks which have sequence locked prevouts.
              // This hash needs to still be on the chain
              // for these LockPoint calculations to be valid
              // Note: It is impossible to correctly calculate a maxInputBlock
              // if any of the sequence locked inputs depend on unconfirmed txs,
              // except in the special case where the relative lock time/height
              // is 0, which is equivalent to no sequence lock. Since we assume
              // input height of tip+1 for mempool txs and test the resulting
              // lockPair from CalculateSequenceLocks against tip+1.  We know
              // EvaluateSequenceLocks will fail if there was a non-zero sequence
              // lock on a mempool input, so we can use the return value of
              // CheckSequenceLocks to indicate the LockPoints validity
              int maxInputHeight = 0;
              BOOST_FOREACH(int height, prevheights) {
                  // Can ignore mempool inputs since we'll fail if they had non-zero locks
                  if (height != tip->nHeight+1) {
                      maxInputHeight = std::max(maxInputHeight, height);
                  }
              }
              lp->maxInputBlock = tip->GetAncestor(maxInputHeight);
          }
      }
      return EvaluateSequenceLocks(index, lockPair);
  }
  
  
  unsigned int GetLegacySigOpCount(const CTransaction& tx)
  {
      unsigned int nSigOps = 0;
      BOOST_FOREACH(const CTxIn& txin, tx.vin)
      {
          nSigOps += txin.scriptSig.GetSigOpCount(false);
      }
      BOOST_FOREACH(const CTxOut& txout, tx.vout)
      {
          nSigOps += txout.scriptPubKey.GetSigOpCount(false);
      }
      return nSigOps;
  }
  
  unsigned int GetP2SHSigOpCount(const CTransaction& tx, const CCoinsViewCache& inputs)
  {
      if (tx.IsCoinBase())
          return 0;
  
      unsigned int nSigOps = 0;
      for (unsigned int i = 0; i < tx.vin.size(); i++)
      {
          const CTxOut &prevout = inputs.GetOutputFor(tx.vin[i]);
          if (prevout.scriptPubKey.IsPayToScriptHash())
              nSigOps += prevout.scriptPubKey.GetSigOpCount(tx.vin[i].scriptSig);
      }
      return nSigOps;
  }
  
  
  
  
  
  
  
  
  bool CheckTransaction(const CTransaction& tx, CValidationState &state)
  {
      // Basic checks that don't depend on any context
      if (tx.vin.empty())
          return state.DoS(10, false, REJECT_INVALID, "bad-txns-vin-empty");
      if (tx.vout.empty())
          return state.DoS(10, false, REJECT_INVALID, "bad-txns-vout-empty");
      // Size limits
      if (::GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION) > MAX_BLOCK_SIZE)
          return state.DoS(100, false, REJECT_INVALID, "bad-txns-oversize");
  
      // Check for negative or overflow output values
      CAmount nValueOut = 0;
      BOOST_FOREACH(const CTxOut& txout, tx.vout)
      {
          if (txout.nValue < 0)
              return state.DoS(100, false, REJECT_INVALID, "bad-txns-vout-negative");
          if (txout.nValue > MAX_MONEY)
              return state.DoS(100, false, REJECT_INVALID, "bad-txns-vout-toolarge");
          nValueOut += txout.nValue;
          if (!MoneyRange(nValueOut))
              return state.DoS(100, false, REJECT_INVALID, "bad-txns-txouttotal-toolarge");
      }
  
      // Check for duplicate inputs
      set<COutPoint> vInOutPoints;
      BOOST_FOREACH(const CTxIn& txin, tx.vin)
      {
          if (vInOutPoints.count(txin.prevout))
              return state.DoS(100, false, REJECT_INVALID, "bad-txns-inputs-duplicate");
          vInOutPoints.insert(txin.prevout);
      }
  
      if (tx.IsCoinBase())
      {
          if (tx.vin[0].scriptSig.size() < 2 || tx.vin[0].scriptSig.size() > 100)
              return state.DoS(100, false, REJECT_INVALID, "bad-cb-length");
      }
      else
      {
          BOOST_FOREACH(const CTxIn& txin, tx.vin)
              if (txin.prevout.IsNull())
                  return state.DoS(10, false, REJECT_INVALID, "bad-txns-prevout-null");
      }
  
      return true;
  }
  
  void LimitMempoolSize(CTxMemPool& pool, size_t limit, unsigned long age) {
      int expired = pool.Expire(GetTime() - age);
      if (expired != 0)
          LogPrint("mempool", "Expired %i transactions from the memory pool\n", expired);
  
      std::vector<uint256> vNoSpendsRemaining;
      pool.TrimToSize(limit, &vNoSpendsRemaining);
      BOOST_FOREACH(const uint256& removed, vNoSpendsRemaining)
          pcoinsTip->Uncache(removed);
  }
  
  /** Convert CValidationState to a human-readable message for logging */
  std::string FormatStateMessage(const CValidationState &state)
  {
      return strprintf("%s%s (code %i)",
          state.GetRejectReason(),
          state.GetDebugMessage().empty() ? "" : ", "+state.GetDebugMessage(),
          state.GetRejectCode());
  }
  
  bool AcceptToMemoryPoolWorker(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
                                bool* pfMissingInputs, bool fOverrideMempoolLimit, bool fRejectAbsurdFee,
                                std::vector<uint256>& vHashTxnToUncache)
  {
      AssertLockHeld(cs_main);
      if (pfMissingInputs)
          *pfMissingInputs = false;
  
      if (!CheckTransaction(tx, state))
          return false;
  
      // Coinbase is only valid in a block, not as a loose transaction
      if (tx.IsCoinBase())
          return state.DoS(100, false, REJECT_INVALID, "coinbase");
  
      // Rather not work on nonstandard transactions (unless -testnet/-regtest)
      string reason;
      if (fRequireStandard && !IsStandardTx(tx, reason))
          return state.DoS(0, false, REJECT_NONSTANDARD, reason);
  
      // Don't relay version 2 transactions until CSV is active, and we can be
      // sure that such transactions will be mined (unless we're on
      // -testnet/-regtest).
      const CChainParams& chainparams = Params();
      if (fRequireStandard && tx.nVersion >= 2 && VersionBitsTipState(chainparams.GetConsensus(), Consensus::DEPLOYMENT_CSV) != THRESHOLD_ACTIVE) {
          return state.DoS(0, false, REJECT_NONSTANDARD, "premature-version2-tx");
      }
  
      // Only accept nLockTime-using transactions that can be mined in the next
      // block; we don't want our mempool filled up with transactions that can't
      // be mined yet.
      if (!CheckFinalTx(tx, STANDARD_LOCKTIME_VERIFY_FLAGS))
          return state.DoS(0, false, REJECT_NONSTANDARD, "non-final");
  
      // is it already in the memory pool?
      uint256 hash = tx.GetHash();
      if (pool.exists(hash))
          return state.Invalid(false, REJECT_ALREADY_KNOWN, "txn-already-in-mempool");
  
      // Check for conflicts with in-memory transactions
      set<uint256> setConflicts;
      {
      LOCK(pool.cs); // protect pool.mapNextTx
      BOOST_FOREACH(const CTxIn &txin, tx.vin)
      {
          if (pool.mapNextTx.count(txin.prevout))
          {
              const CTransaction *ptxConflicting = pool.mapNextTx[txin.prevout].ptx;
              if (!setConflicts.count(ptxConflicting->GetHash()))
              {
                  // Allow opt-out of transaction replacement by setting
                  // nSequence >= maxint-1 on all inputs.
                  //
                  // maxint-1 is picked to still allow use of nLockTime by
                  // non-replacable transactions. All inputs rather than just one
                  // is for the sake of multi-party protocols, where we don't
                  // want a single party to be able to disable replacement.
                  //
                  // The opt-out ignores descendants as anyone relying on
                  // first-seen mempool behavior should be checking all
                  // unconfirmed ancestors anyway; doing otherwise is hopelessly
                  // insecure.
                  bool fReplacementOptOut = true;
                  if (fEnableReplacement)
                  {
                      BOOST_FOREACH(const CTxIn &txin, ptxConflicting->vin)
                      {
                          if (txin.nSequence < std::numeric_limits<unsigned int>::max()-1)
                          {
                              fReplacementOptOut = false;
                              break;
                          }
                      }
                  }
                  if (fReplacementOptOut)
                      return state.Invalid(false, REJECT_CONFLICT, "txn-mempool-conflict");
  
                  setConflicts.insert(ptxConflicting->GetHash());
              }
          }
      }
      }
  
      {
          CCoinsView dummy;
          CCoinsViewCache view(&dummy);
  
          CAmount nValueIn = 0;
          LockPoints lp;
          {
          LOCK(pool.cs);
          CCoinsViewMemPool viewMemPool(pcoinsTip, pool);
          view.SetBackend(viewMemPool);
  
          // do we already have it?
          bool fHadTxInCache = pcoinsTip->HaveCoinsInCache(hash);
          if (view.HaveCoins(hash)) {
              if (!fHadTxInCache)
                  vHashTxnToUncache.push_back(hash);
              return state.Invalid(false, REJECT_ALREADY_KNOWN, "txn-already-known");
          }
  
          // do all inputs exist?
          // Note that this does not check for the presence of actual outputs (see the next check for that),
          // and only helps with filling in pfMissingInputs (to determine missing vs spent).
          BOOST_FOREACH(const CTxIn txin, tx.vin) {
              if (!pcoinsTip->HaveCoinsInCache(txin.prevout.hash))
                  vHashTxnToUncache.push_back(txin.prevout.hash);
              if (!view.HaveCoins(txin.prevout.hash)) {
                  if (pfMissingInputs)
                      *pfMissingInputs = true;
                  return false; // fMissingInputs and !state.IsInvalid() is used to detect this condition, don't set state.Invalid()
              }
          }
  
          // are the actual inputs available?
          if (!view.HaveInputs(tx))
              return state.Invalid(false, REJECT_DUPLICATE, "bad-txns-inputs-spent");
  
          // Bring the best block into scope
          view.GetBestBlock();
  
          nValueIn = view.GetValueIn(tx);
  
          // we have all inputs cached now, so switch back to dummy, so we don't need to keep lock on mempool
          view.SetBackend(dummy);
  
          // Only accept BIP68 sequence locked transactions that can be mined in the next
          // block; we don't want our mempool filled up with transactions that can't
          // be mined yet.
          // Must keep pool.cs for this unless we change CheckSequenceLocks to take a
          // CoinsViewCache instead of create its own
          if (!CheckSequenceLocks(tx, STANDARD_LOCKTIME_VERIFY_FLAGS, &lp))
              return state.DoS(0, false, REJECT_NONSTANDARD, "non-BIP68-final");
          }
  
          // Check for non-standard pay-to-script-hash in inputs
          if (fRequireStandard && !AreInputsStandard(tx, view))
              return state.Invalid(false, REJECT_NONSTANDARD, "bad-txns-nonstandard-inputs");
  
          unsigned int nSigOps = GetLegacySigOpCount(tx);
          nSigOps += GetP2SHSigOpCount(tx, view);
  
          CAmount nValueOut = tx.GetValueOut();
          CAmount nFees = nValueIn-nValueOut;
          // nModifiedFees includes any fee deltas from PrioritiseTransaction
          CAmount nModifiedFees = nFees;
          double nPriorityDummy = 0;
          pool.ApplyDeltas(hash, nPriorityDummy, nModifiedFees);
  
          CAmount inChainInputValue;
          double dPriority = view.GetPriority(tx, chainActive.Height(), inChainInputValue);
  
          // Keep track of transactions that spend a coinbase, which we re-scan
          // during reorgs to ensure COINBASE_MATURITY is still met.
          bool fSpendsCoinbase = false;
          BOOST_FOREACH(const CTxIn &txin, tx.vin) {
              const CCoins *coins = view.AccessCoins(txin.prevout.hash);
              if (coins->IsCoinBase()) {
                  fSpendsCoinbase = true;
                  break;
              }
          }
  
          CTxMemPoolEntry entry(tx, nFees, GetTime(), dPriority, chainActive.Height(), pool.HasNoInputsOf(tx), inChainInputValue, fSpendsCoinbase, nSigOps, lp);
          unsigned int nSize = entry.GetTxSize();
  
          // Check that the transaction doesn't have an excessive number of
          // sigops, making it impossible to mine. Since the coinbase transaction
          // itself can contain sigops MAX_STANDARD_TX_SIGOPS is less than
          // MAX_BLOCK_SIGOPS; we still consider this an invalid rather than
          // merely non-standard transaction.
          if ((nSigOps > MAX_STANDARD_TX_SIGOPS) || (nBytesPerSigOp && nSigOps > nSize / nBytesPerSigOp))
              return state.DoS(0, false, REJECT_NONSTANDARD, "bad-txns-too-many-sigops", false,
                  strprintf("%d", nSigOps));
  
          CAmount mempoolRejectFee = pool.GetMinFee(GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFee(nSize);
          if (mempoolRejectFee > 0 && nModifiedFees < mempoolRejectFee) {
              return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "mempool min fee not met", false, strprintf("%d < %d", nFees, mempoolRejectFee));
          } else if (GetBoolArg("-relaypriority", DEFAULT_RELAYPRIORITY) && nModifiedFees < ::minRelayTxFee.GetFee(nSize) && !AllowFree(entry.GetPriority(chainActive.Height() + 1))) {
              // Require that free transactions have sufficient priority to be mined in the next block.
              return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "insufficient priority");
          }
  
          // Continuously rate-limit free (really, very-low-fee) transactions
          // This mitigates 'penny-flooding' -- sending thousands of free transactions just to
          // be annoying or make others' transactions take longer to confirm.
          if (fLimitFree && nModifiedFees < ::minRelayTxFee.GetFee(nSize))
          {
              static CCriticalSection csFreeLimiter;
              static double dFreeCount;
              static int64_t nLastTime;
              int64_t nNow = GetTime();
  
              LOCK(csFreeLimiter);
  
              // Use an exponentially decaying ~10-minute window:
              dFreeCount *= pow(1.0 - 1.0/600.0, (double)(nNow - nLastTime));
              nLastTime = nNow;
              // -limitfreerelay unit is thousand-bytes-per-minute
              // At default rate it would take over a month to fill 1GB
              if (dFreeCount >= GetArg("-limitfreerelay", DEFAULT_LIMITFREERELAY) * 10 * 1000)
                  return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "rate limited free transaction");
              LogPrint("mempool", "Rate limit dFreeCount: %g => %g\n", dFreeCount, dFreeCount+nSize);
              dFreeCount += nSize;
          }
  
          if (fRejectAbsurdFee && nFees > ::minRelayTxFee.GetFee(nSize) * 10000)
              return state.Invalid(false,
                  REJECT_HIGHFEE, "absurdly-high-fee",
                  strprintf("%d > %d", nFees, ::minRelayTxFee.GetFee(nSize) * 10000));
  
          // Calculate in-mempool ancestors, up to a limit.
          CTxMemPool::setEntries setAncestors;
          size_t nLimitAncestors = GetArg("-limitancestorcount", DEFAULT_ANCESTOR_LIMIT);
          size_t nLimitAncestorSize = GetArg("-limitancestorsize", DEFAULT_ANCESTOR_SIZE_LIMIT)*1000;
          size_t nLimitDescendants = GetArg("-limitdescendantcount", DEFAULT_DESCENDANT_LIMIT);
          size_t nLimitDescendantSize = GetArg("-limitdescendantsize", DEFAULT_DESCENDANT_SIZE_LIMIT)*1000;
          std::string errString;
          if (!pool.CalculateMemPoolAncestors(entry, setAncestors, nLimitAncestors, nLimitAncestorSize, nLimitDescendants, nLimitDescendantSize, errString)) {
              return state.DoS(0, false, REJECT_NONSTANDARD, "too-long-mempool-chain", false, errString);
          }
  
          // A transaction that spends outputs that would be replaced by it is invalid. Now
          // that we have the set of all ancestors we can detect this
          // pathological case by making sure setConflicts and setAncestors don't
          // intersect.
          BOOST_FOREACH(CTxMemPool::txiter ancestorIt, setAncestors)
          {
              const uint256 &hashAncestor = ancestorIt->GetTx().GetHash();
              if (setConflicts.count(hashAncestor))
              {
                  return state.DoS(10, error("AcceptToMemoryPool: %s spends conflicting transaction %s",
                                             hash.ToString(),
                                             hashAncestor.ToString()),
                                   REJECT_INVALID, "bad-txns-spends-conflicting-tx");
              }
          }
  
          // Check if it's economically rational to mine this transaction rather
          // than the ones it replaces.
          CAmount nConflictingFees = 0;
          size_t nConflictingSize = 0;
          uint64_t nConflictingCount = 0;
          CTxMemPool::setEntries allConflicting;
  
          // If we don't hold the lock allConflicting might be incomplete; the
          // subsequent RemoveStaged() and addUnchecked() calls don't guarantee
          // mempool consistency for us.
          LOCK(pool.cs);
          if (setConflicts.size())
          {
              CFeeRate newFeeRate(nModifiedFees, nSize);
              set<uint256> setConflictsParents;
              const int maxDescendantsToVisit = 100;
              CTxMemPool::setEntries setIterConflicting;
              BOOST_FOREACH(const uint256 &hashConflicting, setConflicts)
              {
                  CTxMemPool::txiter mi = pool.mapTx.find(hashConflicting);
                  if (mi == pool.mapTx.end())
                      continue;
  
                  // Save these to avoid repeated lookups
                  setIterConflicting.insert(mi);
  
                  // If this entry is "dirty", then we don't have descendant
                  // state for this transaction, which means we probably have
                  // lots of in-mempool descendants.
                  // Don't allow replacements of dirty transactions, to ensure
                  // that we don't spend too much time walking descendants.
                  // This should be rare.
                  if (mi->IsDirty()) {
                      return state.DoS(0,
                              error("AcceptToMemoryPool: rejecting replacement %s; cannot replace tx %s with untracked descendants",
                                  hash.ToString(),
                                  mi->GetTx().GetHash().ToString()),
                              REJECT_NONSTANDARD, "too many potential replacements");
                  }
  
                  // Don't allow the replacement to reduce the feerate of the
                  // mempool.
                  //
                  // We usually don't want to accept replacements with lower
                  // feerates than what they replaced as that would lower the
                  // feerate of the next block. Requiring that the feerate always
                  // be increased is also an easy-to-reason about way to prevent
                  // DoS attacks via replacements.
                  //
                  // The mining code doesn't (currently) take children into
                  // account (CPFP) so we only consider the feerates of
                  // transactions being directly replaced, not their indirect
                  // descendants. While that does mean high feerate children are
                  // ignored when deciding whether or not to replace, we do
                  // require the replacement to pay more overall fees too,
                  // mitigating most cases.
                  CFeeRate oldFeeRate(mi->GetModifiedFee(), mi->GetTxSize());
                  if (newFeeRate <= oldFeeRate)
                  {
                      return state.DoS(0,
                              error("AcceptToMemoryPool: rejecting replacement %s; new feerate %s <= old feerate %s",
                                    hash.ToString(),
                                    newFeeRate.ToString(),
                                    oldFeeRate.ToString()),
                              REJECT_INSUFFICIENTFEE, "insufficient fee");
                  }
  
                  BOOST_FOREACH(const CTxIn &txin, mi->GetTx().vin)
                  {
                      setConflictsParents.insert(txin.prevout.hash);
                  }
  
                  nConflictingCount += mi->GetCountWithDescendants();
              }
              // This potentially overestimates the number of actual descendants
              // but we just want to be conservative to avoid doing too much
              // work.
              if (nConflictingCount <= maxDescendantsToVisit) {
                  // If not too many to replace, then calculate the set of
                  // transactions that would have to be evicted
                  BOOST_FOREACH(CTxMemPool::txiter it, setIterConflicting) {
                      pool.CalculateDescendants(it, allConflicting);
                  }
                  BOOST_FOREACH(CTxMemPool::txiter it, allConflicting) {
                      nConflictingFees += it->GetModifiedFee();
                      nConflictingSize += it->GetTxSize();
                  }
              } else {
                  return state.DoS(0,
                          error("AcceptToMemoryPool: rejecting replacement %s; too many potential replacements (%d > %d)\n",
                              hash.ToString(),
                              nConflictingCount,
                              maxDescendantsToVisit),
                          REJECT_NONSTANDARD, "too many potential replacements");
              }
  
              for (unsigned int j = 0; j < tx.vin.size(); j++)
              {
                  // We don't want to accept replacements that require low
                  // feerate junk to be mined first. Ideally we'd keep track of
                  // the ancestor feerates and make the decision based on that,
                  // but for now requiring all new inputs to be confirmed works.
                  if (!setConflictsParents.count(tx.vin[j].prevout.hash))
                  {
                      // Rather than check the UTXO set - potentially expensive -
                      // it's cheaper to just check if the new input refers to a
                      // tx that's in the mempool.
                      if (pool.mapTx.find(tx.vin[j].prevout.hash) != pool.mapTx.end())
                          return state.DoS(0, error("AcceptToMemoryPool: replacement %s adds unconfirmed input, idx %d",
                                                    hash.ToString(), j),
                                           REJECT_NONSTANDARD, "replacement-adds-unconfirmed");
                  }
              }
  
              // The replacement must pay greater fees than the transactions it
              // replaces - if we did the bandwidth used by those conflicting
              // transactions would not be paid for.
              if (nModifiedFees < nConflictingFees)
              {
                  return state.DoS(0, error("AcceptToMemoryPool: rejecting replacement %s, less fees than conflicting txs; %s < %s",
                                            hash.ToString(), FormatMoney(nModifiedFees), FormatMoney(nConflictingFees)),
                                   REJECT_INSUFFICIENTFEE, "insufficient fee");
              }
  
              // Finally in addition to paying more fees than the conflicts the
              // new transaction must pay for its own bandwidth.
              CAmount nDeltaFees = nModifiedFees - nConflictingFees;
              if (nDeltaFees < ::minRelayTxFee.GetFee(nSize))
              {
                  return state.DoS(0,
                          error("AcceptToMemoryPool: rejecting replacement %s, not enough additional fees to relay; %s < %s",
                                hash.ToString(),
                                FormatMoney(nDeltaFees),
                                FormatMoney(::minRelayTxFee.GetFee(nSize))),
                          REJECT_INSUFFICIENTFEE, "insufficient fee");
              }
          }
  
          // Check against previous transactions
          // This is done last to help prevent CPU exhaustion denial-of-service attacks.
          if (!CheckInputs(tx, state, view, true, STANDARD_SCRIPT_VERIFY_FLAGS, true))
              return false;
  
          // Check again against just the consensus-critical mandatory script
          // verification flags, in case of bugs in the standard flags that cause
          // transactions to pass as valid when they're actually invalid. For
          // instance the STRICTENC flag was incorrectly allowing certain
          // CHECKSIG NOT scripts to pass, even though they were invalid.
          //
          // There is a similar check in CreateNewBlock() to prevent creating
          // invalid blocks, however allowing such transactions into the mempool
          // can be exploited as a DoS attack.
          if (!CheckInputs(tx, state, view, true, MANDATORY_SCRIPT_VERIFY_FLAGS, true))
          {
              return error("%s: BUG! PLEASE REPORT THIS! ConnectInputs failed against MANDATORY but not STANDARD flags %s, %s",
                  __func__, hash.ToString(), FormatStateMessage(state));
          }
  
          // Remove conflicting transactions from the mempool
          BOOST_FOREACH(const CTxMemPool::txiter it, allConflicting)
          {
              LogPrint("mempool", "replacing tx %s with %s for %s BTC additional fees, %d delta bytes\n",
                      it->GetTx().GetHash().ToString(),
                      hash.ToString(),
                      FormatMoney(nModifiedFees - nConflictingFees),
                      (int)nSize - (int)nConflictingSize);
          }
          pool.RemoveStaged(allConflicting);
  
          // Store transaction in memory
          pool.addUnchecked(hash, entry, setAncestors, !IsInitialBlockDownload());
  
          // trim mempool and check if tx was trimmed
          if (!fOverrideMempoolLimit) {
              LimitMempoolSize(pool, GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
              if (!pool.exists(hash))
                  return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "mempool full");
          }
      }
  
      SyncWithWallets(tx, NULL);
  
      return true;
  }
  
  bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
                          bool* pfMissingInputs, bool fOverrideMempoolLimit, bool fRejectAbsurdFee)
  {
      std::vector<uint256> vHashTxToUncache;
      bool res = AcceptToMemoryPoolWorker(pool, state, tx, fLimitFree, pfMissingInputs, fOverrideMempoolLimit, fRejectAbsurdFee, vHashTxToUncache);
      if (!res) {
          BOOST_FOREACH(const uint256& hashTx, vHashTxToUncache)
              pcoinsTip->Uncache(hashTx);
      }
      return res;
  }
  
  /** Return transaction in tx, and if it was found inside a block, its hash is placed in hashBlock */
  bool GetTransaction(const uint256 &hash, CTransaction &txOut, const Consensus::Params& consensusParams, uint256 &hashBlock, bool fAllowSlow)
  {
      CBlockIndex *pindexSlow = NULL;
  
      LOCK(cs_main);
  
      if (mempool.lookup(hash, txOut))
      {
          return true;
      }
  
      if (fTxIndex) {
          CDiskTxPos postx;
          if (pblocktree->ReadTxIndex(hash, postx)) {
              CAutoFile file(OpenBlockFile(postx, true), SER_DISK, CLIENT_VERSION);
              if (file.IsNull())
                  return error("%s: OpenBlockFile failed", __func__);
              CBlockHeader header;
              try {
                  file >> header;
                  fseek(file.Get(), postx.nTxOffset, SEEK_CUR);
                  file >> txOut;
              } catch (const std::exception& e) {
                  return error("%s: Deserialize or I/O error - %s", __func__, e.what());
              }
              hashBlock = header.GetHash();
              if (txOut.GetHash() != hash)
                  return error("%s: txid mismatch", __func__);
              return true;
          }
      }
  
      if (fAllowSlow) { // use coin database to locate block that contains transaction, and scan it
          int nHeight = -1;
          {
              CCoinsViewCache &view = *pcoinsTip;
              const CCoins* coins = view.AccessCoins(hash);
              if (coins)
                  nHeight = coins->nHeight;
          }
          if (nHeight > 0)
              pindexSlow = chainActive[nHeight];
      }
  
      if (pindexSlow) {
          CBlock block;
          if (ReadBlockFromDisk(block, pindexSlow, consensusParams)) {
              BOOST_FOREACH(const CTransaction &tx, block.vtx) {
                  if (tx.GetHash() == hash) {
                      txOut = tx;
                      hashBlock = pindexSlow->GetBlockHash();
                      return true;
                  }
              }
          }
      }
  
      return false;
  }
  
  
  
  
  
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // CBlock and CBlockIndex
  //
  
  bool WriteBlockToDisk(const CBlock& block, CDiskBlockPos& pos, const CMessageHeader::MessageStartChars& messageStart)
  {
      // Open history file to append
      CAutoFile fileout(OpenBlockFile(pos), SER_DISK, CLIENT_VERSION);
      if (fileout.IsNull())
          return error("WriteBlockToDisk: OpenBlockFile failed");
  
      // Write index header
      unsigned int nSize = fileout.GetSerializeSize(block);
      fileout << FLATDATA(messageStart) << nSize;
  
      // Write block
      long fileOutPos = ftell(fileout.Get());
      if (fileOutPos < 0)
          return error("WriteBlockToDisk: ftell failed");
      pos.nPos = (unsigned int)fileOutPos;
      fileout << block;
  
      return true;
  }
  
  bool ReadBlockFromDisk(CBlock& block, const CDiskBlockPos& pos, const Consensus::Params& consensusParams)
  {
      block.SetNull();
  
      // Open history file to read
      CAutoFile filein(OpenBlockFile(pos, true), SER_DISK, CLIENT_VERSION);
      if (filein.IsNull())
          return error("ReadBlockFromDisk: OpenBlockFile failed for %s", pos.ToString());
  
      // Read block
      try {
          filein >> block;
      }
      catch (const std::exception& e) {
          return error("%s: Deserialize or I/O error - %s at %s", __func__, e.what(), pos.ToString());
      }
  
      // Check the header
      if (!CheckProofOfWork(block.GetHash(), block.nBits, consensusParams))
          return error("ReadBlockFromDisk: Errors in block header at %s", pos.ToString());
  
      return true;
  }
  
  bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams)
  {
      if (!ReadBlockFromDisk(block, pindex->GetBlockPos(), consensusParams))
          return false;
      if (block.GetHash() != pindex->GetBlockHash())
          return error("ReadBlockFromDisk(CBlock&, CBlockIndex*): GetHash() doesn't match index for %s at %s",
                  pindex->ToString(), pindex->GetBlockPos().ToString());
      return true;
  }
  
  CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams)
  {
      int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;	
  	if (nHeight==1)
  		return 60000000*COIN;
  	else 
  		return 0;
  	
  	//第一块生成2亿，后面挖到的都是0
  
      // Force block reward to zero when right shift is undefined.
      if (halvings >= 64)
          return 0;
  
      CAmount nSubsidy = 50 * COIN;
      // Subsidy is cut in half every 210,000 blocks which will occur approximately every 4 years.
      nSubsidy >>= halvings;
      return nSubsidy;
  }
  
  bool IsInitialBlockDownload()
  {
      const CChainParams& chainParams = Params();
      LOCK(cs_main);
      if (fImporting || fReindex)
          return true;
      if (fCheckpointsEnabled && chainActive.Height() < Checkpoints::GetTotalBlocksEstimate(chainParams.Checkpoints()))
          return true;
      static bool lockIBDState = false;
      if (lockIBDState)
          return false;
      bool state = (chainActive.Height() < pindexBestHeader->nHeight - 24 * 6 ||
              pindexBestHeader->GetBlockTime() < GetTime() - chainParams.MaxTipAge());
      if (!state)
          lockIBDState = true;
      return state;
  }
  
  bool fLargeWorkForkFound = false;
  bool fLargeWorkInvalidChainFound = false;
  CBlockIndex *pindexBestForkTip = NULL, *pindexBestForkBase = NULL;
  
  void CheckForkWarningConditions()
  {
      AssertLockHeld(cs_main);
      // Before we get past initial download, we cannot reliably alert about forks
      // (we assume we don't get stuck on a fork before the last checkpoint)
      if (IsInitialBlockDownload())
          return;
  
      // If our best fork is no longer within 72 blocks (+/- 12 hours if no one mines it)
      // of our head, drop it
      if (pindexBestForkTip && chainActive.Height() - pindexBestForkTip->nHeight >= 72)
          pindexBestForkTip = NULL;
  
      if (pindexBestForkTip || (pindexBestInvalid && pindexBestInvalid->nChainWork > chainActive.Tip()->nChainWork + (GetBlockProof(*chainActive.Tip()) * 6)))
      {
          if (!fLargeWorkForkFound && pindexBestForkBase)
          {
              std::string warning = std::string("'Warning: Large-work fork detected, forking after block ") +
                  pindexBestForkBase->phashBlock->ToString() + std::string("'");
              CAlert::Notify(warning, true);
          }
          if (pindexBestForkTip && pindexBestForkBase)
          {
              LogPrintf("%s: Warning: Large valid fork found\n  forking the chain at height %d (%s)\n  lasting to height %d (%s).\nChain state database corruption likely.\n", __func__,
                     pindexBestForkBase->nHeight, pindexBestForkBase->phashBlock->ToString(),
                     pindexBestForkTip->nHeight, pindexBestForkTip->phashBlock->ToString());
              fLargeWorkForkFound = true;
          }
          else
          {
              LogPrintf("%s: Warning: Found invalid chain at least ~6 blocks longer than our best chain.\nChain state database corruption likely.\n", __func__);
              fLargeWorkInvalidChainFound = true;
          }
      }
      else
      {
          fLargeWorkForkFound = false;
          fLargeWorkInvalidChainFound = false;
      }
  }
  
  void CheckForkWarningConditionsOnNewFork(CBlockIndex* pindexNewForkTip)
  {
      AssertLockHeld(cs_main);
      // If we are on a fork that is sufficiently large, set a warning flag
      CBlockIndex* pfork = pindexNewForkTip;
      CBlockIndex* plonger = chainActive.Tip();
      while (pfork && pfork != plonger)
      {
          while (plonger && plonger->nHeight > pfork->nHeight)
              plonger = plonger->pprev;
          if (pfork == plonger)
              break;
          pfork = pfork->pprev;
      }
  
      // We define a condition where we should warn the user about as a fork of at least 7 blocks
      // with a tip within 72 blocks (+/- 12 hours if no one mines it) of ours
      // We use 7 blocks rather arbitrarily as it represents just under 10% of sustained network
      // hash rate operating on the fork.
      // or a chain that is entirely longer than ours and invalid (note that this should be detected by both)
      // We define it this way because it allows us to only store the highest fork tip (+ base) which meets
      // the 7-block condition and from this always have the most-likely-to-cause-warning fork
      if (pfork && (!pindexBestForkTip || (pindexBestForkTip && pindexNewForkTip->nHeight > pindexBestForkTip->nHeight)) &&
              pindexNewForkTip->nChainWork - pfork->nChainWork > (GetBlockProof(*pfork) * 7) &&
              chainActive.Height() - pindexNewForkTip->nHeight < 72)
      {
          pindexBestForkTip = pindexNewForkTip;
          pindexBestForkBase = pfork;
      }
  
      CheckForkWarningConditions();
  }
  
  // Requires cs_main.
  void Misbehaving(NodeId pnode, int howmuch)
  {
      if (howmuch == 0)
          return;
  
      CNodeState *state = State(pnode);
      if (state == NULL)
          return;
  
      state->nMisbehavior += howmuch;
      int banscore = GetArg("-banscore", DEFAULT_BANSCORE_THRESHOLD);
      if (state->nMisbehavior >= banscore && state->nMisbehavior - howmuch < banscore)
      {
          LogPrintf("%s: %s (%d -> %d) BAN THRESHOLD EXCEEDED\n", __func__, state->name, state->nMisbehavior-howmuch, state->nMisbehavior);
          state->fShouldBan = true;
      } else
          LogPrintf("%s: %s (%d -> %d)\n", __func__, state->name, state->nMisbehavior-howmuch, state->nMisbehavior);
  }
  
  void static InvalidChainFound(CBlockIndex* pindexNew)
  {
      if (!pindexBestInvalid || pindexNew->nChainWork > pindexBestInvalid->nChainWork)
          pindexBestInvalid = pindexNew;
  
      LogPrintf("%s: invalid block=%s  height=%d  log2_work=%.8g  date=%s\n", __func__,
        pindexNew->GetBlockHash().ToString(), pindexNew->nHeight,
        log(pindexNew->nChainWork.getdouble())/log(2.0), DateTimeStrFormat("%Y-%m-%d %H:%M:%S",
        pindexNew->GetBlockTime()));
      CBlockIndex *tip = chainActive.Tip();
      assert (tip);
      LogPrintf("%s:  current best=%s  height=%d  log2_work=%.8g  date=%s\n", __func__,
        tip->GetBlockHash().ToString(), chainActive.Height(), log(tip->nChainWork.getdouble())/log(2.0),
        DateTimeStrFormat("%Y-%m-%d %H:%M:%S", tip->GetBlockTime()));
      CheckForkWarningConditions();
  }
  
  void static InvalidBlockFound(CBlockIndex *pindex, const CValidationState &state) {
      int nDoS = 0;
      if (state.IsInvalid(nDoS)) {
          std::map<uint256, NodeId>::iterator it = mapBlockSource.find(pindex->GetBlockHash());
          if (it != mapBlockSource.end() && State(it->second)) {
              assert (state.GetRejectCode() < REJECT_INTERNAL); // Blocks are never rejected with internal reject codes
              CBlockReject reject = {(unsigned char)state.GetRejectCode(), state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), pindex->GetBlockHash()};
              State(it->second)->rejects.push_back(reject);
              if (nDoS > 0)
                  Misbehaving(it->second, nDoS);
          }
      }
      if (!state.CorruptionPossible()) {
          pindex->nStatus |= BLOCK_FAILED_VALID;
          setDirtyBlockIndex.insert(pindex);
          setBlockIndexCandidates.erase(pindex);
          InvalidChainFound(pindex);
      }
  }
  
  void UpdateCoins(const CTransaction& tx, CValidationState &state, CCoinsViewCache &inputs, CTxUndo &txundo, int nHeight)
  {
      // mark inputs spent
      if (!tx.IsCoinBase()) {
          txundo.vprevout.reserve(tx.vin.size());
          BOOST_FOREACH(const CTxIn &txin, tx.vin) {
              CCoinsModifier coins = inputs.ModifyCoins(txin.prevout.hash);
              unsigned nPos = txin.prevout.n;
  
              if (nPos >= coins->vout.size() || coins->vout[nPos].IsNull())
                  assert(false);
              // mark an outpoint spent, and construct undo information
              txundo.vprevout.push_back(CTxInUndo(coins->vout[nPos]));
              coins->Spend(nPos);
              if (coins->vout.size() == 0) {
                  CTxInUndo& undo = txundo.vprevout.back();
                  undo.nHeight = coins->nHeight;
                  undo.fCoinBase = coins->fCoinBase;
                  undo.nVersion = coins->nVersion;
              }
          }
          // add outputs
          inputs.ModifyNewCoins(tx.GetHash())->FromTx(tx, nHeight);
      }
      else {
          // add outputs for coinbase tx
          // In this case call the full ModifyCoins which will do a database
          // lookup to be sure the coins do not already exist otherwise we do not
          // know whether to mark them fresh or not.  We want the duplicate coinbases
          // before BIP30 to still be properly overwritten.
          inputs.ModifyCoins(tx.GetHash())->FromTx(tx, nHeight);
      }
  }
  
  void UpdateCoins(const CTransaction& tx, CValidationState &state, CCoinsViewCache &inputs, int nHeight)
  {
      CTxUndo txundo;
      UpdateCoins(tx, state, inputs, txundo, nHeight);
  }
  
  bool CScriptCheck::operator()() {
      const CScript &scriptSig = ptxTo->vin[nIn].scriptSig;
      if (!VerifyScript(scriptSig, scriptPubKey, nFlags, CachingTransactionSignatureChecker(ptxTo, nIn, cacheStore), &error)) {
          return false;
      }
      return true;
  }
  
  int GetSpendHeight(const CCoinsViewCache& inputs)
  {
      LOCK(cs_main);
      CBlockIndex* pindexPrev = mapBlockIndex.find(inputs.GetBestBlock())->second;
      return pindexPrev->nHeight + 1;
  }
  
  namespace Consensus {
  bool CheckTxInputs(const CTransaction& tx, CValidationState& state, const CCoinsViewCache& inputs, int nSpendHeight)
  {
          // This doesn't trigger the DoS code on purpose; if it did, it would make it easier
          // for an attacker to attempt to split the network.
          if (!inputs.HaveInputs(tx))
              return state.Invalid(false, 0, "", "Inputs unavailable");
  
          CAmount nValueIn = 0;
          CAmount nFees = 0;
          for (unsigned int i = 0; i < tx.vin.size(); i++)
          {
              const COutPoint &prevout = tx.vin[i].prevout;
              const CCoins *coins = inputs.AccessCoins(prevout.hash);
              assert(coins);
  
              // If prev is coinbase, check that it's matured
              if (coins->IsCoinBase()) {
                  if (nSpendHeight - coins->nHeight < COINBASE_MATURITY)
                      return state.Invalid(false,
                          REJECT_INVALID, "bad-txns-premature-spend-of-coinbase",
                          strprintf("tried to spend coinbase at depth %d", nSpendHeight - coins->nHeight));
              }
  
              // Check for negative or overflow input values
              nValueIn += coins->vout[prevout.n].nValue;
              if (!MoneyRange(coins->vout[prevout.n].nValue) || !MoneyRange(nValueIn))
                  return state.DoS(100, false, REJECT_INVALID, "bad-txns-inputvalues-outofrange");
  
          }
  
          if (nValueIn < tx.GetValueOut())
              return state.DoS(100, false, REJECT_INVALID, "bad-txns-in-belowout", false,
                  strprintf("value in (%s) < value out (%s)", FormatMoney(nValueIn), FormatMoney(tx.GetValueOut())));
  
          // Tally transaction fees
          CAmount nTxFee = nValueIn - tx.GetValueOut();
          if (nTxFee < 0)
              return state.DoS(100, false, REJECT_INVALID, "bad-txns-fee-negative");
          nFees += nTxFee;
          if (!MoneyRange(nFees))
              return state.DoS(100, false, REJECT_INVALID, "bad-txns-fee-outofrange");
      return true;
  }
  }// namespace Consensus
  
  bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheStore, std::vector<CScriptCheck> *pvChecks)
  {
      if (!tx.IsCoinBase())
      {
          if (!Consensus::CheckTxInputs(tx, state, inputs, GetSpendHeight(inputs)))
              return false;
  
          if (pvChecks)
              pvChecks->reserve(tx.vin.size());
  
          // The first loop above does all the inexpensive checks.
          // Only if ALL inputs pass do we perform expensive ECDSA signature checks.
          // Helps prevent CPU exhaustion attacks.
  
          // Skip ECDSA signature verification when connecting blocks
          // before the last block chain checkpoint. This is safe because block merkle hashes are
          // still computed and checked, and any change will be caught at the next checkpoint.
          if (fScriptChecks) {
              for (unsigned int i = 0; i < tx.vin.size(); i++) {
                  const COutPoint &prevout = tx.vin[i].prevout;
                  const CCoins* coins = inputs.AccessCoins(prevout.hash);
                  assert(coins);
  
                  // Verify signature
                  CScriptCheck check(*coins, tx, i, flags, cacheStore);
                  if (pvChecks) {
                      pvChecks->push_back(CScriptCheck());
                      check.swap(pvChecks->back());
                  } else if (!check()) {
                      if (flags & STANDARD_NOT_MANDATORY_VERIFY_FLAGS) {
                          // Check whether the failure was caused by a
                          // non-mandatory script verification check, such as
                          // non-standard DER encodings or non-null dummy
                          // arguments; if so, don't trigger DoS protection to
                          // avoid splitting the network between upgraded and
                          // non-upgraded nodes.
                          CScriptCheck check2(*coins, tx, i,
                                  flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS, cacheStore);
                          if (check2())
                              return state.Invalid(false, REJECT_NONSTANDARD, strprintf("non-mandatory-script-verify-flag (%s)", ScriptErrorString(check.GetScriptError())));
                      }
                      // Failures of other flags indicate a transaction that is
                      // invalid in new blocks, e.g. a invalid P2SH. We DoS ban
                      // such nodes as they are not following the protocol. That
                      // said during an upgrade careful thought should be taken
                      // as to the correct behavior - we may want to continue
                      // peering with non-upgraded nodes even after a soft-fork
                      // super-majority vote has passed.
                      return state.DoS(100,false, REJECT_INVALID, strprintf("mandatory-script-verify-flag-failed (%s)", ScriptErrorString(check.GetScriptError())));
                  }
              }
          }
      }
  
      return true;
  }
  
  namespace {
  
  bool UndoWriteToDisk(const CBlockUndo& blockundo, CDiskBlockPos& pos, const uint256& hashBlock, const CMessageHeader::MessageStartChars& messageStart)
  {
      // Open history file to append
      CAutoFile fileout(OpenUndoFile(pos), SER_DISK, CLIENT_VERSION);
      if (fileout.IsNull())
          return error("%s: OpenUndoFile failed", __func__);
  
      // Write index header
      unsigned int nSize = fileout.GetSerializeSize(blockundo);
      fileout << FLATDATA(messageStart) << nSize;
  
      // Write undo data
      long fileOutPos = ftell(fileout.Get());
      if (fileOutPos < 0)
          return error("%s: ftell failed", __func__);
      pos.nPos = (unsigned int)fileOutPos;
      fileout << blockundo;
  
      // calculate & write checksum
      CHashWriter hasher(SER_GETHASH, PROTOCOL_VERSION);
      hasher << hashBlock;
      hasher << blockundo;
      fileout << hasher.GetHash();
  
      return true;
  }
  
  bool UndoReadFromDisk(CBlockUndo& blockundo, const CDiskBlockPos& pos, const uint256& hashBlock)
  {
      // Open history file to read
      CAutoFile filein(OpenUndoFile(pos, true), SER_DISK, CLIENT_VERSION);
      if (filein.IsNull())
          return error("%s: OpenBlockFile failed", __func__);
  
      // Read block
      uint256 hashChecksum;
      try {
          filein >> blockundo;
          filein >> hashChecksum;
      }
      catch (const std::exception& e) {
          return error("%s: Deserialize or I/O error - %s", __func__, e.what());
      }
  
      // Verify checksum
      CHashWriter hasher(SER_GETHASH, PROTOCOL_VERSION);
      hasher << hashBlock;
      hasher << blockundo;
      if (hashChecksum != hasher.GetHash())
          return error("%s: Checksum mismatch", __func__);
  
      return true;
  }
  
  /** Abort with a message */
  bool AbortNode(const std::string& strMessage, const std::string& userMessage="")
  {
      strMiscWarning = strMessage;
      LogPrintf("*** %s\n", strMessage);
      uiInterface.ThreadSafeMessageBox(
          userMessage.empty() ? _("Error: A fatal internal error occurred, see debug.log for details") : userMessage,
          "", CClientUIInterface::MSG_ERROR);
      StartShutdown();
      return false;
  }
  
  bool AbortNode(CValidationState& state, const std::string& strMessage, const std::string& userMessage="")
  {
      AbortNode(strMessage, userMessage);
      return state.Error(strMessage);
  }
  
  } // anon namespace
  
  /**
   * Apply the undo operation of a CTxInUndo to the given chain state.
   * @param undo The undo object.
   * @param view The coins view to which to apply the changes.
   * @param out The out point that corresponds to the tx input.
   * @return True on success.
   */
  static bool ApplyTxInUndo(const CTxInUndo& undo, CCoinsViewCache& view, const COutPoint& out)
  {
      bool fClean = true;
  
      CCoinsModifier coins = view.ModifyCoins(out.hash);
      if (undo.nHeight != 0) {
          // undo data contains height: this is the last output of the prevout tx being spent
          if (!coins->IsPruned())
              fClean = fClean && error("%s: undo data overwriting existing transaction", __func__);
          coins->Clear();
          coins->fCoinBase = undo.fCoinBase;
          coins->nHeight = undo.nHeight;
          coins->nVersion = undo.nVersion;
      } else {
          if (coins->IsPruned())
              fClean = fClean && error("%s: undo data adding output to missing transaction", __func__);
      }
      if (coins->IsAvailable(out.n))
          fClean = fClean && error("%s: undo data overwriting existing output", __func__);
      if (coins->vout.size() < out.n+1)
          coins->vout.resize(out.n+1);
      coins->vout[out.n] = undo.txout;
  
      return fClean;
  }
  
  bool DisconnectBlock(const CBlock& block, CValidationState& state, const CBlockIndex* pindex, CCoinsViewCache& view, bool* pfClean)
  {
      assert(pindex->GetBlockHash() == view.GetBestBlock());
  
      if (pfClean)
          *pfClean = false;
  
      bool fClean = true;
  
      CBlockUndo blockUndo;
      CDiskBlockPos pos = pindex->GetUndoPos();
      if (pos.IsNull())
          return error("DisconnectBlock(): no undo data available");
      if (!UndoReadFromDisk(blockUndo, pos, pindex->pprev->GetBlockHash()))
          return error("DisconnectBlock(): failure reading undo data");
  
      if (blockUndo.vtxundo.size() + 1 != block.vtx.size())
          return error("DisconnectBlock(): block and undo data inconsistent");
  
      // undo transactions in reverse order
      for (int i = block.vtx.size() - 1; i >= 0; i--) {
          const CTransaction &tx = block.vtx[i];
          uint256 hash = tx.GetHash();
  
          // Check that all outputs are available and match the outputs in the block itself
          // exactly.
          {
          CCoinsModifier outs = view.ModifyCoins(hash);
          outs->ClearUnspendable();
  
          CCoins outsBlock(tx, pindex->nHeight);
          // The CCoins serialization does not serialize negative numbers.
          // No network rules currently depend on the version here, so an inconsistency is harmless
          // but it must be corrected before txout nversion ever influences a network rule.
          if (outsBlock.nVersion < 0)
              outs->nVersion = outsBlock.nVersion;
          if (*outs != outsBlock)
              fClean = fClean && error("DisconnectBlock(): added transaction mismatch? database corrupted");
  
          // remove outputs
          outs->Clear();
          }
  
          // restore inputs
          if (i > 0) { // not coinbases
              const CTxUndo &txundo = blockUndo.vtxundo[i-1];
              if (txundo.vprevout.size() != tx.vin.size())
                  return error("DisconnectBlock(): transaction and undo data inconsistent");
              for (unsigned int j = tx.vin.size(); j-- > 0;) {
                  const COutPoint &out = tx.vin[j].prevout;
                  const CTxInUndo &undo = txundo.vprevout[j];
                  if (!ApplyTxInUndo(undo, view, out))
                      fClean = false;
              }
          }
      }
  
      // move best block pointer to prevout block
      view.SetBestBlock(pindex->pprev->GetBlockHash());
  
      if (pfClean) {
          *pfClean = fClean;
          return true;
      }
  
      return fClean;
  }
  
  void static FlushBlockFile(bool fFinalize = false)
  {
      LOCK(cs_LastBlockFile);
  
      CDiskBlockPos posOld(nLastBlockFile, 0);
  
      FILE *fileOld = OpenBlockFile(posOld);
      if (fileOld) {
          if (fFinalize)
              TruncateFile(fileOld, vinfoBlockFile[nLastBlockFile].nSize);
          FileCommit(fileOld);
          fclose(fileOld);
      }
  
      fileOld = OpenUndoFile(posOld);
      if (fileOld) {
          if (fFinalize)
              TruncateFile(fileOld, vinfoBlockFile[nLastBlockFile].nUndoSize);
          FileCommit(fileOld);
          fclose(fileOld);
      }
  }
  
  bool FindUndoPos(CValidationState &state, int nFile, CDiskBlockPos &pos, unsigned int nAddSize);
  
  static CCheckQueue<CScriptCheck> scriptcheckqueue(128);
  
  void ThreadScriptCheck() {
      RenameThread("bitcoin-scriptch");
      scriptcheckqueue.Thread();
  }
  
  //
  // Called periodically asynchronously; alerts if it smells like
  // we're being fed a bad chain (blocks being generated much
  // too slowly or too quickly).
  //
  void PartitionCheck(bool (*initialDownloadCheck)(), CCriticalSection& cs, const CBlockIndex *const &bestHeader,
                      int64_t nPowTargetSpacing)
  {
      if (bestHeader == NULL || initialDownloadCheck()) return;
  
      static int64_t lastAlertTime = 0;
      int64_t now = GetAdjustedTime();
      if (lastAlertTime > now-60*60*24) return; // Alert at most once per day
  
      const int SPAN_HOURS=4;
      const int SPAN_SECONDS=SPAN_HOURS*60*60;
      int BLOCKS_EXPECTED = SPAN_SECONDS / nPowTargetSpacing;
  
      boost::math::poisson_distribution<double> poisson(BLOCKS_EXPECTED);
  
      std::string strWarning;
      int64_t startTime = GetAdjustedTime()-SPAN_SECONDS;
  
      LOCK(cs);
      const CBlockIndex* i = bestHeader;
      int nBlocks = 0;
      while (i->GetBlockTime() >= startTime) {
          ++nBlocks;
          i = i->pprev;
          if (i == NULL) return; // Ran out of chain, we must not be fully sync'ed
      }
  
      // How likely is it to find that many by chance?
      double p = boost::math::pdf(poisson, nBlocks);
  
      LogPrint("partitioncheck", "%s: Found %d blocks in the last %d hours\n", __func__, nBlocks, SPAN_HOURS);
      LogPrint("partitioncheck", "%s: likelihood: %g\n", __func__, p);
  
      // Aim for one false-positive about every fifty years of normal running:
      const int FIFTY_YEARS = 50*365*24*60*60;
      double alertThreshold = 1.0 / (FIFTY_YEARS / SPAN_SECONDS);
  
      if (p <= alertThreshold && nBlocks < BLOCKS_EXPECTED)
      {
          // Many fewer blocks than expected: alert!
          strWarning = strprintf(_("WARNING: check your network connection, %d blocks received in the last %d hours (%d expected)"),
                                 nBlocks, SPAN_HOURS, BLOCKS_EXPECTED);
      }
      else if (p <= alertThreshold && nBlocks > BLOCKS_EXPECTED)
      {
          // Many more blocks than expected: alert!
          strWarning = strprintf(_("WARNING: abnormally high number of blocks generated, %d blocks received in the last %d hours (%d expected)"),
                                 nBlocks, SPAN_HOURS, BLOCKS_EXPECTED);
      }
      if (!strWarning.empty())
      {
          strMiscWarning = strWarning;
          CAlert::Notify(strWarning, true);
          lastAlertTime = now;
      }
  }
  
  // Protected by cs_main
  static VersionBitsCache versionbitscache;
  
  int32_t ComputeBlockVersion(const CBlockIndex* pindexPrev, const Consensus::Params& params)
  {
      LOCK(cs_main);
      int32_t nVersion = VERSIONBITS_TOP_BITS;
  
      for (int i = 0; i < (int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; i++) {
          ThresholdState state = VersionBitsState(pindexPrev, params, (Consensus::DeploymentPos)i, versionbitscache);
          if (state == THRESHOLD_LOCKED_IN || state == THRESHOLD_STARTED) {
              nVersion |= VersionBitsMask(params, (Consensus::DeploymentPos)i);
          }
      }
  
      return nVersion;
  }
  
  /**
   * Threshold condition checker that triggers when unknown versionbits are seen on the network.
   */
  class WarningBitsConditionChecker : public AbstractThresholdConditionChecker
  {
  private:
      int bit;
  
  public:
      WarningBitsConditionChecker(int bitIn) : bit(bitIn) {}
  
      int64_t BeginTime(const Consensus::Params& params) const { return 0; }
      int64_t EndTime(const Consensus::Params& params) const { return std::numeric_limits<int64_t>::max(); }
      int Period(const Consensus::Params& params) const { return params.nMinerConfirmationWindow; }
      int Threshold(const Consensus::Params& params) const { return params.nRuleChangeActivationThreshold; }
  
      bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const
      {
          return ((pindex->nVersion & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS) &&
                 ((pindex->nVersion >> bit) & 1) != 0 &&
                 ((ComputeBlockVersion(pindex->pprev, params) >> bit) & 1) == 0;
      }
  };
  
  // Protected by cs_main
  static ThresholdConditionCache warningcache[VERSIONBITS_NUM_BITS];
  
  static int64_t nTimeCheck = 0;
  static int64_t nTimeForks = 0;
  static int64_t nTimeVerify = 0;
  static int64_t nTimeConnect = 0;
  static int64_t nTimeIndex = 0;
  static int64_t nTimeCallbacks = 0;
  static int64_t nTimeTotal = 0;
  
  bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pindex, CCoinsViewCache& view, bool fJustCheck)
  {
      const CChainParams& chainparams = Params();
      AssertLockHeld(cs_main);
  
      int64_t nTimeStart = GetTimeMicros();
  
      // Check it again in case a previous version let a bad block in
      if (!CheckBlock(block, state, !fJustCheck, !fJustCheck))
          return false;
  
      // verify that the view's current state corresponds to the previous block
      uint256 hashPrevBlock = pindex->pprev == NULL ? uint256() : pindex->pprev->GetBlockHash();
      assert(hashPrevBlock == view.GetBestBlock());
  
      // Special case for the genesis block, skipping connection of its transactions
      // (its coinbase is unspendable)
      if (block.GetHash() == chainparams.GetConsensus().hashGenesisBlock) {
          if (!fJustCheck)
              view.SetBestBlock(pindex->GetBlockHash());
          return true;
      }
  
      bool fScriptChecks = true;
      if (fCheckpointsEnabled) {
          CBlockIndex *pindexLastCheckpoint = Checkpoints::GetLastCheckpoint(chainparams.Checkpoints());
          if (pindexLastCheckpoint && pindexLastCheckpoint->GetAncestor(pindex->nHeight) == pindex) {
              // This block is an ancestor of a checkpoint: disable script checks
              fScriptChecks = false;
          }
      }
  
      int64_t nTime1 = GetTimeMicros(); nTimeCheck += nTime1 - nTimeStart;
      LogPrint("bench", "    - Sanity checks: %.2fms [%.2fs]\n", 0.001 * (nTime1 - nTimeStart), nTimeCheck * 0.000001);
  
      // Do not allow blocks that contain transactions which 'overwrite' older transactions,
      // unless those are already completely spent.
      // If such overwrites are allowed, coinbases and transactions depending upon those
      // can be duplicated to remove the ability to spend the first instance -- even after
      // being sent to another address.
      // See BIP30 and http://r6.ca/blog/20120206T005236Z.html for more information.
      // This logic is not necessary for memory pool transactions, as AcceptToMemoryPool
      // already refuses previously-known transaction ids entirely.
      // This rule was originally applied to all blocks with a timestamp after March 15, 2012, 0:00 UTC.
      // Now that the whole chain is irreversibly beyond that time it is applied to all blocks except the
      // two in the chain that violate it. This prevents exploiting the issue against nodes during their
      // initial block download.
      bool fEnforceBIP30 = (!pindex->phashBlock) || // Enforce on CreateNewBlock invocations which don't have a hash.
                            !((pindex->nHeight==91842 && pindex->GetBlockHash() == uint256S("0x00000000000a4d0a398161ffc163c503763b1f4360639393e0e4c8e300e0caec")) ||
                             (pindex->nHeight==91880 && pindex->GetBlockHash() == uint256S("0x00000000000743f190a18c5577a3c2d2a1f610ae9601ac046a38084ccb7cd721")));
  
      // Once BIP34 activated it was not possible to create new duplicate coinbases and thus other than starting
      // with the 2 existing duplicate coinbase pairs, not possible to create overwriting txs.  But by the
      // time BIP34 activated, in each of the existing pairs the duplicate coinbase had overwritten the first
      // before the first had been spent.  Since those coinbases are sufficiently buried its no longer possible to create further
      // duplicate transactions descending from the known pairs either.
      // If we're on the known chain at height greater than where BIP34 activated, we can save the db accesses needed for the BIP30 check.
      CBlockIndex *pindexBIP34height = pindex->pprev->GetAncestor(chainparams.GetConsensus().BIP34Height);
      //Only continue to enforce if we're below BIP34 activation height or the block hash at that height doesn't correspond.
      fEnforceBIP30 = fEnforceBIP30 && (!pindexBIP34height || !(pindexBIP34height->GetBlockHash() == chainparams.GetConsensus().BIP34Hash));
  
      if (fEnforceBIP30) {
          BOOST_FOREACH(const CTransaction& tx, block.vtx) {
              const CCoins* coins = view.AccessCoins(tx.GetHash());
              if (coins && !coins->IsPruned())
                  return state.DoS(100, error("ConnectBlock(): tried to overwrite transaction"),
                                   REJECT_INVALID, "bad-txns-BIP30");
          }
      }
  
      // BIP16 didn't become active until Apr 1 2012
      int64_t nBIP16SwitchTime = 1333238400;
      bool fStrictPayToScriptHash = (pindex->GetBlockTime() >= nBIP16SwitchTime);
  
      unsigned int flags = fStrictPayToScriptHash ? SCRIPT_VERIFY_P2SH : SCRIPT_VERIFY_NONE;
  
      // Start enforcing the DERSIG (BIP66) rules, for block.nVersion=3 blocks,
      // when 75% of the network has upgraded:
      if (block.nVersion >= 3 && IsSuperMajority(3, pindex->pprev, chainparams.GetConsensus().nMajorityEnforceBlockUpgrade, chainparams.GetConsensus())) {
          flags |= SCRIPT_VERIFY_DERSIG;
      }
  
      // Start enforcing CHECKLOCKTIMEVERIFY, (BIP65) for block.nVersion=4
      // blocks, when 75% of the network has upgraded:
      if (block.nVersion >= 4 && IsSuperMajority(4, pindex->pprev, chainparams.GetConsensus().nMajorityEnforceBlockUpgrade, chainparams.GetConsensus())) {
          flags |= SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY;
      }
  
      // Start enforcing BIP68 (sequence locks) and BIP112 (CHECKSEQUENCEVERIFY) using versionbits logic.
      int nLockTimeFlags = 0;
      if (VersionBitsState(pindex->pprev, chainparams.GetConsensus(), Consensus::DEPLOYMENT_CSV, versionbitscache) == THRESHOLD_ACTIVE) {
          flags |= SCRIPT_VERIFY_CHECKSEQUENCEVERIFY;
          nLockTimeFlags |= LOCKTIME_VERIFY_SEQUENCE;
      }
  
      int64_t nTime2 = GetTimeMicros(); nTimeForks += nTime2 - nTime1;
      LogPrint("bench", "    - Fork checks: %.2fms [%.2fs]\n", 0.001 * (nTime2 - nTime1), nTimeForks * 0.000001);
  
      CBlockUndo blockundo;
  
      CCheckQueueControl<CScriptCheck> control(fScriptChecks && nScriptCheckThreads ? &scriptcheckqueue : NULL);
  
      std::vector<int> prevheights;
      CAmount nFees = 0;
      int nInputs = 0;
      unsigned int nSigOps = 0;
      CDiskTxPos pos(pindex->GetBlockPos(), GetSizeOfCompactSize(block.vtx.size()));
      std::vector<std::pair<uint256, CDiskTxPos> > vPos;
      vPos.reserve(block.vtx.size());
      blockundo.vtxundo.reserve(block.vtx.size() - 1);
      for (unsigned int i = 0; i < block.vtx.size(); i++)
      {
          const CTransaction &tx = block.vtx[i];
  
          nInputs += tx.vin.size();
          nSigOps += GetLegacySigOpCount(tx);
          if (nSigOps > MAX_BLOCK_SIGOPS)
              return state.DoS(100, error("ConnectBlock(): too many sigops"),
                               REJECT_INVALID, "bad-blk-sigops");
  
          if (!tx.IsCoinBase())
          {
              if (!view.HaveInputs(tx))
                  return state.DoS(100, error("ConnectBlock(): inputs missing/spent"),
                                   REJECT_INVALID, "bad-txns-inputs-missingorspent");
  
              // Check that transaction is BIP68 final
              // BIP68 lock checks (as opposed to nLockTime checks) must
              // be in ConnectBlock because they require the UTXO set
              prevheights.resize(tx.vin.size());
              for (size_t j = 0; j < tx.vin.size(); j++) {
                  prevheights[j] = view.AccessCoins(tx.vin[j].prevout.hash)->nHeight;
              }
  
              if (!SequenceLocks(tx, nLockTimeFlags, &prevheights, *pindex)) {
                  return state.DoS(100, error("%s: contains a non-BIP68-final transaction", __func__),
                                   REJECT_INVALID, "bad-txns-nonfinal");
              }
  
              if (fStrictPayToScriptHash)
              {
                  // Add in sigops done by pay-to-script-hash inputs;
                  // this is to prevent a "rogue miner" from creating
                  // an incredibly-expensive-to-validate block.
                  nSigOps += GetP2SHSigOpCount(tx, view);
                  if (nSigOps > MAX_BLOCK_SIGOPS)
                      return state.DoS(100, error("ConnectBlock(): too many sigops"),
                                       REJECT_INVALID, "bad-blk-sigops");
              }
  
              nFees += view.GetValueIn(tx)-tx.GetValueOut();
  
              std::vector<CScriptCheck> vChecks;
              bool fCacheResults = fJustCheck; /* Don't cache results if we're actually connecting blocks (still consult the cache, though) */
              if (!CheckInputs(tx, state, view, fScriptChecks, flags, fCacheResults, nScriptCheckThreads ? &vChecks : NULL))
                  return error("ConnectBlock(): CheckInputs on %s failed with %s",
                      tx.GetHash().ToString(), FormatStateMessage(state));
              control.Add(vChecks);
          }
  
          CTxUndo undoDummy;
          if (i > 0) {
              blockundo.vtxundo.push_back(CTxUndo());
          }
          UpdateCoins(tx, state, view, i == 0 ? undoDummy : blockundo.vtxundo.back(), pindex->nHeight);
  
          vPos.push_back(std::make_pair(tx.GetHash(), pos));
          pos.nTxOffset += ::GetSerializeSize(tx, SER_DISK, CLIENT_VERSION);
      }
      int64_t nTime3 = GetTimeMicros(); nTimeConnect += nTime3 - nTime2;
      LogPrint("bench", "      - Connect %u transactions: %.2fms (%.3fms/tx, %.3fms/txin) [%.2fs]\n", (unsigned)block.vtx.size(), 0.001 * (nTime3 - nTime2), 0.001 * (nTime3 - nTime2) / block.vtx.size(), nInputs <= 1 ? 0 : 0.001 * (nTime3 - nTime2) / (nInputs-1), nTimeConnect * 0.000001);
  
      CAmount blockReward = nFees + GetBlockSubsidy(pindex->nHeight, chainparams.GetConsensus());
      if (block.vtx[0].GetValueOut() > blockReward)
          return state.DoS(100,
                           error("ConnectBlock(): coinbase pays too much (actual=%d vs limit=%d)",
                                 block.vtx[0].GetValueOut(), blockReward),
                                 REJECT_INVALID, "bad-cb-amount");
  
      if (!control.Wait())
          return state.DoS(100, false);
      int64_t nTime4 = GetTimeMicros(); nTimeVerify += nTime4 - nTime2;
      LogPrint("bench", "    - Verify %u txins: %.2fms (%.3fms/txin) [%.2fs]\n", nInputs - 1, 0.001 * (nTime4 - nTime2), nInputs <= 1 ? 0 : 0.001 * (nTime4 - nTime2) / (nInputs-1), nTimeVerify * 0.000001);
  
      if (fJustCheck)
          return true;
  
      // Write undo information to disk
      if (pindex->GetUndoPos().IsNull() || !pindex->IsValid(BLOCK_VALID_SCRIPTS))
      {
          if (pindex->GetUndoPos().IsNull()) {
              CDiskBlockPos pos;
              if (!FindUndoPos(state, pindex->nFile, pos, ::GetSerializeSize(blockundo, SER_DISK, CLIENT_VERSION) + 40))
                  return error("ConnectBlock(): FindUndoPos failed");
              if (!UndoWriteToDisk(blockundo, pos, pindex->pprev->GetBlockHash(), chainparams.MessageStart()))
                  return AbortNode(state, "Failed to write undo data");
  
              // update nUndoPos in block index
              pindex->nUndoPos = pos.nPos;
              pindex->nStatus |= BLOCK_HAVE_UNDO;
          }
  
          pindex->RaiseValidity(BLOCK_VALID_SCRIPTS);
          setDirtyBlockIndex.insert(pindex);
      }
  
      if (fTxIndex)
          if (!pblocktree->WriteTxIndex(vPos))
              return AbortNode(state, "Failed to write transaction index");
  
      // add this block to the view's block chain
      view.SetBestBlock(pindex->GetBlockHash());
  
      int64_t nTime5 = GetTimeMicros(); nTimeIndex += nTime5 - nTime4;
      LogPrint("bench", "    - Index writing: %.2fms [%.2fs]\n", 0.001 * (nTime5 - nTime4), nTimeIndex * 0.000001);
  
      // Watch for changes to the previous coinbase transaction.
      static uint256 hashPrevBestCoinBase;
      GetMainSignals().UpdatedTransaction(hashPrevBestCoinBase);
      hashPrevBestCoinBase = block.vtx[0].GetHash();
  
      int64_t nTime6 = GetTimeMicros(); nTimeCallbacks += nTime6 - nTime5;
      LogPrint("bench", "    - Callbacks: %.2fms [%.2fs]\n", 0.001 * (nTime6 - nTime5), nTimeCallbacks * 0.000001);
  
      return true;
  }
  
  enum FlushStateMode {
      FLUSH_STATE_NONE,
      FLUSH_STATE_IF_NEEDED,
      FLUSH_STATE_PERIODIC,
      FLUSH_STATE_ALWAYS
  };
  
  /**
   * Update the on-disk chain state.
   * The caches and indexes are flushed depending on the mode we're called with
   * if they're too large, if it's been a while since the last write,
   * or always and in all cases if we're in prune mode and are deleting files.
   */
  bool static FlushStateToDisk(CValidationState &state, FlushStateMode mode) {
      const CChainParams& chainparams = Params();
      LOCK2(cs_main, cs_LastBlockFile);
      static int64_t nLastWrite = 0;
      static int64_t nLastFlush = 0;
      static int64_t nLastSetChain = 0;
      std::set<int> setFilesToPrune;
      bool fFlushForPrune = false;
      try {
      if (fPruneMode && fCheckForPruning && !fReindex) {
          FindFilesToPrune(setFilesToPrune, chainparams.PruneAfterHeight());
          fCheckForPruning = false;
          if (!setFilesToPrune.empty()) {
              fFlushForPrune = true;
              if (!fHavePruned) {
                  pblocktree->WriteFlag("prunedblockfiles", true);
                  fHavePruned = true;
              }
          }
      }
      int64_t nNow = GetTimeMicros();
      // Avoid writing/flushing immediately after startup.
      if (nLastWrite == 0) {
          nLastWrite = nNow;
      }
      if (nLastFlush == 0) {
          nLastFlush = nNow;
      }
      if (nLastSetChain == 0) {
          nLastSetChain = nNow;
      }
      size_t cacheSize = pcoinsTip->DynamicMemoryUsage();
      // The cache is large and close to the limit, but we have time now (not in the middle of a block processing).
      bool fCacheLarge = mode == FLUSH_STATE_PERIODIC && cacheSize * (10.0/9) > nCoinCacheUsage;
      // The cache is over the limit, we have to write now.
      bool fCacheCritical = mode == FLUSH_STATE_IF_NEEDED && cacheSize > nCoinCacheUsage;
      // It's been a while since we wrote the block index to disk. Do this frequently, so we don't need to redownload after a crash.
      bool fPeriodicWrite = mode == FLUSH_STATE_PERIODIC && nNow > nLastWrite + (int64_t)DATABASE_WRITE_INTERVAL * 1000000;
      // It's been very long since we flushed the cache. Do this infrequently, to optimize cache usage.
      bool fPeriodicFlush = mode == FLUSH_STATE_PERIODIC && nNow > nLastFlush + (int64_t)DATABASE_FLUSH_INTERVAL * 1000000;
      // Combine all conditions that result in a full cache flush.
      bool fDoFullFlush = (mode == FLUSH_STATE_ALWAYS) || fCacheLarge || fCacheCritical || fPeriodicFlush || fFlushForPrune;
      // Write blocks and block index to disk.
      if (fDoFullFlush || fPeriodicWrite) {
          // Depend on nMinDiskSpace to ensure we can write block index
          if (!CheckDiskSpace(0))
              return state.Error("out of disk space");
          // First make sure all block and undo data is flushed to disk.
          FlushBlockFile();
          // Then update all block file information (which may refer to block and undo files).
          {
              std::vector<std::pair<int, const CBlockFileInfo*> > vFiles;
              vFiles.reserve(setDirtyFileInfo.size());
              for (set<int>::iterator it = setDirtyFileInfo.begin(); it != setDirtyFileInfo.end(); ) {
                  vFiles.push_back(make_pair(*it, &vinfoBlockFile[*it]));
                  setDirtyFileInfo.erase(it++);
              }
              std::vector<const CBlockIndex*> vBlocks;
              vBlocks.reserve(setDirtyBlockIndex.size());
              for (set<CBlockIndex*>::iterator it = setDirtyBlockIndex.begin(); it != setDirtyBlockIndex.end(); ) {
                  vBlocks.push_back(*it);
                  setDirtyBlockIndex.erase(it++);
              }
              if (!pblocktree->WriteBatchSync(vFiles, nLastBlockFile, vBlocks)) {
                  return AbortNode(state, "Files to write to block index database");
              }
          }
          // Finally remove any pruned files
          if (fFlushForPrune)
              UnlinkPrunedFiles(setFilesToPrune);
          nLastWrite = nNow;
      }
      // Flush best chain related state. This can only be done if the blocks / block index write was also done.
      if (fDoFullFlush) {
          // Typical CCoins structures on disk are around 128 bytes in size.
          // Pushing a new one to the database can cause it to be written
          // twice (once in the log, and once in the tables). This is already
          // an overestimation, as most will delete an existing entry or
          // overwrite one. Still, use a conservative safety factor of 2.
          if (!CheckDiskSpace(128 * 2 * 2 * pcoinsTip->GetCacheSize()))
              return state.Error("out of disk space");
          // Flush the chainstate (which may refer to block index entries).
          if (!pcoinsTip->Flush())
              return AbortNode(state, "Failed to write to coin database");
          nLastFlush = nNow;
      }
      if (fDoFullFlush || ((mode == FLUSH_STATE_ALWAYS || mode == FLUSH_STATE_PERIODIC) && nNow > nLastSetChain + (int64_t)DATABASE_WRITE_INTERVAL * 1000000)) {
          // Update best block in wallet (so we can detect restored wallets).
          GetMainSignals().SetBestChain(chainActive.GetLocator());
          nLastSetChain = nNow;
      }
      } catch (const std::runtime_error& e) {
          return AbortNode(state, std::string("System error while flushing: ") + e.what());
      }
      return true;
  }
  
  void FlushStateToDisk() {
      CValidationState state;
      FlushStateToDisk(state, FLUSH_STATE_ALWAYS);
  }
  
  void PruneAndFlush() {
      CValidationState state;
      fCheckForPruning = true;
      FlushStateToDisk(state, FLUSH_STATE_NONE);
  }
  
  /** Update chainActive and related internal data structures. */
  void static UpdateTip(CBlockIndex *pindexNew) {
      const CChainParams& chainParams = Params();
      chainActive.SetTip(pindexNew);
  
      // New best block
      nTimeBestReceived = GetTime();
      mempool.AddTransactionsUpdated(1);
  
      LogPrintf("%s: new best=%s  height=%d  log2_work=%.8g  tx=%lu  date=%s progress=%f  cache=%.1fMiB(%utx)\n", __func__,
        chainActive.Tip()->GetBlockHash().ToString(), chainActive.Height(), log(chainActive.Tip()->nChainWork.getdouble())/log(2.0), (unsigned long)chainActive.Tip()->nChainTx,
        DateTimeStrFormat("%Y-%m-%d %H:%M:%S", chainActive.Tip()->GetBlockTime()),
        Checkpoints::GuessVerificationProgress(chainParams.Checkpoints(), chainActive.Tip()), pcoinsTip->DynamicMemoryUsage() * (1.0 / (1<<20)), pcoinsTip->GetCacheSize());
  
      cvBlockChange.notify_all();
  
      // Check the version of the last 100 blocks to see if we need to upgrade:
      static bool fWarned = false;
      if (!IsInitialBlockDownload())
      {
          int nUpgraded = 0;
          const CBlockIndex* pindex = chainActive.Tip();
          for (int bit = 0; bit < VERSIONBITS_NUM_BITS; bit++) {
              WarningBitsConditionChecker checker(bit);
              ThresholdState state = checker.GetStateFor(pindex, chainParams.GetConsensus(), warningcache[bit]);
              if (state == THRESHOLD_ACTIVE || state == THRESHOLD_LOCKED_IN) {
                  if (state == THRESHOLD_ACTIVE) {
                      strMiscWarning = strprintf(_("Warning: unknown new rules activated (versionbit %i)"), bit);
                      if (!fWarned) {
                          CAlert::Notify(strMiscWarning, true);
                          fWarned = true;
                      }
                  } else {
                      LogPrintf("%s: unknown new rules are about to activate (versionbit %i)\n", __func__, bit);
                  }
              }
          }
          for (int i = 0; i < 100 && pindex != NULL; i++)
          {
              int32_t nExpectedVersion = ComputeBlockVersion(pindex->pprev, chainParams.GetConsensus());
              if (pindex->nVersion > VERSIONBITS_LAST_OLD_BLOCK_VERSION && (pindex->nVersion & ~nExpectedVersion) != 0)
                  ++nUpgraded;
              pindex = pindex->pprev;
          }
          if (nUpgraded > 0)
              LogPrintf("%s: %d of last 100 blocks have unexpected version\n", __func__, nUpgraded);
          if (nUpgraded > 100/2)
          {
              // strMiscWarning is read by GetWarnings(), called by Qt and the JSON-RPC code to warn the user:
              strMiscWarning = _("Warning: Unknown block versions being mined! It's possible unknown rules are in effect");
              if (!fWarned) {
                  CAlert::Notify(strMiscWarning, true);
                  fWarned = true;
              }
          }
      }
  }
  
  /** Disconnect chainActive's tip. You probably want to call mempool.removeForReorg and manually re-limit mempool size after this, with cs_main held. */
  bool static DisconnectTip(CValidationState& state, const Consensus::Params& consensusParams)
  {
      CBlockIndex *pindexDelete = chainActive.Tip();
      assert(pindexDelete);
      // Read block from disk.
      CBlock block;
      if (!ReadBlockFromDisk(block, pindexDelete, consensusParams))
          return AbortNode(state, "Failed to read block");
      // Apply the block atomically to the chain state.
      int64_t nStart = GetTimeMicros();
      {
          CCoinsViewCache view(pcoinsTip);
          if (!DisconnectBlock(block, state, pindexDelete, view))
              return error("DisconnectTip(): DisconnectBlock %s failed", pindexDelete->GetBlockHash().ToString());
          assert(view.Flush());
      }
      LogPrint("bench", "- Disconnect block: %.2fms\n", (GetTimeMicros() - nStart) * 0.001);
      // Write the chain state to disk, if necessary.
      if (!FlushStateToDisk(state, FLUSH_STATE_IF_NEEDED))
          return false;
      // Resurrect mempool transactions from the disconnected block.
      std::vector<uint256> vHashUpdate;
      BOOST_FOREACH(const CTransaction &tx, block.vtx) {
          // ignore validation errors in resurrected transactions
          list<CTransaction> removed;
          CValidationState stateDummy;
          if (tx.IsCoinBase() || !AcceptToMemoryPool(mempool, stateDummy, tx, false, NULL, true)) {
              mempool.remove(tx, removed, true);
          } else if (mempool.exists(tx.GetHash())) {
              vHashUpdate.push_back(tx.GetHash());
          }
      }
      // AcceptToMemoryPool/addUnchecked all assume that new mempool entries have
      // no in-mempool children, which is generally not true when adding
      // previously-confirmed transactions back to the mempool.
      // UpdateTransactionsFromBlock finds descendants of any transactions in this
      // block that were added back and cleans up the mempool state.
      mempool.UpdateTransactionsFromBlock(vHashUpdate);
      // Update chainActive and related variables.
      UpdateTip(pindexDelete->pprev);
      // Let wallets know transactions went from 1-confirmed to
      // 0-confirmed or conflicted:
      BOOST_FOREACH(const CTransaction &tx, block.vtx) {
          SyncWithWallets(tx, NULL);
      }
      return true;
  }
  
  static int64_t nTimeReadFromDisk = 0;
  static int64_t nTimeConnectTotal = 0;
  static int64_t nTimeFlush = 0;
  static int64_t nTimeChainState = 0;
  static int64_t nTimePostConnect = 0;
  
  /**
   * Connect a new block to chainActive. pblock is either NULL or a pointer to a CBlock
   * corresponding to pindexNew, to bypass loading it again from disk.
   */
  bool static ConnectTip(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexNew, const CBlock* pblock)
  {
      assert(pindexNew->pprev == chainActive.Tip());
      // Read block from disk.
      int64_t nTime1 = GetTimeMicros();
      CBlock block;
      if (!pblock) {
          if (!ReadBlockFromDisk(block, pindexNew, chainparams.GetConsensus()))
              return AbortNode(state, "Failed to read block");
          pblock = &block;
      }
      // Apply the block atomically to the chain state.
      int64_t nTime2 = GetTimeMicros(); nTimeReadFromDisk += nTime2 - nTime1;
      int64_t nTime3;
      LogPrint("bench", "  - Load block from disk: %.2fms [%.2fs]\n", (nTime2 - nTime1) * 0.001, nTimeReadFromDisk * 0.000001);
      {
          CCoinsViewCache view(pcoinsTip);
          bool rv = ConnectBlock(*pblock, state, pindexNew, view);
          GetMainSignals().BlockChecked(*pblock, state);
          if (!rv) {
              if (state.IsInvalid())
                  InvalidBlockFound(pindexNew, state);
              return error("ConnectTip(): ConnectBlock %s failed", pindexNew->GetBlockHash().ToString());
          }
          mapBlockSource.erase(pindexNew->GetBlockHash());
          nTime3 = GetTimeMicros(); nTimeConnectTotal += nTime3 - nTime2;
          LogPrint("bench", "  - Connect total: %.2fms [%.2fs]\n", (nTime3 - nTime2) * 0.001, nTimeConnectTotal * 0.000001);
          assert(view.Flush());
      }
      int64_t nTime4 = GetTimeMicros(); nTimeFlush += nTime4 - nTime3;
      LogPrint("bench", "  - Flush: %.2fms [%.2fs]\n", (nTime4 - nTime3) * 0.001, nTimeFlush * 0.000001);
      // Write the chain state to disk, if necessary.
      if (!FlushStateToDisk(state, FLUSH_STATE_IF_NEEDED))
          return false;
      int64_t nTime5 = GetTimeMicros(); nTimeChainState += nTime5 - nTime4;
      LogPrint("bench", "  - Writing chainstate: %.2fms [%.2fs]\n", (nTime5 - nTime4) * 0.001, nTimeChainState * 0.000001);
      // Remove conflicting transactions from the mempool.
      list<CTransaction> txConflicted;
      mempool.removeForBlock(pblock->vtx, pindexNew->nHeight, txConflicted, !IsInitialBlockDownload());
      // Update chainActive & related variables.
      UpdateTip(pindexNew);
      // Tell wallet about transactions that went from mempool
      // to conflicted:
      BOOST_FOREACH(const CTransaction &tx, txConflicted) {
          SyncWithWallets(tx, NULL);
      }
      // ... and about transactions that got confirmed:
      BOOST_FOREACH(const CTransaction &tx, pblock->vtx) {
          SyncWithWallets(tx, pblock);
      }
  
      int64_t nTime6 = GetTimeMicros(); nTimePostConnect += nTime6 - nTime5; nTimeTotal += nTime6 - nTime1;
      LogPrint("bench", "  - Connect postprocess: %.2fms [%.2fs]\n", (nTime6 - nTime5) * 0.001, nTimePostConnect * 0.000001);
      LogPrint("bench", "- Connect block: %.2fms [%.2fs]\n", (nTime6 - nTime1) * 0.001, nTimeTotal * 0.000001);
      return true;
  }
  
  /**
   * Return the tip of the chain with the most work in it, that isn't
   * known to be invalid (it's however far from certain to be valid).
   */
  static CBlockIndex* FindMostWorkChain() {
      do {
          CBlockIndex *pindexNew = NULL;
  
          // Find the best candidate header.
          {
              std::set<CBlockIndex*, CBlockIndexWorkComparator>::reverse_iterator it = setBlockIndexCandidates.rbegin();
              if (it == setBlockIndexCandidates.rend())
                  return NULL;
              pindexNew = *it;
          }
  
          // Check whether all blocks on the path between the currently active chain and the candidate are valid.
          // Just going until the active chain is an optimization, as we know all blocks in it are valid already.
          CBlockIndex *pindexTest = pindexNew;
          bool fInvalidAncestor = false;
          while (pindexTest && !chainActive.Contains(pindexTest)) {
              assert(pindexTest->nChainTx || pindexTest->nHeight == 0);
  
              // Pruned nodes may have entries in setBlockIndexCandidates for
              // which block files have been deleted.  Remove those as candidates
              // for the most work chain if we come across them; we can't switch
              // to a chain unless we have all the non-active-chain parent blocks.
              bool fFailedChain = pindexTest->nStatus & BLOCK_FAILED_MASK;
              bool fMissingData = !(pindexTest->nStatus & BLOCK_HAVE_DATA);
              if (fFailedChain || fMissingData) {
                  // Candidate chain is not usable (either invalid or missing data)
                  if (fFailedChain && (pindexBestInvalid == NULL || pindexNew->nChainWork > pindexBestInvalid->nChainWork))
                      pindexBestInvalid = pindexNew;
                  CBlockIndex *pindexFailed = pindexNew;
                  // Remove the entire chain from the set.
                  while (pindexTest != pindexFailed) {
                      if (fFailedChain) {
                          pindexFailed->nStatus |= BLOCK_FAILED_CHILD;
                      } else if (fMissingData) {
                          // If we're missing data, then add back to mapBlocksUnlinked,
                          // so that if the block arrives in the future we can try adding
                          // to setBlockIndexCandidates again.
                          mapBlocksUnlinked.insert(std::make_pair(pindexFailed->pprev, pindexFailed));
                      }
                      setBlockIndexCandidates.erase(pindexFailed);
                      pindexFailed = pindexFailed->pprev;
                  }
                  setBlockIndexCandidates.erase(pindexTest);
                  fInvalidAncestor = true;
                  break;
              }
              pindexTest = pindexTest->pprev;
          }
          if (!fInvalidAncestor)
              return pindexNew;
      } while(true);
  }
  
  /** Delete all entries in setBlockIndexCandidates that are worse than the current tip. */
  static void PruneBlockIndexCandidates() {
      // Note that we can't delete the current block itself, as we may need to return to it later in case a
      // reorganization to a better block fails.
      std::set<CBlockIndex*, CBlockIndexWorkComparator>::iterator it = setBlockIndexCandidates.begin();
      while (it != setBlockIndexCandidates.end() && setBlockIndexCandidates.value_comp()(*it, chainActive.Tip())) {
          setBlockIndexCandidates.erase(it++);
      }
      // Either the current tip or a successor of it we're working towards is left in setBlockIndexCandidates.
      assert(!setBlockIndexCandidates.empty());
  }
  
  /**
   * Try to make some progress towards making pindexMostWork the active block.
   * pblock is either NULL or a pointer to a CBlock corresponding to pindexMostWork.
   */
  static bool ActivateBestChainStep(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const CBlock* pblock)
  {
      AssertLockHeld(cs_main);
      bool fInvalidFound = false;
      const CBlockIndex *pindexOldTip = chainActive.Tip();
      const CBlockIndex *pindexFork = chainActive.FindFork(pindexMostWork);
  
      // Disconnect active blocks which are no longer in the best chain.
      bool fBlocksDisconnected = false;
      while (chainActive.Tip() && chainActive.Tip() != pindexFork) {
          if (!DisconnectTip(state, chainparams.GetConsensus()))
              return false;
          fBlocksDisconnected = true;
      }
  
      // Build list of new blocks to connect.
      std::vector<CBlockIndex*> vpindexToConnect;
      bool fContinue = true;
      int nHeight = pindexFork ? pindexFork->nHeight : -1;
      while (fContinue && nHeight != pindexMostWork->nHeight) {
          // Don't iterate the entire list of potential improvements toward the best tip, as we likely only need
          // a few blocks along the way.
          int nTargetHeight = std::min(nHeight + 32, pindexMostWork->nHeight);
          vpindexToConnect.clear();
          vpindexToConnect.reserve(nTargetHeight - nHeight);
          CBlockIndex *pindexIter = pindexMostWork->GetAncestor(nTargetHeight);
          while (pindexIter && pindexIter->nHeight != nHeight) {
              vpindexToConnect.push_back(pindexIter);
              pindexIter = pindexIter->pprev;
          }
          nHeight = nTargetHeight;
  
          // Connect new blocks.
          BOOST_REVERSE_FOREACH(CBlockIndex *pindexConnect, vpindexToConnect) {
              if (!ConnectTip(state, chainparams, pindexConnect, pindexConnect == pindexMostWork ? pblock : NULL)) {
                  if (state.IsInvalid()) {
                      // The block violates a consensus rule.
                      if (!state.CorruptionPossible())
                          InvalidChainFound(vpindexToConnect.back());
                      state = CValidationState();
                      fInvalidFound = true;
                      fContinue = false;
                      break;
                  } else {
                      // A system error occurred (disk space, database error, ...).
                      return false;
                  }
              } else {
                  PruneBlockIndexCandidates();
                  if (!pindexOldTip || chainActive.Tip()->nChainWork > pindexOldTip->nChainWork) {
                      // We're in a better position than we were. Return temporarily to release the lock.
                      fContinue = false;
                      break;
                  }
              }
          }
      }
  
      if (fBlocksDisconnected) {
          mempool.removeForReorg(pcoinsTip, chainActive.Tip()->nHeight + 1, STANDARD_LOCKTIME_VERIFY_FLAGS);
          LimitMempoolSize(mempool, GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
      }
      mempool.check(pcoinsTip);
  
      // Callbacks/notifications for a new best chain.
      if (fInvalidFound)
          CheckForkWarningConditionsOnNewFork(vpindexToConnect.back());
      else
          CheckForkWarningConditions();
  
      return true;
  }
  
  /**
   * Make the best chain active, in multiple steps. The result is either failure
   * or an activated best chain. pblock is either NULL or a pointer to a block
   * that is already loaded (to avoid loading it again from disk).
   */
  bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, const CBlock *pblock) {
      CBlockIndex *pindexMostWork = NULL;
      do {
          boost::this_thread::interruption_point();
          if (ShutdownRequested())
              break;
  
          CBlockIndex *pindexNewTip = NULL;
          const CBlockIndex *pindexFork;
          bool fInitialDownload;
          {
              LOCK(cs_main);
              CBlockIndex *pindexOldTip = chainActive.Tip();
              pindexMostWork = FindMostWorkChain();
  
              // Whether we have anything to do at all.
              if (pindexMostWork == NULL || pindexMostWork == chainActive.Tip())
                  return true;
  
              if (!ActivateBestChainStep(state, chainparams, pindexMostWork, pblock && pblock->GetHash() == pindexMostWork->GetBlockHash() ? pblock : NULL))
                  return false;
  
              pindexNewTip = chainActive.Tip();
              pindexFork = chainActive.FindFork(pindexOldTip);
              fInitialDownload = IsInitialBlockDownload();
          }
          // When we reach this point, we switched to a new tip (stored in pindexNewTip).
  
          // Notifications/callbacks that can run without cs_main
          // Always notify the UI if a new block tip was connected
          if (pindexFork != pindexNewTip) {
              uiInterface.NotifyBlockTip(fInitialDownload, pindexNewTip);
  
              if (!fInitialDownload) {
                  // Find the hashes of all blocks that weren't previously in the best chain.
                  std::vector<uint256> vHashes;
                  CBlockIndex *pindexToAnnounce = pindexNewTip;
                  while (pindexToAnnounce != pindexFork) {
                      vHashes.push_back(pindexToAnnounce->GetBlockHash());
                      pindexToAnnounce = pindexToAnnounce->pprev;
                      if (vHashes.size() == MAX_BLOCKS_TO_ANNOUNCE) {
                          // Limit announcements in case of a huge reorganization.
                          // Rely on the peer's synchronization mechanism in that case.
                          break;
                      }
                  }
                  // Relay inventory, but don't relay old inventory during initial block download.
                  int nBlockEstimate = 0;
                  if (fCheckpointsEnabled)
                      nBlockEstimate = Checkpoints::GetTotalBlocksEstimate(chainparams.Checkpoints());
                  {
                      LOCK(cs_vNodes);
                      BOOST_FOREACH(CNode* pnode, vNodes) {
                          if (chainActive.Height() > (pnode->nStartingHeight != -1 ? pnode->nStartingHeight - 2000 : nBlockEstimate)) {
                              BOOST_REVERSE_FOREACH(const uint256& hash, vHashes) {
                                  pnode->PushBlockHash(hash);
                              }
                          }
                      }
                  }
                  // Notify external listeners about the new tip.
                  if (!vHashes.empty()) {
                      GetMainSignals().UpdatedBlockTip(pindexNewTip);
                  }
              }
          }
      } while(pindexMostWork != chainActive.Tip());
      CheckBlockIndex(chainparams.GetConsensus());
  
      // Write changes periodically to disk, after relay.
      if (!FlushStateToDisk(state, FLUSH_STATE_PERIODIC)) {
          return false;
      }
  
      return true;
  }
  
  bool InvalidateBlock(CValidationState& state, const Consensus::Params& consensusParams, CBlockIndex *pindex)
  {
      AssertLockHeld(cs_main);
  
      // Mark the block itself as invalid.
      pindex->nStatus |= BLOCK_FAILED_VALID;
      setDirtyBlockIndex.insert(pindex);
      setBlockIndexCandidates.erase(pindex);
  
      while (chainActive.Contains(pindex)) {
          CBlockIndex *pindexWalk = chainActive.Tip();
          pindexWalk->nStatus |= BLOCK_FAILED_CHILD;
          setDirtyBlockIndex.insert(pindexWalk);
          setBlockIndexCandidates.erase(pindexWalk);
          // ActivateBestChain considers blocks already in chainActive
          // unconditionally valid already, so force disconnect away from it.
          if (!DisconnectTip(state, consensusParams)) {
              mempool.removeForReorg(pcoinsTip, chainActive.Tip()->nHeight + 1, STANDARD_LOCKTIME_VERIFY_FLAGS);
              return false;
          }
      }
  
      LimitMempoolSize(mempool, GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
  
      // The resulting new best tip may not be in setBlockIndexCandidates anymore, so
      // add it again.
      BlockMap::iterator it = mapBlockIndex.begin();
      while (it != mapBlockIndex.end()) {
          if (it->second->IsValid(BLOCK_VALID_TRANSACTIONS) && it->second->nChainTx && !setBlockIndexCandidates.value_comp()(it->second, chainActive.Tip())) {
              setBlockIndexCandidates.insert(it->second);
          }
          it++;
      }
  
      InvalidChainFound(pindex);
      mempool.removeForReorg(pcoinsTip, chainActive.Tip()->nHeight + 1, STANDARD_LOCKTIME_VERIFY_FLAGS);
      return true;
  }
  
  bool ReconsiderBlock(CValidationState& state, CBlockIndex *pindex) {
      AssertLockHeld(cs_main);
  
      int nHeight = pindex->nHeight;
  
      // Remove the invalidity flag from this block and all its descendants.
      BlockMap::iterator it = mapBlockIndex.begin();
      while (it != mapBlockIndex.end()) {
          if (!it->second->IsValid() && it->second->GetAncestor(nHeight) == pindex) {
              it->second->nStatus &= ~BLOCK_FAILED_MASK;
              setDirtyBlockIndex.insert(it->second);
              if (it->second->IsValid(BLOCK_VALID_TRANSACTIONS) && it->second->nChainTx && setBlockIndexCandidates.value_comp()(chainActive.Tip(), it->second)) {
                  setBlockIndexCandidates.insert(it->second);
              }
              if (it->second == pindexBestInvalid) {
                  // Reset invalid block marker if it was pointing to one of those.
                  pindexBestInvalid = NULL;
              }
          }
          it++;
      }
  
      // Remove the invalidity flag from all ancestors too.
      while (pindex != NULL) {
          if (pindex->nStatus & BLOCK_FAILED_MASK) {
              pindex->nStatus &= ~BLOCK_FAILED_MASK;
              setDirtyBlockIndex.insert(pindex);
          }
          pindex = pindex->pprev;
      }
      return true;
  }
  
  CBlockIndex* AddToBlockIndex(const CBlockHeader& block)
  {
      // Check for duplicate
      uint256 hash = block.GetHash();
      BlockMap::iterator it = mapBlockIndex.find(hash);
      if (it != mapBlockIndex.end())
          return it->second;
  
      // Construct new block index object
      CBlockIndex* pindexNew = new CBlockIndex(block);
      assert(pindexNew);
      // We assign the sequence id to blocks only when the full data is available,
      // to avoid miners withholding blocks but broadcasting headers, to get a
      // competitive advantage.
      pindexNew->nSequenceId = 0;
      BlockMap::iterator mi = mapBlockIndex.insert(make_pair(hash, pindexNew)).first;
      pindexNew->phashBlock = &((*mi).first);
      BlockMap::iterator miPrev = mapBlockIndex.find(block.hashPrevBlock);
      if (miPrev != mapBlockIndex.end())
      {
          pindexNew->pprev = (*miPrev).second;
          pindexNew->nHeight = pindexNew->pprev->nHeight + 1;
          pindexNew->BuildSkip();
      }
      pindexNew->nChainWork = (pindexNew->pprev ? pindexNew->pprev->nChainWork : 0) + GetBlockProof(*pindexNew);
      pindexNew->RaiseValidity(BLOCK_VALID_TREE);
      if (pindexBestHeader == NULL || pindexBestHeader->nChainWork < pindexNew->nChainWork)
          pindexBestHeader = pindexNew;
  
      setDirtyBlockIndex.insert(pindexNew);
  
      return pindexNew;
  }
  
  /** Mark a block as having its data received and checked (up to BLOCK_VALID_TRANSACTIONS). */
  bool ReceivedBlockTransactions(const CBlock &block, CValidationState& state, CBlockIndex *pindexNew, const CDiskBlockPos& pos)
  {
      pindexNew->nTx = block.vtx.size();
      pindexNew->nChainTx = 0;
      pindexNew->nFile = pos.nFile;
      pindexNew->nDataPos = pos.nPos;
      pindexNew->nUndoPos = 0;
      pindexNew->nStatus |= BLOCK_HAVE_DATA;
      pindexNew->RaiseValidity(BLOCK_VALID_TRANSACTIONS);
      setDirtyBlockIndex.insert(pindexNew);
  
      if (pindexNew->pprev == NULL || pindexNew->pprev->nChainTx) {
          // If pindexNew is the genesis block or all parents are BLOCK_VALID_TRANSACTIONS.
          deque<CBlockIndex*> queue;
          queue.push_back(pindexNew);
  
          // Recursively process any descendant blocks that now may be eligible to be connected.
          while (!queue.empty()) {
              CBlockIndex *pindex = queue.front();
              queue.pop_front();
              pindex->nChainTx = (pindex->pprev ? pindex->pprev->nChainTx : 0) + pindex->nTx;
              {
                  LOCK(cs_nBlockSequenceId);
                  pindex->nSequenceId = nBlockSequenceId++;
              }
              if (chainActive.Tip() == NULL || !setBlockIndexCandidates.value_comp()(pindex, chainActive.Tip())) {
                  setBlockIndexCandidates.insert(pindex);
              }
              std::pair<std::multimap<CBlockIndex*, CBlockIndex*>::iterator, std::multimap<CBlockIndex*, CBlockIndex*>::iterator> range = mapBlocksUnlinked.equal_range(pindex);
              while (range.first != range.second) {
                  std::multimap<CBlockIndex*, CBlockIndex*>::iterator it = range.first;
                  queue.push_back(it->second);
                  range.first++;
                  mapBlocksUnlinked.erase(it);
              }
          }
      } else {
          if (pindexNew->pprev && pindexNew->pprev->IsValid(BLOCK_VALID_TREE)) {
              mapBlocksUnlinked.insert(std::make_pair(pindexNew->pprev, pindexNew));
          }
      }
  
      return true;
  }
  
  bool FindBlockPos(CValidationState &state, CDiskBlockPos &pos, unsigned int nAddSize, unsigned int nHeight, uint64_t nTime, bool fKnown = false)
  {
      LOCK(cs_LastBlockFile);
  
      unsigned int nFile = fKnown ? pos.nFile : nLastBlockFile;
      if (vinfoBlockFile.size() <= nFile) {
          vinfoBlockFile.resize(nFile + 1);
      }
  
      if (!fKnown) {
          while (vinfoBlockFile[nFile].nSize + nAddSize >= MAX_BLOCKFILE_SIZE) {
              nFile++;
              if (vinfoBlockFile.size() <= nFile) {
                  vinfoBlockFile.resize(nFile + 1);
              }
          }
          pos.nFile = nFile;
          pos.nPos = vinfoBlockFile[nFile].nSize;
      }
  
      if ((int)nFile != nLastBlockFile) {
          if (!fKnown) {
              LogPrintf("Leaving block file %i: %s\n", nLastBlockFile, vinfoBlockFile[nLastBlockFile].ToString());
          }
          FlushBlockFile(!fKnown);
          nLastBlockFile = nFile;
      }
  
      vinfoBlockFile[nFile].AddBlock(nHeight, nTime);
      if (fKnown)
          vinfoBlockFile[nFile].nSize = std::max(pos.nPos + nAddSize, vinfoBlockFile[nFile].nSize);
      else
          vinfoBlockFile[nFile].nSize += nAddSize;
  
      if (!fKnown) {
          unsigned int nOldChunks = (pos.nPos + BLOCKFILE_CHUNK_SIZE - 1) / BLOCKFILE_CHUNK_SIZE;
          unsigned int nNewChunks = (vinfoBlockFile[nFile].nSize + BLOCKFILE_CHUNK_SIZE - 1) / BLOCKFILE_CHUNK_SIZE;
          if (nNewChunks > nOldChunks) {
              if (fPruneMode)
                  fCheckForPruning = true;
              if (CheckDiskSpace(nNewChunks * BLOCKFILE_CHUNK_SIZE - pos.nPos)) {
                  FILE *file = OpenBlockFile(pos);
                  if (file) {
                      LogPrintf("Pre-allocating up to position 0x%x in blk%05u.dat\n", nNewChunks * BLOCKFILE_CHUNK_SIZE, pos.nFile);
                      AllocateFileRange(file, pos.nPos, nNewChunks * BLOCKFILE_CHUNK_SIZE - pos.nPos);
                      fclose(file);
                  }
              }
              else
                  return state.Error("out of disk space");
          }
      }
  
      setDirtyFileInfo.insert(nFile);
      return true;
  }
  
  bool FindUndoPos(CValidationState &state, int nFile, CDiskBlockPos &pos, unsigned int nAddSize)
  {
      pos.nFile = nFile;
  
      LOCK(cs_LastBlockFile);
  
      unsigned int nNewSize;
      pos.nPos = vinfoBlockFile[nFile].nUndoSize;
      nNewSize = vinfoBlockFile[nFile].nUndoSize += nAddSize;
      setDirtyFileInfo.insert(nFile);
  
      unsigned int nOldChunks = (pos.nPos + UNDOFILE_CHUNK_SIZE - 1) / UNDOFILE_CHUNK_SIZE;
      unsigned int nNewChunks = (nNewSize + UNDOFILE_CHUNK_SIZE - 1) / UNDOFILE_CHUNK_SIZE;
      if (nNewChunks > nOldChunks) {
          if (fPruneMode)
              fCheckForPruning = true;
          if (CheckDiskSpace(nNewChunks * UNDOFILE_CHUNK_SIZE - pos.nPos)) {
              FILE *file = OpenUndoFile(pos);
              if (file) {
                  LogPrintf("Pre-allocating up to position 0x%x in rev%05u.dat\n", nNewChunks * UNDOFILE_CHUNK_SIZE, pos.nFile);
                  AllocateFileRange(file, pos.nPos, nNewChunks * UNDOFILE_CHUNK_SIZE - pos.nPos);
                  fclose(file);
              }
          }
          else
              return state.Error("out of disk space");
      }
  
      return true;
  }
  
  bool CheckBlockHeader(const CBlockHeader& block, CValidationState& state, bool fCheckPOW)
  {
      // Check proof of work matches claimed amount
      if (fCheckPOW && !CheckProofOfWork(block.GetHash(), block.nBits, Params().GetConsensus()))
          return state.DoS(50, error("CheckBlockHeader(): proof of work failed"),
                           REJECT_INVALID, "high-hash");
  
      // Check timestamp
      if (block.GetBlockTime() > GetAdjustedTime() + 2 * 60 * 60)
          return state.Invalid(error("CheckBlockHeader(): block timestamp too far in the future"),
                               REJECT_INVALID, "time-too-new");
  
      return true;
  }
  
  bool CheckBlock(const CBlock& block, CValidationState& state, bool fCheckPOW, bool fCheckMerkleRoot)
  {
      // These are checks that are independent of context.
  
      if (block.fChecked)
          return true;
  
      // Check that the header is valid (particularly PoW).  This is mostly
      // redundant with the call in AcceptBlockHeader.
      if (!CheckBlockHeader(block, state, fCheckPOW))
          return false;
  
      // Check the merkle root.
      if (fCheckMerkleRoot) {
          bool mutated;
          uint256 hashMerkleRoot2 = BlockMerkleRoot(block, &mutated);
          if (block.hashMerkleRoot != hashMerkleRoot2)
              return state.DoS(100, error("CheckBlock(): hashMerkleRoot mismatch"),
                               REJECT_INVALID, "bad-txnmrklroot", true);
  
          // Check for merkle tree malleability (CVE-2012-2459): repeating sequences
          // of transactions in a block without affecting the merkle root of a block,
          // while still invalidating it.
          if (mutated)
              return state.DoS(100, error("CheckBlock(): duplicate transaction"),
                               REJECT_INVALID, "bad-txns-duplicate", true);
      }
  
      // All potential-corruption validation must be done before we do any
      // transaction validation, as otherwise we may mark the header as invalid
      // because we receive the wrong transactions for it.
  
      // Size limits
      if (block.vtx.empty() || block.vtx.size() > MAX_BLOCK_SIZE || ::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION) > MAX_BLOCK_SIZE)
          return state.DoS(100, error("CheckBlock(): size limits failed"),
                           REJECT_INVALID, "bad-blk-length");
  
      // First transaction must be coinbase, the rest must not be
      if (block.vtx.empty() || !block.vtx[0].IsCoinBase())
          return state.DoS(100, error("CheckBlock(): first tx is not coinbase"),
                           REJECT_INVALID, "bad-cb-missing");
      for (unsigned int i = 1; i < block.vtx.size(); i++)
          if (block.vtx[i].IsCoinBase())
              return state.DoS(100, error("CheckBlock(): more than one coinbase"),
                               REJECT_INVALID, "bad-cb-multiple");
  
      // Check transactions
      BOOST_FOREACH(const CTransaction& tx, block.vtx)
          if (!CheckTransaction(tx, state))
              return error("CheckBlock(): CheckTransaction of %s failed with %s",
                  tx.GetHash().ToString(),
                  FormatStateMessage(state));
  
      unsigned int nSigOps = 0;
      BOOST_FOREACH(const CTransaction& tx, block.vtx)
      {
          nSigOps += GetLegacySigOpCount(tx);
      }
      if (nSigOps > MAX_BLOCK_SIGOPS)
          return state.DoS(100, error("CheckBlock(): out-of-bounds SigOpCount"),
                           REJECT_INVALID, "bad-blk-sigops");
  
      if (fCheckPOW && fCheckMerkleRoot)
          block.fChecked = true;
  
      return true;
  }
  
  static bool CheckIndexAgainstCheckpoint(const CBlockIndex* pindexPrev, CValidationState& state, const CChainParams& chainparams, const uint256& hash)
  {
      if (*pindexPrev->phashBlock == chainparams.GetConsensus().hashGenesisBlock)
          return true;
  
      int nHeight = pindexPrev->nHeight+1;
      // Don't accept any forks from the main chain prior to last checkpoint
      CBlockIndex* pcheckpoint = Checkpoints::GetLastCheckpoint(chainparams.Checkpoints());
      if (pcheckpoint && nHeight < pcheckpoint->nHeight)
          return state.DoS(100, error("%s: forked chain older than last checkpoint (height %d)", __func__, nHeight));
  
      return true;
  }
  
  bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationState& state, CBlockIndex * const pindexPrev)
  {
      const Consensus::Params& consensusParams = Params().GetConsensus();
      // Check proof of work
      if (block.nBits != GetNextWorkRequired(pindexPrev, &block, consensusParams))
          return state.DoS(100, error("%s: incorrect proof of work", __func__),
                           REJECT_INVALID, "bad-diffbits");
  
      // Check timestamp against prev
      if (block.GetBlockTime() <= pindexPrev->GetMedianTimePast())
          return state.Invalid(error("%s: block's timestamp is too early", __func__),
                               REJECT_INVALID, "time-too-old");
  
      // Reject block.nVersion=1 blocks when 95% (75% on testnet) of the network has upgraded:
      if (block.nVersion < 2 && IsSuperMajority(2, pindexPrev, consensusParams.nMajorityRejectBlockOutdated, consensusParams))
          return state.Invalid(error("%s: rejected nVersion=1 block", __func__),
                               REJECT_OBSOLETE, "bad-version");
  
      // Reject block.nVersion=2 blocks when 95% (75% on testnet) of the network has upgraded:
      if (block.nVersion < 3 && IsSuperMajority(3, pindexPrev, consensusParams.nMajorityRejectBlockOutdated, consensusParams))
          return state.Invalid(error("%s: rejected nVersion=2 block", __func__),
                               REJECT_OBSOLETE, "bad-version");
  
      // Reject block.nVersion=3 blocks when 95% (75% on testnet) of the network has upgraded:
      if (block.nVersion < 4 && IsSuperMajority(4, pindexPrev, consensusParams.nMajorityRejectBlockOutdated, consensusParams))
          return state.Invalid(error("%s : rejected nVersion=3 block", __func__),
                               REJECT_OBSOLETE, "bad-version");
  
      return true;
  }
  
  bool ContextualCheckBlock(const CBlock& block, CValidationState& state, CBlockIndex * const pindexPrev)
  {
      const int nHeight = pindexPrev == NULL ? 0 : pindexPrev->nHeight + 1;
      const Consensus::Params& consensusParams = Params().GetConsensus();
  
      // Start enforcing BIP113 (Median Time Past) using versionbits logic.
      int nLockTimeFlags = 0;
      if (VersionBitsState(pindexPrev, consensusParams, Consensus::DEPLOYMENT_CSV, versionbitscache) == THRESHOLD_ACTIVE) {
          nLockTimeFlags |= LOCKTIME_MEDIAN_TIME_PAST;
      }
  
      int64_t nLockTimeCutoff = (nLockTimeFlags & LOCKTIME_MEDIAN_TIME_PAST)
                                ? pindexPrev->GetMedianTimePast()
                                : block.GetBlockTime();
  
      // Check that all transactions are finalized
      BOOST_FOREACH(const CTransaction& tx, block.vtx) {
          if (!IsFinalTx(tx, nHeight, nLockTimeCutoff)) {
              return state.DoS(10, error("%s: contains a non-final transaction", __func__), REJECT_INVALID, "bad-txns-nonfinal");
          }
      }
  
      // Enforce block.nVersion=2 rule that the coinbase starts with serialized block height
      // if 750 of the last 1,000 blocks are version 2 or greater (51/100 if testnet):
      if (block.nVersion >= 2 && IsSuperMajority(2, pindexPrev, consensusParams.nMajorityEnforceBlockUpgrade, consensusParams))
      {
          CScript expect = CScript() << nHeight;
          if (block.vtx[0].vin[0].scriptSig.size() < expect.size() ||
              !std::equal(expect.begin(), expect.end(), block.vtx[0].vin[0].scriptSig.begin())) {
              return state.DoS(100, error("%s: block height mismatch in coinbase", __func__), REJECT_INVALID, "bad-cb-height");
          }
      }
  
      return true;
  }
  
  static bool AcceptBlockHeader(const CBlockHeader& block, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex=NULL)
  {
      AssertLockHeld(cs_main);
      // Check for duplicate
      uint256 hash = block.GetHash();
      BlockMap::iterator miSelf = mapBlockIndex.find(hash);
      CBlockIndex *pindex = NULL;
      if (hash != chainparams.GetConsensus().hashGenesisBlock) {
  
          if (miSelf != mapBlockIndex.end()) {
              // Block header is already known.
              pindex = miSelf->second;
              if (ppindex)
                  *ppindex = pindex;
              if (pindex->nStatus & BLOCK_FAILED_MASK)
                  return state.Invalid(error("%s: block is marked invalid", __func__), 0, "duplicate");
              return true;
          }
  
          if (!CheckBlockHeader(block, state))
              return false;
  
          // Get prev block index
          CBlockIndex* pindexPrev = NULL;
          BlockMap::iterator mi = mapBlockIndex.find(block.hashPrevBlock);
          if (mi == mapBlockIndex.end())
              return state.DoS(10, error("%s: prev block not found", __func__), 0, "bad-prevblk");
          pindexPrev = (*mi).second;
          if (pindexPrev->nStatus & BLOCK_FAILED_MASK)
              return state.DoS(100, error("%s: prev block invalid", __func__), REJECT_INVALID, "bad-prevblk");
  
          assert(pindexPrev);
          if (fCheckpointsEnabled && !CheckIndexAgainstCheckpoint(pindexPrev, state, chainparams, hash))
              return error("%s: CheckIndexAgainstCheckpoint(): %s", __func__, state.GetRejectReason().c_str());
  
          if (!ContextualCheckBlockHeader(block, state, pindexPrev))
              return false;
      }
      if (pindex == NULL)
          pindex = AddToBlockIndex(block);
  
      if (ppindex)
          *ppindex = pindex;
  
      return true;
  }
  
  /** Store block on disk. If dbp is non-NULL, the file is known to already reside on disk */
  static bool AcceptBlock(const CBlock& block, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex, bool fRequested, CDiskBlockPos* dbp)
  {
      AssertLockHeld(cs_main);
  
      CBlockIndex *&pindex = *ppindex;
  
      if (!AcceptBlockHeader(block, state, chainparams, &pindex))
          return false;
  
      // Try to process all requested blocks that we don't have, but only
      // process an unrequested block if it's new and has enough work to
      // advance our tip, and isn't too many blocks ahead.
      bool fAlreadyHave = pindex->nStatus & BLOCK_HAVE_DATA;
      bool fHasMoreWork = (chainActive.Tip() ? pindex->nChainWork > chainActive.Tip()->nChainWork : true);
      // Blocks that are too out-of-order needlessly limit the effectiveness of
      // pruning, because pruning will not delete block files that contain any
      // blocks which are too close in height to the tip.  Apply this test
      // regardless of whether pruning is enabled; it should generally be safe to
      // not process unrequested blocks.
      bool fTooFarAhead = (pindex->nHeight > int(chainActive.Height() + MIN_BLOCKS_TO_KEEP));
  
      // TODO: deal better with return value and error conditions for duplicate
      // and unrequested blocks.
      if (fAlreadyHave) return true;
      if (!fRequested) {  // If we didn't ask for it:
          if (pindex->nTx != 0) return true;  // This is a previously-processed block that was pruned
          if (!fHasMoreWork) return true;     // Don't process less-work chains
          if (fTooFarAhead) return true;      // Block height is too high
      }
  
      if ((!CheckBlock(block, state)) || !ContextualCheckBlock(block, state, pindex->pprev)) {
          if (state.IsInvalid() && !state.CorruptionPossible()) {
              pindex->nStatus |= BLOCK_FAILED_VALID;
              setDirtyBlockIndex.insert(pindex);
          }
          return false;
      }
  
      int nHeight = pindex->nHeight;
  
      // Write block to history file
      try {
          unsigned int nBlockSize = ::GetSerializeSize(block, SER_DISK, CLIENT_VERSION);
          CDiskBlockPos blockPos;
          if (dbp != NULL)
              blockPos = *dbp;
          if (!FindBlockPos(state, blockPos, nBlockSize+8, nHeight, block.GetBlockTime(), dbp != NULL))
              return error("AcceptBlock(): FindBlockPos failed");
          if (dbp == NULL)
              if (!WriteBlockToDisk(block, blockPos, chainparams.MessageStart()))
                  AbortNode(state, "Failed to write block");
          if (!ReceivedBlockTransactions(block, state, pindex, blockPos))
              return error("AcceptBlock(): ReceivedBlockTransactions failed");
      } catch (const std::runtime_error& e) {
          return AbortNode(state, std::string("System error: ") + e.what());
      }
  
      if (fCheckForPruning)
          FlushStateToDisk(state, FLUSH_STATE_NONE); // we just allocated more disk space for block files
  
      return true;
  }
  
  static bool IsSuperMajority(int minVersion, const CBlockIndex* pstart, unsigned nRequired, const Consensus::Params& consensusParams)
  {
      unsigned int nFound = 0;
      for (int i = 0; i < consensusParams.nMajorityWindow && nFound < nRequired && pstart != NULL; i++)
      {
          if (pstart->nVersion >= minVersion)
              ++nFound;
          pstart = pstart->pprev;
      }
      return (nFound >= nRequired);
  }
  
  
  bool ProcessNewBlock(CValidationState& state, const CChainParams& chainparams, const CNode* pfrom, const CBlock* pblock, bool fForceProcessing, CDiskBlockPos* dbp)
  {
      // Preliminary checks
      bool checked = CheckBlock(*pblock, state);
  
      {
          LOCK(cs_main);
          bool fRequested = MarkBlockAsReceived(pblock->GetHash());
          fRequested |= fForceProcessing;
          if (!checked) {
              return error("%s: CheckBlock FAILED", __func__);
          }
  
          // Store to disk
          CBlockIndex *pindex = NULL;
          bool ret = AcceptBlock(*pblock, state, chainparams, &pindex, fRequested, dbp);
          if (pindex && pfrom) {
              mapBlockSource[pindex->GetBlockHash()] = pfrom->GetId();
          }
          CheckBlockIndex(chainparams.GetConsensus());
          if (!ret)
              return error("%s: AcceptBlock FAILED", __func__);
      }
  
      if (!ActivateBestChain(state, chainparams, pblock))
          return error("%s: ActivateBestChain failed", __func__);
  
      return true;
  }
  
  bool TestBlockValidity(CValidationState& state, const CChainParams& chainparams, const CBlock& block, CBlockIndex* pindexPrev, bool fCheckPOW, bool fCheckMerkleRoot)
  {
      AssertLockHeld(cs_main);
      assert(pindexPrev && pindexPrev == chainActive.Tip());
      if (fCheckpointsEnabled && !CheckIndexAgainstCheckpoint(pindexPrev, state, chainparams, block.GetHash()))
          return error("%s: CheckIndexAgainstCheckpoint(): %s", __func__, state.GetRejectReason().c_str());
  
      CCoinsViewCache viewNew(pcoinsTip);
      CBlockIndex indexDummy(block);
      indexDummy.pprev = pindexPrev;
      indexDummy.nHeight = pindexPrev->nHeight + 1;
  
      // NOTE: CheckBlockHeader is called by CheckBlock
      if (!ContextualCheckBlockHeader(block, state, pindexPrev))
          return false;
      if (!CheckBlock(block, state, fCheckPOW, fCheckMerkleRoot))
          return false;
      if (!ContextualCheckBlock(block, state, pindexPrev))
          return false;
      if (!ConnectBlock(block, state, &indexDummy, viewNew, true))
          return false;
      assert(state.IsValid());
  
      return true;
  }
  
  /**
   * BLOCK PRUNING CODE
   */
  
  /* Calculate the amount of disk space the block & undo files currently use */
  uint64_t CalculateCurrentUsage()
  {
      uint64_t retval = 0;
      BOOST_FOREACH(const CBlockFileInfo &file, vinfoBlockFile) {
          retval += file.nSize + file.nUndoSize;
      }
      return retval;
  }
  
  /* Prune a block file (modify associated database entries)*/
  void PruneOneBlockFile(const int fileNumber)
  {
      for (BlockMap::iterator it = mapBlockIndex.begin(); it != mapBlockIndex.end(); ++it) {
          CBlockIndex* pindex = it->second;
          if (pindex->nFile == fileNumber) {
              pindex->nStatus &= ~BLOCK_HAVE_DATA;
              pindex->nStatus &= ~BLOCK_HAVE_UNDO;
              pindex->nFile = 0;
              pindex->nDataPos = 0;
              pindex->nUndoPos = 0;
              setDirtyBlockIndex.insert(pindex);
  
              // Prune from mapBlocksUnlinked -- any block we prune would have
              // to be downloaded again in order to consider its chain, at which
              // point it would be considered as a candidate for
              // mapBlocksUnlinked or setBlockIndexCandidates.
              std::pair<std::multimap<CBlockIndex*, CBlockIndex*>::iterator, std::multimap<CBlockIndex*, CBlockIndex*>::iterator> range = mapBlocksUnlinked.equal_range(pindex->pprev);
              while (range.first != range.second) {
                  std::multimap<CBlockIndex *, CBlockIndex *>::iterator it = range.first;
                  range.first++;
                  if (it->second == pindex) {
                      mapBlocksUnlinked.erase(it);
                  }
              }
          }
      }
  
      vinfoBlockFile[fileNumber].SetNull();
      setDirtyFileInfo.insert(fileNumber);
  }
  
  
  void UnlinkPrunedFiles(std::set<int>& setFilesToPrune)
  {
      for (set<int>::iterator it = setFilesToPrune.begin(); it != setFilesToPrune.end(); ++it) {
          CDiskBlockPos pos(*it, 0);
          boost::filesystem::remove(GetBlockPosFilename(pos, "blk"));
          boost::filesystem::remove(GetBlockPosFilename(pos, "rev"));
          LogPrintf("Prune: %s deleted blk/rev (%05u)\n", __func__, *it);
      }
  }
  
  /* Calculate the block/rev files that should be deleted to remain under target*/
  void FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight)
  {
      LOCK2(cs_main, cs_LastBlockFile);
      if (chainActive.Tip() == NULL || nPruneTarget == 0) {
          return;
      }
      if ((uint64_t)chainActive.Tip()->nHeight <= nPruneAfterHeight) {
          return;
      }
  
      unsigned int nLastBlockWeCanPrune = chainActive.Tip()->nHeight - MIN_BLOCKS_TO_KEEP;
      uint64_t nCurrentUsage = CalculateCurrentUsage();
      // We don't check to prune until after we've allocated new space for files
      // So we should leave a buffer under our target to account for another allocation
      // before the next pruning.
      uint64_t nBuffer = BLOCKFILE_CHUNK_SIZE + UNDOFILE_CHUNK_SIZE;
      uint64_t nBytesToPrune;
      int count=0;
  
      if (nCurrentUsage + nBuffer >= nPruneTarget) {
          for (int fileNumber = 0; fileNumber < nLastBlockFile; fileNumber++) {
              nBytesToPrune = vinfoBlockFile[fileNumber].nSize + vinfoBlockFile[fileNumber].nUndoSize;
  
              if (vinfoBlockFile[fileNumber].nSize == 0)
                  continue;
  
              if (nCurrentUsage + nBuffer < nPruneTarget)  // are we below our target?
                  break;
  
              // don't prune files that could have a block within MIN_BLOCKS_TO_KEEP of the main chain's tip but keep scanning
              if (vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune)
                  continue;
  
              PruneOneBlockFile(fileNumber);
              // Queue up the files for removal
              setFilesToPrune.insert(fileNumber);
              nCurrentUsage -= nBytesToPrune;
              count++;
          }
      }
  
      LogPrint("prune", "Prune: target=%dMiB actual=%dMiB diff=%dMiB max_prune_height=%d removed %d blk/rev pairs\n",
             nPruneTarget/1024/1024, nCurrentUsage/1024/1024,
             ((int64_t)nPruneTarget - (int64_t)nCurrentUsage)/1024/1024,
             nLastBlockWeCanPrune, count);
  }
  
  bool CheckDiskSpace(uint64_t nAdditionalBytes)
  {
      uint64_t nFreeBytesAvailable = boost::filesystem::space(GetDataDir()).available;
  
      // Check for nMinDiskSpace bytes (currently 50MB)
      if (nFreeBytesAvailable < nMinDiskSpace + nAdditionalBytes)
          return AbortNode("Disk space is low!", _("Error: Disk space is low!"));
  
      return true;
  }
  
  FILE* OpenDiskFile(const CDiskBlockPos &pos, const char *prefix, bool fReadOnly)
  {
      if (pos.IsNull())
          return NULL;
      boost::filesystem::path path = GetBlockPosFilename(pos, prefix);
      boost::filesystem::create_directories(path.parent_path());
      FILE* file = fopen(path.string().c_str(), "rb+");
      if (!file && !fReadOnly)
          file = fopen(path.string().c_str(), "wb+");
      if (!file) {
          LogPrintf("Unable to open file %s\n", path.string());
          return NULL;
      }
      if (pos.nPos) {
          if (fseek(file, pos.nPos, SEEK_SET)) {
              LogPrintf("Unable to seek to position %u of %s\n", pos.nPos, path.string());
              fclose(file);
              return NULL;
          }
      }
      return file;
  }
  
  FILE* OpenBlockFile(const CDiskBlockPos &pos, bool fReadOnly) {
      return OpenDiskFile(pos, "blk", fReadOnly);
  }
  
  FILE* OpenUndoFile(const CDiskBlockPos &pos, bool fReadOnly) {
      return OpenDiskFile(pos, "rev", fReadOnly);
  }
  
  boost::filesystem::path GetBlockPosFilename(const CDiskBlockPos &pos, const char *prefix)
  {
      return GetDataDir() / "blocks" / strprintf("%s%05u.dat", prefix, pos.nFile);
  }
  
  CBlockIndex * InsertBlockIndex(uint256 hash)
  {
      if (hash.IsNull())
          return NULL;
  
      // Return existing
      BlockMap::iterator mi = mapBlockIndex.find(hash);
      if (mi != mapBlockIndex.end())
          return (*mi).second;
  
      // Create new
      CBlockIndex* pindexNew = new CBlockIndex();
      if (!pindexNew)
          throw runtime_error("LoadBlockIndex(): new CBlockIndex failed");
      mi = mapBlockIndex.insert(make_pair(hash, pindexNew)).first;
      pindexNew->phashBlock = &((*mi).first);
  
      return pindexNew;
  }
  
  bool static LoadBlockIndexDB()
  {
      const CChainParams& chainparams = Params();
      if (!pblocktree->LoadBlockIndexGuts())
          return false;
  
      boost::this_thread::interruption_point();
  
      // Calculate nChainWork
      vector<pair<int, CBlockIndex*> > vSortedByHeight;
      vSortedByHeight.reserve(mapBlockIndex.size());
      BOOST_FOREACH(const PAIRTYPE(uint256, CBlockIndex*)& item, mapBlockIndex)
      {
          CBlockIndex* pindex = item.second;
          vSortedByHeight.push_back(make_pair(pindex->nHeight, pindex));
      }
      sort(vSortedByHeight.begin(), vSortedByHeight.end());
      BOOST_FOREACH(const PAIRTYPE(int, CBlockIndex*)& item, vSortedByHeight)
      {
          CBlockIndex* pindex = item.second;
          pindex->nChainWork = (pindex->pprev ? pindex->pprev->nChainWork : 0) + GetBlockProof(*pindex);
          // We can link the chain of blocks for which we've received transactions at some point.
          // Pruned nodes may have deleted the block.
          if (pindex->nTx > 0) {
              if (pindex->pprev) {
                  if (pindex->pprev->nChainTx) {
                      pindex->nChainTx = pindex->pprev->nChainTx + pindex->nTx;
                  } else {
                      pindex->nChainTx = 0;
                      mapBlocksUnlinked.insert(std::make_pair(pindex->pprev, pindex));
                  }
              } else {
                  pindex->nChainTx = pindex->nTx;
              }
          }
          if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && (pindex->nChainTx || pindex->pprev == NULL))
              setBlockIndexCandidates.insert(pindex);
          if (pindex->nStatus & BLOCK_FAILED_MASK && (!pindexBestInvalid || pindex->nChainWork > pindexBestInvalid->nChainWork))
              pindexBestInvalid = pindex;
          if (pindex->pprev)
              pindex->BuildSkip();
          if (pindex->IsValid(BLOCK_VALID_TREE) && (pindexBestHeader == NULL || CBlockIndexWorkComparator()(pindexBestHeader, pindex)))
              pindexBestHeader = pindex;
      }
  
      // Load block file info
      pblocktree->ReadLastBlockFile(nLastBlockFile);
      vinfoBlockFile.resize(nLastBlockFile + 1);
      LogPrintf("%s: last block file = %i\n", __func__, nLastBlockFile);
      for (int nFile = 0; nFile <= nLastBlockFile; nFile++) {
          pblocktree->ReadBlockFileInfo(nFile, vinfoBlockFile[nFile]);
      }
      LogPrintf("%s: last block file info: %s\n", __func__, vinfoBlockFile[nLastBlockFile].ToString());
      for (int nFile = nLastBlockFile + 1; true; nFile++) {
          CBlockFileInfo info;
          if (pblocktree->ReadBlockFileInfo(nFile, info)) {
              vinfoBlockFile.push_back(info);
          } else {
              break;
          }
      }
  
      // Check presence of blk files
      LogPrintf("Checking all blk files are present...\n");
      set<int> setBlkDataFiles;
      BOOST_FOREACH(const PAIRTYPE(uint256, CBlockIndex*)& item, mapBlockIndex)
      {
          CBlockIndex* pindex = item.second;
          if (pindex->nStatus & BLOCK_HAVE_DATA) {
              setBlkDataFiles.insert(pindex->nFile);
          }
      }
      for (std::set<int>::iterator it = setBlkDataFiles.begin(); it != setBlkDataFiles.end(); it++)
      {
          CDiskBlockPos pos(*it, 0);
          if (CAutoFile(OpenBlockFile(pos, true), SER_DISK, CLIENT_VERSION).IsNull()) {
              return false;
          }
      }
  
      // Check whether we have ever pruned block & undo files
      pblocktree->ReadFlag("prunedblockfiles", fHavePruned);
      if (fHavePruned)
          LogPrintf("LoadBlockIndexDB(): Block files have previously been pruned\n");
  
      // Check whether we need to continue reindexing
      bool fReindexing = false;
      pblocktree->ReadReindexing(fReindexing);
      fReindex |= fReindexing;
  
      // Check whether we have a transaction index
      pblocktree->ReadFlag("txindex", fTxIndex);
      LogPrintf("%s: transaction index %s\n", __func__, fTxIndex ? "enabled" : "disabled");
  
      // Load pointer to end of best chain
      BlockMap::iterator it = mapBlockIndex.find(pcoinsTip->GetBestBlock());
      if (it == mapBlockIndex.end())
          return true;
      chainActive.SetTip(it->second);
  
      PruneBlockIndexCandidates();
  
      LogPrintf("%s: hashBestChain=%s height=%d date=%s progress=%f\n", __func__,
          chainActive.Tip()->GetBlockHash().ToString(), chainActive.Height(),
          DateTimeStrFormat("%Y-%m-%d %H:%M:%S", chainActive.Tip()->GetBlockTime()),
          Checkpoints::GuessVerificationProgress(chainparams.Checkpoints(), chainActive.Tip()));
  
      return true;
  }
  
  CVerifyDB::CVerifyDB()
  {
      uiInterface.ShowProgress(_("Verifying blocks..."), 0);
  }
  
  CVerifyDB::~CVerifyDB()
  {
      uiInterface.ShowProgress("", 100);
  }
  
  bool CVerifyDB::VerifyDB(const CChainParams& chainparams, CCoinsView *coinsview, int nCheckLevel, int nCheckDepth)
  {
      LOCK(cs_main);
      if (chainActive.Tip() == NULL || chainActive.Tip()->pprev == NULL)
          return true;
  
      // Verify blocks in the best chain
      if (nCheckDepth <= 0)
          nCheckDepth = 1000000000; // suffices until the year 19000
      if (nCheckDepth > chainActive.Height())
          nCheckDepth = chainActive.Height();
      nCheckLevel = std::max(0, std::min(4, nCheckLevel));
      LogPrintf("Verifying last %i blocks at level %i\n", nCheckDepth, nCheckLevel);
      CCoinsViewCache coins(coinsview);
      CBlockIndex* pindexState = chainActive.Tip();
      CBlockIndex* pindexFailure = NULL;
      int nGoodTransactions = 0;
      CValidationState state;
      for (CBlockIndex* pindex = chainActive.Tip(); pindex && pindex->pprev; pindex = pindex->pprev)
      {
          boost::this_thread::interruption_point();
          uiInterface.ShowProgress(_("Verifying blocks..."), std::max(1, std::min(99, (int)(((double)(chainActive.Height() - pindex->nHeight)) / (double)nCheckDepth * (nCheckLevel >= 4 ? 50 : 100)))));
          if (pindex->nHeight < chainActive.Height()-nCheckDepth)
              break;
          CBlock block;
          // check level 0: read from disk
          if (!ReadBlockFromDisk(block, pindex, chainparams.GetConsensus()))
              return error("VerifyDB(): *** ReadBlockFromDisk failed at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
          // check level 1: verify block validity
          if (nCheckLevel >= 1 && !CheckBlock(block, state))
              return error("VerifyDB(): *** found bad block at %d, hash=%s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
          // check level 2: verify undo validity
          if (nCheckLevel >= 2 && pindex) {
              CBlockUndo undo;
              CDiskBlockPos pos = pindex->GetUndoPos();
              if (!pos.IsNull()) {
                  if (!UndoReadFromDisk(undo, pos, pindex->pprev->GetBlockHash()))
                      return error("VerifyDB(): *** found bad undo data at %d, hash=%s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
              }
          }
          // check level 3: check for inconsistencies during memory-only disconnect of tip blocks
          if (nCheckLevel >= 3 && pindex == pindexState && (coins.DynamicMemoryUsage() + pcoinsTip->DynamicMemoryUsage()) <= nCoinCacheUsage) {
              bool fClean = true;
              if (!DisconnectBlock(block, state, pindex, coins, &fClean))
                  return error("VerifyDB(): *** irrecoverable inconsistency in block data at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
              pindexState = pindex->pprev;
              if (!fClean) {
                  nGoodTransactions = 0;
                  pindexFailure = pindex;
              } else
                  nGoodTransactions += block.vtx.size();
          }
          if (ShutdownRequested())
              return true;
      }
      if (pindexFailure)
          return error("VerifyDB(): *** coin database inconsistencies found (last %i blocks, %i good transactions before that)\n", chainActive.Height() - pindexFailure->nHeight + 1, nGoodTransactions);
  
      // check level 4: try reconnecting blocks
      if (nCheckLevel >= 4) {
          CBlockIndex *pindex = pindexState;
          while (pindex != chainActive.Tip()) {
              boost::this_thread::interruption_point();
              uiInterface.ShowProgress(_("Verifying blocks..."), std::max(1, std::min(99, 100 - (int)(((double)(chainActive.Height() - pindex->nHeight)) / (double)nCheckDepth * 50))));
              pindex = chainActive.Next(pindex);
              CBlock block;
              if (!ReadBlockFromDisk(block, pindex, chainparams.GetConsensus()))
                  return error("VerifyDB(): *** ReadBlockFromDisk failed at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
              if (!ConnectBlock(block, state, pindex, coins))
                  return error("VerifyDB(): *** found unconnectable block at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
          }
      }
  
      LogPrintf("No coin database inconsistencies in last %i blocks (%i transactions)\n", chainActive.Height() - pindexState->nHeight, nGoodTransactions);
  
      return true;
  }
  
  void UnloadBlockIndex()
  {
      LOCK(cs_main);
      setBlockIndexCandidates.clear();
      chainActive.SetTip(NULL);
      pindexBestInvalid = NULL;
      pindexBestHeader = NULL;
      mempool.clear();
      mapOrphanTransactions.clear();
      mapOrphanTransactionsByPrev.clear();
      nSyncStarted = 0;
      mapBlocksUnlinked.clear();
      vinfoBlockFile.clear();
      nLastBlockFile = 0;
      nBlockSequenceId = 1;
      mapBlockSource.clear();
      mapBlocksInFlight.clear();
      nPreferredDownload = 0;
      setDirtyBlockIndex.clear();
      setDirtyFileInfo.clear();
      mapNodeState.clear();
      recentRejects.reset(NULL);
      versionbitscache.Clear();
      for (int b = 0; b < VERSIONBITS_NUM_BITS; b++) {
          warningcache[b].clear();
      }
  
      BOOST_FOREACH(BlockMap::value_type& entry, mapBlockIndex) {
          delete entry.second;
      }
      mapBlockIndex.clear();
      fHavePruned = false;
  }
  
  bool LoadBlockIndex()
  {
      // Load block index from databases
      if (!fReindex && !LoadBlockIndexDB())
          return false;
      return true;
  }
  
  bool InitBlockIndex(const CChainParams& chainparams) 
  {
      LOCK(cs_main);
  
      // Initialize global variables that cannot be constructed at startup.
      recentRejects.reset(new CRollingBloomFilter(120000, 0.000001));
  
      // Check whether we're already initialized
      if (chainActive.Genesis() != NULL)
          return true;
  
      // Use the provided setting for -txindex in the new database
      fTxIndex = GetBoolArg("-txindex", DEFAULT_TXINDEX);
      pblocktree->WriteFlag("txindex", fTxIndex);
      LogPrintf("Initializing databases...\n");
  
      // Only add the genesis block if not reindexing (in which case we reuse the one already on disk)
      if (!fReindex) {
          try {
              CBlock &block = const_cast<CBlock&>(chainparams.GenesisBlock());
              // Start new block file
              unsigned int nBlockSize = ::GetSerializeSize(block, SER_DISK, CLIENT_VERSION);
              CDiskBlockPos blockPos;
              CValidationState state;
              if (!FindBlockPos(state, blockPos, nBlockSize+8, 0, block.GetBlockTime()))
                  return error("LoadBlockIndex(): FindBlockPos failed");
              if (!WriteBlockToDisk(block, blockPos, chainparams.MessageStart()))
                  return error("LoadBlockIndex(): writing genesis block to disk failed");
              CBlockIndex *pindex = AddToBlockIndex(block);
              if (!ReceivedBlockTransactions(block, state, pindex, blockPos))
                  return error("LoadBlockIndex(): genesis block not accepted");
              if (!ActivateBestChain(state, chainparams, &block))
                  return error("LoadBlockIndex(): genesis block cannot be activated");
              // Force a chainstate write so that when we VerifyDB in a moment, it doesn't check stale data
              return FlushStateToDisk(state, FLUSH_STATE_ALWAYS);
          } catch (const std::runtime_error& e) {
              return error("LoadBlockIndex(): failed to initialize block database: %s", e.what());
          }
      }
  
      return true;
  }
  
  bool LoadExternalBlockFile(const CChainParams& chainparams, FILE* fileIn, CDiskBlockPos *dbp)
  {
      // Map of disk positions for blocks with unknown parent (only used for reindex)
      static std::multimap<uint256, CDiskBlockPos> mapBlocksUnknownParent;
      int64_t nStart = GetTimeMillis();
  
      int nLoaded = 0;
      try {
          // This takes over fileIn and calls fclose() on it in the CBufferedFile destructor
          CBufferedFile blkdat(fileIn, 2*MAX_BLOCK_SIZE, MAX_BLOCK_SIZE+8, SER_DISK, CLIENT_VERSION);
          uint64_t nRewind = blkdat.GetPos();
          while (!blkdat.eof()) {
              boost::this_thread::interruption_point();
  
              blkdat.SetPos(nRewind);
              nRewind++; // start one byte further next time, in case of failure
              blkdat.SetLimit(); // remove former limit
              unsigned int nSize = 0;
              try {
                  // locate a header
                  unsigned char buf[MESSAGE_START_SIZE];
                  blkdat.FindByte(chainparams.MessageStart()[0]);
                  nRewind = blkdat.GetPos()+1;
                  blkdat >> FLATDATA(buf);
                  if (memcmp(buf, chainparams.MessageStart(), MESSAGE_START_SIZE))
                      continue;
                  // read size
                  blkdat >> nSize;
                  if (nSize < 80 || nSize > MAX_BLOCK_SIZE)
                      continue;
              } catch (const std::exception&) {
                  // no valid block header found; don't complain
                  break;
              }
              try {
                  // read block
                  uint64_t nBlockPos = blkdat.GetPos();
                  if (dbp)
                      dbp->nPos = nBlockPos;
                  blkdat.SetLimit(nBlockPos + nSize);
                  blkdat.SetPos(nBlockPos);
                  CBlock block;
                  blkdat >> block;
                  nRewind = blkdat.GetPos();
  
                  // detect out of order blocks, and store them for later
                  uint256 hash = block.GetHash();
                  if (hash != chainparams.GetConsensus().hashGenesisBlock && mapBlockIndex.find(block.hashPrevBlock) == mapBlockIndex.end()) {
                      LogPrint("reindex", "%s: Out of order block %s, parent %s not known\n", __func__, hash.ToString(),
                              block.hashPrevBlock.ToString());
                      if (dbp)
                          mapBlocksUnknownParent.insert(std::make_pair(block.hashPrevBlock, *dbp));
                      continue;
                  }
  
                  // process in case the block isn't known yet
                  if (mapBlockIndex.count(hash) == 0 || (mapBlockIndex[hash]->nStatus & BLOCK_HAVE_DATA) == 0) {
                      CValidationState state;
                      if (ProcessNewBlock(state, chainparams, NULL, &block, true, dbp))
                          nLoaded++;
                      if (state.IsError())
                          break;
                  } else if (hash != chainparams.GetConsensus().hashGenesisBlock && mapBlockIndex[hash]->nHeight % 1000 == 0) {
                      LogPrintf("Block Import: already had block %s at height %d\n", hash.ToString(), mapBlockIndex[hash]->nHeight);
                  }
  
                  // Recursively process earlier encountered successors of this block
                  deque<uint256> queue;
                  queue.push_back(hash);
                  while (!queue.empty()) {
                      uint256 head = queue.front();
                      queue.pop_front();
                      std::pair<std::multimap<uint256, CDiskBlockPos>::iterator, std::multimap<uint256, CDiskBlockPos>::iterator> range = mapBlocksUnknownParent.equal_range(head);
                      while (range.first != range.second) {
                          std::multimap<uint256, CDiskBlockPos>::iterator it = range.first;
                          if (ReadBlockFromDisk(block, it->second, chainparams.GetConsensus()))
                          {
                              LogPrintf("%s: Processing out of order child %s of %s\n", __func__, block.GetHash().ToString(),
                                      head.ToString());
                              CValidationState dummy;
                              if (ProcessNewBlock(dummy, chainparams, NULL, &block, true, &it->second))
                              {
                                  nLoaded++;
                                  queue.push_back(block.GetHash());
                              }
                          }
                          range.first++;
                          mapBlocksUnknownParent.erase(it);
                      }
                  }
              } catch (const std::exception& e) {
                  LogPrintf("%s: Deserialize or I/O error - %s\n", __func__, e.what());
              }
          }
      } catch (const std::runtime_error& e) {
          AbortNode(std::string("System error: ") + e.what());
      }
      if (nLoaded > 0)
          LogPrintf("Loaded %i blocks from external file in %dms\n", nLoaded, GetTimeMillis() - nStart);
      return nLoaded > 0;
  }
  
  void static CheckBlockIndex(const Consensus::Params& consensusParams)
  {
      if (!fCheckBlockIndex) {
          return;
      }
  
      LOCK(cs_main);
  
      // During a reindex, we read the genesis block and call CheckBlockIndex before ActivateBestChain,
      // so we have the genesis block in mapBlockIndex but no active chain.  (A few of the tests when
      // iterating the block tree require that chainActive has been initialized.)
      if (chainActive.Height() < 0) {
          assert(mapBlockIndex.size() <= 1);
          return;
      }
  
      // Build forward-pointing map of the entire block tree.
      std::multimap<CBlockIndex*,CBlockIndex*> forward;
      for (BlockMap::iterator it = mapBlockIndex.begin(); it != mapBlockIndex.end(); it++) {
          forward.insert(std::make_pair(it->second->pprev, it->second));
      }
  
      assert(forward.size() == mapBlockIndex.size());
  
      std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> rangeGenesis = forward.equal_range(NULL);
      CBlockIndex *pindex = rangeGenesis.first->second;
      rangeGenesis.first++;
      assert(rangeGenesis.first == rangeGenesis.second); // There is only one index entry with parent NULL.
  
      // Iterate over the entire block tree, using depth-first search.
      // Along the way, remember whether there are blocks on the path from genesis
      // block being explored which are the first to have certain properties.
      size_t nNodes = 0;
      int nHeight = 0;
      CBlockIndex* pindexFirstInvalid = NULL; // Oldest ancestor of pindex which is invalid.
      CBlockIndex* pindexFirstMissing = NULL; // Oldest ancestor of pindex which does not have BLOCK_HAVE_DATA.
      CBlockIndex* pindexFirstNeverProcessed = NULL; // Oldest ancestor of pindex for which nTx == 0.
      CBlockIndex* pindexFirstNotTreeValid = NULL; // Oldest ancestor of pindex which does not have BLOCK_VALID_TREE (regardless of being valid or not).
      CBlockIndex* pindexFirstNotTransactionsValid = NULL; // Oldest ancestor of pindex which does not have BLOCK_VALID_TRANSACTIONS (regardless of being valid or not).
      CBlockIndex* pindexFirstNotChainValid = NULL; // Oldest ancestor of pindex which does not have BLOCK_VALID_CHAIN (regardless of being valid or not).
      CBlockIndex* pindexFirstNotScriptsValid = NULL; // Oldest ancestor of pindex which does not have BLOCK_VALID_SCRIPTS (regardless of being valid or not).
      while (pindex != NULL) {
          nNodes++;
          if (pindexFirstInvalid == NULL && pindex->nStatus & BLOCK_FAILED_VALID) pindexFirstInvalid = pindex;
          if (pindexFirstMissing == NULL && !(pindex->nStatus & BLOCK_HAVE_DATA)) pindexFirstMissing = pindex;
          if (pindexFirstNeverProcessed == NULL && pindex->nTx == 0) pindexFirstNeverProcessed = pindex;
          if (pindex->pprev != NULL && pindexFirstNotTreeValid == NULL && (pindex->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_TREE) pindexFirstNotTreeValid = pindex;
          if (pindex->pprev != NULL && pindexFirstNotTransactionsValid == NULL && (pindex->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_TRANSACTIONS) pindexFirstNotTransactionsValid = pindex;
          if (pindex->pprev != NULL && pindexFirstNotChainValid == NULL && (pindex->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_CHAIN) pindexFirstNotChainValid = pindex;
          if (pindex->pprev != NULL && pindexFirstNotScriptsValid == NULL && (pindex->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_SCRIPTS) pindexFirstNotScriptsValid = pindex;
  
          // Begin: actual consistency checks.
          if (pindex->pprev == NULL) {
              // Genesis block checks.
              assert(pindex->GetBlockHash() == consensusParams.hashGenesisBlock); // Genesis block's hash must match.
              assert(pindex == chainActive.Genesis()); // The current active chain's genesis block must be this block.
          }
          if (pindex->nChainTx == 0) assert(pindex->nSequenceId == 0);  // nSequenceId can't be set for blocks that aren't linked
          // VALID_TRANSACTIONS is equivalent to nTx > 0 for all nodes (whether or not pruning has occurred).
          // HAVE_DATA is only equivalent to nTx > 0 (or VALID_TRANSACTIONS) if no pruning has occurred.
          if (!fHavePruned) {
              // If we've never pruned, then HAVE_DATA should be equivalent to nTx > 0
              assert(!(pindex->nStatus & BLOCK_HAVE_DATA) == (pindex->nTx == 0));
              assert(pindexFirstMissing == pindexFirstNeverProcessed);
          } else {
              // If we have pruned, then we can only say that HAVE_DATA implies nTx > 0
              if (pindex->nStatus & BLOCK_HAVE_DATA) assert(pindex->nTx > 0);
          }
          if (pindex->nStatus & BLOCK_HAVE_UNDO) assert(pindex->nStatus & BLOCK_HAVE_DATA);
          assert(((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_TRANSACTIONS) == (pindex->nTx > 0)); // This is pruning-independent.
          // All parents having had data (at some point) is equivalent to all parents being VALID_TRANSACTIONS, which is equivalent to nChainTx being set.
          assert((pindexFirstNeverProcessed != NULL) == (pindex->nChainTx == 0)); // nChainTx != 0 is used to signal that all parent blocks have been processed (but may have been pruned).
          assert((pindexFirstNotTransactionsValid != NULL) == (pindex->nChainTx == 0));
          assert(pindex->nHeight == nHeight); // nHeight must be consistent.
          assert(pindex->pprev == NULL || pindex->nChainWork >= pindex->pprev->nChainWork); // For every block except the genesis block, the chainwork must be larger than the parent's.
          assert(nHeight < 2 || (pindex->pskip && (pindex->pskip->nHeight < nHeight))); // The pskip pointer must point back for all but the first 2 blocks.
          assert(pindexFirstNotTreeValid == NULL); // All mapBlockIndex entries must at least be TREE valid
          if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_TREE) assert(pindexFirstNotTreeValid == NULL); // TREE valid implies all parents are TREE valid
          if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_CHAIN) assert(pindexFirstNotChainValid == NULL); // CHAIN valid implies all parents are CHAIN valid
          if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_SCRIPTS) assert(pindexFirstNotScriptsValid == NULL); // SCRIPTS valid implies all parents are SCRIPTS valid
          if (pindexFirstInvalid == NULL) {
              // Checks for not-invalid blocks.
              assert((pindex->nStatus & BLOCK_FAILED_MASK) == 0); // The failed mask cannot be set for blocks without invalid parents.
          }
          if (!CBlockIndexWorkComparator()(pindex, chainActive.Tip()) && pindexFirstNeverProcessed == NULL) {
              if (pindexFirstInvalid == NULL) {
                  // If this block sorts at least as good as the current tip and
                  // is valid and we have all data for its parents, it must be in
                  // setBlockIndexCandidates.  chainActive.Tip() must also be there
                  // even if some data has been pruned.
                  if (pindexFirstMissing == NULL || pindex == chainActive.Tip()) {
                      assert(setBlockIndexCandidates.count(pindex));
                  }
                  // If some parent is missing, then it could be that this block was in
                  // setBlockIndexCandidates but had to be removed because of the missing data.
                  // In this case it must be in mapBlocksUnlinked -- see test below.
              }
          } else { // If this block sorts worse than the current tip or some ancestor's block has never been seen, it cannot be in setBlockIndexCandidates.
              assert(setBlockIndexCandidates.count(pindex) == 0);
          }
          // Check whether this block is in mapBlocksUnlinked.
          std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> rangeUnlinked = mapBlocksUnlinked.equal_range(pindex->pprev);
          bool foundInUnlinked = false;
          while (rangeUnlinked.first != rangeUnlinked.second) {
              assert(rangeUnlinked.first->first == pindex->pprev);
              if (rangeUnlinked.first->second == pindex) {
                  foundInUnlinked = true;
                  break;
              }
              rangeUnlinked.first++;
          }
          if (pindex->pprev && (pindex->nStatus & BLOCK_HAVE_DATA) && pindexFirstNeverProcessed != NULL && pindexFirstInvalid == NULL) {
              // If this block has block data available, some parent was never received, and has no invalid parents, it must be in mapBlocksUnlinked.
              assert(foundInUnlinked);
          }
          if (!(pindex->nStatus & BLOCK_HAVE_DATA)) assert(!foundInUnlinked); // Can't be in mapBlocksUnlinked if we don't HAVE_DATA
          if (pindexFirstMissing == NULL) assert(!foundInUnlinked); // We aren't missing data for any parent -- cannot be in mapBlocksUnlinked.
          if (pindex->pprev && (pindex->nStatus & BLOCK_HAVE_DATA) && pindexFirstNeverProcessed == NULL && pindexFirstMissing != NULL) {
              // We HAVE_DATA for this block, have received data for all parents at some point, but we're currently missing data for some parent.
              assert(fHavePruned); // We must have pruned.
              // This block may have entered mapBlocksUnlinked if:
              //  - it has a descendant that at some point had more work than the
              //    tip, and
              //  - we tried switching to that descendant but were missing
              //    data for some intermediate block between chainActive and the
              //    tip.
              // So if this block is itself better than chainActive.Tip() and it wasn't in
              // setBlockIndexCandidates, then it must be in mapBlocksUnlinked.
              if (!CBlockIndexWorkComparator()(pindex, chainActive.Tip()) && setBlockIndexCandidates.count(pindex) == 0) {
                  if (pindexFirstInvalid == NULL) {
                      assert(foundInUnlinked);
                  }
              }
          }
          // assert(pindex->GetBlockHash() == pindex->GetBlockHeader().GetHash()); // Perhaps too slow
          // End: actual consistency checks.
  
          // Try descending into the first subnode.
          std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> range = forward.equal_range(pindex);
          if (range.first != range.second) {
              // A subnode was found.
              pindex = range.first->second;
              nHeight++;
              continue;
          }
          // This is a leaf node.
          // Move upwards until we reach a node of which we have not yet visited the last child.
          while (pindex) {
              // We are going to either move to a parent or a sibling of pindex.
              // If pindex was the first with a certain property, unset the corresponding variable.
              if (pindex == pindexFirstInvalid) pindexFirstInvalid = NULL;
              if (pindex == pindexFirstMissing) pindexFirstMissing = NULL;
              if (pindex == pindexFirstNeverProcessed) pindexFirstNeverProcessed = NULL;
              if (pindex == pindexFirstNotTreeValid) pindexFirstNotTreeValid = NULL;
              if (pindex == pindexFirstNotTransactionsValid) pindexFirstNotTransactionsValid = NULL;
              if (pindex == pindexFirstNotChainValid) pindexFirstNotChainValid = NULL;
              if (pindex == pindexFirstNotScriptsValid) pindexFirstNotScriptsValid = NULL;
              // Find our parent.
              CBlockIndex* pindexPar = pindex->pprev;
              // Find which child we just visited.
              std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> rangePar = forward.equal_range(pindexPar);
              while (rangePar.first->second != pindex) {
                  assert(rangePar.first != rangePar.second); // Our parent must have at least the node we're coming from as child.
                  rangePar.first++;
              }
              // Proceed to the next one.
              rangePar.first++;
              if (rangePar.first != rangePar.second) {
                  // Move to the sibling.
                  pindex = rangePar.first->second;
                  break;
              } else {
                  // Move up further.
                  pindex = pindexPar;
                  nHeight--;
                  continue;
              }
          }
      }
  
      // Check that we actually traversed the entire map.
      assert(nNodes == forward.size());
  }
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // CAlert
  //
  
  std::string GetWarnings(const std::string& strFor)
  {
      int nPriority = 0;
      string strStatusBar;
      string strRPC;
      string strGUI;
  
      if (!CLIENT_VERSION_IS_RELEASE) {
          strStatusBar = "This is a pre-release test build - use at your own risk - do not use for mining or merchant applications";
          strGUI = _("This is a pre-release test build - use at your own risk - do not use for mining or merchant applications");
      }
  
      if (GetBoolArg("-testsafemode", DEFAULT_TESTSAFEMODE))
          strStatusBar = strRPC = strGUI = "testsafemode enabled";
  
      // Misc warnings like out of disk space and clock is wrong
      if (strMiscWarning != "")
      {
          nPriority = 1000;
          strStatusBar = strGUI = strMiscWarning;
      }
  
      if (fLargeWorkForkFound)
      {
          nPriority = 2000;
          strStatusBar = strRPC = "Warning: The network does not appear to fully agree! Some miners appear to be experiencing issues.";
          strGUI = _("Warning: The network does not appear to fully agree! Some miners appear to be experiencing issues.");
      }
      else if (fLargeWorkInvalidChainFound)
      {
          nPriority = 2000;
          strStatusBar = strRPC = "Warning: We do not appear to fully agree with our peers! You may need to upgrade, or other nodes may need to upgrade.";
          strGUI = _("Warning: We do not appear to fully agree with our peers! You may need to upgrade, or other nodes may need to upgrade.");
      }
  
      // Alerts
      {
          LOCK(cs_mapAlerts);
          BOOST_FOREACH(PAIRTYPE(const uint256, CAlert)& item, mapAlerts)
          {
              const CAlert& alert = item.second;
              if (alert.AppliesToMe() && alert.nPriority > nPriority)
              {
                  nPriority = alert.nPriority;
                  strStatusBar = strGUI = alert.strStatusBar;
              }
          }
      }
  
      if (strFor == "gui")
          return strGUI;
      else if (strFor == "statusbar")
          return strStatusBar;
      else if (strFor == "rpc")
          return strRPC;
      assert(!"GetWarnings(): invalid parameter");
      return "error";
  }
  
  
  
  
  
  
  
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // Messages
  //
  
  
  bool static AlreadyHave(const CInv& inv) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
  {
      switch (inv.type)
      {
      case MSG_TX:
          {
              assert(recentRejects);
              if (chainActive.Tip()->GetBlockHash() != hashRecentRejectsChainTip)
              {
                  // If the chain tip has changed previously rejected transactions
                  // might be now valid, e.g. due to a nLockTime'd tx becoming valid,
                  // or a double-spend. Reset the rejects filter and give those
                  // txs a second chance.
                  hashRecentRejectsChainTip = chainActive.Tip()->GetBlockHash();
                  recentRejects->reset();
              }
  
              return recentRejects->contains(inv.hash) ||
                     mempool.exists(inv.hash) ||
                     mapOrphanTransactions.count(inv.hash) ||
                     pcoinsTip->HaveCoins(inv.hash);
          }
      case MSG_BLOCK:
          return mapBlockIndex.count(inv.hash);
      }
      // Don't know what it is, just say we already got one
      return true;
  }
  
  void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParams)
  {
      std::deque<CInv>::iterator it = pfrom->vRecvGetData.begin();
  
      vector<CInv> vNotFound;
  
      LOCK(cs_main);
  
      while (it != pfrom->vRecvGetData.end()) {
          // Don't bother if send buffer is too full to respond anyway
          if (pfrom->nSendSize >= SendBufferSize())
              break;
  
          const CInv &inv = *it;
          {
              boost::this_thread::interruption_point();
              it++;
  
              if (inv.type == MSG_BLOCK || inv.type == MSG_FILTERED_BLOCK)
              {
                  bool send = false;
                  BlockMap::iterator mi = mapBlockIndex.find(inv.hash);
                  if (mi != mapBlockIndex.end())
                  {
                      if (chainActive.Contains(mi->second)) {
                          send = true;
                      } else {
                          static const int nOneMonth = 30 * 24 * 60 * 60;
                          // To prevent fingerprinting attacks, only send blocks outside of the active
                          // chain if they are valid, and no more than a month older (both in time, and in
                          // best equivalent proof of work) than the best header chain we know about.
                          send = mi->second->IsValid(BLOCK_VALID_SCRIPTS) && (pindexBestHeader != NULL) &&
                              (pindexBestHeader->GetBlockTime() - mi->second->GetBlockTime() < nOneMonth) &&
                              (GetBlockProofEquivalentTime(*pindexBestHeader, *mi->second, *pindexBestHeader, consensusParams) < nOneMonth);
                          if (!send) {
                              LogPrintf("%s: ignoring request from peer=%i for old block that isn't in the main chain\n", __func__, pfrom->GetId());
                          }
                      }
                  }
                  // disconnect node in case we have reached the outbound limit for serving historical blocks
                  // never disconnect whitelisted nodes
                  static const int nOneWeek = 7 * 24 * 60 * 60; // assume > 1 week = historical
                  if (send && CNode::OutboundTargetReached(true) && ( ((pindexBestHeader != NULL) && (pindexBestHeader->GetBlockTime() - mi->second->GetBlockTime() > nOneWeek)) || inv.type == MSG_FILTERED_BLOCK) && !pfrom->fWhitelisted)
                  {
                      LogPrint("net", "historical block serving limit reached, disconnect peer=%d\n", pfrom->GetId());
  
                      //disconnect node
                      pfrom->fDisconnect = true;
                      send = false;
                  }
                  // Pruned nodes may have deleted the block, so check whether
                  // it's available before trying to send.
                  if (send && (mi->second->nStatus & BLOCK_HAVE_DATA))
                  {
                      // Send block from disk
                      CBlock block;
                      if (!ReadBlockFromDisk(block, (*mi).second, consensusParams))
                          assert(!"cannot load block from disk");
                      if (inv.type == MSG_BLOCK)
                          pfrom->PushMessage(NetMsgType::BLOCK, block);
                      else // MSG_FILTERED_BLOCK)
                      {
                          LOCK(pfrom->cs_filter);
                          if (pfrom->pfilter)
                          {
                              CMerkleBlock merkleBlock(block, *pfrom->pfilter);
                              pfrom->PushMessage(NetMsgType::MERKLEBLOCK, merkleBlock);
                              // CMerkleBlock just contains hashes, so also push any transactions in the block the client did not see
                              // This avoids hurting performance by pointlessly requiring a round-trip
                              // Note that there is currently no way for a node to request any single transactions we didn't send here -
                              // they must either disconnect and retry or request the full block.
                              // Thus, the protocol spec specified allows for us to provide duplicate txn here,
                              // however we MUST always provide at least what the remote peer needs
                              typedef std::pair<unsigned int, uint256> PairType;
                              BOOST_FOREACH(PairType& pair, merkleBlock.vMatchedTxn)
                                  pfrom->PushMessage(NetMsgType::TX, block.vtx[pair.first]);
                          }
                          // else
                              // no response
                      }
  
                      // Trigger the peer node to send a getblocks request for the next batch of inventory
                      if (inv.hash == pfrom->hashContinue)
                      {
                          // Bypass PushInventory, this must send even if redundant,
                          // and we want it right after the last block so they don't
                          // wait for other stuff first.
                          vector<CInv> vInv;
                          vInv.push_back(CInv(MSG_BLOCK, chainActive.Tip()->GetBlockHash()));
                          pfrom->PushMessage(NetMsgType::INV, vInv);
                          pfrom->hashContinue.SetNull();
                      }
                  }
              }
              else if (inv.IsKnownType())
              {
                  // Send stream from relay memory
                  bool pushed = false;
                  {
                      LOCK(cs_mapRelay);
                      map<CInv, CDataStream>::iterator mi = mapRelay.find(inv);
                      if (mi != mapRelay.end()) {
                          pfrom->PushMessage(inv.GetCommand(), (*mi).second);
                          pushed = true;
                      }
                  }
                  if (!pushed && inv.type == MSG_TX) {
                      CTransaction tx;
                      if (mempool.lookup(inv.hash, tx)) {
                          CDataStream ss(SER_NETWORK, PROTOCOL_VERSION);
                          ss.reserve(1000);
                          ss << tx;
                          pfrom->PushMessage(NetMsgType::TX, ss);
                          pushed = true;
                      }
                  }
                  if (!pushed) {
                      vNotFound.push_back(inv);
                  }
              }
  
              // Track requests for our stuff.
              GetMainSignals().Inventory(inv.hash);
  
              if (inv.type == MSG_BLOCK || inv.type == MSG_FILTERED_BLOCK)
                  break;
          }
      }
  
      pfrom->vRecvGetData.erase(pfrom->vRecvGetData.begin(), it);
  
      if (!vNotFound.empty()) {
          // Let the peer know that we didn't find what it asked for, so it doesn't
          // have to wait around forever. Currently only SPV clients actually care
          // about this message: it's needed when they are recursively walking the
          // dependencies of relevant unconfirmed transactions. SPV clients want to
          // do that because they want to know about (and store and rebroadcast and
          // risk analyze) the dependencies of transactions relevant to them, without
          // having to download the entire memory pool.
          pfrom->PushMessage(NetMsgType::NOTFOUND, vNotFound);
      }
  }
  
  bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv, int64_t nTimeReceived)
  {
      const CChainParams& chainparams = Params();
      RandAddSeedPerfmon();
      LogPrint("net", "received: %s (%u bytes) peer=%d\n", SanitizeString(strCommand), vRecv.size(), pfrom->id);
      if (mapArgs.count("-dropmessagestest") && GetRand(atoi(mapArgs["-dropmessagestest"])) == 0)
      {
          LogPrintf("dropmessagestest DROPPING RECV MESSAGE\n");
          return true;
      }
  
  
      if (!(nLocalServices & NODE_BLOOM) &&
                (strCommand == NetMsgType::FILTERLOAD ||
                 strCommand == NetMsgType::FILTERADD ||
                 strCommand == NetMsgType::FILTERCLEAR))
      {
          if (pfrom->nVersion >= NO_BLOOM_VERSION) {
              Misbehaving(pfrom->GetId(), 100);
              return false;
          } else if (GetBoolArg("-enforcenodebloom", false)) {
              pfrom->fDisconnect = true;
              return false;
          }
      }
  
  
      if (strCommand == NetMsgType::VERSION)
      {
          // Each connection can only send one version message
          if (pfrom->nVersion != 0)
          {
              pfrom->PushMessage(NetMsgType::REJECT, strCommand, REJECT_DUPLICATE, string("Duplicate version message"));
              Misbehaving(pfrom->GetId(), 1);
              return false;
          }
  
          int64_t nTime;
          CAddress addrMe;
          CAddress addrFrom;
          uint64_t nNonce = 1;
          vRecv >> pfrom->nVersion >> pfrom->nServices >> nTime >> addrMe;
          if (pfrom->nVersion < MIN_PEER_PROTO_VERSION)
          {
              // disconnect from peers older than this proto version
              LogPrintf("peer=%d using obsolete version %i; disconnecting\n", pfrom->id, pfrom->nVersion);
              pfrom->PushMessage(NetMsgType::REJECT, strCommand, REJECT_OBSOLETE,
                                 strprintf("Version must be %d or greater", MIN_PEER_PROTO_VERSION));
              pfrom->fDisconnect = true;
              return false;
          }
  
          if (pfrom->nVersion == 10300)
              pfrom->nVersion = 300;
          if (!vRecv.empty())
              vRecv >> addrFrom >> nNonce;
          if (!vRecv.empty()) {
              vRecv >> LIMITED_STRING(pfrom->strSubVer, MAX_SUBVERSION_LENGTH);
              pfrom->cleanSubVer = SanitizeString(pfrom->strSubVer);
          }
          if (!vRecv.empty())
              vRecv >> pfrom->nStartingHeight;
          if (!vRecv.empty())
              vRecv >> pfrom->fRelayTxes; // set to true after we get the first filter* message
          else
              pfrom->fRelayTxes = true;
  
          // Disconnect if we connected to ourself
          if (nNonce == nLocalHostNonce && nNonce > 1)
          {
              LogPrintf("connected to self at %s, disconnecting\n", pfrom->addr.ToString());
              pfrom->fDisconnect = true;
              return true;
          }
  
          pfrom->addrLocal = addrMe;
          if (pfrom->fInbound && addrMe.IsRoutable())
          {
              SeenLocal(addrMe);
          }
  
          // Be shy and don't send version until we hear
          if (pfrom->fInbound)
              pfrom->PushVersion();
  
          pfrom->fClient = !(pfrom->nServices & NODE_NETWORK);
  
          // Potentially mark this peer as a preferred download peer.
          UpdatePreferredDownload(pfrom, State(pfrom->GetId()));
  
          // Change version
          pfrom->PushMessage(NetMsgType::VERACK);
          pfrom->ssSend.SetVersion(min(pfrom->nVersion, PROTOCOL_VERSION));
  
          if (!pfrom->fInbound)
          {
              // Advertise our address
              if (fListen && !IsInitialBlockDownload())
              {
                  CAddress addr = GetLocalAddress(&pfrom->addr);
                  if (addr.IsRoutable())
                  {
                      LogPrintf("ProcessMessages: advertizing address %s\n", addr.ToString());
                      pfrom->PushAddress(addr);
                  } else if (IsPeerAddrLocalGood(pfrom)) {
                      addr.SetIP(pfrom->addrLocal);
                      LogPrintf("ProcessMessages: advertizing address %s\n", addr.ToString());
                      pfrom->PushAddress(addr);
                  }
              }
  
              // Get recent addresses
              if (pfrom->fOneShot || pfrom->nVersion >= CADDR_TIME_VERSION || addrman.size() < 1000)
              {
                  pfrom->PushMessage(NetMsgType::GETADDR);
                  pfrom->fGetAddr = true;
              }
              addrman.Good(pfrom->addr);
          } else {
              if (((CNetAddr)pfrom->addr) == (CNetAddr)addrFrom)
              {
                  addrman.Add(addrFrom, addrFrom);
                  addrman.Good(addrFrom);
              }
          }
  
          // Relay alerts
          {
              LOCK(cs_mapAlerts);
              BOOST_FOREACH(PAIRTYPE(const uint256, CAlert)& item, mapAlerts)
                  item.second.RelayTo(pfrom);
          }
  
          pfrom->fSuccessfullyConnected = true;
  
          string remoteAddr;
          if (fLogIPs)
              remoteAddr = ", peeraddr=" + pfrom->addr.ToString();
  
          LogPrintf("receive version message: %s: version %d, blocks=%d, us=%s, peer=%d%s\n",
                    pfrom->cleanSubVer, pfrom->nVersion,
                    pfrom->nStartingHeight, addrMe.ToString(), pfrom->id,
                    remoteAddr);
  
          int64_t nTimeOffset = nTime - GetTime();
          pfrom->nTimeOffset = nTimeOffset;
          AddTimeData(pfrom->addr, nTimeOffset);
      }
  
  
      else if (pfrom->nVersion == 0)
      {
          // Must have a version message before anything else
          Misbehaving(pfrom->GetId(), 1);
          return false;
      }
  
  
      else if (strCommand == NetMsgType::VERACK)
      {
          pfrom->SetRecvVersion(min(pfrom->nVersion, PROTOCOL_VERSION));
  
          // Mark this node as currently connected, so we update its timestamp later.
          if (pfrom->fNetworkNode) {
              LOCK(cs_main);
              State(pfrom->GetId())->fCurrentlyConnected = true;
          }
  
          if (pfrom->nVersion >= SENDHEADERS_VERSION) {
              // Tell our peer we prefer to receive headers rather than inv's
              // We send this to non-NODE NETWORK peers as well, because even
              // non-NODE NETWORK peers can announce blocks (such as pruning
              // nodes)
              pfrom->PushMessage(NetMsgType::SENDHEADERS);
          }
      }
  
  
      else if (strCommand == NetMsgType::ADDR)
      {
          vector<CAddress> vAddr;
          vRecv >> vAddr;
  
          // Don't want addr from older versions unless seeding
          if (pfrom->nVersion < CADDR_TIME_VERSION && addrman.size() > 1000)
              return true;
          if (vAddr.size() > 1000)
          {
              Misbehaving(pfrom->GetId(), 20);
              return error("message addr size() = %u", vAddr.size());
          }
  
          // Store the new addresses
          vector<CAddress> vAddrOk;
          int64_t nNow = GetAdjustedTime();
          int64_t nSince = nNow - 10 * 60;
          BOOST_FOREACH(CAddress& addr, vAddr)
          {
              boost::this_thread::interruption_point();
  
              if (addr.nTime <= 100000000 || addr.nTime > nNow + 10 * 60)
                  addr.nTime = nNow - 5 * 24 * 60 * 60;
              pfrom->AddAddressKnown(addr);
              bool fReachable = IsReachable(addr);
              if (addr.nTime > nSince && !pfrom->fGetAddr && vAddr.size() <= 10 && addr.IsRoutable())
              {
                  // Relay to a limited number of other nodes
                  {
                      LOCK(cs_vNodes);
                      // Use deterministic randomness to send to the same nodes for 24 hours
                      // at a time so the addrKnowns of the chosen nodes prevent repeats
                      static uint256 hashSalt;
                      if (hashSalt.IsNull())
                          hashSalt = GetRandHash();
                      uint64_t hashAddr = addr.GetHash();
                      uint256 hashRand = ArithToUint256(UintToArith256(hashSalt) ^ (hashAddr<<32) ^ ((GetTime()+hashAddr)/(24*60*60)));
                      hashRand = Hash(BEGIN(hashRand), END(hashRand));
                      multimap<uint256, CNode*> mapMix;
                      BOOST_FOREACH(CNode* pnode, vNodes)
                      {
                          if (pnode->nVersion < CADDR_TIME_VERSION)
                              continue;
                          unsigned int nPointer;
                          memcpy(&nPointer, &pnode, sizeof(nPointer));
                          uint256 hashKey = ArithToUint256(UintToArith256(hashRand) ^ nPointer);
                          hashKey = Hash(BEGIN(hashKey), END(hashKey));
                          mapMix.insert(make_pair(hashKey, pnode));
                      }
                      int nRelayNodes = fReachable ? 2 : 1; // limited relaying of addresses outside our network(s)
                      for (multimap<uint256, CNode*>::iterator mi = mapMix.begin(); mi != mapMix.end() && nRelayNodes-- > 0; ++mi)
                          ((*mi).second)->PushAddress(addr);
                  }
              }
              // Do not store addresses outside our network
              if (fReachable)
                  vAddrOk.push_back(addr);
          }
          addrman.Add(vAddrOk, pfrom->addr, 2 * 60 * 60);
          if (vAddr.size() < 1000)
              pfrom->fGetAddr = false;
          if (pfrom->fOneShot)
              pfrom->fDisconnect = true;
      }
  
      else if (strCommand == NetMsgType::SENDHEADERS)
      {
          LOCK(cs_main);
          State(pfrom->GetId())->fPreferHeaders = true;
      }
  
  
      else if (strCommand == NetMsgType::INV)
      {
          vector<CInv> vInv;
          vRecv >> vInv;
          if (vInv.size() > MAX_INV_SZ)
          {
              Misbehaving(pfrom->GetId(), 20);
              return error("message inv size() = %u", vInv.size());
          }
  
          bool fBlocksOnly = GetBoolArg("-blocksonly", DEFAULT_BLOCKSONLY);
  
          // Allow whitelisted peers to send data other than blocks in blocks only mode if whitelistrelay is true
          if (pfrom->fWhitelisted && GetBoolArg("-whitelistrelay", DEFAULT_WHITELISTRELAY))
              fBlocksOnly = false;
  
          LOCK(cs_main);
  
          std::vector<CInv> vToFetch;
  
          for (unsigned int nInv = 0; nInv < vInv.size(); nInv++)
          {
              const CInv &inv = vInv[nInv];
  
              boost::this_thread::interruption_point();
              pfrom->AddInventoryKnown(inv);
  
              bool fAlreadyHave = AlreadyHave(inv);
              LogPrint("net", "got inv: %s  %s peer=%d\n", inv.ToString(), fAlreadyHave ? "have" : "new", pfrom->id);
  
              if (inv.type == MSG_BLOCK) {
                  UpdateBlockAvailability(pfrom->GetId(), inv.hash);
                  if (!fAlreadyHave && !fImporting && !fReindex && !mapBlocksInFlight.count(inv.hash)) {
                      // First request the headers preceding the announced block. In the normal fully-synced
                      // case where a new block is announced that succeeds the current tip (no reorganization),
                      // there are no such headers.
                      // Secondly, and only when we are close to being synced, we request the announced block directly,
                      // to avoid an extra round-trip. Note that we must *first* ask for the headers, so by the
                      // time the block arrives, the header chain leading up to it is already validated. Not
                      // doing this will result in the received block being rejected as an orphan in case it is
                      // not a direct successor.
                      pfrom->PushMessage(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexBestHeader), inv.hash);
                      CNodeState *nodestate = State(pfrom->GetId());
                      if (CanDirectFetch(chainparams.GetConsensus()) &&
                          nodestate->nBlocksInFlight < MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                          vToFetch.push_back(inv);
                          // Mark block as in flight already, even though the actual "getdata" message only goes out
                          // later (within the same cs_main lock, though).
                          MarkBlockAsInFlight(pfrom->GetId(), inv.hash, chainparams.GetConsensus());
                      }
                      LogPrint("net", "getheaders (%d) %s to peer=%d\n", pindexBestHeader->nHeight, inv.hash.ToString(), pfrom->id);
                  }
              }
              else
              {
                  if (fBlocksOnly)
                      LogPrint("net", "transaction (%s) inv sent in violation of protocol peer=%d\n", inv.hash.ToString(), pfrom->id);
                  else if (!fAlreadyHave && !fImporting && !fReindex)
                      pfrom->AskFor(inv);
              }
  
              // Track requests for our stuff
              GetMainSignals().Inventory(inv.hash);
  
              if (pfrom->nSendSize > (SendBufferSize() * 2)) {
                  Misbehaving(pfrom->GetId(), 50);
                  return error("send buffer size() = %u", pfrom->nSendSize);
              }
          }
  
          if (!vToFetch.empty())
              pfrom->PushMessage(NetMsgType::GETDATA, vToFetch);
      }
  
  
      else if (strCommand == NetMsgType::GETDATA)
      {
          vector<CInv> vInv;
          vRecv >> vInv;
          if (vInv.size() > MAX_INV_SZ)
          {
              Misbehaving(pfrom->GetId(), 20);
              return error("message getdata size() = %u", vInv.size());
          }
  
          if (fDebug || (vInv.size() != 1))
              LogPrint("net", "received getdata (%u invsz) peer=%d\n", vInv.size(), pfrom->id);
  
          if ((fDebug && vInv.size() > 0) || (vInv.size() == 1))
              LogPrint("net", "received getdata for: %s peer=%d\n", vInv[0].ToString(), pfrom->id);
  
          pfrom->vRecvGetData.insert(pfrom->vRecvGetData.end(), vInv.begin(), vInv.end());
          ProcessGetData(pfrom, chainparams.GetConsensus());
      }
  
  
      else if (strCommand == NetMsgType::GETBLOCKS)
      {
          CBlockLocator locator;
          uint256 hashStop;
          vRecv >> locator >> hashStop;
  
          LOCK(cs_main);
  
          // Find the last block the caller has in the main chain
          CBlockIndex* pindex = FindForkInGlobalIndex(chainActive, locator);
  
          // Send the rest of the chain
          if (pindex)
              pindex = chainActive.Next(pindex);
          int nLimit = 500;
          LogPrint("net", "getblocks %d to %s limit %d from peer=%d\n", (pindex ? pindex->nHeight : -1), hashStop.IsNull() ? "end" : hashStop.ToString(), nLimit, pfrom->id);
          for (; pindex; pindex = chainActive.Next(pindex))
          {
              if (pindex->GetBlockHash() == hashStop)
              {
                  LogPrint("net", "  getblocks stopping at %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
                  break;
              }
              // If pruning, don't inv blocks unless we have on disk and are likely to still have
              // for some reasonable time window (1 hour) that block relay might require.
              const int nPrunedBlocksLikelyToHave = MIN_BLOCKS_TO_KEEP - 3600 / chainparams.GetConsensus().nPowTargetSpacing;
              if (fPruneMode && (!(pindex->nStatus & BLOCK_HAVE_DATA) || pindex->nHeight <= chainActive.Tip()->nHeight - nPrunedBlocksLikelyToHave))
              {
                  LogPrint("net", " getblocks stopping, pruned or too old block at %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
                  break;
              }
              pfrom->PushInventory(CInv(MSG_BLOCK, pindex->GetBlockHash()));
              if (--nLimit <= 0)
              {
                  // When this block is requested, we'll send an inv that'll
                  // trigger the peer to getblocks the next batch of inventory.
                  LogPrint("net", "  getblocks stopping at limit %d %s\n", pindex->nHeight, pindex->GetBlockHash().ToString());
                  pfrom->hashContinue = pindex->GetBlockHash();
                  break;
              }
          }
      }
  
  
      else if (strCommand == NetMsgType::GETHEADERS)
      {
          CBlockLocator locator;
          uint256 hashStop;
          vRecv >> locator >> hashStop;
  
          LOCK(cs_main);
          if (IsInitialBlockDownload() && !pfrom->fWhitelisted) {
              LogPrint("net", "Ignoring getheaders from peer=%d because node is in initial block download\n", pfrom->id);
              return true;
          }
  
          CNodeState *nodestate = State(pfrom->GetId());
          CBlockIndex* pindex = NULL;
          if (locator.IsNull())
          {
              // If locator is null, return the hashStop block
              BlockMap::iterator mi = mapBlockIndex.find(hashStop);
              if (mi == mapBlockIndex.end())
                  return true;
              pindex = (*mi).second;
          }
          else
          {
              // Find the last block the caller has in the main chain
              pindex = FindForkInGlobalIndex(chainActive, locator);
              if (pindex)
                  pindex = chainActive.Next(pindex);
          }
  
          // we must use CBlocks, as CBlockHeaders won't include the 0x00 nTx count at the end
          vector<CBlock> vHeaders;
          int nLimit = MAX_HEADERS_RESULTS;
          LogPrint("net", "getheaders %d to %s from peer=%d\n", (pindex ? pindex->nHeight : -1), hashStop.ToString(), pfrom->id);
          for (; pindex; pindex = chainActive.Next(pindex))
          {
              vHeaders.push_back(pindex->GetBlockHeader());
              if (--nLimit <= 0 || pindex->GetBlockHash() == hashStop)
                  break;
          }
          // pindex can be NULL either if we sent chainActive.Tip() OR
          // if our peer has chainActive.Tip() (and thus we are sending an empty
          // headers message). In both cases it's safe to update
          // pindexBestHeaderSent to be our tip.
          nodestate->pindexBestHeaderSent = pindex ? pindex : chainActive.Tip();
          pfrom->PushMessage(NetMsgType::HEADERS, vHeaders);
      }
  
  
      else if (strCommand == NetMsgType::TX)
      {
          // Stop processing the transaction early if
          // We are in blocks only mode and peer is either not whitelisted or whitelistrelay is off
          if (GetBoolArg("-blocksonly", DEFAULT_BLOCKSONLY) && (!pfrom->fWhitelisted || !GetBoolArg("-whitelistrelay", DEFAULT_WHITELISTRELAY)))
          {
              LogPrint("net", "transaction sent in violation of protocol peer=%d\n", pfrom->id);
              return true;
          }
  
          vector<uint256> vWorkQueue;
          vector<uint256> vEraseQueue;
          CTransaction tx;
          vRecv >> tx;
  
          CInv inv(MSG_TX, tx.GetHash());
          pfrom->AddInventoryKnown(inv);
  
          LOCK(cs_main);
  
          bool fMissingInputs = false;
          CValidationState state;
  
          pfrom->setAskFor.erase(inv.hash);
          mapAlreadyAskedFor.erase(inv);
  
          if (!AlreadyHave(inv) && AcceptToMemoryPool(mempool, state, tx, true, &fMissingInputs))
          {
              mempool.check(pcoinsTip);
              RelayTransaction(tx);
              vWorkQueue.push_back(inv.hash);
  
              LogPrint("mempool", "AcceptToMemoryPool: peer=%d: accepted %s (poolsz %u txn, %u kB)\n",
                  pfrom->id,
                  tx.GetHash().ToString(),
                  mempool.size(), mempool.DynamicMemoryUsage() / 1000);
  
              // Recursively process any orphan transactions that depended on this one
              set<NodeId> setMisbehaving;
              for (unsigned int i = 0; i < vWorkQueue.size(); i++)
              {
                  map<uint256, set<uint256> >::iterator itByPrev = mapOrphanTransactionsByPrev.find(vWorkQueue[i]);
                  if (itByPrev == mapOrphanTransactionsByPrev.end())
                      continue;
                  for (set<uint256>::iterator mi = itByPrev->second.begin();
                       mi != itByPrev->second.end();
                       ++mi)
                  {
                      const uint256& orphanHash = *mi;
                      const CTransaction& orphanTx = mapOrphanTransactions[orphanHash].tx;
                      NodeId fromPeer = mapOrphanTransactions[orphanHash].fromPeer;
                      bool fMissingInputs2 = false;
                      // Use a dummy CValidationState so someone can't setup nodes to counter-DoS based on orphan
                      // resolution (that is, feeding people an invalid transaction based on LegitTxX in order to get
                      // anyone relaying LegitTxX banned)
                      CValidationState stateDummy;
  
  
                      if (setMisbehaving.count(fromPeer))
                          continue;
                      if (AcceptToMemoryPool(mempool, stateDummy, orphanTx, true, &fMissingInputs2))
                      {
                          LogPrint("mempool", "   accepted orphan tx %s\n", orphanHash.ToString());
                          RelayTransaction(orphanTx);
                          vWorkQueue.push_back(orphanHash);
                          vEraseQueue.push_back(orphanHash);
                      }
                      else if (!fMissingInputs2)
                      {
                          int nDos = 0;
                          if (stateDummy.IsInvalid(nDos) && nDos > 0)
                          {
                              // Punish peer that gave us an invalid orphan tx
                              Misbehaving(fromPeer, nDos);
                              setMisbehaving.insert(fromPeer);
                              LogPrint("mempool", "   invalid orphan tx %s\n", orphanHash.ToString());
                          }
                          // Has inputs but not accepted to mempool
                          // Probably non-standard or insufficient fee/priority
                          LogPrint("mempool", "   removed orphan tx %s\n", orphanHash.ToString());
                          vEraseQueue.push_back(orphanHash);
                          assert(recentRejects);
                          recentRejects->insert(orphanHash);
                      }
                      mempool.check(pcoinsTip);
                  }
              }
  
              BOOST_FOREACH(uint256 hash, vEraseQueue)
                  EraseOrphanTx(hash);
          }
          else if (fMissingInputs)
          {
              AddOrphanTx(tx, pfrom->GetId());
  
              // DoS prevention: do not allow mapOrphanTransactions to grow unbounded
              unsigned int nMaxOrphanTx = (unsigned int)std::max((int64_t)0, GetArg("-maxorphantx", DEFAULT_MAX_ORPHAN_TRANSACTIONS));
              unsigned int nEvicted = LimitOrphanTxSize(nMaxOrphanTx);
              if (nEvicted > 0)
                  LogPrint("mempool", "mapOrphan overflow, removed %u tx\n", nEvicted);
          } else {
              assert(recentRejects);
              recentRejects->insert(tx.GetHash());
  
              if (pfrom->fWhitelisted && GetBoolArg("-whitelistforcerelay", DEFAULT_WHITELISTFORCERELAY)) {
                  // Always relay transactions received from whitelisted peers, even
                  // if they were already in the mempool or rejected from it due
                  // to policy, allowing the node to function as a gateway for
                  // nodes hidden behind it.
                  //
                  // Never relay transactions that we would assign a non-zero DoS
                  // score for, as we expect peers to do the same with us in that
                  // case.
                  int nDoS = 0;
                  if (!state.IsInvalid(nDoS) || nDoS == 0) {
                      LogPrintf("Force relaying tx %s from whitelisted peer=%d\n", tx.GetHash().ToString(), pfrom->id);
                      RelayTransaction(tx);
                  } else {
                      LogPrintf("Not relaying invalid transaction %s from whitelisted peer=%d (%s)\n", tx.GetHash().ToString(), pfrom->id, FormatStateMessage(state));
                  }
              }
          }
          int nDoS = 0;
          if (state.IsInvalid(nDoS))
          {
              LogPrint("mempoolrej", "%s from peer=%d was not accepted: %s\n", tx.GetHash().ToString(),
                  pfrom->id,
                  FormatStateMessage(state));
              if (state.GetRejectCode() < REJECT_INTERNAL) // Never send AcceptToMemoryPool's internal codes over P2P
                  pfrom->PushMessage(NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
                                     state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash);
              if (nDoS > 0)
                  Misbehaving(pfrom->GetId(), nDoS);
          }
          FlushStateToDisk(state, FLUSH_STATE_PERIODIC);
      }
  
  
      else if (strCommand == NetMsgType::HEADERS && !fImporting && !fReindex) // Ignore headers received while importing
      {
          std::vector<CBlockHeader> headers;
  
          // Bypass the normal CBlock deserialization, as we don't want to risk deserializing 2000 full blocks.
          unsigned int nCount = ReadCompactSize(vRecv);
          if (nCount > MAX_HEADERS_RESULTS) {
              Misbehaving(pfrom->GetId(), 20);
              return error("headers message size = %u", nCount);
          }
          headers.resize(nCount);
          for (unsigned int n = 0; n < nCount; n++) {
              vRecv >> headers[n];
              ReadCompactSize(vRecv); // ignore tx count; assume it is 0.
          }
  
          LOCK(cs_main);
  
          if (nCount == 0) {
              // Nothing interesting. Stop asking this peers for more headers.
              return true;
          }
  
          CBlockIndex *pindexLast = NULL;
          BOOST_FOREACH(const CBlockHeader& header, headers) {
              CValidationState state;
              if (pindexLast != NULL && header.hashPrevBlock != pindexLast->GetBlockHash()) {
                  Misbehaving(pfrom->GetId(), 20);
                  return error("non-continuous headers sequence");
              }
              if (!AcceptBlockHeader(header, state, chainparams, &pindexLast)) {
                  int nDoS;
                  if (state.IsInvalid(nDoS)) {
                      if (nDoS > 0)
                          Misbehaving(pfrom->GetId(), nDoS);
                      return error("invalid header received");
                  }
              }
          }
  
          if (pindexLast)
              UpdateBlockAvailability(pfrom->GetId(), pindexLast->GetBlockHash());
  
          if (nCount == MAX_HEADERS_RESULTS && pindexLast) {
              // Headers message had its maximum size; the peer may have more headers.
              // TODO: optimize: if pindexLast is an ancestor of chainActive.Tip or pindexBestHeader, continue
              // from there instead.
              LogPrint("net", "more getheaders (%d) to end to peer=%d (startheight:%d)\n", pindexLast->nHeight, pfrom->id, pfrom->nStartingHeight);
              pfrom->PushMessage(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexLast), uint256());
          }
  
          bool fCanDirectFetch = CanDirectFetch(chainparams.GetConsensus());
          CNodeState *nodestate = State(pfrom->GetId());
          // If this set of headers is valid and ends in a block with at least as
          // much work as our tip, download as much as possible.
          if (fCanDirectFetch && pindexLast->IsValid(BLOCK_VALID_TREE) && chainActive.Tip()->nChainWork <= pindexLast->nChainWork) {
              vector<CBlockIndex *> vToFetch;
              CBlockIndex *pindexWalk = pindexLast;
              // Calculate all the blocks we'd need to switch to pindexLast, up to a limit.
              while (pindexWalk && !chainActive.Contains(pindexWalk) && vToFetch.size() <= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                  if (!(pindexWalk->nStatus & BLOCK_HAVE_DATA) &&
                          !mapBlocksInFlight.count(pindexWalk->GetBlockHash())) {
                      // We don't have this block, and it's not yet in flight.
                      vToFetch.push_back(pindexWalk);
                  }
                  pindexWalk = pindexWalk->pprev;
              }
              // If pindexWalk still isn't on our main chain, we're looking at a
              // very large reorg at a time we think we're close to caught up to
              // the main chain -- this shouldn't really happen.  Bail out on the
              // direct fetch and rely on parallel download instead.
              if (!chainActive.Contains(pindexWalk)) {
                  LogPrint("net", "Large reorg, won't direct fetch to %s (%d)\n",
                          pindexLast->GetBlockHash().ToString(),
                          pindexLast->nHeight);
              } else {
                  vector<CInv> vGetData;
                  // Download as much as possible, from earliest to latest.
                  BOOST_REVERSE_FOREACH(CBlockIndex *pindex, vToFetch) {
                      if (nodestate->nBlocksInFlight >= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                          // Can't download any more from this peer
                          break;
                      }
                      vGetData.push_back(CInv(MSG_BLOCK, pindex->GetBlockHash()));
                      MarkBlockAsInFlight(pfrom->GetId(), pindex->GetBlockHash(), chainparams.GetConsensus(), pindex);
                      LogPrint("net", "Requesting block %s from  peer=%d\n",
                              pindex->GetBlockHash().ToString(), pfrom->id);
                  }
                  if (vGetData.size() > 1) {
                      LogPrint("net", "Downloading blocks toward %s (%d) via headers direct fetch\n",
                              pindexLast->GetBlockHash().ToString(), pindexLast->nHeight);
                  }
                  if (vGetData.size() > 0) {
                      pfrom->PushMessage(NetMsgType::GETDATA, vGetData);
                  }
              }
          }
  
          CheckBlockIndex(chainparams.GetConsensus());
      }
  
      else if (strCommand == NetMsgType::BLOCK && !fImporting && !fReindex) // Ignore blocks received while importing
      {
          CBlock block;
          vRecv >> block;
  
          CInv inv(MSG_BLOCK, block.GetHash());
          LogPrint("net", "received block %s peer=%d\n", inv.hash.ToString(), pfrom->id);
  
          pfrom->AddInventoryKnown(inv);
  
          CValidationState state;
          // Process all blocks from whitelisted peers, even if not requested,
          // unless we're still syncing with the network.
          // Such an unrequested block may still be processed, subject to the
          // conditions in AcceptBlock().
          bool forceProcessing = pfrom->fWhitelisted && !IsInitialBlockDownload();
          ProcessNewBlock(state, chainparams, pfrom, &block, forceProcessing, NULL);
          int nDoS;
          if (state.IsInvalid(nDoS)) {
              assert (state.GetRejectCode() < REJECT_INTERNAL); // Blocks are never rejected with internal reject codes
              pfrom->PushMessage(NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
                                 state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash);
              if (nDoS > 0) {
                  LOCK(cs_main);
                  Misbehaving(pfrom->GetId(), nDoS);
              }
          }
  
      }
  
  
      // This asymmetric behavior for inbound and outbound connections was introduced
      // to prevent a fingerprinting attack: an attacker can send specific fake addresses
      // to users' AddrMan and later request them by sending getaddr messages.
      // Making nodes which are behind NAT and can only make outgoing connections ignore
      // the getaddr message mitigates the attack.
      else if ((strCommand == NetMsgType::GETADDR) && (pfrom->fInbound))
      {
          pfrom->vAddrToSend.clear();
          vector<CAddress> vAddr = addrman.GetAddr();
          BOOST_FOREACH(const CAddress &addr, vAddr)
              pfrom->PushAddress(addr);
      }
  
  
      else if (strCommand == NetMsgType::MEMPOOL)
      {
          if (CNode::OutboundTargetReached(false) && !pfrom->fWhitelisted)
          {
              LogPrint("net", "mempool request with bandwidth limit reached, disconnect peer=%d\n", pfrom->GetId());
              pfrom->fDisconnect = true;
              return true;
          }
          LOCK2(cs_main, pfrom->cs_filter);
  
          std::vector<uint256> vtxid;
          mempool.queryHashes(vtxid);
          vector<CInv> vInv;
          BOOST_FOREACH(uint256& hash, vtxid) {
              CInv inv(MSG_TX, hash);
              if (pfrom->pfilter) {
                  CTransaction tx;
                  bool fInMemPool = mempool.lookup(hash, tx);
                  if (!fInMemPool) continue; // another thread removed since queryHashes, maybe...
                  if (!pfrom->pfilter->IsRelevantAndUpdate(tx)) continue;
              }
              vInv.push_back(inv);
              if (vInv.size() == MAX_INV_SZ) {
                  pfrom->PushMessage(NetMsgType::INV, vInv);
                  vInv.clear();
              }
          }
          if (vInv.size() > 0)
              pfrom->PushMessage(NetMsgType::INV, vInv);
      }
  
  
      else if (strCommand == NetMsgType::PING)
      {
          if (pfrom->nVersion > BIP0031_VERSION)
          {
              uint64_t nonce = 0;
              vRecv >> nonce;
              // Echo the message back with the nonce. This allows for two useful features:
              //
              // 1) A remote node can quickly check if the connection is operational
              // 2) Remote nodes can measure the latency of the network thread. If this node
              //    is overloaded it won't respond to pings quickly and the remote node can
              //    avoid sending us more work, like chain download requests.
              //
              // The nonce stops the remote getting confused between different pings: without
              // it, if the remote node sends a ping once per second and this node takes 5
              // seconds to respond to each, the 5th ping the remote sends would appear to
              // return very quickly.
              pfrom->PushMessage(NetMsgType::PONG, nonce);
          }
      }
  
  
      else if (strCommand == NetMsgType::PONG)
      {
          int64_t pingUsecEnd = nTimeReceived;
          uint64_t nonce = 0;
          size_t nAvail = vRecv.in_avail();
          bool bPingFinished = false;
          std::string sProblem;
  
          if (nAvail >= sizeof(nonce)) {
              vRecv >> nonce;
  
              // Only process pong message if there is an outstanding ping (old ping without nonce should never pong)
              if (pfrom->nPingNonceSent != 0) {
                  if (nonce == pfrom->nPingNonceSent) {
                      // Matching pong received, this ping is no longer outstanding
                      bPingFinished = true;
                      int64_t pingUsecTime = pingUsecEnd - pfrom->nPingUsecStart;
                      if (pingUsecTime > 0) {
                          // Successful ping time measurement, replace previous
                          pfrom->nPingUsecTime = pingUsecTime;
                          pfrom->nMinPingUsecTime = std::min(pfrom->nMinPingUsecTime, pingUsecTime);
                      } else {
                          // This should never happen
                          sProblem = "Timing mishap";
                      }
                  } else {
                      // Nonce mismatches are normal when pings are overlapping
                      sProblem = "Nonce mismatch";
                      if (nonce == 0) {
                          // This is most likely a bug in another implementation somewhere; cancel this ping
                          bPingFinished = true;
                          sProblem = "Nonce zero";
                      }
                  }
              } else {
                  sProblem = "Unsolicited pong without ping";
              }
          } else {
              // This is most likely a bug in another implementation somewhere; cancel this ping
              bPingFinished = true;
              sProblem = "Short payload";
          }
  
          if (!(sProblem.empty())) {
              LogPrint("net", "pong peer=%d: %s, %x expected, %x received, %u bytes\n",
                  pfrom->id,
                  sProblem,
                  pfrom->nPingNonceSent,
                  nonce,
                  nAvail);
          }
          if (bPingFinished) {
              pfrom->nPingNonceSent = 0;
          }
      }
  
  
      else if (fAlerts && strCommand == NetMsgType::ALERT)
      {
          CAlert alert;
          vRecv >> alert;
  
          uint256 alertHash = alert.GetHash();
          if (pfrom->setKnown.count(alertHash) == 0)
          {
              if (alert.ProcessAlert(chainparams.AlertKey()))
              {
                  // Relay
                  pfrom->setKnown.insert(alertHash);
                  {
                      LOCK(cs_vNodes);
                      BOOST_FOREACH(CNode* pnode, vNodes)
                          alert.RelayTo(pnode);
                  }
              }
              else {
                  // Small DoS penalty so peers that send us lots of
                  // duplicate/expired/invalid-signature/whatever alerts
                  // eventually get banned.
                  // This isn't a Misbehaving(100) (immediate ban) because the
                  // peer might be an older or different implementation with
                  // a different signature key, etc.
                  Misbehaving(pfrom->GetId(), 10);
              }
          }
      }
  
  
      else if (strCommand == NetMsgType::FILTERLOAD)
      {
          CBloomFilter filter;
          vRecv >> filter;
  
          if (!filter.IsWithinSizeConstraints())
              // There is no excuse for sending a too-large filter
              Misbehaving(pfrom->GetId(), 100);
          else
          {
              LOCK(pfrom->cs_filter);
              delete pfrom->pfilter;
              pfrom->pfilter = new CBloomFilter(filter);
              pfrom->pfilter->UpdateEmptyFull();
          }
          pfrom->fRelayTxes = true;
      }
  
  
      else if (strCommand == NetMsgType::FILTERADD)
      {
          vector<unsigned char> vData;
          vRecv >> vData;
  
          // Nodes must NEVER send a data item > 520 bytes (the max size for a script data object,
          // and thus, the maximum size any matched object can have) in a filteradd message
          if (vData.size() > MAX_SCRIPT_ELEMENT_SIZE)
          {
              Misbehaving(pfrom->GetId(), 100);
          } else {
              LOCK(pfrom->cs_filter);
              if (pfrom->pfilter)
                  pfrom->pfilter->insert(vData);
              else
                  Misbehaving(pfrom->GetId(), 100);
          }
      }
  
  
      else if (strCommand == NetMsgType::FILTERCLEAR)
      {
          LOCK(pfrom->cs_filter);
          delete pfrom->pfilter;
          pfrom->pfilter = new CBloomFilter();
          pfrom->fRelayTxes = true;
      }
  
  
      else if (strCommand == NetMsgType::REJECT)
      {
          if (fDebug) {
              try {
                  string strMsg; unsigned char ccode; string strReason;
                  vRecv >> LIMITED_STRING(strMsg, CMessageHeader::COMMAND_SIZE) >> ccode >> LIMITED_STRING(strReason, MAX_REJECT_MESSAGE_LENGTH);
  
                  ostringstream ss;
                  ss << strMsg << " code " << itostr(ccode) << ": " << strReason;
  
                  if (strMsg == NetMsgType::BLOCK || strMsg == NetMsgType::TX)
                  {
                      uint256 hash;
                      vRecv >> hash;
                      ss << ": hash " << hash.ToString();
                  }
                  LogPrint("net", "Reject %s\n", SanitizeString(ss.str()));
              } catch (const std::ios_base::failure&) {
                  // Avoid feedback loops by preventing reject messages from triggering a new reject message.
                  LogPrint("net", "Unparseable reject message received\n");
              }
          }
      }
  
      else
      {
          // Ignore unknown commands for extensibility
          LogPrint("net", "Unknown command \"%s\" from peer=%d\n", SanitizeString(strCommand), pfrom->id);
      }
  
  
  
      return true;
  }
  
  // requires LOCK(cs_vRecvMsg)
  bool ProcessMessages(CNode* pfrom)
  {
      const CChainParams& chainparams = Params();
      //if (fDebug)
      //    LogPrintf("%s(%u messages)\n", __func__, pfrom->vRecvMsg.size());
  
      //
      // Message format
      //  (4) message start
      //  (12) command
      //  (4) size
      //  (4) checksum
      //  (x) data
      //
      bool fOk = true;
  
      if (!pfrom->vRecvGetData.empty())
          ProcessGetData(pfrom, chainparams.GetConsensus());
  
      // this maintains the order of responses
      if (!pfrom->vRecvGetData.empty()) return fOk;
  
      std::deque<CNetMessage>::iterator it = pfrom->vRecvMsg.begin();
      while (!pfrom->fDisconnect && it != pfrom->vRecvMsg.end()) {
          // Don't bother if send buffer is too full to respond anyway
          if (pfrom->nSendSize >= SendBufferSize())
              break;
  
          // get next message
          CNetMessage& msg = *it;
  
          //if (fDebug)
          //    LogPrintf("%s(message %u msgsz, %u bytes, complete:%s)\n", __func__,
          //            msg.hdr.nMessageSize, msg.vRecv.size(),
          //            msg.complete() ? "Y" : "N");
  
          // end, if an incomplete message is found
          if (!msg.complete())
              break;
  
          // at this point, any failure means we can delete the current message
          it++;
  
          // Scan for message start
          if (memcmp(msg.hdr.pchMessageStart, chainparams.MessageStart(), MESSAGE_START_SIZE) != 0) {
              LogPrintf("PROCESSMESSAGE: INVALID MESSAGESTART %s peer=%d\n", SanitizeString(msg.hdr.GetCommand()), pfrom->id);
              fOk = false;
              break;
          }
  
          // Read header
          CMessageHeader& hdr = msg.hdr;
          if (!hdr.IsValid(chainparams.MessageStart()))
          {
              LogPrintf("PROCESSMESSAGE: ERRORS IN HEADER %s peer=%d\n", SanitizeString(hdr.GetCommand()), pfrom->id);
              continue;
          }
          string strCommand = hdr.GetCommand();
  
          // Message size
          unsigned int nMessageSize = hdr.nMessageSize;
  
          // Checksum
          CDataStream& vRecv = msg.vRecv;
          uint256 hash = Hash(vRecv.begin(), vRecv.begin() + nMessageSize);
          unsigned int nChecksum = ReadLE32((unsigned char*)&hash);
          if (nChecksum != hdr.nChecksum)
          {
              LogPrintf("%s(%s, %u bytes): CHECKSUM ERROR nChecksum=%08x hdr.nChecksum=%08x\n", __func__,
                 SanitizeString(strCommand), nMessageSize, nChecksum, hdr.nChecksum);
              continue;
          }
  
          // Process message
          bool fRet = false;
          try
          {
              fRet = ProcessMessage(pfrom, strCommand, vRecv, msg.nTime);
              boost::this_thread::interruption_point();
          }
          catch (const std::ios_base::failure& e)
          {
              pfrom->PushMessage(NetMsgType::REJECT, strCommand, REJECT_MALFORMED, string("error parsing message"));
              if (strstr(e.what(), "end of data"))
              {
                  // Allow exceptions from under-length message on vRecv
                  LogPrintf("%s(%s, %u bytes): Exception '%s' caught, normally caused by a message being shorter than its stated length\n", __func__, SanitizeString(strCommand), nMessageSize, e.what());
              }
              else if (strstr(e.what(), "size too large"))
              {
                  // Allow exceptions from over-long size
                  LogPrintf("%s(%s, %u bytes): Exception '%s' caught\n", __func__, SanitizeString(strCommand), nMessageSize, e.what());
              }
              else
              {
                  PrintExceptionContinue(&e, "ProcessMessages()");
              }
          }
          catch (const boost::thread_interrupted&) {
              throw;
          }
          catch (const std::exception& e) {
              PrintExceptionContinue(&e, "ProcessMessages()");
          } catch (...) {
              PrintExceptionContinue(NULL, "ProcessMessages()");
          }
  
          if (!fRet)
              LogPrintf("%s(%s, %u bytes) FAILED peer=%d\n", __func__, SanitizeString(strCommand), nMessageSize, pfrom->id);
  
          break;
      }
  
      // In case the connection got shut down, its receive buffer was wiped
      if (!pfrom->fDisconnect)
          pfrom->vRecvMsg.erase(pfrom->vRecvMsg.begin(), it);
  
      return fOk;
  }
  
  
  bool SendMessages(CNode* pto)
  {
      const Consensus::Params& consensusParams = Params().GetConsensus();
      {
          // Don't send anything until we get its version message
          if (pto->nVersion == 0)
              return true;
  
          //
          // Message: ping
          //
          bool pingSend = false;
          if (pto->fPingQueued) {
              // RPC ping request by user
              pingSend = true;
          }
          if (pto->nPingNonceSent == 0 && pto->nPingUsecStart + PING_INTERVAL * 1000000 < GetTimeMicros()) {
              // Ping automatically sent as a latency probe & keepalive.
              pingSend = true;
          }
          if (pingSend) {
              uint64_t nonce = 0;
              while (nonce == 0) {
                  GetRandBytes((unsigned char*)&nonce, sizeof(nonce));
              }
              pto->fPingQueued = false;
              pto->nPingUsecStart = GetTimeMicros();
              if (pto->nVersion > BIP0031_VERSION) {
                  pto->nPingNonceSent = nonce;
                  pto->PushMessage(NetMsgType::PING, nonce);
              } else {
                  // Peer is too old to support ping command with nonce, pong will never arrive.
                  pto->nPingNonceSent = 0;
                  pto->PushMessage(NetMsgType::PING);
              }
          }
  
          TRY_LOCK(cs_main, lockMain); // Acquire cs_main for IsInitialBlockDownload() and CNodeState()
          if (!lockMain)
              return true;
  
          // Address refresh broadcast
          int64_t nNow = GetTimeMicros();
          if (!IsInitialBlockDownload() && pto->nNextLocalAddrSend < nNow) {
              AdvertizeLocal(pto);
              pto->nNextLocalAddrSend = PoissonNextSend(nNow, AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL);
          }
  
          //
          // Message: addr
          //
          if (pto->nNextAddrSend < nNow) {
              pto->nNextAddrSend = PoissonNextSend(nNow, AVG_ADDRESS_BROADCAST_INTERVAL);
              vector<CAddress> vAddr;
              vAddr.reserve(pto->vAddrToSend.size());
              BOOST_FOREACH(const CAddress& addr, pto->vAddrToSend)
              {
                  if (!pto->addrKnown.contains(addr.GetKey()))
                  {
                      pto->addrKnown.insert(addr.GetKey());
                      vAddr.push_back(addr);
                      // receiver rejects addr messages larger than 1000
                      if (vAddr.size() >= 1000)
                      {
                          pto->PushMessage(NetMsgType::ADDR, vAddr);
                          vAddr.clear();
                      }
                  }
              }
              pto->vAddrToSend.clear();
              if (!vAddr.empty())
                  pto->PushMessage(NetMsgType::ADDR, vAddr);
          }
  
          CNodeState &state = *State(pto->GetId());
          if (state.fShouldBan) {
              if (pto->fWhitelisted)
                  LogPrintf("Warning: not punishing whitelisted peer %s!\n", pto->addr.ToString());
              else {
                  pto->fDisconnect = true;
                  if (pto->addr.IsLocal())
                      LogPrintf("Warning: not banning local peer %s!\n", pto->addr.ToString());
                  else
                  {
                      CNode::Ban(pto->addr, BanReasonNodeMisbehaving);
                  }
              }
              state.fShouldBan = false;
          }
  
          BOOST_FOREACH(const CBlockReject& reject, state.rejects)
              pto->PushMessage(NetMsgType::REJECT, (string)NetMsgType::BLOCK, reject.chRejectCode, reject.strRejectReason, reject.hashBlock);
          state.rejects.clear();
  
          // Start block sync
          if (pindexBestHeader == NULL)
              pindexBestHeader = chainActive.Tip();
          bool fFetch = state.fPreferredDownload || (nPreferredDownload == 0 && !pto->fClient && !pto->fOneShot); // Download if this is a nice peer, or we have no nice peers and this one might do.
          if (!state.fSyncStarted && !pto->fClient && !fImporting && !fReindex) {
              // Only actively request headers from a single peer, unless we're close to today.
              if ((nSyncStarted == 0 && fFetch) || pindexBestHeader->GetBlockTime() > GetAdjustedTime() - 24 * 60 * 60) {
                  state.fSyncStarted = true;
                  nSyncStarted++;
                  const CBlockIndex *pindexStart = pindexBestHeader;
                  /* If possible, start at the block preceding the currently
                     best known header.  This ensures that we always get a
                     non-empty list of headers back as long as the peer
                     is up-to-date.  With a non-empty response, we can initialise
                     the peer's known best block.  This wouldn't be possible
                     if we requested starting at pindexBestHeader and
                     got back an empty response.  */
                  if (pindexStart->pprev)
                      pindexStart = pindexStart->pprev;
                  LogPrint("net", "initial getheaders (%d) to peer=%d (startheight:%d)\n", pindexStart->nHeight, pto->id, pto->nStartingHeight);
                  pto->PushMessage(NetMsgType::GETHEADERS, chainActive.GetLocator(pindexStart), uint256());
              }
          }
  
          // Resend wallet transactions that haven't gotten in a block yet
          // Except during reindex, importing and IBD, when old wallet
          // transactions become unconfirmed and spams other nodes.
          if (!fReindex && !fImporting && !IsInitialBlockDownload())
          {
              GetMainSignals().Broadcast(nTimeBestReceived);
          }
  
          //
          // Try sending block announcements via headers
          //
          {
              // If we have less than MAX_BLOCKS_TO_ANNOUNCE in our
              // list of block hashes we're relaying, and our peer wants
              // headers announcements, then find the first header
              // not yet known to our peer but would connect, and send.
              // If no header would connect, or if we have too many
              // blocks, or if the peer doesn't want headers, just
              // add all to the inv queue.
              LOCK(pto->cs_inventory);
              vector<CBlock> vHeaders;
              bool fRevertToInv = (!state.fPreferHeaders || pto->vBlockHashesToAnnounce.size() > MAX_BLOCKS_TO_ANNOUNCE);
              CBlockIndex *pBestIndex = NULL; // last header queued for delivery
              ProcessBlockAvailability(pto->id); // ensure pindexBestKnownBlock is up-to-date
  
              if (!fRevertToInv) {
                  bool fFoundStartingHeader = false;
                  // Try to find first header that our peer doesn't have, and
                  // then send all headers past that one.  If we come across any
                  // headers that aren't on chainActive, give up.
                  BOOST_FOREACH(const uint256 &hash, pto->vBlockHashesToAnnounce) {
                      BlockMap::iterator mi = mapBlockIndex.find(hash);
                      assert(mi != mapBlockIndex.end());
                      CBlockIndex *pindex = mi->second;
                      if (chainActive[pindex->nHeight] != pindex) {
                          // Bail out if we reorged away from this block
                          fRevertToInv = true;
                          break;
                      }
                      assert(pBestIndex == NULL || pindex->pprev == pBestIndex);
                      pBestIndex = pindex;
                      if (fFoundStartingHeader) {
                          // add this to the headers message
                          vHeaders.push_back(pindex->GetBlockHeader());
                      } else if (PeerHasHeader(&state, pindex)) {
                          continue; // keep looking for the first new block
                      } else if (pindex->pprev == NULL || PeerHasHeader(&state, pindex->pprev)) {
                          // Peer doesn't have this header but they do have the prior one.
                          // Start sending headers.
                          fFoundStartingHeader = true;
                          vHeaders.push_back(pindex->GetBlockHeader());
                      } else {
                          // Peer doesn't have this header or the prior one -- nothing will
                          // connect, so bail out.
                          fRevertToInv = true;
                          break;
                      }
                  }
              }
              if (fRevertToInv) {
                  // If falling back to using an inv, just try to inv the tip.
                  // The last entry in vBlockHashesToAnnounce was our tip at some point
                  // in the past.
                  if (!pto->vBlockHashesToAnnounce.empty()) {
                      const uint256 &hashToAnnounce = pto->vBlockHashesToAnnounce.back();
                      BlockMap::iterator mi = mapBlockIndex.find(hashToAnnounce);
                      assert(mi != mapBlockIndex.end());
                      CBlockIndex *pindex = mi->second;
  
                      // Warn if we're announcing a block that is not on the main chain.
                      // This should be very rare and could be optimized out.
                      // Just log for now.
                      if (chainActive[pindex->nHeight] != pindex) {
                          LogPrint("net", "Announcing block %s not on main chain (tip=%s)\n",
                              hashToAnnounce.ToString(), chainActive.Tip()->GetBlockHash().ToString());
                      }
  
                      // If the peer announced this block to us, don't inv it back.
                      // (Since block announcements may not be via inv's, we can't solely rely on
                      // setInventoryKnown to track this.)
                      if (!PeerHasHeader(&state, pindex)) {
                          pto->PushInventory(CInv(MSG_BLOCK, hashToAnnounce));
                          LogPrint("net", "%s: sending inv peer=%d hash=%s\n", __func__,
                              pto->id, hashToAnnounce.ToString());
                      }
                  }
              } else if (!vHeaders.empty()) {
                  if (vHeaders.size() > 1) {
                      LogPrint("net", "%s: %u headers, range (%s, %s), to peer=%d\n", __func__,
                              vHeaders.size(),
                              vHeaders.front().GetHash().ToString(),
                              vHeaders.back().GetHash().ToString(), pto->id);
                  } else {
                      LogPrint("net", "%s: sending header %s to peer=%d\n", __func__,
                              vHeaders.front().GetHash().ToString(), pto->id);
                  }
                  pto->PushMessage(NetMsgType::HEADERS, vHeaders);
                  state.pindexBestHeaderSent = pBestIndex;
              }
              pto->vBlockHashesToAnnounce.clear();
          }
  
          //
          // Message: inventory
          //
          vector<CInv> vInv;
          vector<CInv> vInvWait;
          {
              bool fSendTrickle = pto->fWhitelisted;
              if (pto->nNextInvSend < nNow) {
                  fSendTrickle = true;
                  pto->nNextInvSend = PoissonNextSend(nNow, AVG_INVENTORY_BROADCAST_INTERVAL);
              }
              LOCK(pto->cs_inventory);
              vInv.reserve(std::min<size_t>(1000, pto->vInventoryToSend.size()));
              vInvWait.reserve(pto->vInventoryToSend.size());
              BOOST_FOREACH(const CInv& inv, pto->vInventoryToSend)
              {
                  if (inv.type == MSG_TX && pto->filterInventoryKnown.contains(inv.hash))
                      continue;
  
                  // trickle out tx inv to protect privacy
                  if (inv.type == MSG_TX && !fSendTrickle)
                  {
                      // 1/4 of tx invs blast to all immediately
                      static uint256 hashSalt;
                      if (hashSalt.IsNull())
                          hashSalt = GetRandHash();
                      uint256 hashRand = ArithToUint256(UintToArith256(inv.hash) ^ UintToArith256(hashSalt));
                      hashRand = Hash(BEGIN(hashRand), END(hashRand));
                      bool fTrickleWait = ((UintToArith256(hashRand) & 3) != 0);
  
                      if (fTrickleWait)
                      {
                          vInvWait.push_back(inv);
                          continue;
                      }
                  }
  
                  pto->filterInventoryKnown.insert(inv.hash);
  
                  vInv.push_back(inv);
                  if (vInv.size() >= 1000)
                  {
                      pto->PushMessage(NetMsgType::INV, vInv);
                      vInv.clear();
                  }
              }
              pto->vInventoryToSend = vInvWait;
          }
          if (!vInv.empty())
              pto->PushMessage(NetMsgType::INV, vInv);
  
          // Detect whether we're stalling
          nNow = GetTimeMicros();
          if (!pto->fDisconnect && state.nStallingSince && state.nStallingSince < nNow - 1000000 * BLOCK_STALLING_TIMEOUT) {
              // Stalling only triggers when the block download window cannot move. During normal steady state,
              // the download window should be much larger than the to-be-downloaded set of blocks, so disconnection
              // should only happen during initial block download.
              LogPrintf("Peer=%d is stalling block download, disconnecting\n", pto->id);
              pto->fDisconnect = true;
          }
          // In case there is a block that has been in flight from this peer for 2 + 0.5 * N times the block interval
          // (with N the number of peers from which we're downloading validated blocks), disconnect due to timeout.
          // We compensate for other peers to prevent killing off peers due to our own downstream link
          // being saturated. We only count validated in-flight blocks so peers can't advertise non-existing block hashes
          // to unreasonably increase our timeout.
          if (!pto->fDisconnect && state.vBlocksInFlight.size() > 0) {
              QueuedBlock &queuedBlock = state.vBlocksInFlight.front();
              int nOtherPeersWithValidatedDownloads = nPeersWithValidatedDownloads - (state.nBlocksInFlightValidHeaders > 0);
              if (nNow > state.nDownloadingSince + consensusParams.nPowTargetSpacing * (BLOCK_DOWNLOAD_TIMEOUT_BASE + BLOCK_DOWNLOAD_TIMEOUT_PER_PEER * nOtherPeersWithValidatedDownloads)) {
                  LogPrintf("Timeout downloading block %s from peer=%d, disconnecting\n", queuedBlock.hash.ToString(), pto->id);
                  pto->fDisconnect = true;
              }
          }
  
          //
          // Message: getdata (blocks)
          //
          vector<CInv> vGetData;
          if (!pto->fDisconnect && !pto->fClient && (fFetch || !IsInitialBlockDownload()) && state.nBlocksInFlight < MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
              vector<CBlockIndex*> vToDownload;
              NodeId staller = -1;
              FindNextBlocksToDownload(pto->GetId(), MAX_BLOCKS_IN_TRANSIT_PER_PEER - state.nBlocksInFlight, vToDownload, staller);
              BOOST_FOREACH(CBlockIndex *pindex, vToDownload) {
                  vGetData.push_back(CInv(MSG_BLOCK, pindex->GetBlockHash()));
                  MarkBlockAsInFlight(pto->GetId(), pindex->GetBlockHash(), consensusParams, pindex);
                  LogPrint("net", "Requesting block %s (%d) peer=%d\n", pindex->GetBlockHash().ToString(),
                      pindex->nHeight, pto->id);
              }
              if (state.nBlocksInFlight == 0 && staller != -1) {
                  if (State(staller)->nStallingSince == 0) {
                      State(staller)->nStallingSince = nNow;
                      LogPrint("net", "Stall started peer=%d\n", staller);
                  }
              }
          }
  
          //
          // Message: getdata (non-blocks)
          //
          while (!pto->fDisconnect && !pto->mapAskFor.empty() && (*pto->mapAskFor.begin()).first <= nNow)
          {
              const CInv& inv = (*pto->mapAskFor.begin()).second;
              if (!AlreadyHave(inv))
              {
                  if (fDebug)
                      LogPrint("net", "Requesting %s peer=%d\n", inv.ToString(), pto->id);
                  vGetData.push_back(inv);
                  if (vGetData.size() >= 1000)
                  {
                      pto->PushMessage(NetMsgType::GETDATA, vGetData);
                      vGetData.clear();
                  }
              } else {
                  //If we're not going to ask, don't expect a response.
                  pto->setAskFor.erase(inv.hash);
              }
              pto->mapAskFor.erase(pto->mapAskFor.begin());
          }
          if (!vGetData.empty())
              pto->PushMessage(NetMsgType::GETDATA, vGetData);
  
      }
      return true;
  }
  
   std::string CBlockFileInfo::ToString() const {
       return strprintf("CBlockFileInfo(blocks=%u, size=%u, heights=%u...%u, time=%s...%s)", nBlocks, nSize, nHeightFirst, nHeightLast, DateTimeStrFormat("%Y-%m-%d", nTimeFirst), DateTimeStrFormat("%Y-%m-%d", nTimeLast));
   }
  
  ThresholdState VersionBitsTipState(const Consensus::Params& params, Consensus::DeploymentPos pos)
  {
      LOCK(cs_main);
      return VersionBitsState(chainActive.Tip(), params, pos, versionbitscache);
  }
  
  class CMainCleanup
  {
  public:
      CMainCleanup() {}
      ~CMainCleanup() {
          // block headers
          BlockMap::iterator it1 = mapBlockIndex.begin();
          for (; it1 != mapBlockIndex.end(); it1++)
              delete (*it1).second;
          mapBlockIndex.clear();
  
          // orphan transactions
          mapOrphanTransactions.clear();
          mapOrphanTransactionsByPrev.clear();
      }
  } instance_of_cmaincleanup;
  