text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2014 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 "arith_uint256.h"
  #include "bip64_getutxo.h"
  #include "blockannounce.h"
  #include "blockencodings.h"
  #include "blockheaderprocessor.h"
  #include "blocksender.h"
  #include "chainparams.h"
  #include "checkpoints.h"
  #include "checkqueue.h"
  #include "compactblockprocessor.h"
  #include "compactthin.h"
  #include "consensus/consensus.h"
  #include "consensus/merkle.h"
  #include "consensus/tx_verify.h"
  #include "consensus/validation.h"
  #include "inflightindex.h"
  #include "init.h"
  #include "maxblocksize.h"
  #include "merkleblock.h"
  #include "mempoolaccepter.h"
  #include "net.h"
  #include "netmessagemaker.h"
  #include "netbase.h"
  #include "nodestate.h"
  #include "options.h"
  #include "policy/policy.h"
  #include "policy/txpriority.h"
  #include "pow.h"
  #include "process_xthinblock.h"
  #include "respend/respenddetector.h"
  #include "thinblockbuilder.h"
  #include "thinblockconcluder.h"
  #include "thinblockmanager.h"
  #include "txdb.h"
  #include "txmempool.h"
  #include "ui_interface.h"
  #include "undo.h"
  #include "util.h"
  #include "utilfork.h"
  #include "utilmoneystr.h"
  #include "utilprocessmsg.h"
  #include "validationinterface.h"
  #include "xthin.h"
  #include "versionbits.h"
  
  #include <sstream>
  #include <algorithm>
  
  #include <boost/dynamic_bitset.hpp>
  #include <boost/algorithm/string/replace.hpp>
  #include <boost/assign/list_of.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;
  std::atomic_bool fImporting(false);
  bool fReindex = false;
  bool fTxIndex = false;
  bool fHavePruned = false;
  bool fPruneMode = false;
  bool fIsBareMultisigStd = true;
  bool fCheckBlockIndex = false;
  bool fCheckpointsEnabled = true;
  size_t nCoinCacheUsage = 5000 * 300;
  uint64_t nPruneTarget = 0;
  
  /** Fees smaller than this (in satoshi) are considered zero fee (for relaying and mining) */
  CFeeRate minRelayTxFee = CFeeRate(1000);
  
  CTxMemPool mempool(::minRelayTxFee);
  
  struct COrphanTx {
      CTransaction tx;
      NodeId fromPeer;
  };
  map<uint256, COrphanTx> mapOrphanTransactions;
  map<uint256, set<uint256> > mapOrphanTransactionsByPrev;
  void EraseOrphansFor(NodeId peer);
  
  static bool SanityCheckMessage(CNode* peer, const CNetMessage& msg);
  
  /**
   * 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();
  
  /** Constant stuff for coinbase transactions we create: */
  CScript COINBASE_FLAGS;
  
  const string strMessageMagic = "Bitcoin Signed Message:\n";
  
  static const uint64_t RANDOMIZER_ID_ADDRESS_RELAY = 0x3cac0035b5866b90ULL; // SHA256("main address relay")[0:8]
  
  // Internal stuff
  namespace {
  
      struct CBlockIndexWorkComparator
      {
          bool operator()(const CBlockIndex *pa, const 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 if 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;
  
      /**
       * 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: 1.3 MB
       */
      boost::scoped_ptr<CRollingBloomFilter> recentRejects;
      uint256 hashRecentRejectsChainTip;
  
      InFlightIndex blocksInFlight;
  
      /** Number of blocks in flight with validated headers. */
      int nQueuedValidatedHeaders = 0;
  
      /** Number of preferable block download peers. */
      std::atomic<int> nPreferredDownload(0);
  
      /** Dirty block index entries. */
      set<CBlockIndex*> setDirtyBlockIndex;
  
      /** Dirty block file entries. */
      set<int> setDirtyFileInfo;
  } // anon namespace
  
  // UAHF chain considers an OP_RETURN that commits to this string invalid
  static const std::string ANTI_REPLAY_COMMITMENT = "Bitcoin: A Peer-to-Peer Electronic Cash System";
  std::vector<unsigned char>& GetAntiReplayCommitment() {
      static std::vector<unsigned char> vchARC = std::vector<unsigned char>(std::begin(ANTI_REPLAY_COMMITMENT),
                                                                            std::end(ANTI_REPLAY_COMMITMENT));
      return vchARC;
  }
  
  class OnBlockFinished : public ThinBlockFinishedCallb {
      public:
          OnBlockFinished(bool canMisbehave)
              : canMisbehave(canMisbehave) { }
  
          OnBlockFinished(bool canMisbehave, const std::string& strCommand)
              : canMisbehave(canMisbehave), strCommand(strCommand) { }
  
          virtual void operator()(const CBlock& block, const std::vector<NodeId>& ids);
  
      private:
          bool canMisbehave;
          const std::string strCommand;
  
          bool hasWhitelistedNode(const std::vector<NodeId>& ids) const;
          void rejectAndPunish(const CValidationState& state, const uint256& hash,
                  const std::vector<NodeId>& ids);
  };
  
  struct InFlightEraserImpl : public InFlightEraser {
      virtual void operator()(NodeId, const uint256& block);
  };
  ThinBlockManager thinblockmg(
          std::unique_ptr<ThinBlockFinishedCallb>(new OnBlockFinished(false)),
          std::unique_ptr<InFlightEraser>(new InFlightEraserImpl()));
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // Registration of network node signals.
  //
  
  namespace {
  
  uint64_t GetMaxBlockSizeInsecure()
  {
      return chainActive.MaxBlockSizeInsecure();
  }
  
  void UpdatePreferredDownload(CNode* node, NodeStatePtr& 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;
  }
  
  // Returns time at which to timeout block request (nTime in microseconds)
  int64_t GetBlockTimeout(int64_t nTime, int nValidatedQueuedBefore, const Consensus::Params &consensusParams)
  {
      return nTime + 500000 * consensusParams.nPowTargetSpacing * (4 + nValidatedQueuedBefore);
  }
  
  void PushNodeVersion(CNode *pnode, CConnman& connman, int64_t nTime)
  {
      uint64_t nLocalNodeServices = pnode->GetLocalServices();
      uint64_t nonce = pnode->GetLocalNonce();
      int nNodeStartingHeight = pnode->GetMyStartingHeight();
      NodeId nodeid = pnode->GetId();
      CAddress addr = pnode->addr;
  
      CAddress addrYou = (addr.IsRoutable() && !IsProxy(addr) ? addr : CAddress(CService("0.0.0.0"), 0));
      CAddress addrMe = CAddress(CService(), nLocalNodeServices);
  
      int nMaxBlockSize = GetMaxBlockSizeInsecure();
      std::string userAgent = XTSubVersion(nMaxBlockSize, Opt().UserAgent(),
                                           Opt().UAComment(),
                                           Opt().HidePlatform());
      connman.PushMessage(pnode, CNetMsgMaker(INIT_PROTO_VERSION).Make(
                                  NetMsgType::VERSION, PROTOCOL_VERSION,
                                  (uint64_t)nLocalNodeServices, nTime, addrYou,
                                  addrMe, nonce, userAgent,
                                  nNodeStartingHeight, true));
  
      if (fLogIPs)
          LogPrint(Log::NET, "send version message: version %d, blocks=%d, us=%s, them=%s, peer=%d\n", PROTOCOL_VERSION, nNodeStartingHeight, addrMe.ToString(), addrYou.ToString(), nodeid);
      else
          LogPrint(Log::NET, "send version message: version %d, blocks=%d, us=%s, peer=%d\n", PROTOCOL_VERSION, nNodeStartingHeight, addrMe.ToString(), nodeid);
  }
  
  void InitializeNode(CNode *pnode, CConnman& connman) {
      NodeStatePtr::insert(pnode->GetId(), pnode, thinblockmg);
      if(!pnode->fInbound)
          PushNodeVersion(pnode, connman, GetTime());
  }
  
  void FinalizeNode(NodeId nodeid, bool& fUpdateConnectionTime) {
      fUpdateConnectionTime = false;
      LOCK(cs_main);
      NodeStatePtr state(nodeid);
  
      if (state->fSyncStarted)
          nSyncStarted--;
  
      if (state->nMisbehavior == 0 && state->fCurrentlyConnected) {
          fUpdateConnectionTime = true;
      }
  
      BOOST_FOREACH(const QueuedBlock& entry, state->vBlocksInFlight)
          blocksInFlight.erase(nodeid, entry.hash);
      EraseOrphansFor(nodeid);
      nPreferredDownload -= state->fPreferredDownload;
  
      state.erase();
  }
  
  // Requires cs_main.
  // Returns a bool indicating whether we requested this block.
  bool MarkBlockAsReceived(const uint256& hash) {
      AssertLockHeld(cs_main);
      if (!blocksInFlight.isInFlight(hash))
          return false;
  
      std::vector<QueuedBlockPtr> queued = blocksInFlight.queuedPtrsFor(hash);
      typedef std::vector<QueuedBlockPtr>::const_iterator auto_;
      for (auto_ q = queued.begin(); q != queued.end(); ++q) {
          InFlightEraserImpl erase;
          erase((*q)->node, hash);
      }
      thinblockmg.removeIfExists(hash);
      return !queued.empty();
  }
  
  struct MarkBlockAsInFlight : public BlockInFlightMarker {
  
      void operator()(NodeId nodeid, const uint256& hash,
                      const Consensus::Params& consensusParams,
                      const CBlockIndex *pindex = NULL) override
      {
          AssertLockHeld(cs_main);
  
          NodeStatePtr state(nodeid);
          assert(!state.IsNull());
  
          int64_t nNow = GetTimeMicros();
          QueuedBlock newentry = {hash, pindex, nNow, pindex != NULL, GetBlockTimeout(nNow, nQueuedValidatedHeaders, consensusParams), nodeid};
          nQueuedValidatedHeaders += newentry.fValidatedHeaders;
          list<QueuedBlock>::iterator it = state->vBlocksInFlight.insert(state->vBlocksInFlight.end(), newentry);
          state->nBlocksInFlight++;
          if (state->nBlocksInFlight > MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
              LogPrintf("Warning: Too many blocks in flight (%d of max %d) for peer=%d\n",
                        state->nBlocksInFlight, MAX_BLOCKS_IN_TRANSIT_PER_PEER, nodeid);
          }
          state->nBlocksInFlightValidHeaders += newentry.fValidatedHeaders;
          blocksInFlight.insert(it);
      };
  };
  
  /** Check whether the last unknown block a peer advertized is not yet known. */
  static void ProcessBlockAvailability(NodeStatePtr& state) {
      AssertLockHeld(cs_main);
  
      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 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<const CBlockIndex*>& vBlocks, std::set<NodeId>& nodeStaller) {
      if (count == 0)
          return;
  
      AssertLockHeld(cs_main);
      vBlocks.reserve(vBlocks.size() + count);
      NodeStatePtr state(nodeid);
      assert(!state.IsNull());
  
      // Make sure pindexBestKnownBlock is up to date, we'll need it.
      ProcessBlockAvailability(state);
  
      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<const CBlockIndex*> vToFetch;
      const 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);
      std::set<NodeId> waitingfor;
      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).
          for (const 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 (!(blocksInFlight.isInFlight(pindex->GetBlockHash())
                      || state->thinblock->isWorkingOn(pindex->GetBlockHash()))) {
                  // The block is not already downloaded, not yet in flight and
                  // not being received as a thin block announcement.
                  if (pindex->nHeight > nWindowEnd) {
                      // We reached the end of the window.
                      if (vBlocks.size() == 0 && !waitingfor.count(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.empty()) {
                  // This is the first already-in-flight block.
                  waitingfor = blocksInFlight.nodesWithQueued(pindex->GetBlockHash());
              }
          }
      }
  }
  
  } // anon namespace
  
  /** Update tracking information about which blocks a peer is assumed to have. */
  void UpdateBlockAvailability(NodeId nodeid, const uint256 &hash) {
      AssertLockHeld(cs_main);
      NodeStatePtr state(nodeid);
      assert(!state.IsNull());
  
      ProcessBlockAvailability(state);
  
      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;
      }
  }
  
  void OnBlockFinished::operator()(const CBlock& block, const std::vector<NodeId>& ids) {
      AssertLockHeld(cs_main);
  
      CValidationState state;
      std::set<NodeId> nodes(begin(ids), end(ids));
      BlockSource source(block.GetHash(), nodes, canMisbehave);
  
      // 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 = hasWhitelistedNode(ids) && !IsInitialBlockDownload();
  
      CBlock copy(block);
      // TODO: Have g_connman passed to the constructor of OnBlockFinished
      if (!ProcessNewBlock(state, source, &copy, forceProcessing, nullptr, g_connman.get())) {
          LogPrintf("ProcessNewBlock failed in %s\n", __func__);
      }
      rejectAndPunish(state, block.GetHash(), ids);
  }
  
  /// Did a whitelisted node help with this block?
  bool OnBlockFinished::hasWhitelistedNode(const std::vector<NodeId>& ids) const {
      for (NodeId id : ids) {
          bool whitelisted =  g_connman->ForNode(id, [](CNode* n) {
                      return n->fWhitelisted;
           });
          if (whitelisted)
              return true;
      }
      return false;
  }
  
  void OnBlockFinished::rejectAndPunish(const CValidationState& state,
          const uint256& hash, const std::vector<NodeId>& ids) {
      int dos = 0;
      if (!state.IsInvalid(dos))
          return;
  
      const std::string reason = state.GetRejectReason();
  
      LogPrintf("Invalid block due to %s\n", reason.c_str());
  
      auto rejectPunishFunc = [=](CNode* pnode) {
          if (!strCommand.empty()) {
              g_connman->PushMessage(pnode, NetMsg(pnode, NetMsgType::REJECT,
                                                   strCommand, state.GetRejectCode(),
                                                   reason.substr(0, MAX_REJECT_MESSAGE_LENGTH), hash));
          }
          if (dos <= 0)
              return true;
          Misbehaving(pnode->id, dos, "invalid block: " + reason);
          return true;
      };
  
      AssertLockHeld(cs_main);
      for (NodeId id : ids) {
          g_connman->ForNode(id, rejectPunishFunc);
      }
  }
  
  void InFlightEraserImpl::operator()(NodeId node, const uint256& hash) {
      LOCK(cs_main);
      QueuedBlockPtr q = blocksInFlight.queuedItem(node, hash);
      if (q == QueuedBlockPtr())
          return;
  
      nQueuedValidatedHeaders -= q->fValidatedHeaders;
      NodeStatePtr state(q->node);
      if (!state.IsNull()) {
          // state can be null if a node that has a block
          // in flight is being destructed.
          state->nBlocksInFlightValidHeaders -= q->fValidatedHeaders;
          state->vBlocksInFlight.erase(q);
          state->nBlocksInFlight--;
          state->nStallingSince = 0;
      }
      int64_t getdataTime = q->nTime;
      blocksInFlight.erase(q);
  
      int64_t now = GetTimeMicros();
      LogPrint(Log::BLOCK, "Block no longer in flight %s %.2f seconds after requesting it peer=%d\n",
              hash.ToString(), (now - getdataTime) / 1000000.0, (node));
  }
  
  bool GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats) {
      NodeStatePtr state(nodeid);
      if (state.IsNull())
          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.SanityCheckMessages.connect(&SanityCheckMessage);
      nodeSignals.ProcessMessages.connect(&ProcessMessages);
      nodeSignals.SendMessages.connect(&SendMessages);
      nodeSignals.InitializeNode.connect(&InitializeNode);
      nodeSignals.FinalizeNode.connect(&FinalizeNode);
      nodeSignals.GetMaxBlockSizeInsecure.connect(&GetMaxBlockSizeInsecure);
  }
  
  void UnregisterNodeSignals(CNodeSignals& nodeSignals)
  {
      nodeSignals.SanityCheckMessages.disconnect(&SanityCheckMessage);
      nodeSignals.ProcessMessages.disconnect(&ProcessMessages);
      nodeSignals.SendMessages.disconnect(&SendMessages);
      nodeSignals.InitializeNode.disconnect(&InitializeNode);
      nodeSignals.FinalizeNode.disconnect(&FinalizeNode);
      nodeSignals.GetMaxBlockSizeInsecure.disconnect(&GetMaxBlockSizeInsecure);
  }
  
  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)
  {
      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 = GetSerializeSize(tx, SER_NETWORK, CTransaction::CURRENT_VERSION);
      if (sz > 5000)
      {
          LogPrint(Log::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(Log::MEMPOOL, "stored orphan tx %s (mapsz %u prevsz %u)\n", hash.ToString(),
               mapOrphanTransactions.size(), mapOrphanTransactionsByPrev.size());
      return true;
  }
  
  void static EraseOrphanTx(uint256 hash)
  {
      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(Log::MEMPOOL, "Erased %d orphan tx from peer %d\n", nErased, peer);
  }
  
  
  unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
  {
      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 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);
  }
  
  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];
              Coin coin;
              if (!viewMemPool.GetCoin(txin.prevout, coin)) {
                  return error("%s: Missing input", __func__);
              }
              if (coin.nHeight == MEMPOOL_HEIGHT) {
                  // Assume all mempool transaction confirm in the next block
                  prevheights[txinIndex] = tip->nHeight + 1;
              } else {
                  prevheights[txinIndex] = coin.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);
  }
  
  /** 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());
  }
  
  static bool IsCashHFEnabled(int64_t nMedianTimePast) {
      return nMedianTimePast >=
             Params().GetConsensus().cashHardForkActivationTime;
  }
  
  bool IsCashHFEnabled(const CBlockIndex *pindexPrev) {
      if (pindexPrev == nullptr) {
          return false;
      }
  
      return IsCashHFEnabled(pindexPrev->GetMedianTimePast());
  }
  
  bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransaction &tx, bool fLimitFree,
                          bool* pfMissingInputs, CConnman* connman, bool fOverrideMempoolLimit, bool fRejectAbsurdFee)
  {
      AssertLockHeld(cs_main);
      if (pfMissingInputs)
          *pfMissingInputs = false;
  
      if (!CheckTransaction(tx, state))
          return error("AcceptToMemoryPool: CheckTransaction failed");
  
      // Coinbase is only valid in a block, not as a loose transaction
      if (tx.IsCoinBase()) {
          return state.DoS(100, error("AcceptToMemoryPool: coinbase as individual tx"),
                           REJECT_INVALID, "coinbase");
      }
  
      // Rather not work on nonstandard transactions (unless -testnet/-regtest)
      string reason;
      if (Params().RequireStandard() && !IsStandardTx(tx, reason))
          return state.DoS(0,
                           error("AcceptToMemoryPool: nonstandard transaction: %s", reason),
                           REJECT_NONSTANDARD, reason);
  
      // 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, error("AcceptToMemoryPool: non-final"),
                           REJECT_NONSTANDARD, "non-final");
  
      // is it already in the memory pool?
      uint256 hash = tx.GetHash();
      if (pool.exists(hash))
          return false;
  
      // Check for conflicts with in-memory transactions and triggers actions at
      // end of scope (relay tx, sync wallet, etc)
      respend::RespendDetector respend(pool, tx, respend::CreateDefaultActions(connman));
  
      if (respend.IsRespend() && !respend.IsInteresting())
      {
          // Tx is a respend, and it's not an interesting one (we don't care to
          // validate it further)
          return false;
      }
  
      {
          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?
          for (size_t out = 0; out < tx.vout.size(); out++) {
              COutPoint outpoint(hash, out);
              if (view.HaveCoin(outpoint)) {
                  return false;
              }
          }
  
          // do all inputs exist?
          BOOST_FOREACH(const CTxIn txin, tx.vin) {
              if (!view.HaveCoin(txin.prevout)) {
                  if (pfMissingInputs) {
                      *pfMissingInputs = true;
                  }
                  return false; // fMissingInputs and !state.IsInvalid() is used to detect this condition, don't set state.Invalid()
              }
          }
  
          // 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 (Params().RequireStandard() && !AreInputsStandard(tx, view))
              return error("AcceptToMemoryPool: nonstandard transaction input");
  
          // 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
          // MaxBlockSigops(), we still consider this an invalid rather than
          // merely non-standard transaction.
          unsigned int nSigOps = GetLegacySigOpCount(tx);
          nSigOps += GetP2SHSigOpCount(tx, view);
          if (nSigOps > MAX_STANDARD_TX_SIGOPS)
              return state.DoS(0,
                               error("AcceptToMemoryPool: too many sigops %s, %d > %d",
                                     hash.ToString(), nSigOps, MAX_STANDARD_TX_SIGOPS),
                               REJECT_NONSTANDARD, "bad-txns-too-many-sigops");
  
          CAmount nValueOut = tx.GetValueOut();
          CAmount nFees = nValueIn-nValueOut;
  
          // 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 Coin &coin = view.AccessCoin(txin.prevout);
              if (coin.IsCoinBase()) {
                  fSpendsCoinbase = true;
                  break;
              }
          }
  
          CTxMemPoolEntry entry(tx, nFees, GetTime(), chainActive.Height(), pool.HasNoInputsOf(tx), fSpendsCoinbase, lp, nSigOps);
  
          FeeEvaluator feeEval(Opt().AllowFreeTx(), mempool.GetFeeModifier(),
                               ::minRelayTxFee);
          FeeEvaluator::FeeState feestate = feeEval.HasSufficientFee(view, entry,
                                                                     chainActive.Height());
          if (!fLimitFree) {
              // Don't accept it if it can't get into a block
              bool ok = feestate == FeeEvaluator::FEE_OK
                  || feestate == FeeEvaluator::ABSURD_HIGH_FEE;
              if (!ok) {
                  std::string err = FeeEvaluator::ToString(feestate);
                  return state.DoS(0, false, REJECT_INSUFFICIENTFEE, err);
              }
          }
          if (fRejectAbsurdFee && feestate == FeeEvaluator::ABSURD_HIGH_FEE) {
              return error("AcceptToMemoryPool: absurdly high fees %s amount: %d size: %d",
                           hash.ToString(),
                           nFees, entry.GetTxSize());
          }
  
          // 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);
          }
  
          const int64_t mtpChainTip = chainActive.Tip()->GetMedianTimePast();
          unsigned int forkVerifyFlags = 0;
  
          if (IsUAHFActive(mtpChainTip)) {
              forkVerifyFlags |= SCRIPT_ENABLE_SIGHASH_FORKID;
          }
  
          if (IsThirdHFActive(mtpChainTip)) {
              forkVerifyFlags |= SCRIPT_ENABLE_MONOLITH_OPCODES;
          }
  
          // Check against previous transactions
          // This is done last to help prevent CPU exhaustion denial-of-service attacks.
          PrecomputedTransactionData txdata(tx);
          if (!CheckInputs(tx, state, view, true, STANDARD_SCRIPT_VERIFY_FLAGS | forkVerifyFlags,
  	                    true, txdata))
          {
              return error("AcceptToMemoryPool: ConnectInputs failed %s", hash.ToString());
          }
  
          // 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 | forkVerifyFlags,
  	                    true, txdata))
          {
              return error("AcceptToMemoryPool: BUG! PLEASE REPORT THIS! ConnectInputs failed against MANDATORY but not STANDARD flags %s", hash.ToString());
          }
  
          respend.SetValid(true);
          if (respend.IsRespend())
              return false;
  
          // Set a fee delta to protect local wallet transactions from mempool size-based eviction
          if (!fLimitFree) {
              pool.GetFeeModifier().AddDelta(hash, 1);
          }
  
          // Store transaction in memory
          pool.addUnchecked(hash, entry, setAncestors, !IsInitialBlockDownload());
  
          if (!fOverrideMempoolLimit) {
              // Expire
              int expired = pool.Expire(GetTime() - GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
              if (expired != 0)
                  LogPrint(Log::MEMPOOL, "Expired %i transactions from the memory pool\n", expired);
  
              // Trim
              pool.TrimToSize(GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000);
              if (!pool.exists(tx.GetHash()))
                  return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "mempool full");
          }
  
          SyncWithWallets(tx, NULL, false);
      }
  
      return true;
  }
  
  /** 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, 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
              const Coin& coin = AccessByTxid(*pcoinsTip, hash);
              if (!coin.IsSpent()) pindexSlow = chainActive[coin.nHeight];
          }
      }
  
      if (pindexSlow) {
          CBlock block;
          if (ReadBlockFromDisk(block, pindexSlow, Params().GetConsensus())) {
              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(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 = GetSerializeSize(fileout, 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;
      // 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 fForceInitialBlockDownload = false;
  bool IsInitialBlockDownload()
  {
      if (fForceInitialBlockDownload)
          return false;
  
      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 ||
              std::max(chainActive.Tip()->GetBlockTime(), pindexBestHeader->GetBlockTime()) < GetTime() - 24 * 60 * 60);
      if (!state) {
          lockIBDState = true;
          LogPrintf("No longer initial block download\n");
      }
      return state;
  }
  
  bool fLargeWorkForkFound = false;
  bool fLargeWorkInvalidChainFound = false;
  CBlockIndex *pindexBestForkTip = NULL, *pindexBestForkBase = NULL;
  
  static void AlertNotify(const std::string& strMessage, bool fThread)
  {
      uiInterface.NotifyAlertChanged();
      std::string strCmd = GetArg("-alertnotify", "");
      if (strCmd.empty()) return;
  
      // Alert text should be plain ascii coming from a trusted source, but to
      // be safe we first strip anything not in safeChars, then add single quotes around
      // the whole string before passing it to the shell:
      std::string singleQuote("'");
      std::string safeStatus = SanitizeString(strMessage);
      safeStatus = singleQuote+safeStatus+singleQuote;
      boost::replace_all(strCmd, "%s", safeStatus);
  
      if (fThread)
          boost::thread t(runCommand, strCmd); // thread runs free
      else
          runCommand(strCmd);
  }
  
  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("'");
              AlertNotify(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();
  }
  
  void Misbehaving(NodeId pnode, int howmuch, const std::string& what)
  {
      if (howmuch == 0)
          return;
  
      NodeStatePtr state(pnode);
      if (state.IsNull())
          return;
  
      state->nMisbehavior += howmuch;
      int banscore = GetArg("-banscore", 100);
      if (state->nMisbehavior >= banscore && state->nMisbehavior - howmuch < banscore)
      {
          LogPrintf("%s: %s (%d -> %d) [%s] BAN THRESHOLD EXCEEDED\n", __func__,
                    state->name, state->nMisbehavior-howmuch, state->nMisbehavior, what);
          state->fShouldBan = true;
      } else
          LogPrintf("%s: %s (%d -> %d) [%s]\n", __func__, state->name,
                    state->nMisbehavior-howmuch, state->nMisbehavior, what);
  }
  
  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()));
      LogPrintf("%s:  current best=%s  height=%d  log2_work=%.8g  date=%s\n", __func__,
        chainActive.Tip()->GetBlockHash().ToString(), chainActive.Height(), log(chainActive.Tip()->nChainWork.getdouble())/log(2.0),
        DateTimeStrFormat("%Y-%m-%d %H:%M:%S", chainActive.Tip()->GetBlockTime()));
      CheckForkWarningConditions();
  }
  
  void static InvalidBlockFound(CBlockIndex *pindex, const CValidationState &state,
          const BlockSource& blockSource) {
      int nDoS = 0;
      if (state.IsInvalid(nDoS)) {
  
          for (NodeId id : blockSource.nodes) {
              NodeStatePtr nodeState(id);
              if (nodeState.IsNull())
                  continue;
  
              CBlockReject reject = {state.GetRejectCode(), state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), pindex->GetBlockHash()};
              LogPrint(Log::BLOCK, "Rejecting block from %d, code %d, reason %s",
                       id, state.GetRejectCode(), state.GetRejectReason());
              nodeState->rejects.push_back(reject);
              if (blockSource.canMisbehave && nDoS > 0)
                  Misbehaving(id, nDoS, "invalid block: " + state.GetRejectReason());
          }
      }
      if (!state.CorruptionPossible()) {
          pindex->nStatus |= BLOCK_FAILED_VALID;
          setDirtyBlockIndex.insert(pindex);
          setBlockIndexCandidates.erase(pindex);
          InvalidChainFound(pindex);
      }
  }
  
  void UpdateCoins(const CTransaction& tx, 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) {
              txundo.vprevout.emplace_back();
              bool is_spent = inputs.SpendCoin(txin.prevout, &txundo.vprevout.back());
              assert(is_spent);
          }
      }
  
      // add outputs
      AddCoins(inputs, tx, nHeight);
  }
  
  void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, int nHeight)
  {
      CTxUndo txundo;
      UpdateCoins(tx, inputs, txundo, nHeight);
  }
  
  bool CScriptCheck::operator()() {
      const CScript &scriptSig = ptxTo->vin[nIn].scriptSig;
      if (!VerifyScript(scriptSig, scriptPubKey, nFlags, CachingTransactionSignatureChecker(ptxTo, nIn, amount, cacheStore, *txdata), &error)) {
          return ::error("CScriptCheck(): %s:%d VerifySignature failed: %s", ptxTo->GetHash().ToString(), nIn, ScriptErrorString(error));
      }
      return true;
  }
  
  int GetSpendHeight(const CCoinsViewCache& inputs)
  {
      LOCK(cs_main);
      CBlockIndex* pindexPrev = mapBlockIndex.find(inputs.GetBestBlock())->second;
      return pindexPrev->nHeight + 1;
  }
  
  bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheStore, PrecomputedTransactionData& txdata, 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 Coin& coin = inputs.AccessCoin(prevout);
                  assert(!coin.IsSpent());
  
                  // We are very carefully only pass in things to CScriptCheck which
                  // are clearly committed to by tx' witness hash. This provides
                  // a sanity check that our caching is not introducing consensus
                  // failures through additional data in, eg, the coins being
                  // spent being checked as a part of CScriptCheck.
                  const CScript& scriptPubKey = coin.out.scriptPubKey;
                  const CAmount amount = coin.out.nValue;
  
                  // Verify signature
                  CScriptCheck check(scriptPubKey, amount, tx, i, flags, cacheStore, &txdata);
                  if (pvChecks) {
                      pvChecks->push_back(CScriptCheck());
                      check.swap(pvChecks->back());
                  } else if (!check()) {
                      const bool hasNonMandatoryFlags
                          = (flags & STANDARD_NOT_MANDATORY_VERIFY_FLAGS) != 0;
                      const bool doesNotHaveMonolith
                          = (flags & SCRIPT_ENABLE_MONOLITH_OPCODES) == 0;
  
                      if (hasNonMandatoryFlags || doesNotHaveMonolith) {
                          // 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.
                          //
                          //
                          // We also check activating the monolith opcodes as it is a
                          // strictly additive change and we would not like to ban some of
                          // our peer that are ahead of us and are considering the fork
                          // as activated.
                          unsigned int flagsFiltered = (flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS)
                              | SCRIPT_ENABLE_MONOLITH_OPCODES;
  
                          CScriptCheck check2(scriptPubKey, amount, tx, i,
                                  flagsFiltered, cacheStore, &txdata);
  
                          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 = GetSerializeSize(fileout, 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;
      CHashVerifier<CAutoFile> verifier(&filein); // We need a CHashVerifier as reserializing may lose data
      try {
          verifier << hashBlock;
          verifier >> blockundo;
          filein >> hashChecksum;
      }
      catch (const std::exception& e) {
          return error("%s: Deserialize or I/O error - %s", __func__, e.what());
      }
  
      // Verify checksum
      if (hashChecksum != verifier.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 occured, 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
  
  enum DisconnectResult
  {
      DISCONNECT_OK,      // All good.
      DISCONNECT_UNCLEAN, // Rolled back, but UTXO set was inconsistent with block.
      DISCONNECT_FAILED   // Something else went wrong.
  };
  
  /**
   * Restore the UTXO in a Coin at a given COutPoint
   * @param undo The Coin to be restored.
   * @param view The coins view to which to apply the changes.
   * @param out The out point that corresponds to the tx input.
   * @return A DisconnectResult as an int
   */
  int ApplyTxInUndo(Coin&& undo, CCoinsViewCache& view, const COutPoint& out)
  {
      bool fClean = true;
  
      if (view.HaveCoin(out)) fClean = false; // overwriting transaction output
  
      if (undo.nHeight == 0) {
          // Missing undo metadata (height and coinbase). Older versions included this
          // information only in undo records for the last spend of a transactions'
          // outputs. This implies that it must be present for some other output of the same tx.
          const Coin& alternate = AccessByTxid(view, out.hash);
          if (!alternate.IsSpent()) {
              undo.nHeight = alternate.nHeight;
              undo.fCoinBase = alternate.fCoinBase;
          } else {
              return DISCONNECT_FAILED; // adding output for transaction without known metadata
          }
      }
      // The potential_overwrite parameter to AddCoin is only allowed to be false if we know for
      // sure that the coin did not already exist in the cache. As we have queried for that above
      // using HaveCoin, we don't need to guess. When fClean is false, a coin already existed and
      // it is an overwrite.
      view.AddCoin(out, std::move(undo), !fClean);
  
      return fClean ? DISCONNECT_OK : DISCONNECT_UNCLEAN;
  }
  
  /** Undo the effects of this block (with given index) on the UTXO set represented by coins.
   *  When FAILED is returned, view is left in an indeterminate state. */
  static DisconnectResult DisconnectBlock(const CBlock& block, const CBlockIndex* pindex, CCoinsViewCache& view)
  {
      bool fClean = true;
  
      CBlockUndo blockUndo;
      CDiskBlockPos pos = pindex->GetUndoPos();
      if (pos.IsNull()) {
          error("DisconnectBlock(): no undo data available");
          return DISCONNECT_FAILED;
      }
      if (!UndoReadFromDisk(blockUndo, pos, pindex->pprev->GetBlockHash())) {
          error("DisconnectBlock(): failure reading undo data");
          return DISCONNECT_FAILED;
      }
  
      if (blockUndo.vtxundo.size() + 1 != block.vtx.size()) {
          error("DisconnectBlock(): block and undo data inconsistent");
          return DISCONNECT_FAILED;
      }
  
      // 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();
          bool is_coinbase = tx.IsCoinBase();
  
          // Check that all outputs are available and match the outputs in the block itself
          // exactly.
          for (size_t o = 0; o < tx.vout.size(); o++) {
              if (!tx.vout[o].scriptPubKey.IsUnspendable()) {
                  COutPoint out(hash, o);
                  Coin coin;
                  bool is_spent = view.SpendCoin(out, &coin);
                  if (!is_spent || tx.vout[o] != coin.out || pindex->nHeight != coin.nHeight || is_coinbase != coin.fCoinBase) {
                      fClean = false; // transaction output mismatch
                  }
              }
          }
  
          // restore inputs
          if (i > 0) { // not coinbases
              CTxUndo &txundo = blockUndo.vtxundo[i-1];
              if (txundo.vprevout.size() != tx.vin.size()) {
                  error("DisconnectBlock(): transaction and undo data inconsistent");
                  return DISCONNECT_FAILED;
              }
              for (unsigned int j = tx.vin.size(); j-- > 0;) {
                  const COutPoint &out = tx.vin[j].prevout;
                  int res = ApplyTxInUndo(std::move(txundo.vprevout[j]), view, out);
                  if (res == DISCONNECT_FAILED) return DISCONNECT_FAILED;
                  fClean = fClean && res != DISCONNECT_UNCLEAN;
              }
              // At this point, all of txundo.vprevout should have been moved out.
          }
      }
  
      // move best block pointer to prevout block
      view.SetBestBlock(pindex->pprev->GetBlockHash());
  
      return fClean ? DISCONNECT_OK : DISCONNECT_UNCLEAN;
  }
  
  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).
  // Always returns the constant interval at which it should be scheduled.
  //
  int PartitionCheck(bool (*initialDownloadCheck)(), CCriticalSection& cs, const CBlockIndex *const &bestHeader,
                      int64_t nPowTargetSpacing)
  {
      // Aim for one false-positive about every fifty years of normal running:
      // The sample interval SPAN_SECONDS is chosen as the smallest multiple of target spacing expected
      // to trigger a too-few-blocks alert only once in fifty years (this will be when 0 blocks are seen):
      // blocks  cdf(blocks, 0)  alertThreshold
      //   11    1.67017e-5      4.18569e-6
      //   12    6.14421e-6      4.56621e-6
      //   13    2.26033e-6      4.94673e-6 <--- min such that (cdf < threshold)
      //   14    8.31529e-7      5.32725e-6
      //   15    3.05902e-7      5.70776e-6
      //TODO find BLOCKS_EXPECTED dynamically, for correct timing of non-10-minute intervals
      const int FIFTY_YEARS = 50*365*24*60*60;
      const int BLOCKS_EXPECTED = 13;
      const int SPAN_SECONDS = BLOCKS_EXPECTED * nPowTargetSpacing;
      double alertThreshold = 1.0 / (FIFTY_YEARS / SPAN_SECONDS);
  
      if (bestHeader == NULL || initialDownloadCheck()) return SPAN_SECONDS;
  
      static int64_t lastAlertTime = 0;
      int64_t now = GetAdjustedTime();
      if (lastAlertTime > now-60*60*24) return SPAN_SECONDS; // Alert at most once per day
  
      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 SPAN_SECONDS; // Ran out of chain, we must not be fully sync'ed
      }
  
      // How likely is it to find at least that many by chance?
      double pHigh = 1.0 - boost::math::cdf(poisson, std::max(0, nBlocks - 1));
      // How likely is it to find at most that few by chance?
      double pLow = boost::math::cdf(poisson, nBlocks);
  
      LogPrint(Log::PARTITIONCHECK, "%s: Found %d blocks in the last %d seconds\n", __func__, nBlocks, SPAN_SECONDS);
      LogPrint(Log::PARTITIONCHECK, "%s: likelihood that many: %g, that few: %g\n", __func__, pHigh, pLow);
  
      if (pLow <= alertThreshold)
      {
          // Many fewer blocks than expected: alert!
          strWarning = strprintf(_("WARNING: check your network connection, %d blocks received in the last %d seconds (%d expected)"),
                                 nBlocks, SPAN_SECONDS, BLOCKS_EXPECTED);
      }
      else if (pHigh <= alertThreshold)
      {
          // Many more blocks than expected: alert!
          strWarning = strprintf(_("WARNING: abnormally high number of blocks generated, %d blocks received in the last %d seconds (%d expected)"),
                                 nBlocks, SPAN_SECONDS, BLOCKS_EXPECTED);
      }
      if (!strWarning.empty())
      {
          strMiscWarning = strWarning;
          AlertNotify(strWarning, true);
          lastAlertTime = now;
      }
      return SPAN_SECONDS;
  }
  
  // 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 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);
      // 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;
      }
  
      // Block size limit (BIP100)
      if (block.vtx.size() > pindex->nMaxBlockSize)
          return state.DoS(100, error("%s: size limits failed", __func__), REJECT_INVALID, "bad-vtx-length");
      uint64_t nBlockSize = ::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION);
      if (nBlockSize > pindex->nMaxBlockSize)
          return state.DoS(100, error("%s: size limits failed %d > %d", __func__, nBlockSize, pindex->nMaxBlockSize), REJECT_INVALID, "bad-blk-length");
  
      const int64_t timeBarrier = GetTime() - 24 * 3600 * Opt().CheckpointDays();
      // Blocks that have varius days of POW behind them makes them secure in
      // that actually online nodes checked the scripts, so during initial sync we
      // don't need to check the scripts.
      // All other block validity tests are still checked.
      bool fScriptChecks = !fCheckpointsEnabled || block.nTime > timeBarrier;
  
      // 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) {
          for (const auto& tx : block.vtx) {
              for (size_t o = 0; o < tx.vout.size(); o++) {
                  if (view.HaveCoin(COutPoint(tx.GetHash(), o))) {
                      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;
      }
  
      // Allow UAHF replay-protected signatures if parent is at or after activation time
      if ((Opt().UAHFTime() != 0) && (pindex->pprev != NULL) && (pindex->pprev->GetMedianTimePast() >= Opt().UAHFTime())) {
          flags |= SCRIPT_VERIFY_STRICTENC;
          flags |= SCRIPT_ENABLE_SIGHASH_FORKID;
      }
  
      // If the Cash HF is enabled, we start rejecting transaction that use a high
      // s in their signature. We also make sure that signature that are supposed
      // to fail (for instance in multisig or other forms of smart contracts) are
      // null.
      if ((Opt().UAHFTime() != 0) && IsCashHFEnabled(pindex->pprev)) {
          flags |= SCRIPT_VERIFY_LOW_S;
          flags |= SCRIPT_VERIFY_NULLFAIL;
      }
  
      // Enable more opcodes after the third HD.
      if (IsThirdHFActive(pindex->pprev->GetMedianTimePast())) {
          flags |= SCRIPT_ENABLE_MONOLITH_OPCODES;
      }
  
      CBlockUndo blockundo;
  
      CCheckQueueControl<CScriptCheck> control(fScriptChecks && Opt().ScriptCheckThreads() ? &scriptcheckqueue : NULL);
  
      std::vector<int> prevheights;
  
      int64_t nTimeStart = GetTimeMicros();
      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);
      std::vector<PrecomputedTransactionData> txdata;
      txdata.reserve(block.vtx.size()); // Required so that pointers to individual PrecomputedTransactionData don't get invalidated
      for (unsigned int i = 0; i < block.vtx.size(); i++)
      {
          const CTransaction &tx = block.vtx[i];
  
          nInputs += tx.vin.size();
          unsigned int nTxSigOps = GetLegacySigOpCount(tx);
          nSigOps += nTxSigOps;
          if (nSigOps > MaxBlockSigops(nBlockSize))
              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.AccessCoin(tx.vin[j].prevout).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.
                  unsigned int nP2SHSigOps = GetP2SHSigOpCount(tx, view);
                  nSigOps += nP2SHSigOps;
                  nTxSigOps += nP2SHSigOps;
                  if (nSigOps > MaxBlockSigops(nBlockSize))
                      return state.DoS(100, error("ConnectBlock(): too many sigops"),
                                       REJECT_INVALID, "bad-blk-sigops");
              }
              if (nTxSigOps > MAX_TX_SIGOPS_COUNT) {
                  return state.DoS(100, error("ConnectBlock(): too many sigops in tx"), REJECT_INVALID, "bad-txn-sigops");
              }
          }
          txdata.emplace_back(tx);
          if (!tx.IsCoinBase())
          {
              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) */
              static auto nScriptCheckThreads = Opt().ScriptCheckThreads();
              if (!CheckInputs(tx, state, view, fScriptChecks, flags, fCacheResults,
                               txdata[i], nScriptCheckThreads ? &vChecks : NULL))
                  return false;
              control.Add(vChecks);
          }
  
          CTxUndo undoDummy;
          if (i > 0) {
              blockundo.vtxundo.push_back(CTxUndo());
          }
          UpdateCoins(tx, 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 nTime1 = GetTimeMicros(); nTimeConnect += nTime1 - nTimeStart;
      LogPrint(Log::BENCH, "      - Connect %u transactions: %.2fms (%.3fms/tx, %.3fms/txin) [%.2fs]\n", (unsigned)block.vtx.size(), 0.001 * (nTime1 - nTimeStart), 0.001 * (nTime1 - nTimeStart) / block.vtx.size(), nInputs <= 1 ? 0 : 0.001 * (nTime1 - nTimeStart) / (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, REJECT_INVALID, "blk-bad-inputs",
                           false, "parallel script check failed");
      }
      int64_t nTime2 = GetTimeMicros(); nTimeVerify += nTime2 - nTimeStart;
      LogPrint(Log::BENCH, "    - Verify %u txins: %.2fms (%.3fms/txin) [%.2fs]\n", nInputs - 1, 0.001 * (nTime2 - nTimeStart), nInputs <= 1 ? 0 : 0.001 * (nTime2 - nTimeStart) / (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.DBMagic()))
                  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 nTime3 = GetTimeMicros(); nTimeIndex += nTime3 - nTime2;
      LogPrint(Log::BENCH, "    - Index writing: %.2fms [%.2fs]\n", 0.001 * (nTime3 - nTime2), nTimeIndex * 0.000001);
  
      // Watch for changes to the previous coinbase transaction.
      static uint256 hashPrevBestCoinBase;
      GetMainSignals().UpdatedTransaction(hashPrevBestCoinBase);
      hashPrevBestCoinBase = block.vtx[0].GetHash();
  
      int64_t nTime4 = GetTimeMicros(); nTimeCallbacks += nTime4 - nTime3;
      LogPrint(Log::BENCH, "    - Callbacks: %.2fms [%.2fs]\n", 0.001 * (nTime4 - nTime3), 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) {
      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) {
          FindFilesToPrune(setFilesToPrune);
          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 Coin structures on disk are around 48 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(48 * 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 ((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(%utxo)\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) {
                          AlertNotify(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) {
                  AlertNotify(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) {
      CBlockIndex *pindexDelete = chainActive.Tip();
      assert(pindexDelete);
      // Read block from disk.
      CBlock block;
      if (!ReadBlockFromDisk(block, pindexDelete, Params().GetConsensus()))
          return AbortNode(state, "Failed to read block");
      // Apply the block atomically to the chain state.
      int64_t nStart = GetTimeMicros();
      {
          CCoinsViewCache view(pcoinsTip);
          assert(view.GetBestBlock() == pindexDelete->GetBlockHash());
          if (DisconnectBlock(block, pindexDelete, view) != DISCONNECT_OK)
              return error("DisconnectTip(): DisconnectBlock %s failed", pindexDelete->GetBlockHash().ToString());
          assert(view.Flush());
      }
      LogPrint(Log::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, nullptr, true)) {
              mempool.removeRecursive(tx, removed);
          } 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, false);
      }
      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, CBlockIndex *pindexNew,
          CBlock *pblock, const BlockSource& blockSource) {
      assert(pindexNew->pprev == chainActive.Tip());
      // Read block from disk.
      int64_t nTime1 = GetTimeMicros();
      CBlock block;
      if (!pblock) {
          if (!ReadBlockFromDisk(block, pindexNew, Params().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(Log::BENCH, "  - Load block from disk: %.2fms [%.2fs]\n", (nTime2 - nTime1) * 0.001, nTimeReadFromDisk * 0.000001);
      {
          CCoinsViewCache view(pcoinsTip);
          CInv inv(MSG_BLOCK, pindexNew->GetBlockHash());
          bool rv = ConnectBlock(*pblock, state, pindexNew, view);
          GetMainSignals().BlockChecked(*pblock, state);
          if (!rv) {
              if (state.IsInvalid())
                  InvalidBlockFound(pindexNew, state, blockSource);
              return error("ConnectTip(): ConnectBlock %s failed", pindexNew->GetBlockHash().ToString());
          }
          nTime3 = GetTimeMicros(); nTimeConnectTotal += nTime3 - nTime2;
          LogPrint(Log::BENCH, "  - Connect total: %.2fms [%.2fs]\n", (nTime3 - nTime2) * 0.001, nTimeConnectTotal * 0.000001);
          assert(view.Flush());
      }
      int64_t nTime4 = GetTimeMicros(); nTimeFlush += nTime4 - nTime3;
      LogPrint(Log::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(Log::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, false);
      }
      // ... and about transactions that got confirmed:
      BOOST_FOREACH(const CTransaction &tx, pblock->vtx) {
          SyncWithWallets(tx, pblock, false);
      }
  
      int64_t nTime6 = GetTimeMicros(); nTimePostConnect += nTime6 - nTime5; nTimeTotal += nTime6 - nTime1;
      LogPrint(Log::BENCH, "  - Connect postprocess: %.2fms [%.2fs]\n", (nTime6 - nTime5) * 0.001, nTimePostConnect * 0.000001);
      LogPrint(Log::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, CBlockIndex *pindexMostWork, CBlock *pblock, const BlockSource& blockSource, bool& fInvalidFound) {
      AssertLockHeld(cs_main);
      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))
              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) {
              CBlock* mostWork = pindexConnect == pindexMostWork ? pblock : nullptr;
              if (!ConnectTip(state, pindexConnect, mostWork, blockSource)) {
                  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);
          mempool.TrimToSize(GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000);
      }
      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, CBlock *pblock, const BlockSource& blockSource, CConnman* connman) {
      CBlockIndex *pindexMostWork = NULL;
      CBlockIndex *pindexNewTip = nullptr;
      int nStopAtHeight = GetArg("-stopatheight", DEFAULT_STOPATHEIGHT);
      const CChainParams& chainParams = Params();
      do {
          boost::this_thread::interruption_point();
          if (ShutdownRequested())
              break;
  
          const CBlockIndex *pindexFork;
          bool fInitialDownload;
          int nNewHeight;
          {
              LOCK(cs_main);
              CBlockIndex* pindexOldTip = chainActive.Tip();
              if (pindexMostWork == NULL) {
                  pindexMostWork = FindMostWorkChain();
              }
  
              // Whether we have anything to do at all.
              if (pindexMostWork == NULL || pindexMostWork == chainActive.Tip())
                  return true;
  
              bool fInvalidFound = false;
              CBlock* mostWork = pblock && (pblock->GetHash() == pindexMostWork->GetBlockHash()) ? pblock : nullptr;
              if (!ActivateBestChainStep(state, pindexMostWork, mostWork, blockSource, fInvalidFound))
                  return false;
  
              if (fInvalidFound) {
                  // Wipe cache, we may need another branch now.
                  pindexMostWork = NULL;
              }
              pindexNewTip = chainActive.Tip();
              pindexFork = chainActive.FindFork(pindexOldTip);
              fInitialDownload = IsInitialBlockDownload();
              nNewHeight = chainActive.Height();
          }
          // When we reach this point, we switched to a new tip (stored in pindexNewTip).
  
          // Notifications/callbacks that can run without cs_main
          if(connman)
              connman->SetBestHeight(nNewHeight);
  
          // Notify external listeners about the new tip.
          uiInterface.NotifyBlockTip(fInitialDownload, pindexNewTip);
  
          if (connman && !fInitialDownload) {
              std::vector<uint256> hashesToAnnounce
                  = findHeadersToAnnounce(pindexFork, pindexNewTip);
  
              // Relay inventory, but don't relay old inventory during initial block download.
              int nBlockEstimate = 0;
              if (fCheckpointsEnabled)
                  nBlockEstimate = Checkpoints::GetTotalBlocksEstimate(chainParams.Checkpoints());
  
              connman->ForEachNode([nBlockEstimate, &hashesToAnnounce, nNewHeight](CNode *pnode) {
                      int announceMinHeight = pnode->nStartingHeight == - 1
                          ? nBlockEstimate : pnode->nStartingHeight - 2000;
  
                      // Don't announce if our height is far below theirs
                      if (nNewHeight < announceMinHeight)
                          return;
  
                      for (auto h : hashesToAnnounce)
                          pnode->PushBlockHash(h);
                  });
              connman->WakeMessageHandler();
          }
          if (nStopAtHeight && pindexNewTip && pindexNewTip->nHeight >= nStopAtHeight) StartShutdown();
      } while(pindexNewTip != pindexMostWork);
      CheckBlockIndex();
  
      // Write changes periodically to disk, after relay.
      if (!FlushStateToDisk(state, FLUSH_STATE_PERIODIC)) {
          return false;
      }
  
      return true;
  }
  
  bool InvalidateBlock(CValidationState& state, 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)) {
              mempool.removeForReorg(pcoinsTip, chainActive.Tip()->nHeight + 1, STANDARD_LOCKTIME_VERIFY_FLAGS);
              return false;
          }
      }
  
      mempool.TrimToSize(GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000);
  
      // 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->nMaxBlockSizeVote = GetMaxBlockSizeVote(block.vtx[0].vin[0].scriptSig, pindexNew->nHeight);
      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++;
              }
              pindex->nMaxBlockSize = GetNextMaxBlockSize(pindex->pprev, Params().GetConsensus());
              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 >=
                 GetNextMaxBlockSize(chainActive.Tip(), Params().GetConsensus()) * Params().MinBlockFileBlocks()) {
              LogPrintf("Leaving block file %i: %s\n", nFile, vinfoBlockFile[nFile].ToString());
              FlushBlockFile(true);
              nFile++;
              if (vinfoBlockFile.size() <= nFile) {
                  vinfoBlockFile.resize(nFile + 1);
              }
          }
          pos.nFile = nFile;
          pos.nPos = vinfoBlockFile[nFile].nSize;
      }
  
      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.
  
      // 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())
          return state.DoS(100, error("CheckBlock(): no transactions"), 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 failed");
  
      unsigned int nSigOps = 0;
      BOOST_FOREACH(const CTransaction& tx, block.vtx)
      {
          nSigOps += GetLegacySigOpCount(tx);
      }
      if (nSigOps > MaxBlockSigops(::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION)))
          return state.DoS(100, error("CheckBlock(): out-of-bounds SigOpCount"), REJECT_INVALID, "bad-blk-sigops", true);
  
      return true;
  }
  
  bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationState& state, CBlockIndex * const pindexPrev)
  {
      const CChainParams& chainParams = Params();
      const Consensus::Params& consensusParams = chainParams.GetConsensus();
      uint256 hash = block.GetHash();
      if (hash == consensusParams.hashGenesisBlock)
          return true;
  
      assert(pindexPrev);
  
      int nHeight = pindexPrev->nHeight+1;
  
      // 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");
  
      if(fCheckpointsEnabled)
      {
          // Check that the block chain matches the known block chain up to a checkpoint
          if (!Checkpoints::CheckBlock(chainParams.Checkpoints(), nHeight, hash))
              return state.DoS(100, error("%s: rejected by checkpoint lock-in at %d", __func__, nHeight),
                               REJECT_CHECKPOINT, "checkpoint mismatch");
  
          // 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));
      }
  
      // 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 ContextualCheckTransaction(const CTransaction &tx, CValidationState &state, int nHeight,
                                  int64_t nLockTimeCutoff, int64_t nMedianTimePastPrev) {
      if (!IsFinalTx(tx, nHeight, nLockTimeCutoff)) {
          return state.DoS(10, error("%s: contains a non-final transaction", __func__), REJECT_INVALID, "bad-txns-nonfinal");
      }
      if ((Opt().UAHFTime() != 0) &&
          (nMedianTimePastPrev >= Opt().UAHFTime()) &&
          (nHeight <= Opt().UAHFProtectSunset())) {
          for (const CTxOut &o : tx.vout) {
              if (o.scriptPubKey.IsCommitment(GetAntiReplayCommitment())) {
                  return state.DoS(10, error("%s: chain protected from tx", __func__), REJECT_INVALID, "bad-txn-replay");
              }
          }
      }
      return true;
  }
  
  bool ContextualCheckBlock(const CBlock& block, CValidationState& state, CBlockIndex * const pindexPrev)
  {
      const int nHeight = pindexPrev == NULL ? 0 : pindexPrev->nHeight + 1;
      const int64_t nMedianTimePastPrev = (pindexPrev == NULL ? 0 : pindexPrev->GetMedianTimePast());
      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;
      }
  
      CBlockIndex* pprevprev = pindexPrev == nullptr
          ? nullptr
          : pindexPrev->pprev;
  
      if (IsUAHFActivatingBlock(nMedianTimePastPrev, pprevprev)
              && !(Params().NetworkIDString() == CBaseChainParams::REGTEST && pprevprev == nullptr)) {
  
          // If UAHF is enabled for the current block, but not for the previous
          // block, this is the fork block, so we must check that the block is larger than 1MB.
          const uint64_t currentBlockSize = ::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION);
          if (currentBlockSize <= MAX_BLOCK_SIZE) {
              return state.DoS(100, error("%s: UAHF fork block must exceed %d, but this block is %d bytes",
                      __func__, MAX_BLOCK_SIZE, currentBlockSize), REJECT_INVALID, "bad-blk-too-small");
          }
      }
  
      int64_t nLockTimeCutoff = (nLockTimeFlags & LOCKTIME_MEDIAN_TIME_PAST)
                                ? nMedianTimePastPrev
                                : block.GetBlockTime();
  
      // Check that all transactions are finalized
      BOOST_FOREACH(const CTransaction& tx, block.vtx) {
          if (!ContextualCheckTransaction(tx, state, nHeight, nLockTimeCutoff, nMedianTimePastPrev)) {
              // state set by ContextualCheckTransaction.
              return false;
          }
      }
  
      // 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;
  }
  
  bool AcceptBlockHeader(const CBlockHeader& block, CValidationState& state, CBlockIndex** ppindex)
  {
      const CChainParams& chainparams = Params();
      AssertLockHeld(cs_main);
      // Check for duplicate
      uint256 hash = block.GetHash();
      BlockMap::iterator miSelf = mapBlockIndex.find(hash);
      CBlockIndex *pindex = NULL;
      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;
      if (hash != chainparams.GetConsensus().hashGenesisBlock) {
          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");
      }
  
      if (!ContextualCheckBlockHeader(block, state, pindexPrev))
          return false;
  
      if (pindex == NULL)
          pindex = AddToBlockIndex(block);
  
      if (ppindex)
          *ppindex = pindex;
  
      return true;
  }
  
  bool AcceptBlock(CBlock& block, CValidationState& state, CBlockIndex** ppindex, bool fRequested, const CDiskBlockPos* dbp)
  {
      const CChainParams& chainparams = Params();
      AssertLockHeld(cs_main);
  
      CBlockIndex *pindexDummy = NULL;
      CBlockIndex *&pindex = ppindex ? *ppindex : pindexDummy;
  
      if (!AcceptBlockHeader(block, state, &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));
  
      if (fAlreadyHave) {
          LogPrint(Log::BLOCK, "%s: Already have block %s\n", __func__, block.GetHash().ToString());
          return true;
      }
      if (!fRequested) {  // If we didn't ask for it:
          if (pindex->nTx != 0) {
              LogPrint(Log::BLOCK, "%s: Block %s was not requested and is a previously-processed block that was pruned\n",
                       __func__, block.GetHash().ToString());
              return true;
          }
          if (!fHasMoreWork) {
              LogPrint(Log::BLOCK, "%s: Block %s was not requested and is in a less-work chain\n",
                       __func__, block.GetHash().ToString());
              return true;
          }
          if (fTooFarAhead) {
              LogPrint(Log::BLOCK, "%s: Block %s was not requested and block height is too high\n",
                       __func__, block.GetHash().ToString());
              return true;
          }
      }
  
      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.DBMagic()))
                  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 BlockSource& from,
                       CBlock* pblock, bool fForceProcessing, const CDiskBlockPos *dbp, CConnman* connman)
  {
      // 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, &pindex, fRequested, dbp);
          CheckBlockIndex();
          if (!ret)
              return error("%s: AcceptBlock FAILED", __func__);
      }
  
      if (!ActivateBestChain(state, pblock, from, connman))
          return error("%s: ActivateBestChain failed", __func__);
  
      return true;
  }
  
  bool TestBlockValidity(CValidationState &state, const CBlock& block, CBlockIndex * const pindexPrev, bool fCheckPOW, bool fCheckMerkleRoot)
  {
      AssertLockHeld(cs_main);
      assert(pindexPrev == chainActive.Tip());
  
      CCoinsViewCache viewNew(pcoinsTip);
      CBlockIndex indexDummy(block);
      indexDummy.pprev = pindexPrev;
      indexDummy.nHeight = pindexPrev->nHeight + 1;
      indexDummy.nMaxBlockSize = GetNextMaxBlockSize(pindexPrev, Params().GetConsensus());
  
      // 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)
  {
      LOCK2(cs_main, cs_LastBlockFile);
      if (chainActive.Tip() == NULL || nPruneTarget == 0) {
          return;
      }
      if (chainActive.Tip()->nHeight <= Params().PruneAfterHeight()) {
          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(Log::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(bool* fRebuildRequired)
  {
      const CChainParams& chainparams = Params();
      if (!pblocktree->LoadBlockIndexGuts(InsertBlockIndex))
          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());
      vector<pair<int, CBlockIndex*>>::iterator firstBIP100Entry = vSortedByHeight.end();
      for (vector<pair<int, CBlockIndex*>>::iterator iter = vSortedByHeight.begin(); iter != vSortedByHeight.end(); iter++)
      {
          const PAIRTYPE(int, CBlockIndex*)& item = *iter;
          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;
          if (!pindex->pprev ||
              ((Opt().UAHFTime() != 0) && (pindex->pprev->GetMedianTimePast() < Opt().UAHFTime())) ||
              ((Opt().UAHFTime() == 0) && (item.first < chainparams.GetConsensus().bip100ActivationHeight))) {
              pindex->nMaxBlockSize = MAX_BLOCK_SIZE;
          } else if (firstBIP100Entry == vSortedByHeight.end()) {
              firstBIP100Entry = iter;
          }
      }
  
      // 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;
  
      // Set max block size variables in any remaining pre-BIP100 index entries
      bool fUpdatedEntries = false;
      for (vector<pair<int, CBlockIndex*>>::iterator iter = firstBIP100Entry; iter != vSortedByHeight.end(); iter++) {
          const PAIRTYPE(int, CBlockIndex*)& item = *iter;
          CBlockIndex* pindex = item.second;
          if (pindex->nSerialVersion < BIP100_DBI_VERSION) {
              if (!fUpdatedEntries) {
                  uiInterface.InitMessage(_("Updating block index for BIP100..."));
                  fUpdatedEntries = true;
              }
              pindex->nSerialVersion = DISK_BLOCK_INDEX_VERSION;
              if (pindex->nChainTx) {
                  CBlock block;
                  if (ReadBlockFromDisk(block, pindex, chainparams.GetConsensus())) {
                      pindex->nMaxBlockSizeVote = GetMaxBlockSizeVote(block.vtx[0].vin[0].scriptSig, pindex->nHeight);
                      pindex->nMaxBlockSize = GetNextMaxBlockSize(pindex->pprev, chainparams.GetConsensus());
                  } else {
                      // Error: Can't reconstruct vote. Rebuild required.
                      // This can happen if the blocks were pruned after BIP100
                      // activation with pre-BIP100 software.
                      *fRebuildRequired = true;
                      return false;
                  }
              }
              LogPrint(Log::REINDEX, "%s: Updating block index entry at height %d for BIP100\n", __func__, pindex->nHeight);
              setDirtyBlockIndex.insert(pindex);
          }
      }
  
      // Check whether we have a transaction index
      pblocktree->ReadFlag("txindex", fTxIndex);
      LogPrintf("%s: transaction index %s\n", __func__, fTxIndex ? "enabled" : "disabled");
  
      return true;
  }
  
  void LoadChainTip(const CChainParams& chainparams)
  {
      if (chainActive.Tip() && chainActive.Tip()->GetBlockHash() == pcoinsTip->GetBestBlock()) return;
  
      // Load pointer to end of best chain
      BlockMap::iterator it = mapBlockIndex.find(pcoinsTip->GetBestBlock());
      if (it == mapBlockIndex.end())
          return;
      chainActive.SetTip(it->second);
  
      PruneBlockIndexCandidates();
  
      LogPrintf("Loaded best chain: hashBestChain=%s height=%d date=%s progress=%f\n",
          chainActive.Tip()->GetBlockHash().ToString(), chainActive.Height(),
          DateTimeStrFormat("%Y-%m-%d %H:%M:%S", chainActive.Tip()->GetBlockTime()),
          Checkpoints::GuessVerificationProgress(chainparams.Checkpoints(), chainActive.Tip()));
  }
  
  CVerifyDB::CVerifyDB()
  {
      uiInterface.ShowProgress(_("Verifying blocks..."), 0);
  }
  
  CVerifyDB::~CVerifyDB()
  {
      uiInterface.ShowProgress("", 100);
  }
  
  bool CVerifyDB::VerifyDB(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, Params().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) {
              assert(coins.GetBestBlock() == pindex->GetBlockHash());
              DisconnectResult res = DisconnectBlock(block, pindex, coins);
              if (res == DISCONNECT_FAILED) {
                  return error("VerifyDB(): *** irrecoverable inconsistency in block data at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
              }
              pindexState = pindex->pprev;
              if (res == DISCONNECT_UNCLEAN) {
                  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, Params().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;
  }
  
  /** Apply the effects of a block on the utxo cache, ignoring that it may already have been applied. */
  static bool RollforwardBlock(const CBlockIndex* pindex, CCoinsViewCache& inputs, const CChainParams& params)
  {
      // TODO: merge with ConnectBlock
      CBlock block;
      if (!ReadBlockFromDisk(block, pindex, params.GetConsensus())) {
          return error("ReplayBlock(): ReadBlockFromDisk failed at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
      }
  
      for (const CTransaction& tx : block.vtx) {
          if (!tx.IsCoinBase()) {
              for (const CTxIn &txin : tx.vin) {
                  inputs.SpendCoin(txin.prevout);
              }
          }
          // Pass check = true as every addition may be an overwrite.
          AddCoins(inputs, tx, pindex->nHeight, true);
      }
      return true;
  }
  
  bool ReplayBlocks(const CChainParams& params, CCoinsView* view)
  {
      LOCK(cs_main);
  
      CCoinsViewCache cache(view);
  
      std::vector<uint256> hashHeads = view->GetHeadBlocks();
      if (hashHeads.empty()) return true; // We're already in a consistent state.
      if (hashHeads.size() != 2) return error("ReplayBlocks(): unknown inconsistent state");
  
      uiInterface.ShowProgress(_("Replaying blocks..."), 0);
      LogPrintf("Replaying blocks\n");
  
      const CBlockIndex* pindexOld = nullptr;  // Old tip during the interrupted flush.
      const CBlockIndex* pindexNew;            // New tip during the interrupted flush.
      const CBlockIndex* pindexFork = nullptr; // Latest block common to both the old and the new tip.
  
      if (mapBlockIndex.count(hashHeads[0]) == 0) {
          return error("ReplayBlocks(): reorganization to unknown block requested");
      }
      pindexNew = mapBlockIndex[hashHeads[0]];
  
      if (!hashHeads[1].IsNull()) { // The old tip is allowed to be 0, indicating it's the first flush.
          if (mapBlockIndex.count(hashHeads[1]) == 0) {
              return error("ReplayBlocks(): reorganization from unknown block requested");
          }
          pindexOld = mapBlockIndex[hashHeads[1]];
          pindexFork = LastCommonAncestor(pindexOld, pindexNew);
          assert(pindexFork != nullptr);
      }
  
      // Rollback along the old branch.
      while (pindexOld != pindexFork) {
          if (pindexOld->nHeight > 0) { // Never disconnect the genesis block.
              CBlock block;
              if (!ReadBlockFromDisk(block, pindexOld, params.GetConsensus())) {
                  return error("RollbackBlock(): ReadBlockFromDisk() failed at %d, hash=%s", pindexOld->nHeight, pindexOld->GetBlockHash().ToString());
              }
              LogPrintf("Rolling back %s (%i)\n", pindexOld->GetBlockHash().ToString(), pindexOld->nHeight);
              DisconnectResult res = DisconnectBlock(block, pindexOld, cache);
              if (res == DISCONNECT_FAILED) {
                  return error("RollbackBlock(): DisconnectBlock failed at %d, hash=%s", pindexOld->nHeight, pindexOld->GetBlockHash().ToString());
              }
              // If DISCONNECT_UNCLEAN is returned, it means a non-existing UTXO was deleted, or an existing UTXO was
              // overwritten. It corresponds to cases where the block-to-be-disconnect never had all its operations
              // applied to the UTXO set. However, as both writing a UTXO and deleting a UTXO are idempotent operations,
              // the result is still a version of the UTXO set with the effects of that block undone.
          }
          pindexOld = pindexOld->pprev;
      }
  
      // Roll forward from the forking point to the new tip.
      int nForkHeight = pindexFork ? pindexFork->nHeight : 0;
      for (int nHeight = nForkHeight + 1; nHeight <= pindexNew->nHeight; ++nHeight) {
          const CBlockIndex* pindex = pindexNew->GetAncestor(nHeight);
          LogPrintf("Rolling forward %s (%i)\n", pindex->GetBlockHash().ToString(), nHeight);
          if (!RollforwardBlock(pindex, cache, params)) return false;
      }
  
      cache.SetBestBlock(pindexNew->GetBlockHash());
      cache.Flush();
      uiInterface.ShowProgress("", 100);
      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;
      blocksInFlight.clear();
      nQueuedValidatedHeaders = 0;
      nPreferredDownload = 0;
      setDirtyBlockIndex.clear();
      setDirtyFileInfo.clear();
      NodeStatePtr::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(bool* fRebuildRequired)
  {
      assert(fRebuildRequired != NULL);
      // Load block index from databases
      if (!fReindex && !LoadBlockIndexDB(fRebuildRequired))
          return false;
      return true;
  }
  
  
  bool InitBlockIndex() {
      const CChainParams& chainparams = Params();
      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", false);
      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&>(Params().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.DBMagic()))
                  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");
          } catch (const std::runtime_error& e) {
              return error("LoadBlockIndex(): failed to initialize block database: %s", e.what());
          }
      }
  
      return true;
  }
  
  
  
  bool LoadExternalBlockFile(FILE* fileIn, CDiskBlockPos *dbp)
  {
      const CChainParams& chainparams = Params();
      // 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(Params().DBMagic()[0]);
                  nRewind = blkdat.GetPos()+1;
                  blkdat >> FLATDATA(buf);
                  if (memcmp(buf, Params().DBMagic(), MESSAGE_START_SIZE))
                      continue;
                  // read size
                  blkdat >> nSize;
                  if (nSize < 80)
                      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(Log::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) {
                      LOCK(cs_main);
                      CValidationState state;
                      if (AcceptBlock(block, state, NULL, true, dbp))
                          nLoaded++;
                      if (state.IsError())
                          break;
                  } else if (hash != chainparams.GetConsensus().hashGenesisBlock && mapBlockIndex[hash]->nHeight % 1000 == 0) {
                      LogPrint(Log::REINDEX, "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()))
                          {
                              LogPrint(Log::REINDEX, "%s: Processing out of order child %s of %s\n", __func__, block.GetHash().ToString(),
                                      head.ToString());
                              LOCK(cs_main);
                              CValidationState dummy;
                              if (AcceptBlock(block, dummy, NULL, 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", __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 = Params().GetConsensus();
      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());
  }
  
  string GetWarnings(string strFor)
  {
      string strStatusBar;
      string strRPC;
  
      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");
  
      if (GetBoolArg("-testsafemode", false))
          strStatusBar = strRPC = "testsafemode enabled";
  
      // Misc warnings like out of disk space and clock is wrong
      if (strMiscWarning != "")
      {
          strStatusBar = strMiscWarning;
      }
  
      if (fLargeWorkForkFound)
      {
          strStatusBar = strRPC = _("Warning: The network does not appear to fully agree! Some miners appear to be experiencing issues.");
      }
      else if (fLargeWorkInvalidChainFound)
      {
          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.");
      }
  
      if (strFor == "statusbar")
          return strStatusBar;
      else if (strFor == "rpc")
          return strRPC;
      assert(!"GetWarnings(): invalid parameter");
      return "error";
  }
  
  
  
  
  
  
  
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // Messages
  //
  
  static std::map<std::string, size_t> maxMessageSizes = boost::assign::map_list_of
      // values list the max size of each part of the message payload currently defined/used.
      // values equate to the max payload size for that respective message type.
      ("getaddr", 0)
      ("mempool", 0)
      ("ping", 8)
      ("pong", 8)
      ("verack", 0)
      ("version", 4 + 8 + 8 + (4 + 8 + 16 + 2) + (4 + 8 + 16 + 2) + 8 + (3 + 256) + 4 + 1)
      ("filterclear", 0)
      ("reject", (1 + 12) + 1 + (1 + 111) + 32) // this is loose max because the max valid is actually 151 bytes as of BIP 61. see the p2p_protocol_tests unit tests.
      ;
  
  bool static SanityCheckMessage(CNode* peer, const CNetMessage& msg)
  {
      const std::string& strCommand = msg.hdr.GetCommand();
      uint64_t nMaxMessageSize = NextBlockRaiseCap(GetMaxBlockSizeInsecure());
      if (msg.hdr.nMessageSize > nMaxMessageSize ||
          (maxMessageSizes.count(strCommand) && msg.hdr.nMessageSize > maxMessageSizes[strCommand])) {
          LogPrint(Log::NET, "Oversized %s message from peer=%i (%d bytes)\n",
                   SanitizeString(strCommand), peer->GetId(), msg.hdr.nMessageSize);
          Misbehaving(peer->GetId(), 20, "oversized message");
          return msg.hdr.nMessageSize <= nMaxMessageSize;
      }
      // This would be a good place for more sophisticated DoS detection/prevention.
      // (e.g. disconnect a peer that is flooding us with excessive messages)
  
      return true;
  }
  
  
  bool static AlreadyHave(const CInv& inv)
  {
      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->HaveCoin(COutPoint(inv.hash, 0)) || // Best effort: only try output 0 and 1
                     pcoinsTip->HaveCoin(COutPoint(inv.hash, 1));
          }
      case MSG_BLOCK:
          return mapBlockIndex.count(inv.hash);
      }
      // Don't know what it is, just say we already got one
      return true;
  }
  
  // Activate thin blocks only if we're not doing bulk downloads (it's faster to use ordinary block messages when
  // catching up with the block chain).
  bool ThinBlocksActive(CNode* n) {
      return !IsInitialBlockDownload() && Opt().UsingThinBlocks()
          && (n->SupportsXThinBlocks() || NodeStatePtr(n->id)->supportsCompactBlocks);
  }
  
  static void RelayAddress(const CAddress& addr, bool fReachable, CConnman* connman)
  {
      if (!connman)
          throw std::invalid_argument(std::string(__func__ )+ " requires connection manager");
  
      int nRelayNodes = fReachable ? 2 : 1; // limited relaying of addresses outside our network(s)
  
      // Relay to a limited number of other nodes
      // Use deterministic randomness to send to the same nodes for 24 hours
      // at a time so the addrKnowns of the chosen nodes prevent repeats
      uint64_t hashAddr = addr.GetHash();
      std::multimap<uint64_t, CNode*> mapMix;
      const CSipHasher hasher = connman->GetDeterministicRandomizer(RANDOMIZER_ID_ADDRESS_RELAY).Write(hashAddr << 32).Write((GetTime() + hashAddr) / (24*60*60));
  
      auto sortfunc = [&mapMix, &hasher](CNode* pnode) {
          if (pnode->nVersion >= CADDR_TIME_VERSION) {
              uint64_t hashKey = CSipHasher(hasher).Write(pnode->id).Finalize();
              mapMix.emplace(hashKey, pnode);
          }
      };
  
      auto pushfunc = [&addr, &mapMix, &nRelayNodes] {
          FastRandomContext insecure_rand;
          for (auto mi = mapMix.begin(); mi != mapMix.end() && nRelayNodes-- > 0; ++mi)
              mi->second->PushAddress(addr, insecure_rand);
      };
  
      connman->ForEachNodeThen(std::move(sortfunc), std::move(pushfunc));
  }
  
  void static ProcessGetData(CNode* pfrom, CConnman* connman, std::atomic<bool>& interruptMsgProc)
  {
      if (!connman)
          throw std::invalid_argument(std::string(__func__ )+ " requires connection manager");
  
      std::deque<CInv>::iterator it = pfrom->vRecvGetData.begin();
      vector<CInv> vNotFound;
      CNetMsgMaker msgMaker(pfrom->GetSendVersion());
      LOCK(cs_main);
  
      while (it != pfrom->vRecvGetData.end()) {
          // Don't bother if send buffer is too full to respond anyway
          if (pfrom->fPauseSend)
              break;
  
          const CInv &inv = *it;
          {
              if (interruptMsgProc)
                  return;
              it++;
  
              BlockSender blockSender;
              if (blockSender.isBlockType(inv.type))
              {
                  BlockMap::iterator mi = mapBlockIndex.find(inv.hash);
                  bool haveBlock = mi != mapBlockIndex.end();
                  bool canSend = haveBlock && blockSender.canSend(
                          chainActive, *(mi->second), pindexBestHeader);
  
                  if (canSend)
                      blockSender.send(chainActive, *connman, *pfrom, *(mi->second), inv);
              }
              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()) {
                          connman->PushMessage(pfrom, NetMsg(pfrom, 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;
                          connman->PushMessage(pfrom, NetMsg(pfrom, 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.
          connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::NOTFOUND, vNotFound));
      }
  }
  
  static std::tuple<std::vector<uint8_t>, std::vector<bip64::CCoin> > ProcessGetUTXOs(
          const vector<COutPoint> &vOutPoints, bool fCheckMemPool, size_t maxBytes)
  {
      AssertLockHeld(cs_main);
      // Defined by BIP 64.
      //
      // Allows a peer to retrieve the CTxOut structures corresponding to the given COutPoints.
      // Note that this data is not authenticated by anything: this code could just invent any
      // old rubbish and hand it back, with the peer being unable to tell unless they are checking
      // the outpoints against some out of band data.
      //
      // Also the answer could change the moment after we give it. However some apps can tolerate
      // this, because they're only using the result as a hint or are willing to trust the results
      // based on something else. For example we may be a "trusted node" for the peer, or it may
      // be checking the results given by several nodes for consistency, it may
      // run the UTXOs returned against scriptSigs of transactions obtained elsewhere (after checking
      // for a standard script form), and because the height in which the UTXO was defined is provided
      // a client that has a map of heights to block headers (as SPV clients do, for recent blocks)
      // can request the creating block via hash.
      //
      // IMPORTANT: Clients expect ordering to be preserved!
      if (vOutPoints.size() > MAX_INV_SZ)
          throw std::invalid_argument("too many outpoints requested");
      // Due to the above check max space the bitmap can use is 50,000 / 8 == 6250 bytes.
  
      LogPrint(Log::NET, "getutxos for %d queries %s mempool\n", vOutPoints.size(), fCheckMemPool ? "with" : "without");
  
      std::unique_ptr<bip64::UTXORetriever> utxos;
      if (fCheckMemPool) {
          LOCK(mempool.cs);
          utxos.reset(new bip64::UTXORetriever(vOutPoints, *pcoinsTip, &mempool, maxBytes));
      }
      else {
          utxos.reset(new bip64::UTXORetriever(vOutPoints, *pcoinsTip, nullptr, maxBytes));
      }
      return std::make_tuple(utxos->GetBitmap(), utxos->GetResults());
  }
  
  
  // Looks for a transaction in our various pools and buffers.
  // Used for reconstructing thin blocks.
  struct TxFinderImpl : public TxFinder {
  
      CTransaction fullLookup(const uint256& h) const {
          CTransaction tx;
          if (mempool.lookup(h, tx))
              return tx;
  
          if (mapOrphanTransactions.count(h))
              return mapOrphanTransactions[h].tx;
  
          // if not found, tx is left alone.
          try {
              FindTransactionInRelayMap(h, tx);
          }
          catch (const std::ios_base::failure& e) {
              LogPrintf("Exception '%s' in FindTransactionInRelayMap ignored\n", e.what());
              return CTransaction();
          }
  
          return tx;
      }
  
      CTransaction lookup(const ThinTx& hash) const {
  
          CTransaction match;
          {
              LOCK(mempool.cs);
              for (auto& t : mempool.mapTx) {
                  if (!hash.equals(t.GetTx().GetHash()))
                      continue;
  
                  if (!match.IsNull()) {
                      LogPrintf("Info: Hash collision in thin block for tx %s\n",
                              t.GetTx().GetHash().ToString());
                      // Return empty tx so it is re-requested.
                      return CTransaction();
  
                  }
                  match = t.GetTx();
              }
          }
          if (!match.IsNull())
              return match;
  
          for (auto t : mapOrphanTransactions)
              if (hash.equals(t.second.tx.GetHash()))
                  return t.second.tx;
  
          // Skip relay map.
          return CTransaction();
      }
  
      CTransaction operator()(const ThinTx& hash) const {
          AssertLockHeld(cs_main);
  
          if (hash.hasFull())
              return fullLookup(hash.full()); // faster lookup
  
          return lookup(hash);
      }
  };
  
  // Lists all hashes in mempool
  struct MempoolHashProvider : public TxHashProvider {
      void operator()(std::vector<uint256>& dst) {
          mempool.queryHashes(dst);
      }
  };
  
  void unexpectedThinError(const std::string& cmd, CConnman& connman, CNode& from, const std::string& err) {
      LogPrintf("Unexpected error handling cmd '%s': '%s' peer=%d\n", cmd, err, from.id);
      {
          LOCK(cs_main);
          NodeStatePtr(from.id)->thinblock->stopAllWork();
          Misbehaving(from.id, 10, "thinblock: " + err);
      }
      connman.PushMessage(&from, NetMsg(&from, NetMsgType::REJECT, cmd, REJECT_MALFORMED, err));
  }
  
  bool ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
                      int64_t nTimeReceived, CConnman* connman, std::atomic<bool>& interruptMsgProc)
  {
      if (!connman)
          throw std::invalid_argument(std::string(__func__ )+ " requires connection manager");
  
      RandAddSeedPerfmon();
  
      LogPrint(Log::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 (strCommand == NetMsgType::REJECT)
      {
          if (LogAcceptCategory(Log::NET)) {
              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(Log::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(Log::NET, "Unparseable reject message received\n");
                  return false;
              }
          }
      }
      else if (strCommand == NetMsgType::VERSION)
      {
          // Each connection can only send one version message
          if (pfrom->nVersion != 0)
          {
              connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_DUPLICATE, string("Duplicate version message")));
              Misbehaving(pfrom->GetId(), 1, "duplicate version messge");
              return false;
          }
  
          int64_t nTime;
          CAddress addrMe;
          CAddress addrFrom;
          uint64_t nNonce = 1;
          uint64_t nServiceInt;
          uint64_t nServices;
          int nVersion;
          int nSendVersion;
          std::string strSubVer;
          int nStartingHeight = -1;
          bool fRelay = true;
  
          vRecv >> nVersion >> nServiceInt >> nTime >> addrMe;
          nSendVersion = std::min(nVersion, PROTOCOL_VERSION);
          nServices = nServiceInt;
          if (nVersion < MIN_PEER_PROTO_VERSION)
          {
              // disconnect from peers older than this proto version
              LogPrintf("peer=%d using obsolete version %i; disconnecting\n", pfrom->id, nVersion);
              connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::REJECT, strCommand, REJECT_OBSOLETE,
                                 strprintf("Version must be %d or greater", MIN_PEER_PROTO_VERSION)));
              pfrom->fDisconnect = true;
              return false;
          }
  
          if (nVersion == 10300)
              nVersion = 300;
          if (!vRecv.empty())
              vRecv >> addrFrom >> nNonce;
          if (!vRecv.empty()) {
              vRecv >> LIMITED_STRING(strSubVer, MAX_SUBVERSION_LENGTH);
          }
          if (!vRecv.empty())
              vRecv >> nStartingHeight;
          if (!vRecv.empty())
              vRecv >> fRelay;
  
          // Disconnect if we connected to ourself
          if (pfrom->fInbound && !connman->CheckIncomingNonce(nNonce))
          {
              LogPrintf("connected to self at %s, disconnecting\n", pfrom->addr.ToString());
              pfrom->fDisconnect = true;
              return true;
          }
  
          if (pfrom->fInbound && addrMe.IsRoutable())
          {
              SeenLocal(addrMe);
          }
  
          // Be shy and don't send version until we hear
          if (pfrom->fInbound)
              PushNodeVersion(pfrom, *connman, GetAdjustedTime());
  
          connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(NetMsgType::VERACK));
  
          pfrom->nServices = nServices;
          pfrom->addrLocal = addrMe;
          pfrom->strSubVer = strSubVer;
          pfrom->cleanSubVer = SanitizeString(strSubVer);
          pfrom->nStartingHeight = nStartingHeight;
          pfrom->fClient = !(nServices & NODE_NETWORK);
          {
              LOCK(pfrom->cs_filter);
              pfrom->fRelayTxes = fRelay;
          }
  
          // Change version
          pfrom->SetSendVersion(nSendVersion);
          pfrom->nVersion = nVersion;
  
          {
              LOCK(cs_main);
              NodeStatePtr ns(pfrom->id);
  
              if (Opt().UsingThinBlocks() && pfrom->SupportsXThinBlocks())
              {
                  ns->thinblock.reset(new XThinWorker(
                      thinblockmg, pfrom->id,
                      std::unique_ptr<TxHashProvider>(new MempoolHashProvider)));
              }
              else { /* keep DummyThinWorker */ }
  
              if (!pfrom->fInbound && !KeepOutgoingPeer(*pfrom)) {
                  LogPrintf("'%s' - peer=%d does not meet criteria for "
                          "outgoing connections, disconnecting.\n",
                          SanitizeString(strSubVer), pfrom->id);
  
                  pfrom->fDisconnect = true;
                  return true;
              }
          }
  
          // Potentially mark this peer as a preferred download peer.
          {
              NodeStatePtr nodeState(pfrom->GetId());
              UpdatePreferredDownload(pfrom, nodeState);
          }
  
          if (!pfrom->fInbound)
          {
              // Advertise our address
              if (fListen && !IsInitialBlockDownload())
              {
                  FastRandomContext insecure_rand;
                  CAddress addr = GetLocalAddress(&pfrom->addr, pfrom->GetLocalServices());
                  if (addr.IsRoutable())
                  {
                      pfrom->PushAddress(addr, insecure_rand);
                  } else if (IsPeerAddrLocalGood(pfrom)) {
                      addr.SetIP(pfrom->addrLocal);
                      pfrom->PushAddress(addr, insecure_rand);
                  }
              }
  
              // Get recent addresses
              if (pfrom->fOneShot || pfrom->nVersion >= CADDR_TIME_VERSION || connman->GetAddressCount() < 1000)
              {
                  connman->PushMessage(pfrom, CNetMsgMaker(nSendVersion).Make(NetMsgType::GETADDR));
                  pfrom->fGetAddr = true;
              }
              connman->MarkAddressGood(pfrom->addr);
          }
  
          string remoteAddr;
          if (fLogIPs)
              remoteAddr = ", peeraddr=" + pfrom->addr.ToString();
  
          CIPGroupData ipgroup = pfrom->ipgroupSlot->Group();
          string group = ipgroup.name != "" ? tfm::format(", ipgroup=%s", ipgroup.name) : "";
  
          LogPrintf("receive version message: %s: version %d, blocks=%d, us=%s, peerid=%d%s%s\n",
                    pfrom->cleanSubVer, pfrom->nVersion,
                    pfrom->nStartingHeight, addrMe.ToString(), pfrom->id,
                    group, remoteAddr);
  
          int64_t nTimeOffset = nTime - GetTime();
          pfrom->nTimeOffset = nTimeOffset;
          AddTimeData(pfrom->addr, nTimeOffset);
  
          // Feeler connections exist only to verify if address is online.
          if (pfrom->fFeeler) {
              assert(pfrom->fInbound == false);
              pfrom->fDisconnect = true;
          }
          return true;
      }
  
  
      else if (pfrom->nVersion == 0)
      {
          // Must have a version message before anything else
          Misbehaving(pfrom->GetId(), 1, "no version received");
          return false;
      }
  
      // At this point, the outgoing message serialization version can't change.
      CNetMsgMaker msgMaker(pfrom->GetSendVersion());
  
      if (strCommand == NetMsgType::VERACK)
      {
          pfrom->SetRecvVersion(min(pfrom->nVersion.load(), PROTOCOL_VERSION));
  
          // Mark this node as currently connected, so we update its timestamp later.
          if (!pfrom->fInbound) {
              NodeStatePtr(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)
              connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::SENDHEADERS));
          }
  
          if (pfrom->nVersion >= SHORT_IDS_BLOCKS_VERSION
                  && !(pfrom->SupportsXThinBlocks() && Opt().PreferXThinBlocks())) {
              enableCompactBlocks(*connman, *pfrom, false);
          }
          pfrom->fSuccessfullyConnected = true;
      }
      else if (!pfrom->fSuccessfullyConnected)
      {
          Misbehaving(pfrom->GetId(), 1, "must have a verack message before anything else");
          return false;
      }
      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 && connman->GetAddressCount() > 1000)
              return true;
          if (vAddr.size() > 1000)
          {
              Misbehaving(pfrom->GetId(), 20, "addr msg exceeded limits");
              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)
          {
              if (interruptMsgProc)
                  return true;
  
              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
                  RelayAddress(addr, fReachable, connman);
              }
              // Do not store addresses outside our network
              if (fReachable)
                  vAddrOk.push_back(addr);
          }
          connman->AddNewAddresses(vAddrOk, pfrom->addr, 2 * 60 * 60);
          if (vAddr.size() < 1000)
              pfrom->fGetAddr = false;
          if (pfrom->fOneShot)
              pfrom->fDisconnect = true;
      }
  
      else if (strCommand == "sendcmpct") {
          if (!Opt().UsingThinBlocks())
              return true;
  
          bool highBandwidth = false;
          uint64_t version = 1;
          vRecv >> highBandwidth >> version;
  
          if (version != 1)
              return true; // Ignore as per BIP152
  
          LOCK(cs_main);
          NodeStatePtr node(pfrom->id);
          node->supportsCompactBlocks = true;
          node->prefersBlocks = highBandwidth;
          node->thinblock.reset(new CompactWorker(thinblockmg, pfrom->id));
      }
  
      else if (strCommand == "sendheaders")
      {
          LOCK(cs_main);
          NodeStatePtr(pfrom->id)->prefersHeaders = true;
      }
  
      else if (strCommand == "inv")
      {
          vector<CInv> vInv;
          vRecv >> vInv;
          if (vInv.size() > MAX_INV_SZ)
          {
              Misbehaving(pfrom->GetId(), 20, "inv msg size exceeded limits");
              return error("message inv size() = %u", vInv.size());
          }
  
          LOCK(cs_main);
  
          std::vector<CInv> vToFetch;
  
          for (unsigned int nInv = 0; nInv < vInv.size(); nInv++)
          {
              const CInv &inv = vInv[nInv];
  
              if (interruptMsgProc)
                  return true;
              // Ignore duplicate advertisements for the same item from the same peer. This check
              // prevents a peer from constantly promising to deliver an item that it never does,
              // thus blinding us to new transactions and blocks.
              if (!pfrom->AddInventoryKnown(inv) && !pfrom->fWhitelisted) {
                  LogPrint(Log::NET, "ignoring inv: %s peer=%d\n", inv.ToString(), pfrom->id);
                  continue;
              }
  
              bool fAlreadyHave = AlreadyHave(inv);
              LogPrint(Log::NET, "got inv: %s  %s peer=%d\n", inv.ToString(), fAlreadyHave ? "have" : "new", pfrom->id);
  
              if (!fAlreadyHave && !fImporting && !fReindex && inv.type != MSG_BLOCK && !IsInitialBlockDownload())
                  pfrom->AskFor(inv);
  
              if (inv.type == MSG_BLOCK) {
                  BlockAnnounceReceiver ann(inv.hash, *connman, *pfrom, thinblockmg, blocksInFlight);
                  if (ann.onBlockAnnounced(vToFetch)) {
                      // This block has been requested from peer.
                      MarkBlockAsInFlight()(pfrom->id, inv.hash, Params().GetConsensus());
                  }
              }
  
              // Track requests for our stuff
              GetMainSignals().Inventory(inv.hash);
          }
  
          if (!vToFetch.empty())
              connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::GETDATA, vToFetch));
      }
  
      else if (strCommand == "getblocktxn")
      {
          if (!Opt().UsingThinBlocks())
              return true;
          // Remote peer is requesting more transactions as part of compact block
          // transfer.
          CompactReRequest req;
          vRecv >> req;
  
          LogPrint(Log::BLOCK, "peer=%d is compactthin re-requesting %d transactions for %s\n",
                  pfrom->id, req.indexes.size(), req.blockhash.ToString());
  
          LOCK(cs_main);
          auto mi = mapBlockIndex.find(req.blockhash);
          bool haveBlock = mi != mapBlockIndex.end();
          BlockSender bs;
          bool canSend = haveBlock && bs.canSend(
                  chainActive, *(mi->second), pindexBestHeader);
  
          try {
              if (canSend) {
                  bs.sendReReqReponse(*connman, *pfrom, *(mi->second), req,
                          chainActive.Height());
              }
              else {
                  LogPrint(Log::BLOCK,
                           "Can't respond to compact re-request for %s\n",
                           req.blockhash.ToString());
              }
          }
          catch (const std::exception& e) {
              LogPrintf("error in re-request from peer=%d: %s\n",
                      pfrom->id, e.what());
          }
      }
  
      else if (strCommand == "getdata")
      {
          vector<CInv> vInv;
          vRecv >> vInv;
          if (vInv.size() > MAX_INV_SZ)
          {
              Misbehaving(pfrom->GetId(), 20, "getdata msg size exceeded");
              return error("message getdata size() = %u", vInv.size());
          }
  
          if (LogAcceptCategory(Log::NET) || (vInv.size() != 1))
              LogPrint(Log::NET, "received getdata (%u invsz) peer=%d\n", vInv.size(), pfrom->id);
  
          if ((LogAcceptCategory(Log::NET) && vInv.size() > 0) || (vInv.size() == 1))
              LogPrint(Log::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, connman, interruptMsgProc);
      }
  
  
      else if (strCommand == "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(Log::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(Log::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 / Params().GetConsensus().nPowTargetSpacing;
              if (fPruneMode && (!(pindex->nStatus & BLOCK_HAVE_DATA) || pindex->nHeight <= chainActive.Tip()->nHeight - nPrunedBlocksLikelyToHave))
              {
                  LogPrint(Log::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(Log::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())
              return true;
  
          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(Log::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
          // bestHeaderSent to be our tip.
          NodeStatePtr(pfrom->id)->bestHeaderSent = pindex ? pindex : chainActive.Tip();
          connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::HEADERS, vHeaders));
      }
      else if (strCommand == "getutxos")
      {
          bool fCheckMemPool;
          std::vector<COutPoint> vOutPoints;
          vRecv >> fCheckMemPool;
          vRecv >> vOutPoints;
  
          try {
              size_t maxBytes = connman->GetSendBufferSize();
              std::vector<unsigned char> bitmap;
              std::vector<bip64::CCoin> outs;
              {
                  LOCK(cs_main);
                  tie(bitmap, outs) = ProcessGetUTXOs(vOutPoints, fCheckMemPool, maxBytes);
              }
              connman->PushMessage(pfrom, NetMsg(pfrom, NetMsgType::UTXOS,
                                                 static_cast<uint32_t>(chainActive.Height()),
                                                 chainActive.Tip()->GetBlockHash(), bitmap, outs));
          }
          catch (const std::exception& e) {
              connman->PushMessage(pfrom, NetMsg(pfrom, NetMsgType::REJECT, strCommand, REJECT_INVALID,
                                                 std::string(e.what()).substr(0, MAX_REJECT_MESSAGE_LENGTH)));
              Misbehaving(pfrom->GetId(), 20, "getutxos request invalid");
          }
          CValidationState state;
          FlushStateToDisk(state, FLUSH_STATE_PERIODIC);
      }
      else if (strCommand == NetMsgType::TX)
      {
          vector<uint256> vWorkQueue;
          vector<uint256> vEraseQueue;
          CTransaction tx;
          vRecv >> tx;
  
          CInv inv(MSG_TX, tx.GetHash());
          pfrom->AddInventoryKnown(inv);
  
          LOCK(cs_main);
  
          NodeStatePtr nodestate(pfrom->GetId());
  
          bool fMissingInputs = false;
          CValidationState state;
  
          mapAlreadyAskedFor.erase(inv);
  
          if (!AlreadyHave(inv) && AcceptToMemoryPool(mempool, state, tx, true, &fMissingInputs, connman))
          {
              mempool.check(pcoinsTip);
              std::vector<uint256> vAncestors;
              mempool.queryAncestors(tx.GetHash(), vAncestors, connman->GetLocalServices());
              connman->RelayTransaction(tx, vAncestors);
              vWorkQueue.push_back(inv.hash);
  
              LogPrint(Log::MEMPOOL, "AcceptToMemoryPool: peer=%d %s: accepted %s (poolsz %u)\n",
                  pfrom->id, pfrom->cleanSubVer,
                  tx.GetHash().ToString(),
                  mempool.size());
  
              // 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, connman))
                      {
                          LogPrint(Log::MEMPOOL, "   accepted orphan tx %s\n", orphanHash.ToString());
                          std::vector<uint256> vAncestors;
                          mempool.queryAncestors(orphanTx.GetHash(), vAncestors, connman->GetLocalServices());
                          connman->RelayTransaction(orphanTx, vAncestors);
                          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, "invalid orphan tx");
                              setMisbehaving.insert(fromPeer);
                              LogPrint(Log::MEMPOOL, "   invalid orphan tx %s\n", orphanHash.ToString());
                          }
                          // Has inputs but not accepted to mempool
                          // Probably non-standard or insufficient fee/priority
                          LogPrint(Log::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(Log::MEMPOOL, "mapOrphan overflow, removed %u tx\n", nEvicted);
          } else {
              assert(recentRejects);
              recentRejects->insert(tx.GetHash());
  
              if (pfrom->fWhitelisted) {
                  // Always relay transactions received from whitelisted peers, even
                  // if they were rejected from the mempool, allowing the node to
                  // function as a gateway for nodes hidden behind it.
                  //
                  // FIXME: This includes invalid transactions, which means a
                  // whitelisted peer could get us banned! We may want to change
                  // that.
                  std::vector<uint256> vAncestors;
                  mempool.queryAncestors(tx.GetHash(), vAncestors, connman->GetLocalServices());
                  connman->RelayTransaction(tx, vAncestors);
              }
          }
          int nDoS = 0;
          if (state.IsInvalid(nDoS))
          {
              LogPrint(Log::MEMPOOL, "%s from peer=%d %s was not accepted into the memory pool: %s\n", tx.GetHash().ToString(),
                  pfrom->id, pfrom->cleanSubVer,
                  state.GetRejectReason());
                  connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::REJECT, strCommand, (unsigned char)state.GetRejectCode(),
                                     state.GetRejectReason().substr(0, MAX_REJECT_MESSAGE_LENGTH), inv.hash));
              if (nDoS > 0)
                  Misbehaving(pfrom->GetId(), nDoS, "tx rejected: " + state.GetRejectReason());
          }
          FlushStateToDisk(state, FLUSH_STATE_PERIODIC);
      }
      else if (strCommand == "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, "headers msg exceeded size limits");
              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;
          }
  
          MarkBlockAsInFlight inFlight;
          DefaultHeaderProcessor p(*connman, pfrom, blocksInFlight, thinblockmg, inFlight, CheckBlockIndex);
  
          if (p.requestConnectHeaders(headers.at(0), *connman, *pfrom, true)) {
              // headers don't connect to active chain, requested
              // new headers to connect.
              return true;
          }
  
          try {
              p(headers, nCount == MAX_HEADERS_RESULTS, true);
          }
          catch (const BlockHeaderError& e) {
              return error(e.what());
          }
      }
      else if (strCommand == "xthinblock" && !fImporting && !fReindex) // Ignore blocks received while importing
      {
          if (!Opt().UsingThinBlocks())
              return true;
          // We are receiving a xthin block.
          try {
              LOCK(cs_main);
              NodeStatePtr nodestate(pfrom->id);
              MarkBlockAsInFlight inFlight;
              DefaultHeaderProcessor headerp(*connman, pfrom, blocksInFlight,
                                             thinblockmg, inFlight, CheckBlockIndex);
              XThinBlockProcessor blockp(*connman, *pfrom, *(nodestate->thinblock), headerp);
              blockp(vRecv, TxFinderImpl(),
                      chainActive.Tip()->nMaxBlockSize, chainActive.Height());
          }
          catch (const std::exception& e) {
              unexpectedThinError(strCommand, *connman, *pfrom, e.what());
              throw;
          }
      }
      else if (strCommand == "cmpctblock" && !fImporting && !fReindex) // Ignore blocks received while importing
      {
          if (!Opt().UsingThinBlocks())
              return true;
          // We are receiving a compact block.
          try {
              LOCK(cs_main);
              NodeStatePtr nodestate(pfrom->id);
              MarkBlockAsInFlight inFlight;
              DefaultHeaderProcessor headerp(*connman, pfrom, blocksInFlight,
                                             thinblockmg, inFlight, CheckBlockIndex);
              CompactBlockProcessor blockp(*connman, *pfrom, *(nodestate->thinblock), headerp);
              blockp(vRecv, mempool, chainActive.Tip()->nMaxBlockSize, chainActive.Height());
          }
          catch (const std::exception& e) {
              unexpectedThinError(strCommand, *connman, *pfrom, e.what());
              throw;
          }
      }
      else if (strCommand == "block" && !fImporting && !fReindex) // Ignore blocks received while importing
      {
          CBlock block;
          vRecv >> block;
  
          CInv inv(MSG_BLOCK, block.GetHash());
          LogPrintf("received block %s peer=%d\n", inv.hash.ToString(), pfrom->id);
  
          pfrom->AddInventoryKnown(inv);
  
          LOCK(cs_main);
          MarkBlockAsInFlight inFlight;
          DefaultHeaderProcessor p(*connman, pfrom, blocksInFlight, thinblockmg,
                                   inFlight, CheckBlockIndex);
  
          if (p.requestConnectHeaders(block.GetBlockHeader(), *connman, *pfrom, true)) {
              LogPrintf("Received block %s from peer=%d, but headers do "
                      "not connect. Discarding.\n",
                      inv.hash.ToString(), pfrom->id);
  
              // thinblock requests may respond with a full block
              NodeStatePtr(pfrom->id)->thinblock->stopWork(block.GetHash());
  
              InFlightEraserImpl erase;
              erase(pfrom->id, inv.hash);
              return true;
          }
  
          OnBlockFinished callb(true, strCommand);
          callb(block, std::vector<NodeId>(1, pfrom->id));
      }
      else if (strCommand == "get_xthin") {
          if (!Opt().UsingThinBlocks())
              return true;
          CBloomFilter dontWant;
          CInv inv;
  
          vRecv >> inv >> dontWant;
  
          if (!dontWant.IsWithinSizeConstraints())
              // There is no excuse for sending a too-large filter
              Misbehaving(pfrom->GetId(), 100, "get_xthin: filter too large");
          else
          {
              LOCK(pfrom->cs_xfilter);
              pfrom->xthinFilter.reset(new CBloomFilter(dontWant));
              pfrom->xthinFilter->UpdateEmptyFull();
  
  
              pfrom->vRecvGetData.push_back(inv);
              ProcessGetData(pfrom, connman, interruptMsgProc);
          }
  
      }
      else if (strCommand == "get_xblocktx") {
          if (!Opt().UsingThinBlocks())
              return true;
          // This is a request for transactions that remote peer wanted
          // as part of a xthinblock, but were not provided.
  
          XThinReRequest req;
          vRecv >> req;
          LogPrint(Log::BLOCK, "peer=%d is xthin re-requesting %d transactions for %s\n",
                  pfrom->id, req.txRequesting.size(), req.block.ToString());
  
          BlockMap::iterator mi = mapBlockIndex.find(req.block);
          bool haveBlock = mi != mapBlockIndex.end();
          LOCK(cs_main);
          BlockSender bs;
          bool canSend = haveBlock && bs.canSend(
                  chainActive, *(mi->second), pindexBestHeader);
  
          try {
              if (canSend)
                  bs.sendReReqReponse(*connman, *pfrom, *(mi->second), req,
                          chainActive.Height());
          }
          catch (const std::exception& e) {
              LogPrintf("error in xthin re-request from peer=%d: %s\n",
                      pfrom->id, e.what());
          }
      }
      else if (strCommand == "xblocktx") {
          if (!Opt().UsingThinBlocks())
              return true;
          // This is a response for us requesting missing transactions from
          // xthinblocks.
  
          XThinReReqResponse resp;
          vRecv >> resp;
          LogPrint(Log::BLOCK, "recieved re-request response from peer=%d with %d txs for %s\n",
              pfrom->id, resp.txRequested.size(), resp.block.ToString());
  
          LOCK(cs_main);
          NodeStatePtr statePtr(pfrom->id);
          MarkBlockAsInFlight m;
          XThinBlockConcluder()(resp, *connman, *pfrom, *(statePtr->thinblock), m);
      }
  
      else if (strCommand == "blocktxn") {
          if (!Opt().UsingThinBlocks())
              return true;
          // This is a response for us requesting missing transactions from
          // xthinblocks.
  
          CompactReReqResponse resp;
          vRecv >> resp;
          LogPrint(Log::BLOCK, "recieved re-request response from peer=%d with %d txs for %s\n",
              pfrom->id, resp.txn.size(), resp.blockhash.ToString());
  
          LOCK(cs_main);
          NodeStatePtr statePtr(pfrom->id);
          MarkBlockAsInFlight m;
          CompactBlockConcluder()(resp, *connman, *pfrom, *(statePtr->thinblock), m);
      }
  
      // 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 == "getaddr") && (pfrom->fInbound))
      {
          // Only send one GetAddr response per connection to reduce resource waste
          //  and discourage addr stamping of INV announcements.
          if (pfrom->fSentAddr) {
              LogPrint(Log::NET, "Ignoring repeated \"getaddr\". peer=%d\n", pfrom->id);
              return true;
          }
          pfrom->fSentAddr = true;
  
          pfrom->vAddrToSend.clear();
          vector<CAddress> vAddr = connman->GetAddresses();
          FastRandomContext insecure_rand;
          for (const CAddress& addr : vAddr) {
              pfrom->PushAddress(addr, insecure_rand);
          }
      }
  
  
      else if (strCommand == "mempool")
      {
          LOCK2(cs_main, pfrom->cs_filter);
  
          std::vector<uint256> vtxid;
          mempool.queryHashes(vtxid);
          std::set<CInv> vInv;
          BOOST_FOREACH(uint256& hash, vtxid) {
              CTransaction tx;
              bool fInMemPool = mempool.lookup(hash, tx);
              if (!fInMemPool) continue; // another thread removed since queryHashes, maybe...
              if (pfrom->pfilter && !pfrom->pfilter->IsRelevantAndUpdate(tx))
                  continue;
  
              // No filter, or filter matched
              std::vector<uint256> vAncestors;
              if (pfrom->pfilter && pfrom->pfilter->WantsAncestors())
                  mempool.queryAncestors(hash, vAncestors, connman->GetLocalServices());
              else
              	vAncestors.push_back(hash);
              BOOST_FOREACH(uint256& hashFound, vAncestors) {
                  if (hashFound != hash && pfrom->pfilter && pfrom->pfilter->WantsAncestors())
                      pfrom->pfilter->insert(hashFound);
                  if (hashFound == hash || (pfrom->pfilter && pfrom->pfilter->WantsAncestors()))
                      vInv.insert(CInv(MSG_TX, hashFound));
                  if (vInv.size() == MAX_INV_SZ) {
                      connman->PushMessage(pfrom, NetMsg(pfrom, NetMsgType::INV, vInv));
                      vInv.clear();
                  }
              }
          }
          if (vInv.size() > 0)
              connman->PushMessage(pfrom, NetMsg(pfrom, NetMsgType::INV, vInv));
      }
  
  
      else if (strCommand == "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.
              connman->PushMessage(pfrom, msgMaker.Make(NetMsgType::PONG, nonce));
          }
      }
  
  
      else if (strCommand == "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 && 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;
                  } else {
                      // This should never happen
                      sProblem = "Timing mishap";
                  }
              }
              else if (pfrom->nPingNonceSent) {
                  // 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(Log::NET, "pong peer=%d %s: %s, %x expected, %x received, %u bytes\n",
                  pfrom->id,
                  pfrom->cleanSubVer,
                  sProblem,
                  pfrom->nPingNonceSent,
                  nonce,
                  nAvail);
          }
          if (bPingFinished) {
              pfrom->nPingNonceSent = 0;
          }
      }
  
  
      else if (strCommand == "filterload")
      {
          CBloomFilter filter;
          vRecv >> filter;
  
          if (!filter.IsWithinSizeConstraints())
              // There is no excuse for sending a too-large filter
              Misbehaving(pfrom->GetId(), 100, "filterload: filter too large");
          else
          {
              LOCK(pfrom->cs_filter);
              pfrom->pfilter.reset(new CBloomFilter(filter));
              pfrom->pfilter->UpdateEmptyFull();
          }
          pfrom->fRelayTxes = true;
      }
  
  
      else if (strCommand == "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, "filteradd: script size limits exceeded");
          } else {
              LOCK(pfrom->cs_filter);
              if (pfrom->pfilter)
                  pfrom->pfilter->insert(vData);
              else
                  Misbehaving(pfrom->GetId(), 100, "filteradd: filter not loaded");
          }
      }
  
  
      else if (strCommand == "filterclear")
      {
          LOCK(pfrom->cs_filter);
          pfrom->pfilter.reset(new CBloomFilter());
          pfrom->fRelayTxes = true;
      }
      else
      {
          // Ignore unknown commands for extensibility
          LogPrint(Log::NET, "Unknown command \"%s\" from peer=%d\n", SanitizeString(strCommand), pfrom->id);
      }
  
  
  
      return true;
  }
  
  bool ProcessMessages(CNode* pfrom, CConnman* connman, std::atomic<bool>& interruptMsgProc)
  {
      //
      // Message format
      //  (4) message start
      //  (12) command
      //  (4) size
      //  (4) checksum
      //  (x) data
      //
      bool fMoreWork = true;
  
      if (!pfrom->vRecvGetData.empty())
          ProcessGetData(pfrom, connman, interruptMsgProc);
  
      if (pfrom->fDisconnect)
          return false;
  
      // this maintains the order of responses
      if (!pfrom->vRecvGetData.empty()) return true;
  
          // Don't bother if send buffer is too full to respond anyway
          if (pfrom->fPauseSend)
              return false;
  
          std::list<CNetMessage> msgs;
          {
              LOCK(pfrom->cs_vProcessMsg);
              if (pfrom->vProcessMsg.empty())
                  return false;
              // Just take one message
              msgs.splice(msgs.begin(), pfrom->vProcessMsg, pfrom->vProcessMsg.begin());
              pfrom->nProcessQueueSize -= msgs.front().vRecv.size() + CMessageHeader::HEADER_SIZE;
              pfrom->fPauseRecv = pfrom->nProcessQueueSize > connman->GetReceiveFloodSize();
          }
          CNetMessage& msg(msgs.front());
  
          msg.SetVersion(pfrom->GetRecvVersion());
          // Scan for message start
          if (memcmp(msg.hdr.pchMessageStart, Params().NetworkMagic(), MESSAGE_START_SIZE) != 0) {
              LogPrintf("PROCESSMESSAGE: INVALID MESSAGESTART %s peer=%d\n", SanitizeString(msg.hdr.GetCommand()), pfrom->id);
              connman->Ban(pfrom->addr);
              pfrom->fDisconnect = true;
              return false;
          }
  
          // Read header
          CMessageHeader& hdr = msg.hdr;
          if (!hdr.IsValid(Params().NetworkMagic()))
          {
              LogPrintf("PROCESSMESSAGE: ERRORS IN HEADER %s peer=%d\n", SanitizeString(hdr.GetCommand()), pfrom->id);
              return fMoreWork;
          }
          string strCommand = hdr.GetCommand();
  
          // Message size
          unsigned int nMessageSize = hdr.nMessageSize;
  
          // Checksum
          CDataStream& vRecv = msg.vRecv;
          const uint256& hash = msg.GetMessageHash();
          if (memcmp(hash.begin(), hdr.pchChecksum, CMessageHeader::CHECKSUM_SIZE) != 0)
          {
              LogPrintf("%s(%s, %u bytes): CHECKSUM ERROR expected %s was %s\n", __func__,
                 SanitizeString(strCommand), nMessageSize,
                 HexStr(hash.begin(), hash.begin()+CMessageHeader::CHECKSUM_SIZE),
                 HexStr(hdr.pchChecksum, hdr.pchChecksum+CMessageHeader::CHECKSUM_SIZE));
              return fMoreWork;
          }
  
          // Process message
          bool fRet = false;
          try
          {
              fRet = ProcessMessage(pfrom, strCommand, vRecv, msg.nTime, connman, interruptMsgProc);
              if (interruptMsgProc)
                  return false;
              if (!pfrom->vRecvGetData.empty())
                  fMoreWork = true;
          }
          catch (const std::ios_base::failure& e)
          {
              connman->PushMessage(pfrom, CNetMsgMaker(INIT_PROTO_VERSION).Make(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 if (strstr(e.what(), "non-canonical ReadCompactSize()"))
              {
                  // Allow exceptions from non-canonical encoding
                  LogPrintf("%s(%s, %u bytes): Exception '%s' caught\n", __func__, SanitizeString(strCommand), nMessageSize, e.what());
              }
              else
              {
                  PrintExceptionContinue(&e, "ProcessMessages()");
              }
          }
          catch (const std::exception& e) {
              PrintExceptionContinue(&e, "ProcessMessages()");
          } catch (...) {
              PrintExceptionContinue(NULL, "ProcessMessages()");
          }
  
          if (!fRet) {
              LogPrint(Log::NET, "%s(%s, %u bytes) FAILED peer=%d\n", __func__, SanitizeString(strCommand), nMessageSize, pfrom->id);
          }
          ProcessRejectsAndBans(connman, pfrom);
  
      return fMoreWork;
  }
  
  // If node is configured to avoid full block downloads,
  // this will determine if we should skip downloading from this peer (for now)
  bool WillDownloadFromNode(CNode* pto, const ThinBlockWorker& worker) {
  
      // We always download full blocks during initial sync.
      if (IsInitialBlockDownload())
          return true;
  
      // We don't mind full blocks.
      if (!Opt().UsingThinBlocks())
          return true;
  
      if (!Opt().AvoidFullBlocks())
          return true;
  
      // We want to download thin blocks only.
      return pto->SupportsXThinBlocks()
          || NodeStatePtr(pto->id)->supportsCompactBlocks;
  }
  
  bool SendMessages(CNode* pto, CConnman* connman, std::atomic<bool>& interruptMsgProc)
  {
      const Consensus::Params& consensusParams = Params().GetConsensus();
      {
          // Don't send anything until we get its version message
          if (!pto->fSuccessfullyConnected || pto->fDisconnect)
              return true;
  
          // If we get here, the outgoing message serialization version is set and can't change.
          CNetMsgMaker msgMaker(pto->GetSendVersion());
  
          //
          // 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;
                  connman->PushMessage(pto, msgMaker.Make(NetMsgType::PING, nonce));
              } else {
                  // Peer is too old to support ping command with nonce, pong will never arrive.
                  pto->nPingNonceSent = 0;
                  connman->PushMessage(pto, msgMaker.Make(NetMsgType::PING));
              }
          }
  
          TRY_LOCK(cs_main, lockMain); // Acquire cs_main for IsInitialBlockDownload() and CNodeState()
          if (!lockMain)
              return true;
  
          if (ProcessRejectsAndBans(connman, pto))
              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)
                      {
                          connman->PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
                          vAddr.clear();
                      }
                  }
              }
              pto->vAddrToSend.clear();
              if (!vAddr.empty())
                  connman->PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
          }
  
          // Start block sync
          if (pindexBestHeader == NULL)
              pindexBestHeader = chainActive.Tip();
          NodeStatePtr statePtr(pto->GetId());
          if (statePtr.IsNull()) {
              LogPrint(Log::NET, "%s statePtr = NULL\n");
              return true;
          }
          bool fFetch = statePtr->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 (!statePtr->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) {
                  statePtr->fSyncStarted = true;
                  nSyncStarted++;
                  CBlockIndex *pindexStart = pindexBestHeader->pprev ? pindexBestHeader->pprev : pindexBestHeader;
                  LogPrint(Log::NET, "initial getheaders (%d) to peer=%d (startheight:%d)\n", pindexStart->nHeight, pto->id, pto->nStartingHeight);
                  connman->PushMessage(pto, msgMaker.Make(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, connman);
          }
  
          // Try sending block announcements via headers
          ProcessBlockAvailability(statePtr); // ensure pindexBestKnownBlock is up-to-date
          BlockAnnounceSender ann(*connman, *pto);
          ann.announce();
  
          //
          // 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)
                  {
                      connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
                      vInv.clear();
                  }
              }
              pto->vInventoryToSend = vInvWait;
          }
          if (!vInv.empty())
              connman->PushMessage(pto, msgMaker.Make(NetMsgType::INV, vInv));
  
          // Detect whether we're stalling
          nNow = GetTimeMicros();
          if (statePtr->nStallingSince && statePtr->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;
              return 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 validated blocks that were in flight at the time it was requested), disconnect due to
          // timeout. We compensate for in-flight blocks 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.
          // We also compare the block download timeout originally calculated against the time at which we'd disconnect
          // if we assumed the block were being requested now (ignoring blocks we've requested from this peer, since we're
          // only looking at this peer's oldest request).  This way a large queue in the past doesn't result in a
          // permanently large window for this block to be delivered (ie if the number of blocks in flight is decreasing
          // more quickly than once every 5 minutes, then we'll shorten the download window for this block).
          if (statePtr->vBlocksInFlight.size() > 0) {
              QueuedBlock &queuedBlock = statePtr->vBlocksInFlight.front();
              int64_t nTimeoutIfRequestedNow = GetBlockTimeout(nNow, nQueuedValidatedHeaders - statePtr->nBlocksInFlightValidHeaders, consensusParams);
              if (queuedBlock.nTimeDisconnect > nTimeoutIfRequestedNow) {
                  LogPrint(Log::NET, "Reducing block download timeout for peer=%d block=%s, orig=%d new=%d\n", pto->id, queuedBlock.hash.ToString(), queuedBlock.nTimeDisconnect, nTimeoutIfRequestedNow);
                  queuedBlock.nTimeDisconnect = nTimeoutIfRequestedNow;
              }
              if (queuedBlock.nTimeDisconnect < nNow) {
                  LogPrintf("Timeout downloading block %s from peer=%d, disconnecting\n", queuedBlock.hash.ToString(), pto->id);
                  pto->fDisconnect = true;
                  return true;
              }
          }
  
          //
          // Message: getdata (blocks)
          //
          ThinBlockWorker& worker = *(statePtr->thinblock);
          bool fetchData = WillDownloadFromNode(pto, worker);
          vector<CInv> vGetData;
          if (fetchData && !pto->fClient && (fFetch || !IsInitialBlockDownload()) && statePtr->nBlocksInFlight < MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
              vector<const CBlockIndex*> vToDownload;
              std::set<NodeId> stallers;
              FindNextBlocksToDownload(pto->GetId(), MAX_BLOCKS_IN_TRANSIT_PER_PEER - statePtr->nBlocksInFlight, vToDownload, stallers);
              for (const CBlockIndex *pindex : vToDownload) {
  
                  if (ThinBlocksActive(pto)) {
                      worker.requestBlock(pindex->GetBlockHash(), vGetData, *connman, *pto);
                      worker.addWork(pindex->GetBlockHash());
                      LogPrint(Log::NET, "Requesting thin block %s (%d) peer=%d\n",
                              pindex->GetBlockHash().ToString(), pindex->nHeight, pto->id);
                  }
                  else
                  {
                      vGetData.push_back(CInv(MSG_BLOCK, pindex->GetBlockHash()));
                      LogPrint(Log::NET, "Requesting full block %s (%d) peer=%d\n", pindex->GetBlockHash().ToString(),
                              pindex->nHeight, pto->id);
  
                  }
                  MarkBlockAsInFlight()(pto->GetId(), pindex->GetBlockHash(), consensusParams, pindex);
              }
              if (statePtr->nBlocksInFlight == 0 && !stallers.empty()) {
                  typedef set<NodeId>::const_iterator auto_;
                  for (auto_ n = stallers.begin(); n != stallers.end(); ++n) {
                      if (NodeStatePtr(*n)->nStallingSince == 0) {
                          NodeStatePtr(*n)->nStallingSince = nNow;
                          LogPrint(Log::NET, "Stall started peer=%d\n", *n);
                      }
                  }
              }
          }
  
          //
          // Message: getdata (non-blocks)
          //
          while (!pto->mapAskFor.empty() && (*pto->mapAskFor.begin()).first <= nNow)
          {
              const CInv& inv = (*pto->mapAskFor.begin()).second;
              if (!AlreadyHave(inv))
              {
                  if (LogAcceptCategory(Log::NET))
                      LogPrint(Log::NET, "Requesting %s peer=%d\n", inv.ToString(), pto->id);
                  vGetData.push_back(inv);
                  if (vGetData.size() >= 1000)
                  {
                      connman->PushMessage(pto, msgMaker.Make(NetMsgType::GETDATA, vGetData));
                      vGetData.clear();
                  }
              }
              pto->mapAskFor.erase(pto->mapAskFor.begin());
          }
          if (!vGetData.empty())
              connman->PushMessage(pto, msgMaker.Make(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;
  