text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2016 The Bitcoin Core developers
  // Copyright (c) 2018 Rarecoin developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "validation.h"
  
  #include "arith_uint256.h"
  #include "chain.h"
  #include "chainparams.h"
  #include "checkpoints.h"
  #include "checkqueue.h"
  #include "consensus/consensus.h"
  #include "consensus/merkle.h"
  #include "consensus/tx_verify.h"
  #include "consensus/validation.h"
  #include "cuckoocache.h"
  #include "fs.h"
  #include "hash.h"
  #include "init.h"
  #include "policy/fees.h"
  #include "policy/policy.h"
  #include "policy/rbf.h"
  #include "pow.h"
  #include "primitives/block.h"
  #include "primitives/transaction.h"
  #include "random.h"
  #include "reverse_iterator.h"
  #include "script/script.h"
  #include "script/sigcache.h"
  #include "script/standard.h"
  #include "timedata.h"
  #include "tinyformat.h"
  #include "txdb.h"
  #include "txmempool.h"
  #include "ui_interface.h"
  #include "undo.h"
  #include "util.h"
  #include "utilmoneystr.h"
  #include "utilstrencodings.h"
  #include "validationinterface.h"
  #include "versionbits.h"
  #include "warnings.h"
  
  #include <atomic>
  #include <sstream>
  
  #include <boost/algorithm/string/replace.hpp>
  #include <boost/algorithm/string/join.hpp>
  #include <boost/thread.hpp>
  
  #if defined(NDEBUG)
  # error "Bitcoin cannot be compiled without assertions."
  #endif
  
  /**
   * Global state
   */
  
  CCriticalSection cs_main;
  
  BlockMap mapBlockIndex;
  CChain chainActive;
  CBlockIndex *pindexBestHeader = nullptr;
  CWaitableCriticalSection csBestBlock;
  CConditionVariable cvBlockChange;
  int nScriptCheckThreads = 0;
  std::atomic_bool fImporting(false);
  bool fReindex = false;
  bool fTxIndex = false;
  bool fHavePruned = false;
  bool fPruneMode = false;
  bool fIsBareMultisigStd = DEFAULT_PERMIT_BAREMULTISIG;
  bool fRequireStandard = true;
  bool fCheckBlockIndex = false;
  bool fCheckpointsEnabled = DEFAULT_CHECKPOINTS_ENABLED;
  size_t nCoinCacheUsage = 5000 * 300;
  uint64_t nPruneTarget = 0;
  int64_t nMaxTipAge = DEFAULT_MAX_TIP_AGE;
  bool fEnableReplacement = DEFAULT_ENABLE_REPLACEMENT;
  
  uint256 hashAssumeValid;
  arith_uint256 nMinimumChainWork;
  
  CFeeRate minRelayTxFee = CFeeRate(0);
  CAmount maxTxFee = DEFAULT_TRANSACTION_MAXFEE;
  
  CBlockPolicyEstimator feeEstimator;
  CTxMemPool mempool(&feeEstimator);
  
  static void CheckBlockIndex(const Consensus::Params& consensusParams);
  
  /** Constant stuff for coinbase transactions we create: */
  CScript COINBASE_FLAGS;
  
  const std::string strMessageMagic = "Bitcoin Signed Message:\n";
  
  // 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.
       */
      std::set<CBlockIndex*, CBlockIndexWorkComparator> setBlockIndexCandidates;
      /** All pairs A->B, where A (or one of its ancestors) misses transactions, but B has transactions.
       * Pruned nodes may have entries where B is missing data.
       */
      std::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. */
      int32_t nBlockSequenceId = 1;
      /** Decreasing counter (used by subsequent preciousblock calls). */
      int32_t nBlockReverseSequenceId = -1;
      /** chainwork for the last block that preciousblock has been applied to. */
      arith_uint256 nLastPreciousChainwork = 0;
  
      /** In order to efficiently track invalidity of headers, we keep the set of
        * blocks which we tried to connect and found to be invalid here (ie which
        * were set to BLOCK_FAILED_VALID since the last restart). We can then
        * walk this set and check if a new header is a descendant of something in
        * this set, preventing us from having to walk mapBlockIndex when we try
        * to connect a bad block and fail.
        *
        * While this is more complicated than marking everything which descends
        * from an invalid block as invalid at the time we discover it to be
        * invalid, doing so would require walking all of mapBlockIndex to find all
        * descendants. Since this case should be very rare, keeping track of all
        * BLOCK_FAILED_VALID blocks in a set should be just fine and work just as
        * well.
        *
        * Because we alreardy walk mapBlockIndex in height-order at startup, we go
        * ahead and mark descendants of invalid blocks as FAILED_CHILD at that time,
        * instead of putting things in this set.
        */
      std::set<CBlockIndex*> g_failed_blocks;
  
      /** Dirty block index entries. */
      std::set<CBlockIndex*> setDirtyBlockIndex;
  
      /** Dirty block file entries. */
      std::set<int> setDirtyFileInfo;
  } // anon namespace
  
  CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator)
  {
      // Find the first block the caller has in the main chain
      for (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;
              if (pindex->GetAncestor(chain.Height()) == chain.Tip()) {
                  return chain.Tip();
              }
          }
      }
      return chain.Genesis();
  }
  
  CCoinsViewDB *pcoinsdbview = nullptr;
  CCoinsViewCache *pcoinsTip = nullptr;
  CBlockTreeDB *pblocktree = nullptr;
  
  enum FlushStateMode {
      FLUSH_STATE_NONE,
      FLUSH_STATE_IF_NEEDED,
      FLUSH_STATE_PERIODIC,
      FLUSH_STATE_ALWAYS
  };
  
  // See definition for documentation
  static bool FlushStateToDisk(const CChainParams& chainParams, CValidationState &state, FlushStateMode mode, int nManualPruneHeight=0);
  static void FindFilesToPruneManual(std::set<int>& setFilesToPrune, int nManualPruneHeight);
  static void FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight);
  bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks = nullptr);
  static FILE* OpenUndoFile(const CDiskBlockPos &pos, bool fReadOnly = false);
  
  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;
              for (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);
  }
  
  // Returns the script flags which should be checked for a given block
  static unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consensus::Params& chainparams);
  
  static void LimitMempoolSize(CTxMemPool& pool, size_t limit, unsigned long age) {
      int expired = pool.Expire(GetTime() - age);
      if (expired != 0) {
          LogPrint(BCLog::MEMPOOL, "Expired %i transactions from the memory pool\n", expired);
      }
  
      std::vector<COutPoint> vNoSpendsRemaining;
      pool.TrimToSize(limit, &vNoSpendsRemaining);
      for (const COutPoint& removed : vNoSpendsRemaining)
          pcoinsTip->Uncache(removed);
  }
  
  /** Convert CValidationState to a human-readable message for logging */
  std::string FormatStateMessage(const CValidationState &state)
  {
      return strprintf("%s%s (code %i)",
          state.GetRejectReason(),
          state.GetDebugMessage().empty() ? "" : ", "+state.GetDebugMessage(),
          state.GetRejectCode());
  }
  
  static bool IsCurrentForFeeEstimation()
  {
      AssertLockHeld(cs_main);
      if (IsInitialBlockDownload())
          return false;
      if (chainActive.Tip()->GetBlockTime() < (GetTime() - MAX_FEE_ESTIMATION_TIP_AGE))
          return false;
      if (chainActive.Height() < pindexBestHeader->nHeight - 1)
          return false;
      return true;
  }
  
  /* Make mempool consistent after a reorg, by re-adding or recursively erasing
   * disconnected block transactions from the mempool, and also removing any
   * other transactions from the mempool that are no longer valid given the new
   * tip/height.
   *
   * Note: we assume that disconnectpool only contains transactions that are NOT
   * confirmed in the current chain nor already in the mempool (otherwise,
   * in-mempool descendants of such transactions would be removed).
   *
   * Passing fAddToMempool=false will skip trying to add the transactions back,
   * and instead just erase from the mempool as needed.
   */
  
  void UpdateMempoolForReorg(DisconnectedBlockTransactions &disconnectpool, bool fAddToMempool)
  {
      AssertLockHeld(cs_main);
      std::vector<uint256> vHashUpdate;
      // disconnectpool's insertion_order index sorts the entries from
      // oldest to newest, but the oldest entry will be the last tx from the
      // latest mined block that was disconnected.
      // Iterate disconnectpool in reverse, so that we add transactions
      // back to the mempool starting with the earliest transaction that had
      // been previously seen in a block.
      auto it = disconnectpool.queuedTx.get<insertion_order>().rbegin();
      while (it != disconnectpool.queuedTx.get<insertion_order>().rend()) {
          // ignore validation errors in resurrected transactions
          CValidationState stateDummy;
          if (!fAddToMempool || (*it)->IsCoinBase() || !AcceptToMemoryPool(mempool, stateDummy, *it, false, nullptr, nullptr, true)) {
              // If the transaction doesn't make it in to the mempool, remove any
              // transactions that depend on it (which would now be orphans).
              mempool.removeRecursive(**it, MemPoolRemovalReason::REORG);
          } else if (mempool.exists((*it)->GetHash())) {
              vHashUpdate.push_back((*it)->GetHash());
          }
          ++it;
      }
      disconnectpool.queuedTx.clear();
      // 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
      // the disconnectpool that were added back and cleans up the mempool state.
      mempool.UpdateTransactionsFromBlock(vHashUpdate);
  
      // We also need to remove any now-immature transactions
      mempool.removeForReorg(pcoinsTip, chainActive.Tip()->nHeight + 1, STANDARD_LOCKTIME_VERIFY_FLAGS);
      // Re-limit mempool size, in case we added any transactions
      LimitMempoolSize(mempool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
  }
  
  // Used to avoid mempool polluting consensus critical paths if CCoinsViewMempool
  // were somehow broken and returning the wrong scriptPubKeys
  static bool CheckInputsFromMempoolAndCache(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &view, CTxMemPool& pool,
                   unsigned int flags, bool cacheSigStore, PrecomputedTransactionData& txdata) {
      AssertLockHeld(cs_main);
  
      // pool.cs should be locked already, but go ahead and re-take the lock here
      // to enforce that mempool doesn't change between when we check the view
      // and when we actually call through to CheckInputs
      LOCK(pool.cs);
  
      assert(!tx.IsCoinBase());
      for (const CTxIn& txin : tx.vin) {
          const Coin& coin = view.AccessCoin(txin.prevout);
  
          // At this point we haven't actually checked if the coins are all
          // available (or shouldn't assume we have, since CheckInputs does).
          // So we just return failure if the inputs are not available here,
          // and then only have to check equivalence for available inputs.
          if (coin.IsSpent()) return false;
  
          const CTransactionRef& txFrom = pool.get(txin.prevout.hash);
          if (txFrom) {
              assert(txFrom->GetHash() == txin.prevout.hash);
              assert(txFrom->vout.size() > txin.prevout.n);
              assert(txFrom->vout[txin.prevout.n] == coin.out);
          } else {
              const Coin& coinFromDisk = pcoinsTip->AccessCoin(txin.prevout);
              assert(!coinFromDisk.IsSpent());
              assert(coinFromDisk.out == coin.out);
          }
      }
  
      return CheckInputs(tx, state, view, true, flags, cacheSigStore, true, txdata);
  }
  
  static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool& pool, CValidationState& state, const CTransactionRef& ptx, bool fLimitFree,
                                bool* pfMissingInputs, int64_t nAcceptTime, std::list<CTransactionRef>* plTxnReplaced,
                                bool fOverrideMempoolLimit, const CAmount& nAbsurdFee, std::vector<COutPoint>& coins_to_uncache)
  {
      const CTransaction& tx = *ptx;
      const uint256 hash = tx.GetHash();
      AssertLockHeld(cs_main);
      if (pfMissingInputs)
          *pfMissingInputs = false;
  
      if (!CheckTransaction(tx, state))
          return false; // state filled in by CheckTransaction
  
      // Coinbase is only valid in a block, not as a loose transaction
      if (tx.IsCoinBase())
          return state.DoS(100, false, REJECT_INVALID, "coinbase");
  
      // Reject transactions with witness before segregated witness activates (override with -prematurewitness)
      bool witnessEnabled = IsWitnessEnabled(chainActive.Tip(), chainparams.GetConsensus());
      if (!gArgs.GetBoolArg("-prematurewitness", false) && tx.HasWitness() && !witnessEnabled) {
          return state.DoS(0, false, REJECT_NONSTANDARD, "no-witness-yet", true);
      }
  
      // Rather not work on nonstandard transactions (unless -testnet/-regtest)
      std::string reason;
      if (fRequireStandard && !IsStandardTx(tx, reason, witnessEnabled))
          return state.DoS(0, false, 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, false, REJECT_NONSTANDARD, "non-final");
  
      // is it already in the memory pool?
      if (pool.exists(hash)) {
          return state.Invalid(false, REJECT_DUPLICATE, "txn-already-in-mempool");
      }
  
      // Check for conflicts with in-memory transactions
      std::set<uint256> setConflicts;
      {
      LOCK(pool.cs); // protect pool.mapNextTx
      for (const CTxIn &txin : tx.vin)
      {
          auto itConflicting = pool.mapNextTx.find(txin.prevout);
          if (itConflicting != pool.mapNextTx.end())
          {
              const CTransaction *ptxConflicting = itConflicting->second;
              if (!setConflicts.count(ptxConflicting->GetHash()))
              {
                  // Allow opt-out of transaction replacement by setting
                  // nSequence > MAX_BIP125_RBF_SEQUENCE (SEQUENCE_FINAL-2) on all inputs.
                  //
                  // SEQUENCE_FINAL-1 is picked to still allow use of nLockTime by
                  // non-replaceable transactions. All inputs rather than just one
                  // is for the sake of multi-party protocols, where we don't
                  // want a single party to be able to disable replacement.
                  //
                  // The opt-out ignores descendants as anyone relying on
                  // first-seen mempool behavior should be checking all
                  // unconfirmed ancestors anyway; doing otherwise is hopelessly
                  // insecure.
                  bool fReplacementOptOut = true;
                  if (fEnableReplacement)
                  {
                      for (const CTxIn &_txin : ptxConflicting->vin)
                      {
                          if (_txin.nSequence <= MAX_BIP125_RBF_SEQUENCE)
                          {
                              fReplacementOptOut = false;
                              break;
                          }
                      }
                  }
                  if (fReplacementOptOut) {
                      return state.Invalid(false, REJECT_DUPLICATE, "txn-mempool-conflict");
                  }
  
                  setConflicts.insert(ptxConflicting->GetHash());
              }
          }
      }
      }
  
      {
          CCoinsView dummy;
          CCoinsViewCache view(&dummy);
  
          CAmount nValueIn = 0;
          LockPoints lp;
          {
          LOCK(pool.cs);
          CCoinsViewMemPool viewMemPool(pcoinsTip, pool);
          view.SetBackend(viewMemPool);
  
          // do all inputs exist?
          for (const CTxIn txin : tx.vin) {
              if (!pcoinsTip->HaveCoinInCache(txin.prevout)) {
                  coins_to_uncache.push_back(txin.prevout);
              }
              if (!view.HaveCoin(txin.prevout)) {
                  // Are inputs missing because we already have the tx?
                  for (size_t out = 0; out < tx.vout.size(); out++) {
                      // Optimistically just do efficient check of cache for outputs
                      if (pcoinsTip->HaveCoinInCache(COutPoint(hash, out))) {
                          return state.Invalid(false, REJECT_DUPLICATE, "txn-already-known");
                      }
                  }
                  // Otherwise assume this might be an orphan tx for which we just haven't seen parents yet
                  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 (fRequireStandard && !AreInputsStandard(tx, view))
              return state.Invalid(false, REJECT_NONSTANDARD, "bad-txns-nonstandard-inputs");
  
          // Check for non-standard witness in P2WSH
          if (tx.HasWitness() && fRequireStandard && !IsWitnessStandard(tx, view))
              return state.DoS(0, false, REJECT_NONSTANDARD, "bad-witness-nonstandard", true);
  
          int64_t nSigOpsCost = GetTransactionSigOpCost(tx, view, STANDARD_SCRIPT_VERIFY_FLAGS);
  
          CAmount nValueOut = tx.GetValueOut();
          CAmount nFees = nValueIn-nValueOut;
          // nModifiedFees includes any fee deltas from PrioritiseTransaction
          CAmount nModifiedFees = nFees;
          pool.ApplyDelta(hash, nModifiedFees);
  
          // Keep track of transactions that spend a coinbase, which we re-scan
          // during reorgs to ensure COINBASE_MATURITY is still met.
          bool fSpendsCoinbase = false;
          for (const CTxIn &txin : tx.vin) {
              const Coin &coin = view.AccessCoin(txin.prevout);
              if (coin.IsCoinBase()) {
                  fSpendsCoinbase = true;
                  break;
              }
          }
  
          CTxMemPoolEntry entry(ptx, nFees, nAcceptTime, chainActive.Height(),
                                fSpendsCoinbase, nSigOpsCost, lp);
          unsigned int nSize = entry.GetTxSize();
  
          // Check that the transaction doesn't have an excessive number of
          // sigops, making it impossible to mine. Since the coinbase transaction
          // itself can contain sigops MAX_STANDARD_TX_SIGOPS is less than
          // MAX_BLOCK_SIGOPS; we still consider this an invalid rather than
          // merely non-standard transaction.
          if (nSigOpsCost > MAX_STANDARD_TX_SIGOPS_COST)
              return state.DoS(0, false, REJECT_NONSTANDARD, "bad-txns-too-many-sigops", false,
                  strprintf("%d", nSigOpsCost));
  
          CAmount mempoolRejectFee = pool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFee(nSize);
          if (mempoolRejectFee > 0 && nModifiedFees < mempoolRejectFee) {
              return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "mempool min fee not met", false, strprintf("%d < %d", nFees, mempoolRejectFee));
          }
  
          // No transactions are allowed below minRelayTxFee except from disconnected blocks
          if (fLimitFree && nModifiedFees < ::minRelayTxFee.GetFee(nSize)) {
              return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "min relay fee not met");
          }
  
          if (nAbsurdFee && nFees > nAbsurdFee)
              return state.Invalid(false,
                  REJECT_HIGHFEE, "absurdly-high-fee",
                  strprintf("%d > %d", nFees, nAbsurdFee));
  
          // Calculate in-mempool ancestors, up to a limit.
          CTxMemPool::setEntries setAncestors;
          size_t nLimitAncestors = gArgs.GetArg("-limitancestorcount", DEFAULT_ANCESTOR_LIMIT);
          size_t nLimitAncestorSize = gArgs.GetArg("-limitancestorsize", DEFAULT_ANCESTOR_SIZE_LIMIT)*1000;
          size_t nLimitDescendants = gArgs.GetArg("-limitdescendantcount", DEFAULT_DESCENDANT_LIMIT);
          size_t nLimitDescendantSize = gArgs.GetArg("-limitdescendantsize", DEFAULT_DESCENDANT_SIZE_LIMIT)*1000;
          std::string errString;
          if (!pool.CalculateMemPoolAncestors(entry, setAncestors, nLimitAncestors, nLimitAncestorSize, nLimitDescendants, nLimitDescendantSize, errString)) {
              return state.DoS(0, false, REJECT_NONSTANDARD, "too-long-mempool-chain", false, errString);
          }
  
          // A transaction that spends outputs that would be replaced by it is invalid. Now
          // that we have the set of all ancestors we can detect this
          // pathological case by making sure setConflicts and setAncestors don't
          // intersect.
          for (CTxMemPool::txiter ancestorIt : setAncestors)
          {
              const uint256 &hashAncestor = ancestorIt->GetTx().GetHash();
              if (setConflicts.count(hashAncestor))
              {
                  return state.DoS(10, false,
                                   REJECT_INVALID, "bad-txns-spends-conflicting-tx", false,
                                   strprintf("%s spends conflicting transaction %s",
                                             hash.ToString(),
                                             hashAncestor.ToString()));
              }
          }
  
          // Check if it's economically rational to mine this transaction rather
          // than the ones it replaces.
          CAmount nConflictingFees = 0;
          size_t nConflictingSize = 0;
          uint64_t nConflictingCount = 0;
          CTxMemPool::setEntries allConflicting;
  
          // If we don't hold the lock allConflicting might be incomplete; the
          // subsequent RemoveStaged() and addUnchecked() calls don't guarantee
          // mempool consistency for us.
          LOCK(pool.cs);
          const bool fReplacementTransaction = setConflicts.size();
          if (fReplacementTransaction)
          {
              CFeeRate newFeeRate(nModifiedFees, nSize);
              std::set<uint256> setConflictsParents;
              const int maxDescendantsToVisit = 100;
              CTxMemPool::setEntries setIterConflicting;
              for (const uint256 &hashConflicting : setConflicts)
              {
                  CTxMemPool::txiter mi = pool.mapTx.find(hashConflicting);
                  if (mi == pool.mapTx.end())
                      continue;
  
                  // Save these to avoid repeated lookups
                  setIterConflicting.insert(mi);
  
                  // Don't allow the replacement to reduce the feerate of the
                  // mempool.
                  //
                  // We usually don't want to accept replacements with lower
                  // feerates than what they replaced as that would lower the
                  // feerate of the next block. Requiring that the feerate always
                  // be increased is also an easy-to-reason about way to prevent
                  // DoS attacks via replacements.
                  //
                  // The mining code doesn't (currently) take children into
                  // account (CPFP) so we only consider the feerates of
                  // transactions being directly replaced, not their indirect
                  // descendants. While that does mean high feerate children are
                  // ignored when deciding whether or not to replace, we do
                  // require the replacement to pay more overall fees too,
                  // mitigating most cases.
                  CFeeRate oldFeeRate(mi->GetModifiedFee(), mi->GetTxSize());
                  if (newFeeRate <= oldFeeRate)
                  {
                      return state.DoS(0, false,
                              REJECT_INSUFFICIENTFEE, "insufficient fee", false,
                              strprintf("rejecting replacement %s; new feerate %s <= old feerate %s",
                                    hash.ToString(),
                                    newFeeRate.ToString(),
                                    oldFeeRate.ToString()));
                  }
  
                  for (const CTxIn &txin : mi->GetTx().vin)
                  {
                      setConflictsParents.insert(txin.prevout.hash);
                  }
  
                  nConflictingCount += mi->GetCountWithDescendants();
              }
              // This potentially overestimates the number of actual descendants
              // but we just want to be conservative to avoid doing too much
              // work.
              if (nConflictingCount <= maxDescendantsToVisit) {
                  // If not too many to replace, then calculate the set of
                  // transactions that would have to be evicted
                  for (CTxMemPool::txiter it : setIterConflicting) {
                      pool.CalculateDescendants(it, allConflicting);
                  }
                  for (CTxMemPool::txiter it : allConflicting) {
                      nConflictingFees += it->GetModifiedFee();
                      nConflictingSize += it->GetTxSize();
                  }
              } else {
                  return state.DoS(0, false,
                          REJECT_NONSTANDARD, "too many potential replacements", false,
                          strprintf("rejecting replacement %s; too many potential replacements (%d > %d)\n",
                              hash.ToString(),
                              nConflictingCount,
                              maxDescendantsToVisit));
              }
  
              for (unsigned int j = 0; j < tx.vin.size(); j++)
              {
                  // We don't want to accept replacements that require low
                  // feerate junk to be mined first. Ideally we'd keep track of
                  // the ancestor feerates and make the decision based on that,
                  // but for now requiring all new inputs to be confirmed works.
                  if (!setConflictsParents.count(tx.vin[j].prevout.hash))
                  {
                      // Rather than check the UTXO set - potentially expensive -
                      // it's cheaper to just check if the new input refers to a
                      // tx that's in the mempool.
                      if (pool.mapTx.find(tx.vin[j].prevout.hash) != pool.mapTx.end())
                          return state.DoS(0, false,
                                           REJECT_NONSTANDARD, "replacement-adds-unconfirmed", false,
                                           strprintf("replacement %s adds unconfirmed input, idx %d",
                                                    hash.ToString(), j));
                  }
              }
  
              // The replacement must pay greater fees than the transactions it
              // replaces - if we did the bandwidth used by those conflicting
              // transactions would not be paid for.
              if (nModifiedFees < nConflictingFees)
              {
                  return state.DoS(0, false,
                                   REJECT_INSUFFICIENTFEE, "insufficient fee", false,
                                   strprintf("rejecting replacement %s, less fees than conflicting txs; %s < %s",
                                            hash.ToString(), FormatMoney(nModifiedFees), FormatMoney(nConflictingFees)));
              }
  
              // Finally in addition to paying more fees than the conflicts the
              // new transaction must pay for its own bandwidth.
              CAmount nDeltaFees = nModifiedFees - nConflictingFees;
              if (nDeltaFees < ::incrementalRelayFee.GetFee(nSize))
              {
                  return state.DoS(0, false,
                          REJECT_INSUFFICIENTFEE, "insufficient fee", false,
                          strprintf("rejecting replacement %s, not enough additional fees to relay; %s < %s",
                                hash.ToString(),
                                FormatMoney(nDeltaFees),
                                FormatMoney(::incrementalRelayFee.GetFee(nSize))));
              }
          }
  
          unsigned int scriptVerifyFlags = STANDARD_SCRIPT_VERIFY_FLAGS;
          if (!chainparams.RequireStandard()) {
              scriptVerifyFlags = gArgs.GetArg("-promiscuousmempoolflags", scriptVerifyFlags);
          }
  
          // 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, scriptVerifyFlags, true, false, txdata)) {
              // SCRIPT_VERIFY_CLEANSTACK requires SCRIPT_VERIFY_WITNESS, so we
              // need to turn both off, and compare against just turning off CLEANSTACK
              // to see if the failure is specifically due to witness validation.
              CValidationState stateDummy; // Want reported failures to be from first CheckInputs
              if (!tx.HasWitness() && CheckInputs(tx, stateDummy, view, true, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true, false, txdata) &&
                  !CheckInputs(tx, stateDummy, view, true, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true, false, txdata)) {
                  // Only the witness is missing, so the transaction itself may be fine.
                  state.SetCorruptionPossible();
              }
              return false; // state filled in by CheckInputs
          }
  
          // Check again against the current block tip's script verification
          // flags to cache our script execution flags. This is, of course,
          // useless if the next block has different script flags from the
          // previous one, but because the cache tracks script flags for us it
          // will auto-invalidate and we'll just have a few blocks of extra
          // misses on soft-fork activation.
          //
          // This is also useful 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 (using TestBlockValidity), however allowing such
          // transactions into the mempool can be exploited as a DoS attack.
          unsigned int currentBlockScriptVerifyFlags = GetBlockScriptFlags(chainActive.Tip(), Params().GetConsensus());
          if (!CheckInputsFromMempoolAndCache(tx, state, view, pool, currentBlockScriptVerifyFlags, true, txdata))
          {
              // If we're using promiscuousmempoolflags, we may hit this normally
              // Check if current block has some flags that scriptVerifyFlags
              // does not before printing an ominous warning
              if (!(~scriptVerifyFlags & currentBlockScriptVerifyFlags)) {
                  return error("%s: BUG! PLEASE REPORT THIS! ConnectInputs failed against latest-block but not STANDARD flags %s, %s",
                      __func__, hash.ToString(), FormatStateMessage(state));
              } else {
                  if (!CheckInputs(tx, state, view, true, MANDATORY_SCRIPT_VERIFY_FLAGS, true, false, txdata)) {
                      return error("%s: ConnectInputs failed against MANDATORY but not STANDARD flags due to promiscuous mempool %s, %s",
                          __func__, hash.ToString(), FormatStateMessage(state));
                  } else {
                      LogPrintf("Warning: -promiscuousmempool flags set to not include currently enforced soft forks, this may break mining or otherwise cause instability!\n");
                  }
              }
          }
  
          // Remove conflicting transactions from the mempool
          for (const CTxMemPool::txiter it : allConflicting)
          {
              LogPrint(BCLog::MEMPOOL, "replacing tx %s with %s for %s BTC additional fees, %d delta bytes\n",
                      it->GetTx().GetHash().ToString(),
                      hash.ToString(),
                      FormatMoney(nModifiedFees - nConflictingFees),
                      (int)nSize - (int)nConflictingSize);
              if (plTxnReplaced)
                  plTxnReplaced->push_back(it->GetSharedTx());
          }
          pool.RemoveStaged(allConflicting, false, MemPoolRemovalReason::REPLACED);
  
          // This transaction should only count for fee estimation if it isn't a
          // BIP 125 replacement transaction (may not be widely supported), the
          // node is not behind, and the transaction is not dependent on any other
          // transactions in the mempool.
          bool validForFeeEstimation = !fReplacementTransaction && IsCurrentForFeeEstimation() && pool.HasNoInputsOf(tx);
  
          // Store transaction in memory
          pool.addUnchecked(hash, entry, setAncestors, validForFeeEstimation);
  
          // trim mempool and check if tx was trimmed
          if (!fOverrideMempoolLimit) {
              LimitMempoolSize(pool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60);
              if (!pool.exists(hash))
                  return state.DoS(0, false, REJECT_INSUFFICIENTFEE, "mempool full");
          }
      }
  
      GetMainSignals().TransactionAddedToMempool(ptx);
  
      return true;
  }
  
  /** (try to) add transaction to memory pool with a specified acceptance time **/
  static bool AcceptToMemoryPoolWithTime(const CChainParams& chainparams, CTxMemPool& pool, CValidationState &state, const CTransactionRef &tx, bool fLimitFree,
                          bool* pfMissingInputs, int64_t nAcceptTime, std::list<CTransactionRef>* plTxnReplaced,
                          bool fOverrideMempoolLimit, const CAmount nAbsurdFee)
  {
      std::vector<COutPoint> coins_to_uncache;
      bool res = AcceptToMemoryPoolWorker(chainparams, pool, state, tx, fLimitFree, pfMissingInputs, nAcceptTime, plTxnReplaced, fOverrideMempoolLimit, nAbsurdFee, coins_to_uncache);
      if (!res) {
          for (const COutPoint& hashTx : coins_to_uncache)
              pcoinsTip->Uncache(hashTx);
      }
      // After we've (potentially) uncached entries, ensure our coins cache is still within its size limits
      CValidationState stateDummy;
      FlushStateToDisk(chainparams, stateDummy, FLUSH_STATE_PERIODIC);
      return res;
  }
  
  bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransactionRef &tx, bool fLimitFree,
                          bool* pfMissingInputs, std::list<CTransactionRef>* plTxnReplaced,
                          bool fOverrideMempoolLimit, const CAmount nAbsurdFee)
  {
      const CChainParams& chainparams = Params();
      return AcceptToMemoryPoolWithTime(chainparams, pool, state, tx, fLimitFree, pfMissingInputs, GetTime(), plTxnReplaced, fOverrideMempoolLimit, nAbsurdFee);
  }
  
  /** Return transaction in txOut, and if it was found inside a block, its hash is placed in hashBlock */
  bool GetTransaction(const uint256 &hash, CTransactionRef &txOut, const Consensus::Params& consensusParams, uint256 &hashBlock, bool fAllowSlow)
  {
      CBlockIndex *pindexSlow = nullptr;
  
      LOCK(cs_main);
  
      CTransactionRef ptx = mempool.get(hash);
      if (ptx)
      {
          txOut = ptx;
          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, consensusParams)) {
              for (const auto& tx : block.vtx) {
                  if (tx->GetHash() == hash) {
                      txOut = tx;
                      hashBlock = pindexSlow->GetBlockHash();
                      return true;
                  }
              }
          }
      }
  
      return false;
  }
  
  
  
  
  
  
  //////////////////////////////////////////////////////////////////////////////
  //
  // CBlock and CBlockIndex
  //
  
  static bool WriteBlockToDisk(const CBlock& block, CDiskBlockPos& pos, const CMessageHeader::MessageStartChars& messageStart)
  {
      // Open history file to append
      CAutoFile fileout(OpenBlockFile(pos), SER_DISK, CLIENT_VERSION);
      if (fileout.IsNull())
          return error("WriteBlockToDisk: OpenBlockFile failed");
  
      // Write index header
      unsigned int nSize = 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)
  {
    CAmount nSubsidy;
  
    //int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;
      // Force block reward to zero when right shift is undefined.
      if (nHeight >= 3019571)
          return 0;
  
      /*Premine */
  
      if(nHeight == 40)
        nSubsidy = 425 * COIN;
      else
        nSubsidy = 0.00317098 * COIN;
  
      return nSubsidy;
  }
  
  bool IsInitialBlockDownload()
  {
      // Once this function has returned false, it must remain false.
      static std::atomic<bool> latchToFalse{false};
      // Optimization: pre-test latch before taking the lock.
      if (latchToFalse.load(std::memory_order_relaxed))
          return false;
  
      LOCK(cs_main);
      if (latchToFalse.load(std::memory_order_relaxed))
          return false;
      if (fImporting || fReindex)
          return true;
      if (chainActive.Tip() == nullptr)
          return true;
      if (chainActive.Tip()->nChainWork < nMinimumChainWork)
          return true;
      //if (chainActive.Tip()->GetBlockTime() < (GetTime() - nMaxTipAge))
      //    return true;
      LogPrintf("Leaving InitialBlockDownload (latching to false)\n");
      latchToFalse.store(true, std::memory_order_relaxed);
      return false;
  }
  
  CBlockIndex *pindexBestForkTip = nullptr, *pindexBestForkBase = nullptr;
  
  static void AlertNotify(const std::string& strMessage)
  {
      uiInterface.NotifyAlertChanged();
      std::string strCmd = gArgs.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);
  
      boost::thread t(runCommand, strCmd); // thread runs free
  }
  
  static 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 finishing our initial sync)
      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 = nullptr;
  
      if (pindexBestForkTip || (pindexBestInvalid && pindexBestInvalid->nChainWork > chainActive.Tip()->nChainWork + (GetBlockProof(*chainActive.Tip()) * 6)))
      {
          if (!GetfLargeWorkForkFound() && pindexBestForkBase)
          {
              std::string warning = std::string("'Warning: Large-work fork detected, forking after block ") +
                  pindexBestForkBase->phashBlock->ToString() + std::string("'");
              AlertNotify(warning);
          }
          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());
              SetfLargeWorkForkFound(true);
          }
          else
          {
              LogPrintf("%s: Warning: Found invalid chain at least ~6 blocks longer than our best chain.\nChain state database corruption likely.\n", __func__);
              SetfLargeWorkInvalidChainFound(true);
          }
      }
      else
      {
          SetfLargeWorkForkFound(false);
          SetfLargeWorkInvalidChainFound(false);
      }
  }
  
  static 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 || pindexNewForkTip->nHeight > pindexBestForkTip->nHeight) &&
              pindexNewForkTip->nChainWork - pfork->nChainWork > (GetBlockProof(*pfork) * 7) &&
              chainActive.Height() - pindexNewForkTip->nHeight < 72)
      {
          pindexBestForkTip = pindexNewForkTip;
          pindexBestForkBase = pfork;
      }
  
      CheckForkWarningConditions();
  }
  
  void static InvalidChainFound(CBlockIndex* pindexNew)
  {
      if (!pindexBestInvalid || pindexNew->nChainWork > pindexBestInvalid->nChainWork)
          pindexBestInvalid = pindexNew;
  
      LogPrintf("%s: invalid block=%s  height=%d  log2_work=%.8g  date=%s\n", __func__,
        pindexNew->GetBlockHash().ToString(), pindexNew->nHeight,
        log(pindexNew->nChainWork.getdouble())/log(2.0), DateTimeStrFormat("%Y-%m-%d %H:%M:%S",
        pindexNew->GetBlockTime()));
      CBlockIndex *tip = chainActive.Tip();
      assert (tip);
      LogPrintf("%s:  current best=%s  height=%d  log2_work=%.8g  date=%s\n", __func__,
        tip->GetBlockHash().ToString(), chainActive.Height(), log(tip->nChainWork.getdouble())/log(2.0),
        DateTimeStrFormat("%Y-%m-%d %H:%M:%S", tip->GetBlockTime()));
      CheckForkWarningConditions();
  }
  
  void static InvalidBlockFound(CBlockIndex *pindex, const CValidationState &state) {
      if (!state.CorruptionPossible()) {
          pindex->nStatus |= BLOCK_FAILED_VALID;
          g_failed_blocks.insert(pindex);
          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());
          for (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;
      const CScriptWitness *witness = &ptxTo->vin[nIn].scriptWitness;
      return VerifyScript(scriptSig, scriptPubKey, witness, nFlags, CachingTransactionSignatureChecker(ptxTo, nIn, amount, cacheStore, *txdata), &error);
  }
  
  int GetSpendHeight(const CCoinsViewCache& inputs)
  {
      LOCK(cs_main);
      CBlockIndex* pindexPrev = mapBlockIndex.find(inputs.GetBestBlock())->second;
      return pindexPrev->nHeight + 1;
  }
  
  
  static CuckooCache::cache<uint256, SignatureCacheHasher> scriptExecutionCache;
  static uint256 scriptExecutionCacheNonce(GetRandHash());
  
  void InitScriptExecutionCache() {
      // nMaxCacheSize is unsigned. If -maxsigcachesize is set to zero,
      // setup_bytes creates the minimum possible cache (2 elements).
      size_t nMaxCacheSize = std::min(std::max((int64_t)0, gArgs.GetArg("-maxsigcachesize", DEFAULT_MAX_SIG_CACHE_SIZE) / 2), MAX_MAX_SIG_CACHE_SIZE) * ((size_t) 1 << 20);
      size_t nElems = scriptExecutionCache.setup_bytes(nMaxCacheSize);
      LogPrintf("Using %zu MiB out of %zu/2 requested for script execution cache, able to store %zu elements\n",
              (nElems*sizeof(uint256)) >>20, (nMaxCacheSize*2)>>20, nElems);
  }
  
  /**
   * Check whether all inputs of this transaction are valid (no double spends, scripts & sigs, amounts)
   * This does not modify the UTXO set.
   *
   * If pvChecks is not nullptr, script checks are pushed onto it instead of being performed inline. Any
   * script checks which are not necessary (eg due to script execution cache hits) are, obviously,
   * not pushed onto pvChecks/run.
   *
   * Setting cacheSigStore/cacheFullScriptStore to false will remove elements from the corresponding cache
   * which are matched. This is useful for checking blocks where we will likely never need the cache
   * entry again.
   *
   * Non-static (and re-declared) in src/test/txvalidationcache_tests.cpp
   */
  bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, 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 script verification when connecting blocks under the
          // assumevalid block. Assuming the assumevalid block is valid this
          // is safe because block merkle hashes are still computed and checked,
          // Of course, if an assumed valid block is invalid due to false scriptSigs
          // this optimization would allow an invalid chain to be accepted.
          if (fScriptChecks) {
              // First check if script executions have been cached with the same
              // flags. Note that this assumes that the inputs provided are
              // correct (ie that the transaction hash which is in tx's prevouts
              // properly commits to the scriptPubKey in the inputs view of that
              // transaction).
              uint256 hashCacheEntry;
              // We only use the first 19 bytes of nonce to avoid a second SHA
              // round - giving us 19 + 32 + 4 = 55 bytes (+ 8 + 1 = 64)
              static_assert(55 - sizeof(flags) - 32 >= 128/8, "Want at least 128 bits of nonce for script execution cache");
              CSHA256().Write(scriptExecutionCacheNonce.begin(), 55 - sizeof(flags) - 32).Write(tx.GetWitnessHash().begin(), 32).Write((unsigned char*)&flags, sizeof(flags)).Finalize(hashCacheEntry.begin());
              AssertLockHeld(cs_main); //TODO: Remove this requirement by making CuckooCache not require external locks
              if (scriptExecutionCache.contains(hashCacheEntry, !cacheFullScriptStore)) {
                  return true;
              }
  
              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 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, cacheSigStore, &txdata);
                  if (pvChecks) {
                      pvChecks->push_back(CScriptCheck());
                      check.swap(pvChecks->back());
                  } else if (!check()) {
                      if (flags & STANDARD_NOT_MANDATORY_VERIFY_FLAGS) {
                          // Check whether the failure was caused by a
                          // non-mandatory script verification check, such as
                          // non-standard DER encodings or non-null dummy
                          // arguments; if so, don't trigger DoS protection to
                          // avoid splitting the network between upgraded and
                          // non-upgraded nodes.
                          CScriptCheck check2(scriptPubKey, amount, tx, i,
                                  flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS, cacheSigStore, &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. an 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 soft-fork
                      // super-majority signaling has occurred.
                      return state.DoS(100,false, REJECT_INVALID, strprintf("mandatory-script-verify-flag-failed (%s)", ScriptErrorString(check.GetScriptError())));
                  }
              }
  
              if (cacheFullScriptStore && !pvChecks) {
                  // We executed all of the provided scripts, and were told to
                  // cache the result. Do so now.
                  scriptExecutionCache.insert(hashCacheEntry);
              }
          }
      }
  
      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: OpenUndoFile 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="")
  {
      SetMiscWarning(strMessage);
      LogPrintf("*** %s\n", strMessage);
      uiInterface.ThreadSafeMessageBox(
          userMessage.empty() ? _("Error: A fatal internal error occurred, see debug.log for details") : userMessage,
          "", CClientUIInterface::MSG_ERROR);
      StartShutdown();
      return false;
  }
  
  bool AbortNode(CValidationState& state, const std::string& strMessage, const std::string& userMessage="")
  {
      AbortNode(strMessage, userMessage);
      return state.Error(strMessage);
  }
  
  } // 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);
      }
  }
  
  static bool FindUndoPos(CValidationState &state, int nFile, CDiskBlockPos &pos, unsigned int nAddSize);
  
  static CCheckQueue<CScriptCheck> scriptcheckqueue(128);
  
  void ThreadScriptCheck() {
      RenameThread("bitcoin-scriptch");
      scriptcheckqueue.Thread();
  }
  
  // Protected by cs_main
  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 override { return 0; }
      int64_t EndTime(const Consensus::Params& params) const override { return std::numeric_limits<int64_t>::max(); }
      int Period(const Consensus::Params& params) const override { return params.nMinerConfirmationWindow; }
      int Threshold(const Consensus::Params& params) const override { return params.nRuleChangeActivationThreshold; }
  
      bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const override
      {
          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 unsigned int GetBlockScriptFlags(const CBlockIndex* pindex, const Consensus::Params& consensusparams) {
      AssertLockHeld(cs_main);
  
      // 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) rule
      if (pindex->nHeight >= consensusparams.BIP66Height) {
          flags |= SCRIPT_VERIFY_DERSIG;
      }
  
      // Start enforcing CHECKLOCKTIMEVERIFY (BIP65) rule
      if (pindex->nHeight >= consensusparams.BIP65Height) {
          flags |= SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY;
      }
  
      // Start enforcing BIP68 (sequence locks) and BIP112 (CHECKSEQUENCEVERIFY) using versionbits logic.
      if (VersionBitsState(pindex->pprev, consensusparams, Consensus::DEPLOYMENT_CSV, versionbitscache) == THRESHOLD_ACTIVE) {
          flags |= SCRIPT_VERIFY_CHECKSEQUENCEVERIFY;
      }
  
      // Start enforcing WITNESS rules using versionbits logic.
      if (IsWitnessEnabled(pindex->pprev, consensusparams)) {
          flags |= SCRIPT_VERIFY_WITNESS;
          flags |= SCRIPT_VERIFY_NULLDUMMY;
      }
  
      return flags;
  }
  
  
  
  static int64_t nTimeCheck = 0;
  static int64_t nTimeForks = 0;
  static int64_t nTimeVerify = 0;
  static int64_t nTimeConnect = 0;
  static int64_t nTimeIndex = 0;
  static int64_t nTimeCallbacks = 0;
  static int64_t nTimeTotal = 0;
  
  /** Apply the effects of this block (with given index) on the UTXO set represented by coins.
   *  Validity checks that depend on the UTXO set are also done; ConnectBlock()
   *  can fail if those validity checks fail (among other reasons). */
  static bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pindex,
                    CCoinsViewCache& view, const CChainParams& chainparams, bool fJustCheck = false)
  {
      AssertLockHeld(cs_main);
      assert(pindex);
      // pindex->phashBlock can be null if called by CreateNewBlock/TestBlockValidity
      assert((pindex->phashBlock == nullptr) ||
             (*pindex->phashBlock == block.GetHash()));
      int64_t nTimeStart = GetTimeMicros();
  
      // Check it again in case a previous version let a bad block in
      if (!CheckBlock(block, state, chainparams.GetConsensus(), !fJustCheck, !fJustCheck))
          return error("%s: Consensus::CheckBlock: %s", __func__, FormatStateMessage(state));
  
      // verify that the view's current state corresponds to the previous block
      uint256 hashPrevBlock = pindex->pprev == nullptr ? uint256() : pindex->pprev->GetBlockHash();
      assert(hashPrevBlock == view.GetBestBlock());
  
      // Special case for the genesis block, skipping connection of its transactions
      // (its coinbase is unspendable)
      if (block.GetHash() == chainparams.GetConsensus().hashGenesisBlock) {
          if (!fJustCheck)
              view.SetBestBlock(pindex->GetBlockHash());
          return true;
      }
  
      bool fScriptChecks = true;
      if (!hashAssumeValid.IsNull()) {
          // We've been configured with the hash of a block which has been externally verified to have a valid history.
          // A suitable default value is included with the software and updated from time to time.  Because validity
          //  relative to a piece of software is an objective fact these defaults can be easily reviewed.
          // This setting doesn't force the selection of any particular chain but makes validating some faster by
          //  effectively caching the result of part of the verification.
          BlockMap::const_iterator  it = mapBlockIndex.find(hashAssumeValid);
          if (it != mapBlockIndex.end()) {
              if (it->second->GetAncestor(pindex->nHeight) == pindex &&
                  pindexBestHeader->GetAncestor(pindex->nHeight) == pindex &&
                  pindexBestHeader->nChainWork >= nMinimumChainWork) {
                  // This block is a member of the assumed verified chain and an ancestor of the best header.
                  // The equivalent time check discourages hash power from extorting the network via DOS attack
                  //  into accepting an invalid block through telling users they must manually set assumevalid.
                  //  Requiring a software change or burying the invalid block, regardless of the setting, makes
                  //  it hard to hide the implication of the demand.  This also avoids having release candidates
                  //  that are hardly doing any signature verification at all in testing without having to
                  //  artificially set the default assumed verified block further back.
                  // The test against nMinimumChainWork prevents the skipping when denied access to any chain at
                  //  least as good as the expected chain.
                  fScriptChecks = (GetBlockProofEquivalentTime(*pindexBestHeader, *pindex, *pindexBestHeader, chainparams.GetConsensus()) <= 60 * 60 * 24 * 7 * 2);
              }
          }
      }
  
      int64_t nTime1 = GetTimeMicros(); nTimeCheck += nTime1 - nTimeStart;
      LogPrint(BCLog::BENCH, "    - Sanity checks: %.2fms [%.2fs]\n", 0.001 * (nTime1 - nTimeStart), nTimeCheck * 0.000001);
  
      // Do not allow blocks that contain transactions which 'overwrite' older transactions,
      // unless those are already completely spent.
      // If such overwrites are allowed, coinbases and transactions depending upon those
      // can be duplicated to remove the ability to spend the first instance -- even after
      // being sent to another address.
      // See BIP30 and http://r6.ca/blog/20120206T005236Z.html for more information.
      // This logic is not necessary for memory pool transactions, as AcceptToMemoryPool
      // already refuses previously-known transaction ids entirely.
      // This rule was originally applied to all blocks with a timestamp after March 15, 2012, 0:00 UTC.
      // Now that the whole chain is irreversibly beyond that time it is applied to all blocks except the
      // two in the chain that violate it. This prevents exploiting the issue against nodes during their
      // initial block download.
      bool fEnforceBIP30 = (!pindex->phashBlock) || // Enforce on CreateNewBlock invocations which don't have a hash.
                            !((pindex->nHeight==91842 && pindex->GetBlockHash() == uint256S("0x00000000000a4d0a398161ffc163c503763b1f4360639393e0e4c8e300e0caec")) ||
                             (pindex->nHeight==91880 && pindex->GetBlockHash() == uint256S("0x00000000000743f190a18c5577a3c2d2a1f610ae9601ac046a38084ccb7cd721")));
  
      // Once BIP34 activated it was not possible to create new duplicate coinbases and thus other than starting
      // with the 2 existing duplicate coinbase pairs, not possible to create overwriting txs.  But by the
      // time BIP34 activated, in each of the existing pairs the duplicate coinbase had overwritten the first
      // before the first had been spent.  Since those coinbases are sufficiently buried its no longer possible to create further
      // duplicate transactions descending from the known pairs either.
      // If we're on the known chain at height greater than where BIP34 activated, we can save the db accesses needed for the BIP30 check.
      CBlockIndex *pindexBIP34height = pindex->pprev->GetAncestor(chainparams.GetConsensus().BIP34Height);
      //Only continue to enforce if we're below BIP34 activation height or the block hash at that height doesn't correspond.
      fEnforceBIP30 = fEnforceBIP30 && (!pindexBIP34height || !(pindexBIP34height->GetBlockHash() == chainparams.GetConsensus().BIP34Hash));
  
      if (fEnforceBIP30) {
          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");
                  }
              }
          }
      }
  
      // 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) {
          nLockTimeFlags |= LOCKTIME_VERIFY_SEQUENCE;
      }
  
      // Get the script flags for this block
      unsigned int flags = GetBlockScriptFlags(pindex, chainparams.GetConsensus());
  
      int64_t nTime2 = GetTimeMicros(); nTimeForks += nTime2 - nTime1;
      LogPrint(BCLog::BENCH, "    - Fork checks: %.2fms [%.2fs]\n", 0.001 * (nTime2 - nTime1), nTimeForks * 0.000001);
  
      CBlockUndo blockundo;
  
      CCheckQueueControl<CScriptCheck> control(fScriptChecks && nScriptCheckThreads ? &scriptcheckqueue : nullptr);
  
      std::vector<int> prevheights;
      CAmount nFees = 0;
      int nInputs = 0;
      int64_t nSigOpsCost = 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();
  
          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");
              }
          }
  
          // GetTransactionSigOpCost counts 3 types of sigops:
          // * legacy (always)
          // * p2sh (when P2SH enabled in flags and excludes coinbase)
          // * witness (when witness enabled in flags and excludes coinbase)
          nSigOpsCost += GetTransactionSigOpCost(tx, view, flags);
          if (nSigOpsCost > MAX_BLOCK_SIGOPS_COST)
              return state.DoS(100, error("ConnectBlock(): too many sigops"),
                               REJECT_INVALID, "bad-blk-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) */
              if (!CheckInputs(tx, state, view, fScriptChecks, flags, fCacheResults, fCacheResults, txdata[i], nScriptCheckThreads ? &vChecks : nullptr))
                  return error("ConnectBlock(): CheckInputs on %s failed with %s",
                      tx.GetHash().ToString(), FormatStateMessage(state));
              control.Add(vChecks);
          }
  
          CTxUndo undoDummy;
          if (i > 0) {
              blockundo.vtxundo.push_back(CTxUndo());
          }
          UpdateCoins(tx, view, i == 0 ? undoDummy : blockundo.vtxundo.back(), pindex->nHeight);
  
          vPos.push_back(std::make_pair(tx.GetHash(), pos));
          pos.nTxOffset += ::GetSerializeSize(tx, SER_DISK, CLIENT_VERSION);
      }
      int64_t nTime3 = GetTimeMicros(); nTimeConnect += nTime3 - nTime2;
      LogPrint(BCLog::BENCH, "      - Connect %u transactions: %.2fms (%.3fms/tx, %.3fms/txin) [%.2fs]\n", (unsigned)block.vtx.size(), 0.001 * (nTime3 - nTime2), 0.001 * (nTime3 - nTime2) / block.vtx.size(), nInputs <= 1 ? 0 : 0.001 * (nTime3 - nTime2) / (nInputs-1), nTimeConnect * 0.000001);
  
      CAmount blockReward = nFees + GetBlockSubsidy(pindex->nHeight, chainparams.GetConsensus());
      if (block.vtx[0]->GetValueOut() > blockReward)
          return state.DoS(100,
                           error("ConnectBlock(): coinbase pays too much (actual=%d vs limit=%d)",
                                 block.vtx[0]->GetValueOut(), blockReward),
                                 REJECT_INVALID, "bad-cb-amount");
  
      if (!control.Wait())
          return state.DoS(100, error("%s: CheckQueue failed", __func__), REJECT_INVALID, "block-validation-failed");
      int64_t nTime4 = GetTimeMicros(); nTimeVerify += nTime4 - nTime2;
      LogPrint(BCLog::BENCH, "    - Verify %u txins: %.2fms (%.3fms/txin) [%.2fs]\n", nInputs - 1, 0.001 * (nTime4 - nTime2), nInputs <= 1 ? 0 : 0.001 * (nTime4 - nTime2) / (nInputs-1), nTimeVerify * 0.000001);
  
      if (fJustCheck)
          return true;
  
      // Write undo information to disk
      if (pindex->GetUndoPos().IsNull() || !pindex->IsValid(BLOCK_VALID_SCRIPTS))
      {
          if (pindex->GetUndoPos().IsNull()) {
              CDiskBlockPos _pos;
              if (!FindUndoPos(state, pindex->nFile, _pos, ::GetSerializeSize(blockundo, SER_DISK, CLIENT_VERSION) + 40))
                  return error("ConnectBlock(): FindUndoPos failed");
              if (!UndoWriteToDisk(blockundo, _pos, pindex->pprev->GetBlockHash(), chainparams.MessageStart()))
                  return AbortNode(state, "Failed to write undo data");
  
              // update nUndoPos in block index
              pindex->nUndoPos = _pos.nPos;
              pindex->nStatus |= BLOCK_HAVE_UNDO;
          }
  
          pindex->RaiseValidity(BLOCK_VALID_SCRIPTS);
          setDirtyBlockIndex.insert(pindex);
      }
  
      if (fTxIndex)
          if (!pblocktree->WriteTxIndex(vPos))
              return AbortNode(state, "Failed to write transaction index");
  
      // add this block to the view's block chain
      view.SetBestBlock(pindex->GetBlockHash());
  
      int64_t nTime5 = GetTimeMicros(); nTimeIndex += nTime5 - nTime4;
      LogPrint(BCLog::BENCH, "    - Index writing: %.2fms [%.2fs]\n", 0.001 * (nTime5 - nTime4), nTimeIndex * 0.000001);
  
      int64_t nTime6 = GetTimeMicros(); nTimeCallbacks += nTime6 - nTime5;
      LogPrint(BCLog::BENCH, "    - Callbacks: %.2fms [%.2fs]\n", 0.001 * (nTime6 - nTime5), nTimeCallbacks * 0.000001);
  
      return true;
  }
  
  /**
   * 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(const CChainParams& chainparams, CValidationState &state, FlushStateMode mode, int nManualPruneHeight) {
      int64_t nMempoolUsage = mempool.DynamicMemoryUsage();
      LOCK(cs_main);
      static int64_t nLastWrite = 0;
      static int64_t nLastFlush = 0;
      static int64_t nLastSetChain = 0;
      std::set<int> setFilesToPrune;
      bool fFlushForPrune = false;
      bool fDoFullFlush = false;
      int64_t nNow = 0;
      try {
      {
          LOCK(cs_LastBlockFile);
          if (fPruneMode && (fCheckForPruning || nManualPruneHeight > 0) && !fReindex) {
              if (nManualPruneHeight > 0) {
                  FindFilesToPruneManual(setFilesToPrune, nManualPruneHeight);
              } else {
                  FindFilesToPrune(setFilesToPrune, chainparams.PruneAfterHeight());
                  fCheckForPruning = false;
              }
              if (!setFilesToPrune.empty()) {
                  fFlushForPrune = true;
                  if (!fHavePruned) {
                      pblocktree->WriteFlag("prunedblockfiles", true);
                      fHavePruned = true;
                  }
              }
          }
          nNow = GetTimeMicros();
          // Avoid writing/flushing immediately after startup.
          if (nLastWrite == 0) {
              nLastWrite = nNow;
          }
          if (nLastFlush == 0) {
              nLastFlush = nNow;
          }
          if (nLastSetChain == 0) {
              nLastSetChain = nNow;
          }
          int64_t nMempoolSizeMax = gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
          int64_t cacheSize = pcoinsTip->DynamicMemoryUsage();
          int64_t nTotalSpace = nCoinCacheUsage + std::max<int64_t>(nMempoolSizeMax - nMempoolUsage, 0);
          // The cache is large and we're within 10% and 10 MiB of the limit, but we have time now (not in the middle of a block processing).
          bool fCacheLarge = mode == FLUSH_STATE_PERIODIC && cacheSize > std::max((9 * nTotalSpace) / 10, nTotalSpace - MAX_BLOCK_COINSDB_USAGE * 1024 * 1024);
          // The cache is over the limit, we have to write now.
          bool fCacheCritical = mode == FLUSH_STATE_IF_NEEDED && cacheSize > nTotalSpace;
          // 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.
          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 (std::set<int>::iterator it = setDirtyFileInfo.begin(); it != setDirtyFileInfo.end(); ) {
                      vFiles.push_back(std::make_pair(*it, &vinfoBlockFile[*it]));
                      setDirtyFileInfo.erase(it++);
                  }
                  std::vector<const CBlockIndex*> vBlocks;
                  vBlocks.reserve(setDirtyBlockIndex.size());
                  for (std::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, "Failed 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 (fDoFullFlush || ((mode == FLUSH_STATE_ALWAYS || mode == FLUSH_STATE_PERIODIC) && nNow > nLastSetChain + (int64_t)DATABASE_WRITE_INTERVAL * 1000000)) {
          // Update best block in wallet (so we can detect restored wallets).
          GetMainSignals().SetBestChain(chainActive.GetLocator());
          nLastSetChain = nNow;
      }
      } catch (const std::runtime_error& e) {
          return AbortNode(state, std::string("System error while flushing: ") + e.what());
      }
      return true;
  }
  
  void FlushStateToDisk() {
      CValidationState state;
      const CChainParams& chainparams = Params();
      FlushStateToDisk(chainparams, state, FLUSH_STATE_ALWAYS);
  }
  
  void PruneAndFlush() {
      CValidationState state;
      fCheckForPruning = true;
      const CChainParams& chainparams = Params();
      FlushStateToDisk(chainparams, state, FLUSH_STATE_NONE);
  }
  
  static void DoWarning(const std::string& strWarning)
  {
      static bool fWarned = false;
      SetMiscWarning(strWarning);
      if (!fWarned) {
          AlertNotify(strWarning);
          fWarned = true;
      }
  }
  
  /** Update chainActive and related internal data structures. */
  void static UpdateTip(CBlockIndex *pindexNew, const CChainParams& chainParams) {
      chainActive.SetTip(pindexNew);
  
      // New best block
      mempool.AddTransactionsUpdated(1);
  
      cvBlockChange.notify_all();
  
      std::vector<std::string> warningMessages;
      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) {
                  const std::string strWarning = strprintf(_("Warning: unknown new rules activated (versionbit %i)"), bit);
                  if (state == THRESHOLD_ACTIVE) {
                      DoWarning(strWarning);
                  } else {
                      warningMessages.push_back(strWarning);
                  }
              }
          }
          // Check the version of the last 100 blocks to see if we need to upgrade:
          for (int i = 0; i < 100 && pindex != nullptr; 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)
              warningMessages.push_back(strprintf(_("%d of last 100 blocks have unexpected version"), nUpgraded));
          if (nUpgraded > 100/2)
          {
              std::string strWarning = _("Warning: Unknown block versions being mined! It's possible unknown rules are in effect");
              // notify GetWarnings(), called by Qt and the JSON-RPC code to warn the user:
              DoWarning(strWarning);
          }
      }
      LogPrintf("%s: new best=%s height=%d version=0x%08x log2_work=%.8g tx=%lu date='%s' progress=%f cache=%.1fMiB(%utxo)", __func__,
        chainActive.Tip()->GetBlockHash().ToString(), chainActive.Height(), chainActive.Tip()->nVersion,
        log(chainActive.Tip()->nChainWork.getdouble())/log(2.0), (unsigned long)chainActive.Tip()->nChainTx,
        DateTimeStrFormat("%Y-%m-%d %H:%M:%S", chainActive.Tip()->GetBlockTime()),
        GuessVerificationProgress(chainParams.TxData(), chainActive.Tip()), pcoinsTip->DynamicMemoryUsage() * (1.0 / (1<<20)), pcoinsTip->GetCacheSize());
      if (!warningMessages.empty())
          LogPrintf(" warning='%s'", boost::algorithm::join(warningMessages, ", "));
      LogPrintf("\n");
  
  }
  
  /** Disconnect chainActive's tip.
    * After calling, the mempool will be in an inconsistent state, with
    * transactions from disconnected blocks being added to disconnectpool.  You
    * should make the mempool consistent again by calling UpdateMempoolForReorg.
    * with cs_main held.
    *
    * If disconnectpool is nullptr, then no disconnected transactions are added to
    * disconnectpool (note that the caller is responsible for mempool consistency
    * in any case).
    */
  bool static DisconnectTip(CValidationState& state, const CChainParams& chainparams, DisconnectedBlockTransactions *disconnectpool)
  {
      CBlockIndex *pindexDelete = chainActive.Tip();
      assert(pindexDelete);
      // Read block from disk.
      std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
      CBlock& block = *pblock;
      if (!ReadBlockFromDisk(block, pindexDelete, chainparams.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());
          bool flushed = view.Flush();
          assert(flushed);
      }
      LogPrint(BCLog::BENCH, "- Disconnect block: %.2fms\n", (GetTimeMicros() - nStart) * 0.001);
      // Write the chain state to disk, if necessary.
      if (!FlushStateToDisk(chainparams, state, FLUSH_STATE_IF_NEEDED))
          return false;
  
      if (disconnectpool) {
          // Save transactions to re-add to mempool at end of reorg
          for (auto it = block.vtx.rbegin(); it != block.vtx.rend(); ++it) {
              disconnectpool->addTransaction(*it);
          }
          while (disconnectpool->DynamicMemoryUsage() > MAX_DISCONNECTED_TX_POOL_SIZE * 1000) {
              // Drop the earliest entry, and remove its children from the mempool.
              auto it = disconnectpool->queuedTx.get<insertion_order>().begin();
              mempool.removeRecursive(**it, MemPoolRemovalReason::REORG);
              disconnectpool->removeEntry(it);
          }
      }
  
      // Update chainActive and related variables.
      UpdateTip(pindexDelete->pprev, chainparams);
      // Let wallets know transactions went from 1-confirmed to
      // 0-confirmed or conflicted:
      GetMainSignals().BlockDisconnected(pblock);
      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;
  
  struct PerBlockConnectTrace {
      CBlockIndex* pindex = nullptr;
      std::shared_ptr<const CBlock> pblock;
      std::shared_ptr<std::vector<CTransactionRef>> conflictedTxs;
      PerBlockConnectTrace() : conflictedTxs(std::make_shared<std::vector<CTransactionRef>>()) {}
  };
  /**
   * Used to track blocks whose transactions were applied to the UTXO state as a
   * part of a single ActivateBestChainStep call.
   *
   * This class also tracks transactions that are removed from the mempool as
   * conflicts (per block) and can be used to pass all those transactions
   * through SyncTransaction.
   *
   * This class assumes (and asserts) that the conflicted transactions for a given
   * block are added via mempool callbacks prior to the BlockConnected() associated
   * with those transactions. If any transactions are marked conflicted, it is
   * assumed that an associated block will always be added.
   *
   * This class is single-use, once you call GetBlocksConnected() you have to throw
   * it away and make a new one.
   */
  class ConnectTrace {
  private:
      std::vector<PerBlockConnectTrace> blocksConnected;
      CTxMemPool &pool;
  
  public:
      ConnectTrace(CTxMemPool &_pool) : blocksConnected(1), pool(_pool) {
          pool.NotifyEntryRemoved.connect(boost::bind(&ConnectTrace::NotifyEntryRemoved, this, _1, _2));
      }
  
      ~ConnectTrace() {
          pool.NotifyEntryRemoved.disconnect(boost::bind(&ConnectTrace::NotifyEntryRemoved, this, _1, _2));
      }
  
      void BlockConnected(CBlockIndex* pindex, std::shared_ptr<const CBlock> pblock) {
          assert(!blocksConnected.back().pindex);
          assert(pindex);
          assert(pblock);
          blocksConnected.back().pindex = pindex;
          blocksConnected.back().pblock = std::move(pblock);
          blocksConnected.emplace_back();
      }
  
      std::vector<PerBlockConnectTrace>& GetBlocksConnected() {
          // We always keep one extra block at the end of our list because
          // blocks are added after all the conflicted transactions have
          // been filled in. Thus, the last entry should always be an empty
          // one waiting for the transactions from the next block. We pop
          // the last entry here to make sure the list we return is sane.
          assert(!blocksConnected.back().pindex);
          assert(blocksConnected.back().conflictedTxs->empty());
          blocksConnected.pop_back();
          return blocksConnected;
      }
  
      void NotifyEntryRemoved(CTransactionRef txRemoved, MemPoolRemovalReason reason) {
          assert(!blocksConnected.back().pindex);
          if (reason == MemPoolRemovalReason::CONFLICT) {
              blocksConnected.back().conflictedTxs->emplace_back(std::move(txRemoved));
          }
      }
  };
  
  /**
   * Connect a new block to chainActive. pblock is either nullptr or a pointer to a CBlock
   * corresponding to pindexNew, to bypass loading it again from disk.
   *
   * The block is added to connectTrace if connection succeeds.
   */
  bool static ConnectTip(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexNew, const std::shared_ptr<const CBlock>& pblock, ConnectTrace& connectTrace, DisconnectedBlockTransactions &disconnectpool)
  {
      assert(pindexNew->pprev == chainActive.Tip());
      // Read block from disk.
      int64_t nTime1 = GetTimeMicros();
      std::shared_ptr<const CBlock> pthisBlock;
      if (!pblock) {
          std::shared_ptr<CBlock> pblockNew = std::make_shared<CBlock>();
          if (!ReadBlockFromDisk(*pblockNew, pindexNew, chainparams.GetConsensus()))
              return AbortNode(state, "Failed to read block");
          pthisBlock = pblockNew;
      } else {
          pthisBlock = pblock;
      }
      const CBlock& blockConnecting = *pthisBlock;
      // Apply the block atomically to the chain state.
      int64_t nTime2 = GetTimeMicros(); nTimeReadFromDisk += nTime2 - nTime1;
      int64_t nTime3;
      LogPrint(BCLog::BENCH, "  - Load block from disk: %.2fms [%.2fs]\n", (nTime2 - nTime1) * 0.001, nTimeReadFromDisk * 0.000001);
      {
          CCoinsViewCache view(pcoinsTip);
          bool rv = ConnectBlock(blockConnecting, state, pindexNew, view, chainparams);
          GetMainSignals().BlockChecked(blockConnecting, state);
          if (!rv) {
              if (state.IsInvalid())
                  InvalidBlockFound(pindexNew, state);
              return error("ConnectTip(): ConnectBlock %s failed", pindexNew->GetBlockHash().ToString());
          }
          nTime3 = GetTimeMicros(); nTimeConnectTotal += nTime3 - nTime2;
          LogPrint(BCLog::BENCH, "  - Connect total: %.2fms [%.2fs]\n", (nTime3 - nTime2) * 0.001, nTimeConnectTotal * 0.000001);
          bool flushed = view.Flush();
          assert(flushed);
      }
      int64_t nTime4 = GetTimeMicros(); nTimeFlush += nTime4 - nTime3;
      LogPrint(BCLog::BENCH, "  - Flush: %.2fms [%.2fs]\n", (nTime4 - nTime3) * 0.001, nTimeFlush * 0.000001);
      // Write the chain state to disk, if necessary.
      if (!FlushStateToDisk(chainparams, state, FLUSH_STATE_IF_NEEDED))
          return false;
      int64_t nTime5 = GetTimeMicros(); nTimeChainState += nTime5 - nTime4;
      LogPrint(BCLog::BENCH, "  - Writing chainstate: %.2fms [%.2fs]\n", (nTime5 - nTime4) * 0.001, nTimeChainState * 0.000001);
      // Remove conflicting transactions from the mempool.;
      mempool.removeForBlock(blockConnecting.vtx, pindexNew->nHeight);
      disconnectpool.removeForBlock(blockConnecting.vtx);
      // Update chainActive & related variables.
      UpdateTip(pindexNew, chainparams);
  
      int64_t nTime6 = GetTimeMicros(); nTimePostConnect += nTime6 - nTime5; nTimeTotal += nTime6 - nTime1;
      LogPrint(BCLog::BENCH, "  - Connect postprocess: %.2fms [%.2fs]\n", (nTime6 - nTime5) * 0.001, nTimePostConnect * 0.000001);
      LogPrint(BCLog::BENCH, "- Connect block: %.2fms [%.2fs]\n", (nTime6 - nTime1) * 0.001, nTimeTotal * 0.000001);
  
      connectTrace.BlockConnected(pindexNew, std::move(pthisBlock));
      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 = nullptr;
  
          // Find the best candidate header.
          {
              std::set<CBlockIndex*, CBlockIndexWorkComparator>::reverse_iterator it = setBlockIndexCandidates.rbegin();
              if (it == setBlockIndexCandidates.rend())
                  return nullptr;
              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 == nullptr || 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 nullptr or a pointer to a CBlock corresponding to pindexMostWork.
   */
  static bool ActivateBestChainStep(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace)
  {
      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;
      DisconnectedBlockTransactions disconnectpool;
      while (chainActive.Tip() && chainActive.Tip() != pindexFork) {
          if (!DisconnectTip(state, chainparams, &disconnectpool)) {
              // This is likely a fatal error, but keep the mempool consistent,
              // just in case. Only remove from the mempool in this case.
              UpdateMempoolForReorg(disconnectpool, false);
              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.
          for (CBlockIndex *pindexConnect : reverse_iterate(vpindexToConnect)) {
              if (!ConnectTip(state, chainparams, pindexConnect, pindexConnect == pindexMostWork ? pblock : std::shared_ptr<const CBlock>(), connectTrace, disconnectpool)) {
                  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, ...).
                      // Make the mempool consistent with the current tip, just in case
                      // any observers try to use it before shutdown.
                      UpdateMempoolForReorg(disconnectpool, false);
                      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) {
          // If any blocks were disconnected, disconnectpool may be non empty.  Add
          // any disconnected transactions back to the mempool.
          UpdateMempoolForReorg(disconnectpool, true);
      }
      mempool.check(pcoinsTip);
  
      // Callbacks/notifications for a new best chain.
      if (fInvalidFound)
          CheckForkWarningConditionsOnNewFork(vpindexToConnect.back());
      else
          CheckForkWarningConditions();
  
      return true;
  }
  
  static void NotifyHeaderTip() {
      bool fNotify = false;
      bool fInitialBlockDownload = false;
      static CBlockIndex* pindexHeaderOld = nullptr;
      CBlockIndex* pindexHeader = nullptr;
      {
          LOCK(cs_main);
          pindexHeader = pindexBestHeader;
  
          if (pindexHeader != pindexHeaderOld) {
              fNotify = true;
              fInitialBlockDownload = IsInitialBlockDownload();
              pindexHeaderOld = pindexHeader;
          }
      }
      // Send block tip changed notifications without cs_main
      if (fNotify) {
          uiInterface.NotifyHeaderTip(fInitialBlockDownload, pindexHeader);
      }
  }
  
  /**
   * Make the best chain active, in multiple steps. The result is either failure
   * or an activated best chain. pblock is either nullptr or a pointer to a block
   * that is already loaded (to avoid loading it again from disk).
   */
  bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock) {
      // Note that while we're often called here from ProcessNewBlock, this is
      // far from a guarantee. Things in the P2P/RPC will often end up calling
      // us in the middle of ProcessNewBlock - do not assume pblock is set
      // sanely for performance or correctness!
  
      CBlockIndex *pindexMostWork = nullptr;
      CBlockIndex *pindexNewTip = nullptr;
      int nStopAtHeight = gArgs.GetArg("-stopatheight", DEFAULT_STOPATHEIGHT);
      do {
          boost::this_thread::interruption_point();
          if (ShutdownRequested())
              break;
  
          const CBlockIndex *pindexFork;
          bool fInitialDownload;
          {
              LOCK(cs_main);
              ConnectTrace connectTrace(mempool); // Destructed before cs_main is unlocked
  
              CBlockIndex *pindexOldTip = chainActive.Tip();
              if (pindexMostWork == nullptr) {
                  pindexMostWork = FindMostWorkChain();
              }
  
              // Whether we have anything to do at all.
              if (pindexMostWork == nullptr || pindexMostWork == chainActive.Tip())
                  return true;
  
              bool fInvalidFound = false;
              std::shared_ptr<const CBlock> nullBlockPtr;
              if (!ActivateBestChainStep(state, chainparams, pindexMostWork, pblock && pblock->GetHash() == pindexMostWork->GetBlockHash() ? pblock : nullBlockPtr, fInvalidFound, connectTrace))
                  return false;
  
              if (fInvalidFound) {
                  // Wipe cache, we may need another branch now.
                  pindexMostWork = nullptr;
              }
              pindexNewTip = chainActive.Tip();
              pindexFork = chainActive.FindFork(pindexOldTip);
              fInitialDownload = IsInitialBlockDownload();
  
              for (const PerBlockConnectTrace& trace : connectTrace.GetBlocksConnected()) {
                  assert(trace.pblock && trace.pindex);
                  GetMainSignals().BlockConnected(trace.pblock, trace.pindex, *trace.conflictedTxs);
              }
          }
          // When we reach this point, we switched to a new tip (stored in pindexNewTip).
  
          // Notifications/callbacks that can run without cs_main
  
          // Notify external listeners about the new tip.
          GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork, fInitialDownload);
  
          // Always notify the UI if a new block tip was connected
          if (pindexFork != pindexNewTip) {
              uiInterface.NotifyBlockTip(fInitialDownload, pindexNewTip);
          }
  
          if (nStopAtHeight && pindexNewTip && pindexNewTip->nHeight >= nStopAtHeight) StartShutdown();
      } while (pindexNewTip != pindexMostWork);
      CheckBlockIndex(chainparams.GetConsensus());
  
      // Write changes periodically to disk, after relay.
      if (!FlushStateToDisk(chainparams, state, FLUSH_STATE_PERIODIC)) {
          return false;
      }
  
      return true;
  }
  
  
  bool PreciousBlock(CValidationState& state, const CChainParams& params, CBlockIndex *pindex)
  {
      {
          LOCK(cs_main);
          if (pindex->nChainWork < chainActive.Tip()->nChainWork) {
              // Nothing to do, this block is not at the tip.
              return true;
          }
          if (chainActive.Tip()->nChainWork > nLastPreciousChainwork) {
              // The chain has been extended since the last call, reset the counter.
              nBlockReverseSequenceId = -1;
          }
          nLastPreciousChainwork = chainActive.Tip()->nChainWork;
          setBlockIndexCandidates.erase(pindex);
          pindex->nSequenceId = nBlockReverseSequenceId;
          if (nBlockReverseSequenceId > std::numeric_limits<int32_t>::min()) {
              // We can't keep reducing the counter if somebody really wants to
              // call preciousblock 2**31-1 times on the same set of tips...
              nBlockReverseSequenceId--;
          }
          if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && pindex->nChainTx) {
              setBlockIndexCandidates.insert(pindex);
              PruneBlockIndexCandidates();
          }
      }
  
      return ActivateBestChain(state, params);
  }
  
  bool InvalidateBlock(CValidationState& state, const CChainParams& chainparams, CBlockIndex *pindex)
  {
      AssertLockHeld(cs_main);
  
      // We first disconnect backwards and then mark the blocks as invalid.
      // This prevents a case where pruned nodes may fail to invalidateblock
      // and be left unable to start as they have no tip candidates (as there
      // are no blocks that meet the "have data and are not invalid per
      // nStatus" criteria for inclusion in setBlockIndexCandidates).
  
      bool pindex_was_in_chain = false;
      CBlockIndex *invalid_walk_tip = chainActive.Tip();
  
      DisconnectedBlockTransactions disconnectpool;
      while (chainActive.Contains(pindex)) {
          pindex_was_in_chain = true;
          // ActivateBestChain considers blocks already in chainActive
          // unconditionally valid already, so force disconnect away from it.
          if (!DisconnectTip(state, chainparams, &disconnectpool)) {
              // It's probably hopeless to try to make the mempool consistent
              // here if DisconnectTip failed, but we can try.
              UpdateMempoolForReorg(disconnectpool, false);
              return false;
          }
      }
  
      // Now mark the blocks we just disconnected as descendants invalid
      // (note this may not be all descendants).
      while (pindex_was_in_chain && invalid_walk_tip != pindex) {
          invalid_walk_tip->nStatus |= BLOCK_FAILED_CHILD;
          setDirtyBlockIndex.insert(invalid_walk_tip);
          setBlockIndexCandidates.erase(invalid_walk_tip);
          invalid_walk_tip = invalid_walk_tip->pprev;
      }
  
      // Mark the block itself as invalid.
      pindex->nStatus |= BLOCK_FAILED_VALID;
      setDirtyBlockIndex.insert(pindex);
      setBlockIndexCandidates.erase(pindex);
      g_failed_blocks.insert(pindex);
  
      // DisconnectTip will add transactions to disconnectpool; try to add these
      // back to the mempool.
      UpdateMempoolForReorg(disconnectpool, true);
  
      // 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);
      uiInterface.NotifyBlockTip(IsInitialBlockDownload(), pindex->pprev);
      return true;
  }
  
  bool ResetBlockFailureFlags(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 = nullptr;
              }
              g_failed_blocks.erase(it->second);
          }
          it++;
      }
  
      // Remove the invalidity flag from all ancestors too.
      while (pindex != nullptr) {
          if (pindex->nStatus & BLOCK_FAILED_MASK) {
              pindex->nStatus &= ~BLOCK_FAILED_MASK;
              setDirtyBlockIndex.insert(pindex);
          }
          pindex = pindex->pprev;
      }
      return true;
  }
  
  static 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(std::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->nTimeMax = (pindexNew->pprev ? std::max(pindexNew->pprev->nTimeMax, pindexNew->nTime) : pindexNew->nTime);
      pindexNew->nChainWork = (pindexNew->pprev ? pindexNew->pprev->nChainWork : 0) + GetBlockProof(*pindexNew);
      pindexNew->RaiseValidity(BLOCK_VALID_TREE);
      if (pindexBestHeader == nullptr || 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). */
  static bool ReceivedBlockTransactions(const CBlock &block, CValidationState& state, CBlockIndex *pindexNew, const CDiskBlockPos& pos, const Consensus::Params& consensusParams)
  {
      pindexNew->nTx = block.vtx.size();
      pindexNew->nChainTx = 0;
      pindexNew->nFile = pos.nFile;
      pindexNew->nDataPos = pos.nPos;
      pindexNew->nUndoPos = 0;
      pindexNew->nStatus |= BLOCK_HAVE_DATA;
      if (IsWitnessEnabled(pindexNew->pprev, consensusParams)) {
          pindexNew->nStatus |= BLOCK_OPT_WITNESS;
      }
      pindexNew->RaiseValidity(BLOCK_VALID_TRANSACTIONS);
      setDirtyBlockIndex.insert(pindexNew);
  
      if (pindexNew->pprev == nullptr || pindexNew->pprev->nChainTx) {
          // If pindexNew is the genesis block or all parents are BLOCK_VALID_TRANSACTIONS.
          std::deque<CBlockIndex*> queue;
          queue.push_back(pindexNew);
  
          // Recursively process any descendant blocks that now may be eligible to be connected.
          while (!queue.empty()) {
              CBlockIndex *pindex = queue.front();
              queue.pop_front();
              pindex->nChainTx = (pindex->pprev ? pindex->pprev->nChainTx : 0) + pindex->nTx;
              {
                  LOCK(cs_nBlockSequenceId);
                  pindex->nSequenceId = nBlockSequenceId++;
              }
              if (chainActive.Tip() == nullptr || !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;
  }
  
  static bool FindBlockPos(CValidationState &state, CDiskBlockPos &pos, unsigned int nAddSize, unsigned int nHeight, uint64_t nTime, bool fKnown = false)
  {
      LOCK(cs_LastBlockFile);
  
      unsigned int nFile = fKnown ? pos.nFile : nLastBlockFile;
      if (vinfoBlockFile.size() <= nFile) {
          vinfoBlockFile.resize(nFile + 1);
      }
  
      if (!fKnown) {
          while (vinfoBlockFile[nFile].nSize + nAddSize >= MAX_BLOCKFILE_SIZE) {
              nFile++;
              if (vinfoBlockFile.size() <= nFile) {
                  vinfoBlockFile.resize(nFile + 1);
              }
          }
          pos.nFile = nFile;
          pos.nPos = vinfoBlockFile[nFile].nSize;
      }
  
      if ((int)nFile != nLastBlockFile) {
          if (!fKnown) {
              LogPrintf("Leaving block file %i: %s\n", nLastBlockFile, vinfoBlockFile[nLastBlockFile].ToString());
          }
          FlushBlockFile(!fKnown);
          nLastBlockFile = nFile;
      }
  
      vinfoBlockFile[nFile].AddBlock(nHeight, nTime);
      if (fKnown)
          vinfoBlockFile[nFile].nSize = std::max(pos.nPos + nAddSize, vinfoBlockFile[nFile].nSize);
      else
          vinfoBlockFile[nFile].nSize += nAddSize;
  
      if (!fKnown) {
          unsigned int nOldChunks = (pos.nPos + BLOCKFILE_CHUNK_SIZE - 1) / BLOCKFILE_CHUNK_SIZE;
          unsigned int nNewChunks = (vinfoBlockFile[nFile].nSize + BLOCKFILE_CHUNK_SIZE - 1) / BLOCKFILE_CHUNK_SIZE;
          if (nNewChunks > nOldChunks) {
              if (fPruneMode)
                  fCheckForPruning = true;
              if (CheckDiskSpace(nNewChunks * BLOCKFILE_CHUNK_SIZE - pos.nPos)) {
                  FILE *file = OpenBlockFile(pos);
                  if (file) {
                      LogPrintf("Pre-allocating up to position 0x%x in blk%05u.dat\n", nNewChunks * BLOCKFILE_CHUNK_SIZE, pos.nFile);
                      AllocateFileRange(file, pos.nPos, nNewChunks * BLOCKFILE_CHUNK_SIZE - pos.nPos);
                      fclose(file);
                  }
              }
              else
                  return state.Error("out of disk space");
          }
      }
  
      setDirtyFileInfo.insert(nFile);
      return true;
  }
  
  static 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;
  }
  
  static bool CheckBlockHeader(const CBlockHeader& block, CValidationState& state, const Consensus::Params& consensusParams, bool fCheckPOW = true)
  {
      // Check proof of work matches claimed amount
      if (fCheckPOW && !CheckProofOfWork(block.GetHash(), block.nBits, consensusParams))
          return state.DoS(50, false, REJECT_INVALID, "high-hash", false, "proof of work failed");
  
      return true;
  }
  
  bool CheckBlock(const CBlock& block, CValidationState& state, const Consensus::Params& consensusParams, bool fCheckPOW, bool fCheckMerkleRoot)
  {
      // These are checks that are independent of context.
  
      if (block.fChecked)
          return true;
  
      // Check that the header is valid (particularly PoW).  This is mostly
      // redundant with the call in AcceptBlockHeader.
      if (!CheckBlockHeader(block, state, consensusParams, fCheckPOW))
          return false;
  
      // Check the merkle root.
      if (fCheckMerkleRoot) {
          bool mutated;
          uint256 hashMerkleRoot2 = BlockMerkleRoot(block, &mutated);
          if (block.hashMerkleRoot != hashMerkleRoot2)
              return state.DoS(100, false, REJECT_INVALID, "bad-txnmrklroot", true, "hashMerkleRoot mismatch");
  
          // 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, false, REJECT_INVALID, "bad-txns-duplicate", true, "duplicate transaction");
      }
  
      // 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.
      // Note that witness malleability is checked in ContextualCheckBlock, so no
      // checks that use witness data may be performed here.
  
      // Size limits
      if (block.vtx.empty() || block.vtx.size() * WITNESS_SCALE_FACTOR > MAX_BLOCK_WEIGHT || ::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION | SERIALIZE_TRANSACTION_NO_WITNESS) * WITNESS_SCALE_FACTOR > MAX_BLOCK_WEIGHT)
          return state.DoS(100, false, REJECT_INVALID, "bad-blk-length", false, "size limits failed");
  
      // First transaction must be coinbase, the rest must not be
      if (block.vtx.empty() || !block.vtx[0]->IsCoinBase())
          return state.DoS(100, false, REJECT_INVALID, "bad-cb-missing", false, "first tx is not coinbase");
      for (unsigned int i = 1; i < block.vtx.size(); i++)
          if (block.vtx[i]->IsCoinBase())
              return state.DoS(100, false, REJECT_INVALID, "bad-cb-multiple", false, "more than one coinbase");
  
      // Check transactions
      for (const auto& tx : block.vtx)
          if (!CheckTransaction(*tx, state, false))
              return state.Invalid(false, state.GetRejectCode(), state.GetRejectReason(),
                                   strprintf("Transaction check failed (tx hash %s) %s", tx->GetHash().ToString(), state.GetDebugMessage()));
  
      unsigned int nSigOps = 0;
      for (const auto& tx : block.vtx)
      {
          nSigOps += GetLegacySigOpCount(*tx);
      }
      if (nSigOps * WITNESS_SCALE_FACTOR > MAX_BLOCK_SIGOPS_COST)
          return state.DoS(100, false, REJECT_INVALID, "bad-blk-sigops", false, "out-of-bounds SigOpCount");
  
      if (fCheckPOW && fCheckMerkleRoot)
          block.fChecked = true;
  
      return true;
  }
  
  bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& params)
  {
      LOCK(cs_main);
      return (VersionBitsState(pindexPrev, params, Consensus::DEPLOYMENT_SEGWIT, versionbitscache) == THRESHOLD_ACTIVE);
  }
  
  // Compute at which vout of the block's coinbase transaction the witness
  // commitment occurs, or -1 if not found.
  static int GetWitnessCommitmentIndex(const CBlock& block)
  {
      int commitpos = -1;
      if (!block.vtx.empty()) {
          for (size_t o = 0; o < block.vtx[0]->vout.size(); o++) {
              if (block.vtx[0]->vout[o].scriptPubKey.size() >= 38 && block.vtx[0]->vout[o].scriptPubKey[0] == OP_RETURN && block.vtx[0]->vout[o].scriptPubKey[1] == 0x24 && block.vtx[0]->vout[o].scriptPubKey[2] == 0xaa && block.vtx[0]->vout[o].scriptPubKey[3] == 0x21 && block.vtx[0]->vout[o].scriptPubKey[4] == 0xa9 && block.vtx[0]->vout[o].scriptPubKey[5] == 0xed) {
                  commitpos = o;
              }
          }
      }
      return commitpos;
  }
  
  void UpdateUncommittedBlockStructures(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams)
  {
      int commitpos = GetWitnessCommitmentIndex(block);
      static const std::vector<unsigned char> nonce(32, 0x00);
      if (commitpos != -1 && IsWitnessEnabled(pindexPrev, consensusParams) && !block.vtx[0]->HasWitness()) {
          CMutableTransaction tx(*block.vtx[0]);
          tx.vin[0].scriptWitness.stack.resize(1);
          tx.vin[0].scriptWitness.stack[0] = nonce;
          block.vtx[0] = MakeTransactionRef(std::move(tx));
      }
  }
  
  std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams)
  {
      std::vector<unsigned char> commitment;
      int commitpos = GetWitnessCommitmentIndex(block);
      std::vector<unsigned char> ret(32, 0x00);
      if (consensusParams.vDeployments[Consensus::DEPLOYMENT_SEGWIT].nTimeout != 0) {
          if (commitpos == -1) {
              uint256 witnessroot = BlockWitnessMerkleRoot(block, nullptr);
              CHash256().Write(witnessroot.begin(), 32).Write(ret.data(), 32).Finalize(witnessroot.begin());
              CTxOut out;
              out.nValue = 0;
              out.scriptPubKey.resize(38);
              out.scriptPubKey[0] = OP_RETURN;
              out.scriptPubKey[1] = 0x24;
              out.scriptPubKey[2] = 0xaa;
              out.scriptPubKey[3] = 0x21;
              out.scriptPubKey[4] = 0xa9;
              out.scriptPubKey[5] = 0xed;
              memcpy(&out.scriptPubKey[6], witnessroot.begin(), 32);
              commitment = std::vector<unsigned char>(out.scriptPubKey.begin(), out.scriptPubKey.end());
              CMutableTransaction tx(*block.vtx[0]);
              tx.vout.push_back(out);
              block.vtx[0] = MakeTransactionRef(std::move(tx));
          }
      }
      UpdateUncommittedBlockStructures(block, pindexPrev, consensusParams);
      return commitment;
  }
  
  /** Context-dependent validity checks.
   *  By "context", we mean only the previous block headers, but not the UTXO
   *  set; UTXO-related validity checks are done in ConnectBlock(). */
  static bool ContextualCheckBlockHeader(const CBlockHeader& block, CValidationState& state, const CChainParams& params, const CBlockIndex* pindexPrev, int64_t nAdjustedTime)
  {
      assert(pindexPrev != nullptr);
      const int nHeight = pindexPrev->nHeight + 1;
  
      // Check proof of work
      const Consensus::Params& consensusParams = params.GetConsensus();
      if (block.nBits != GetNextWorkRequired(pindexPrev, &block, consensusParams))
          return state.DoS(100, false, REJECT_INVALID, "bad-diffbits", false, "incorrect proof of work");
  
      // Check against checkpoints
      if (fCheckpointsEnabled) {
          // Don't accept any forks from the main chain prior to last checkpoint.
          // GetLastCheckpoint finds the last checkpoint in MapCheckpoints that's in our
          // MapBlockIndex.
          CBlockIndex* pcheckpoint = Checkpoints::GetLastCheckpoint(params.Checkpoints());
          if (pcheckpoint && nHeight < pcheckpoint->nHeight)
              return state.DoS(100, error("%s: forked chain older than last checkpoint (height %d)", __func__, nHeight), REJECT_CHECKPOINT, "bad-fork-prior-to-checkpoint");
      }
  
      // Check timestamp against prev
      if (block.GetBlockTime() <= pindexPrev->GetMedianTimePast())
          return state.Invalid(false, REJECT_INVALID, "time-too-old", "block's timestamp is too early");
  
      // Check timestamp
      if (block.GetBlockTime() > nAdjustedTime + MAX_FUTURE_BLOCK_TIME)
          return state.Invalid(false, REJECT_INVALID, "time-too-new", "block timestamp too far in the future");
  
      // Reject outdated version blocks when 95% (75% on testnet) of the network has upgraded:
      // check for version 2, 3 and 4 upgrades
      if((block.nVersion < 2 && nHeight >= consensusParams.BIP34Height) ||
         (block.nVersion < 3 && nHeight >= consensusParams.BIP66Height) ||
         (block.nVersion < 4 && nHeight >= consensusParams.BIP65Height))
              return state.Invalid(false, REJECT_OBSOLETE, strprintf("bad-version(0x%08x)", block.nVersion),
                                   strprintf("rejected nVersion=0x%08x block", block.nVersion));
  
      return true;
  }
  
  static bool ContextualCheckBlock(const CBlock& block, CValidationState& state, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
  {
      const int nHeight = pindexPrev == nullptr ? 0 : pindexPrev->nHeight + 1;
  
      // Start enforcing BIP113 (Median Time Past) using versionbits logic.
      int nLockTimeFlags = 0;
      if (VersionBitsState(pindexPrev, consensusParams, Consensus::DEPLOYMENT_CSV, versionbitscache) == THRESHOLD_ACTIVE) {
          nLockTimeFlags |= LOCKTIME_MEDIAN_TIME_PAST;
      }
  
      int64_t nLockTimeCutoff = (nLockTimeFlags & LOCKTIME_MEDIAN_TIME_PAST)
                                ? pindexPrev->GetMedianTimePast()
                                : block.GetBlockTime();
  
      // Check that all transactions are finalized
      for (const auto& tx : block.vtx) {
          if (!IsFinalTx(*tx, nHeight, nLockTimeCutoff)) {
              return state.DoS(10, false, REJECT_INVALID, "bad-txns-nonfinal", false, "non-final transaction");
          }
      }
  
      // Enforce rule that the coinbase starts with serialized block height
      // Serialization not possible for small nHeight? (see script.h:388 - bug?)
      if (nHeight > 17 && nHeight >= consensusParams.BIP34Height)
      {
          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, false, REJECT_INVALID, "bad-cb-height", false, "block height mismatch in coinbase");
  	    }
      }
  
      // Validation for witness commitments.
      // * We compute the witness hash (which is the hash including witnesses) of all the block's transactions, except the
      //   coinbase (where 0x0000....0000 is used instead).
      // * The coinbase scriptWitness is a stack of a single 32-byte vector, containing a witness nonce (unconstrained).
      // * We build a merkle tree with all those witness hashes as leaves (similar to the hashMerkleRoot in the block header).
      // * There must be at least one output whose scriptPubKey is a single 36-byte push, the first 4 bytes of which are
      //   {0xaa, 0x21, 0xa9, 0xed}, and the following 32 bytes are SHA256^2(witness root, witness nonce). In case there are
      //   multiple, the last one is used.
      bool fHaveWitness = false;
      if (VersionBitsState(pindexPrev, consensusParams, Consensus::DEPLOYMENT_SEGWIT, versionbitscache) == THRESHOLD_ACTIVE) {
          int commitpos = GetWitnessCommitmentIndex(block);
          if (commitpos != -1) {
              bool malleated = false;
              uint256 hashWitness = BlockWitnessMerkleRoot(block, &malleated);
              // The malleation check is ignored; as the transaction tree itself
              // already does not permit it, it is impossible to trigger in the
              // witness tree.
              if (block.vtx[0]->vin[0].scriptWitness.stack.size() != 1 || block.vtx[0]->vin[0].scriptWitness.stack[0].size() != 32) {
                  return state.DoS(100, false, REJECT_INVALID, "bad-witness-nonce-size", true, strprintf("%s : invalid witness nonce size", __func__));
              }
              CHash256().Write(hashWitness.begin(), 32).Write(&block.vtx[0]->vin[0].scriptWitness.stack[0][0], 32).Finalize(hashWitness.begin());
              if (memcmp(hashWitness.begin(), &block.vtx[0]->vout[commitpos].scriptPubKey[6], 32)) {
                  return state.DoS(100, false, REJECT_INVALID, "bad-witness-merkle-match", true, strprintf("%s : witness merkle commitment mismatch", __func__));
              }
              fHaveWitness = true;
          }
      }
  
      // No witness data is allowed in blocks that don't commit to witness data, as this would otherwise leave room for spam
      if (!fHaveWitness) {
        for (const auto& tx : block.vtx) {
              if (tx->HasWitness()) {
                  return state.DoS(100, false, REJECT_INVALID, "unexpected-witness", true, strprintf("%s : unexpected witness data found", __func__));
              }
          }
      }
  
      // After the coinbase witness nonce and commitment are verified,
      // we can check if the block weight passes (before we've checked the
      // coinbase witness, it would be possible for the weight to be too
      // large by filling up the coinbase witness, which doesn't change
      // the block hash, so we couldn't mark the block as permanently
      // failed).
      if (GetBlockWeight(block) > MAX_BLOCK_WEIGHT) {
          return state.DoS(100, false, REJECT_INVALID, "bad-blk-weight", false, strprintf("%s : weight limit failed", __func__));
      }
  
      return true;
  }
  
  static bool AcceptBlockHeader(const CBlockHeader& block, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex)
  {
      AssertLockHeld(cs_main);
      // Check for duplicate
      uint256 hash = block.GetHash();
      BlockMap::iterator miSelf = mapBlockIndex.find(hash);
      CBlockIndex *pindex = nullptr;
      if (hash != chainparams.GetConsensus().hashGenesisBlock) {
  
          if (miSelf != mapBlockIndex.end()) {
              // Block header is already known.
              pindex = miSelf->second;
              if (ppindex)
                  *ppindex = pindex;
              if (pindex->nStatus & BLOCK_FAILED_MASK)
                  return state.Invalid(error("%s: block %s is marked invalid", __func__, hash.ToString()), 0, "duplicate");
              return true;
          }
  
          if (!CheckBlockHeader(block, state, chainparams.GetConsensus()))
              return error("%s: Consensus::CheckBlockHeader: %s, %s", __func__, hash.ToString(), FormatStateMessage(state));
  
          // Get prev block index
          CBlockIndex* pindexPrev = nullptr;
          BlockMap::iterator mi = mapBlockIndex.find(block.hashPrevBlock);
          if (mi == mapBlockIndex.end())
              return state.DoS(10, error("%s: prev block not found", __func__), 0, "prev-blk-not-found");
          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, chainparams, pindexPrev, GetAdjustedTime()))
              return error("%s: Consensus::ContextualCheckBlockHeader: %s, %s", __func__, hash.ToString(), FormatStateMessage(state));
  
          if (!pindexPrev->IsValid(BLOCK_VALID_SCRIPTS)) {
              for (const CBlockIndex* failedit : g_failed_blocks) {
                  if (pindexPrev->GetAncestor(failedit->nHeight) == failedit) {
                      assert(failedit->nStatus & BLOCK_FAILED_VALID);
                      CBlockIndex* invalid_walk = pindexPrev;
                      while (invalid_walk != failedit) {
                          invalid_walk->nStatus |= BLOCK_FAILED_CHILD;
                          setDirtyBlockIndex.insert(invalid_walk);
                          invalid_walk = invalid_walk->pprev;
                      }
                      return state.DoS(100, error("%s: prev block invalid", __func__), REJECT_INVALID, "bad-prevblk");
                  }
              }
          }
      }
      if (pindex == nullptr)
          pindex = AddToBlockIndex(block);
  
      if (ppindex)
          *ppindex = pindex;
  
      CheckBlockIndex(chainparams.GetConsensus());
  
      return true;
  }
  
  // Exposed wrapper for AcceptBlockHeader
  bool ProcessNewBlockHeaders(const std::vector<CBlockHeader>& headers, CValidationState& state, const CChainParams& chainparams, const CBlockIndex** ppindex, CBlockHeader *first_invalid)
  {
      if (first_invalid != nullptr) first_invalid->SetNull();
      {
          LOCK(cs_main);
          for (const CBlockHeader& header : headers) {
              CBlockIndex *pindex = nullptr; // Use a temp pindex instead of ppindex to avoid a const_cast
              if (!AcceptBlockHeader(header, state, chainparams, &pindex)) {
                  if (first_invalid) *first_invalid = header;
                  return false;
              }
              if (ppindex) {
                  *ppindex = pindex;
              }
          }
      }
      NotifyHeaderTip();
      return true;
  }
  
  /** Store block on disk. If dbp is non-nullptr, the file is known to already reside on disk */
  static bool AcceptBlock(const std::shared_ptr<const CBlock>& pblock, CValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex, bool fRequested, const CDiskBlockPos* dbp, bool* fNewBlock)
  {
      const CBlock& block = *pblock;
  
      if (fNewBlock) *fNewBlock = false;
      AssertLockHeld(cs_main);
  
      CBlockIndex *pindexDummy = nullptr;
      CBlockIndex *&pindex = ppindex ? *ppindex : pindexDummy;
  
      if (!AcceptBlockHeader(block, state, chainparams, &pindex))
          return false;
  
      // Try to process all requested blocks that we don't have, but only
      // process an unrequested block if it's new and has enough work to
      // advance our tip, and isn't too many blocks ahead.
      bool fAlreadyHave = pindex->nStatus & BLOCK_HAVE_DATA;
      bool fHasMoreOrSameWork = (chainActive.Tip() ? pindex->nChainWork >= chainActive.Tip()->nChainWork : true);
      // Blocks that are too out-of-order needlessly limit the effectiveness of
      // pruning, because pruning will not delete block files that contain any
      // blocks which are too close in height to the tip.  Apply this test
      // regardless of whether pruning is enabled; it should generally be safe to
      // not process unrequested blocks.
      bool fTooFarAhead = (pindex->nHeight > int(chainActive.Height() + MIN_BLOCKS_TO_KEEP));
  
      // TODO: Decouple this function from the block download logic by removing fRequested
      // This requires some new chain data structure to efficiently look up if a
      // block is in a chain leading to a candidate for best tip, despite not
      // being such a candidate itself.
  
      // TODO: deal better with return value and error conditions for duplicate
      // and unrequested blocks.
      if (fAlreadyHave) return true;
      if (!fRequested) {  // If we didn't ask for it:
          if (pindex->nTx != 0) return true;    // This is a previously-processed block that was pruned
          if (!fHasMoreOrSameWork) return true; // Don't process less-work chains
          if (fTooFarAhead) return true;        // Block height is too high
  
          // Protect against DoS attacks from low-work chains.
          // If our tip is behind, a peer could try to send us
          // low-work blocks on a fake chain that we would never
          // request; don't process these.
          if (pindex->nChainWork < nMinimumChainWork) return true;
      }
      if (fNewBlock) *fNewBlock = true;
  
      if (!CheckBlock(block, state, chainparams.GetConsensus()) ||
          !ContextualCheckBlock(block, state, chainparams.GetConsensus(), pindex->pprev)) {
          if (state.IsInvalid() && !state.CorruptionPossible()) {
              pindex->nStatus |= BLOCK_FAILED_VALID;
              setDirtyBlockIndex.insert(pindex);
          }
          return error("%s: %s", __func__, FormatStateMessage(state));
      }
  
      // Header is valid/has work, merkle tree and segwit merkle tree are good...RELAY NOW
      // (but if it does not build on our best tip, let the SendMessages loop relay it)
      if (!IsInitialBlockDownload() && chainActive.Tip() == pindex->pprev)
          GetMainSignals().NewPoWValidBlock(pindex, pblock);
  
      int nHeight = pindex->nHeight;
  
      // Write block to history file
      try {
          unsigned int nBlockSize = ::GetSerializeSize(block, SER_DISK, CLIENT_VERSION);
          CDiskBlockPos blockPos;
          if (dbp != nullptr)
              blockPos = *dbp;
          if (!FindBlockPos(state, blockPos, nBlockSize+8, nHeight, block.GetBlockTime(), dbp != nullptr))
              return error("AcceptBlock(): FindBlockPos failed");
          if (dbp == nullptr)
              if (!WriteBlockToDisk(block, blockPos, chainparams.MessageStart()))
                  AbortNode(state, "Failed to write block");
          if (!ReceivedBlockTransactions(block, state, pindex, blockPos, chainparams.GetConsensus()))
              return error("AcceptBlock(): ReceivedBlockTransactions failed");
      } catch (const std::runtime_error& e) {
          return AbortNode(state, std::string("System error: ") + e.what());
      }
  
      if (fCheckForPruning)
          FlushStateToDisk(chainparams, state, FLUSH_STATE_NONE); // we just allocated more disk space for block files
  
      return true;
  }
  
  bool ProcessNewBlock(const CChainParams& chainparams, const std::shared_ptr<const CBlock> pblock, bool fForceProcessing, bool *fNewBlock)
  {
      {
          CBlockIndex *pindex = nullptr;
          if (fNewBlock) *fNewBlock = false;
          CValidationState state;
          // Ensure that CheckBlock() passes before calling AcceptBlock, as
          // belt-and-suspenders.
          bool ret = CheckBlock(*pblock, state, chainparams.GetConsensus());
  
          LOCK(cs_main);
  
          if (ret) {
              // Store to disk
              ret = AcceptBlock(pblock, state, chainparams, &pindex, fForceProcessing, nullptr, fNewBlock);
          }
          CheckBlockIndex(chainparams.GetConsensus());
          if (!ret) {
              GetMainSignals().BlockChecked(*pblock, state);
              return error("%s: AcceptBlock FAILED", __func__);
          }
      }
  
      NotifyHeaderTip();
  
      CValidationState state; // Only used to report errors, not invalidity - ignore it
      if (!ActivateBestChain(state, chainparams, pblock))
          return error("%s: ActivateBestChain failed", __func__);
  
      return true;
  }
  
  bool TestBlockValidity(CValidationState& state, const CChainParams& chainparams, const CBlock& block, CBlockIndex* pindexPrev, bool fCheckPOW, bool fCheckMerkleRoot)
  {
      AssertLockHeld(cs_main);
      assert(pindexPrev && pindexPrev == chainActive.Tip());
      CCoinsViewCache viewNew(pcoinsTip);
      CBlockIndex indexDummy(block);
      indexDummy.pprev = pindexPrev;
      indexDummy.nHeight = pindexPrev->nHeight + 1;
  
      // NOTE: CheckBlockHeader is called by CheckBlock
      if (!ContextualCheckBlockHeader(block, state, chainparams, pindexPrev, GetAdjustedTime()))
          return error("%s: Consensus::ContextualCheckBlockHeader: %s", __func__, FormatStateMessage(state));
      if (!CheckBlock(block, state, chainparams.GetConsensus(), fCheckPOW, fCheckMerkleRoot))
          return error("%s: Consensus::CheckBlock: %s", __func__, FormatStateMessage(state));
      if (!ContextualCheckBlock(block, state, chainparams.GetConsensus(), pindexPrev))
          return error("%s: Consensus::ContextualCheckBlock: %s", __func__, FormatStateMessage(state));
      if (!ConnectBlock(block, state, &indexDummy, viewNew, chainparams, true))
          return false;
      assert(state.IsValid());
  
      return true;
  }
  
  /**
   * BLOCK PRUNING CODE
   */
  
  /* Calculate the amount of disk space the block & undo files currently use */
  static uint64_t CalculateCurrentUsage()
  {
      uint64_t retval = 0;
      for (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(const std::set<int>& setFilesToPrune)
  {
      for (std::set<int>::iterator it = setFilesToPrune.begin(); it != setFilesToPrune.end(); ++it) {
          CDiskBlockPos pos(*it, 0);
          fs::remove(GetBlockPosFilename(pos, "blk"));
          fs::remove(GetBlockPosFilename(pos, "rev"));
          LogPrintf("Prune: %s deleted blk/rev (%05u)\n", __func__, *it);
      }
  }
  
  /* Calculate the block/rev files to delete based on height specified by user with RPC command pruneblockchain */
  static void FindFilesToPruneManual(std::set<int>& setFilesToPrune, int nManualPruneHeight)
  {
      assert(fPruneMode && nManualPruneHeight > 0);
  
      LOCK2(cs_main, cs_LastBlockFile);
      if (chainActive.Tip() == nullptr)
          return;
  
      // last block to prune is the lesser of (user-specified height, MIN_BLOCKS_TO_KEEP from the tip)
      unsigned int nLastBlockWeCanPrune = std::min((unsigned)nManualPruneHeight, chainActive.Tip()->nHeight - MIN_BLOCKS_TO_KEEP);
      int count=0;
      for (int fileNumber = 0; fileNumber < nLastBlockFile; fileNumber++) {
          if (vinfoBlockFile[fileNumber].nSize == 0 || vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune)
              continue;
          PruneOneBlockFile(fileNumber);
          setFilesToPrune.insert(fileNumber);
          count++;
      }
      LogPrintf("Prune (Manual): prune_height=%d removed %d blk/rev pairs\n", nLastBlockWeCanPrune, count);
  }
  
  /* This function is called from the RPC code for pruneblockchain */
  void PruneBlockFilesManual(int nManualPruneHeight)
  {
      CValidationState state;
      const CChainParams& chainparams = Params();
      FlushStateToDisk(chainparams, state, FLUSH_STATE_NONE, nManualPruneHeight);
  }
  
  /**
   * Prune block and undo files (blk???.dat and undo???.dat) so that the disk space used is less than a user-defined target.
   * The user sets the target (in MB) on the command line or in config file.  This will be run on startup and whenever new
   * space is allocated in a block or undo file, staying below the target. Changing back to unpruned requires a reindex
   * (which in this case means the blockchain must be re-downloaded.)
   *
   * Pruning functions are called from FlushStateToDisk when the global fCheckForPruning flag has been set.
   * Block and undo files are deleted in lock-step (when blk00003.dat is deleted, so is rev00003.dat.)
   * Pruning cannot take place until the longest chain is at least a certain length (100000 on mainnet, 1000 on testnet, 1000 on regtest).
   * Pruning will never delete a block within a defined distance (currently 288) from the active chain's tip.
   * The block index is updated by unsetting HAVE_DATA and HAVE_UNDO for any blocks that were stored in the deleted files.
   * A db flag records the fact that at least some block files have been pruned.
   *
   * @param[out]   setFilesToPrune   The set of file indices that can be unlinked will be returned
   */
  static void FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight)
  {
      LOCK2(cs_main, cs_LastBlockFile);
      if (chainActive.Tip() == nullptr || nPruneTarget == 0) {
          return;
      }
      if ((uint64_t)chainActive.Tip()->nHeight <= nPruneAfterHeight) {
          return;
      }
  
      unsigned int nLastBlockWeCanPrune = chainActive.Tip()->nHeight - MIN_BLOCKS_TO_KEEP;
      uint64_t nCurrentUsage = CalculateCurrentUsage();
      // We don't check to prune until after we've allocated new space for files
      // So we should leave a buffer under our target to account for another allocation
      // before the next pruning.
      uint64_t nBuffer = BLOCKFILE_CHUNK_SIZE + UNDOFILE_CHUNK_SIZE;
      uint64_t nBytesToPrune;
      int count=0;
  
      if (nCurrentUsage + nBuffer >= nPruneTarget) {
          for (int fileNumber = 0; fileNumber < nLastBlockFile; fileNumber++) {
              nBytesToPrune = vinfoBlockFile[fileNumber].nSize + vinfoBlockFile[fileNumber].nUndoSize;
  
              if (vinfoBlockFile[fileNumber].nSize == 0)
                  continue;
  
              if (nCurrentUsage + nBuffer < nPruneTarget)  // are we below our target?
                  break;
  
              // don't prune files that could have a block within MIN_BLOCKS_TO_KEEP of the main chain's tip but keep scanning
              if (vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune)
                  continue;
  
              PruneOneBlockFile(fileNumber);
              // Queue up the files for removal
              setFilesToPrune.insert(fileNumber);
              nCurrentUsage -= nBytesToPrune;
              count++;
          }
      }
  
      LogPrint(BCLog::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 = fs::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;
  }
  
  static FILE* OpenDiskFile(const CDiskBlockPos &pos, const char *prefix, bool fReadOnly)
  {
      if (pos.IsNull())
          return nullptr;
      fs::path path = GetBlockPosFilename(pos, prefix);
      fs::create_directories(path.parent_path());
      FILE* file = fsbridge::fopen(path, "rb+");
      if (!file && !fReadOnly)
          file = fsbridge::fopen(path, "wb+");
      if (!file) {
          LogPrintf("Unable to open file %s\n", path.string());
          return nullptr;
      }
      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 nullptr;
          }
      }
      return file;
  }
  
  FILE* OpenBlockFile(const CDiskBlockPos &pos, bool fReadOnly) {
      return OpenDiskFile(pos, "blk", fReadOnly);
  }
  
  /** Open an undo file (rev?????.dat) */
  static FILE* OpenUndoFile(const CDiskBlockPos &pos, bool fReadOnly) {
      return OpenDiskFile(pos, "rev", fReadOnly);
  }
  
  fs::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 nullptr;
  
      // Return existing
      BlockMap::iterator mi = mapBlockIndex.find(hash);
      if (mi != mapBlockIndex.end())
          return (*mi).second;
  
      // Create new
      CBlockIndex* pindexNew = new CBlockIndex();
      if (!pindexNew)
          throw std::runtime_error(std::string(__func__) + ": new CBlockIndex failed");
      mi = mapBlockIndex.insert(std::make_pair(hash, pindexNew)).first;
      pindexNew->phashBlock = &((*mi).first);
  
      return pindexNew;
  }
  
  bool static LoadBlockIndexDB(const CChainParams& chainparams)
  {
      if (!pblocktree->LoadBlockIndexGuts(chainparams.GetConsensus(), InsertBlockIndex))
          return false;
  
      boost::this_thread::interruption_point();
  
      // Calculate nChainWork
      std::vector<std::pair<int, CBlockIndex*> > vSortedByHeight;
      vSortedByHeight.reserve(mapBlockIndex.size());
      for (const std::pair<uint256, CBlockIndex*>& item : mapBlockIndex)
      {
          CBlockIndex* pindex = item.second;
          vSortedByHeight.push_back(std::make_pair(pindex->nHeight, pindex));
      }
      sort(vSortedByHeight.begin(), vSortedByHeight.end());
      for (const std::pair<int, CBlockIndex*>& item : vSortedByHeight)
      {
          CBlockIndex* pindex = item.second;
          pindex->nChainWork = (pindex->pprev ? pindex->pprev->nChainWork : 0) + GetBlockProof(*pindex);
          pindex->nTimeMax = (pindex->pprev ? std::max(pindex->pprev->nTimeMax, pindex->nTime) : pindex->nTime);
          // 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->nStatus & BLOCK_FAILED_MASK) && pindex->pprev && (pindex->pprev->nStatus & BLOCK_FAILED_MASK)) {
              pindex->nStatus |= BLOCK_FAILED_CHILD;
              setDirtyBlockIndex.insert(pindex);
          }
          if (pindex->IsValid(BLOCK_VALID_TRANSACTIONS) && (pindex->nChainTx || pindex->pprev == nullptr))
              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 == nullptr || CBlockIndexWorkComparator()(pindexBestHeader, pindex)))
              pindexBestHeader = pindex;
      }
  
      // Load block file info
      pblocktree->ReadLastBlockFile(nLastBlockFile);
      vinfoBlockFile.resize(nLastBlockFile + 1);
      LogPrintf("%s: last block file = %i\n", __func__, nLastBlockFile);
      for (int nFile = 0; nFile <= nLastBlockFile; nFile++) {
          pblocktree->ReadBlockFileInfo(nFile, vinfoBlockFile[nFile]);
      }
      LogPrintf("%s: last block file info: %s\n", __func__, vinfoBlockFile[nLastBlockFile].ToString());
      for (int nFile = nLastBlockFile + 1; true; nFile++) {
          CBlockFileInfo info;
          if (pblocktree->ReadBlockFileInfo(nFile, info)) {
              vinfoBlockFile.push_back(info);
          } else {
              break;
          }
      }
  
      // Check presence of blk files
      LogPrintf("Checking all blk files are present...\n");
      std::set<int> setBlkDataFiles;
      for (const std::pair<uint256, CBlockIndex*>& item : mapBlockIndex)
      {
          CBlockIndex* pindex = item.second;
          if (pindex->nStatus & BLOCK_HAVE_DATA) {
              setBlkDataFiles.insert(pindex->nFile);
          }
      }
      for (std::set<int>::iterator it = setBlkDataFiles.begin(); it != setBlkDataFiles.end(); it++)
      {
          CDiskBlockPos pos(*it, 0);
          if (CAutoFile(OpenBlockFile(pos, true), SER_DISK, CLIENT_VERSION).IsNull()) {
              return false;
          }
      }
  
      // Check whether we have ever pruned block & undo files
      pblocktree->ReadFlag("prunedblockfiles", fHavePruned);
      if (fHavePruned)
          LogPrintf("LoadBlockIndexDB(): Block files have previously been pruned\n");
  
      // Check whether we need to continue reindexing
      bool fReindexing = false;
      pblocktree->ReadReindexing(fReindexing);
      fReindex |= fReindexing;
  
      // Check whether we have a transaction index
      pblocktree->ReadFlag("txindex", fTxIndex);
      LogPrintf("%s: transaction index %s\n", __func__, fTxIndex ? "enabled" : "disabled");
  
      return true;
  }
  
  bool LoadChainTip(const CChainParams& chainparams)
  {
      if (chainActive.Tip() && chainActive.Tip()->GetBlockHash() == pcoinsTip->GetBestBlock()) return true;
  
      if (pcoinsTip->GetBestBlock().IsNull() && mapBlockIndex.size() == 1) {
          // In case we just added the genesis block, connect it now, so
          // that we always have a chainActive.Tip() when we return.
          LogPrintf("%s: Connecting genesis block...\n", __func__);
          CValidationState state;
          if (!ActivateBestChain(state, chainparams)) {
              return false;
          }
      }
  
      // Load pointer to end of best chain
      BlockMap::iterator it = mapBlockIndex.find(pcoinsTip->GetBestBlock());
      if (it == mapBlockIndex.end())
          return false;
      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()),
          GuessVerificationProgress(chainparams.TxData(), chainActive.Tip()));
      return true;
  }
  
  CVerifyDB::CVerifyDB()
  {
      uiInterface.ShowProgress(_("Verifying blocks..."), 0);
  }
  
  CVerifyDB::~CVerifyDB()
  {
      uiInterface.ShowProgress("", 100);
  }
  
  bool CVerifyDB::VerifyDB(const CChainParams& chainparams, CCoinsView *coinsview, int nCheckLevel, int nCheckDepth)
  {
      LOCK(cs_main);
      if (chainActive.Tip() == nullptr || chainActive.Tip()->pprev == nullptr)
          return true;
  
      // Verify blocks in the best chain
      if (nCheckDepth <= 0 || 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 = nullptr;
      int nGoodTransactions = 0;
      CValidationState state;
      int reportDone = 0;
      LogPrintf("[0%%]...");
      for (CBlockIndex* pindex = chainActive.Tip(); pindex && pindex->pprev; pindex = pindex->pprev)
      {
          boost::this_thread::interruption_point();
          int percentageDone = std::max(1, std::min(99, (int)(((double)(chainActive.Height() - pindex->nHeight)) / (double)nCheckDepth * (nCheckLevel >= 4 ? 50 : 100))));
          if (reportDone < percentageDone/10) {
              // report every 10% step
              LogPrintf("[%d%%]...", percentageDone);
              reportDone = percentageDone/10;
          }
          uiInterface.ShowProgress(_("Verifying blocks..."), percentageDone);
          if (pindex->nHeight < chainActive.Height()-nCheckDepth)
              break;
          if (fPruneMode && !(pindex->nStatus & BLOCK_HAVE_DATA)) {
              // If pruning, only go back as far as we have data.
              LogPrintf("VerifyDB(): block verification stopping at height %d (pruning, no data)\n", pindex->nHeight);
              break;
          }
          CBlock block;
          // check level 0: read from disk
          if (!ReadBlockFromDisk(block, pindex, chainparams.GetConsensus()))
              return error("VerifyDB(): *** ReadBlockFromDisk failed at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
          // check level 1: verify block validity
          if (nCheckLevel >= 1 && !CheckBlock(block, state, chainparams.GetConsensus()))
              return error("%s: *** found bad block at %d, hash=%s (%s)\n", __func__,
                           pindex->nHeight, pindex->GetBlockHash().ToString(), FormatStateMessage(state));
          // 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, chainparams.GetConsensus()))
                  return error("VerifyDB(): *** ReadBlockFromDisk failed at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
              if (!ConnectBlock(block, state, pindex, coins, chainparams))
                  return error("VerifyDB(): *** found unconnectable block at %d, hash=%s", pindex->nHeight, pindex->GetBlockHash().ToString());
          }
      }
  
      LogPrintf("[DONE].\n");
      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 CTransactionRef& 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;
  }
  
  bool RewindBlockIndex(const CChainParams& params)
  {
      LOCK(cs_main);
  
      // Note that during -reindex-chainstate we are called with an empty chainActive!
  
      int nHeight = 1;
      while (nHeight <= chainActive.Height()) {
          if (IsWitnessEnabled(chainActive[nHeight - 1], params.GetConsensus()) && !(chainActive[nHeight]->nStatus & BLOCK_OPT_WITNESS)) {
              break;
          }
          nHeight++;
      }
  
      // nHeight is now the height of the first insufficiently-validated block, or tipheight + 1
      CValidationState state;
      CBlockIndex* pindex = chainActive.Tip();
      while (chainActive.Height() >= nHeight) {
          if (fPruneMode && !(chainActive.Tip()->nStatus & BLOCK_HAVE_DATA)) {
              // If pruning, don't try rewinding past the HAVE_DATA point;
              // since older blocks can't be served anyway, there's
              // no need to walk further, and trying to DisconnectTip()
              // will fail (and require a needless reindex/redownload
              // of the blockchain).
              break;
          }
          if (!DisconnectTip(state, params, nullptr)) {
              return error("RewindBlockIndex: unable to disconnect block at height %i", pindex->nHeight);
          }
          // Occasionally flush state to disk.
          if (!FlushStateToDisk(params, state, FLUSH_STATE_PERIODIC))
              return false;
      }
  
      // Reduce validity flag and have-data flags.
      // We do this after actual disconnecting, otherwise we'll end up writing the lack of data
      // to disk before writing the chainstate, resulting in a failure to continue if interrupted.
      for (BlockMap::iterator it = mapBlockIndex.begin(); it != mapBlockIndex.end(); it++) {
          CBlockIndex* pindexIter = it->second;
  
          // Note: If we encounter an insufficiently validated block that
          // is on chainActive, it must be because we are a pruning node, and
          // this block or some successor doesn't HAVE_DATA, so we were unable to
          // rewind all the way.  Blocks remaining on chainActive at this point
          // must not have their validity reduced.
          if (IsWitnessEnabled(pindexIter->pprev, params.GetConsensus()) && !(pindexIter->nStatus & BLOCK_OPT_WITNESS) && !chainActive.Contains(pindexIter)) {
              // Reduce validity
              pindexIter->nStatus = std::min<unsigned int>(pindexIter->nStatus & BLOCK_VALID_MASK, BLOCK_VALID_TREE) | (pindexIter->nStatus & ~BLOCK_VALID_MASK);
              // Remove have-data flags.
              pindexIter->nStatus &= ~(BLOCK_HAVE_DATA | BLOCK_HAVE_UNDO);
              // Remove storage location.
              pindexIter->nFile = 0;
              pindexIter->nDataPos = 0;
              pindexIter->nUndoPos = 0;
              // Remove various other things
              pindexIter->nTx = 0;
              pindexIter->nChainTx = 0;
              pindexIter->nSequenceId = 0;
              // Make sure it gets written.
              setDirtyBlockIndex.insert(pindexIter);
              // Update indexes
              setBlockIndexCandidates.erase(pindexIter);
              std::pair<std::multimap<CBlockIndex*, CBlockIndex*>::iterator, std::multimap<CBlockIndex*, CBlockIndex*>::iterator> ret = mapBlocksUnlinked.equal_range(pindexIter->pprev);
              while (ret.first != ret.second) {
                  if (ret.first->second == pindexIter) {
                      mapBlocksUnlinked.erase(ret.first++);
                  } else {
                      ++ret.first;
                  }
              }
          } else if (pindexIter->IsValid(BLOCK_VALID_TRANSACTIONS) && pindexIter->nChainTx) {
              setBlockIndexCandidates.insert(pindexIter);
          }
      }
  
      if (chainActive.Tip() != nullptr) {
          // We can't prune block index candidates based on our tip if we have
          // no tip due to chainActive being empty!
          PruneBlockIndexCandidates();
  
          CheckBlockIndex(params.GetConsensus());
  
          // FlushStateToDisk can possibly read chainActive. Be conservative
          // and skip it here, we're about to -reindex-chainstate anyway, so
          // it'll get called a bunch real soon.
          if (!FlushStateToDisk(params, state, FLUSH_STATE_ALWAYS)) {
              return false;
          }
      }
  
      return true;
  }
  
  // May NOT be used after any connections are up as much
  // of the peer-processing logic assumes a consistent
  // block index state
  void UnloadBlockIndex()
  {
      LOCK(cs_main);
      setBlockIndexCandidates.clear();
      chainActive.SetTip(nullptr);
      pindexBestInvalid = nullptr;
      pindexBestHeader = nullptr;
      mempool.clear();
      mapBlocksUnlinked.clear();
      vinfoBlockFile.clear();
      nLastBlockFile = 0;
      nBlockSequenceId = 1;
      setDirtyBlockIndex.clear();
      g_failed_blocks.clear();
      setDirtyFileInfo.clear();
      versionbitscache.Clear();
      for (int b = 0; b < VERSIONBITS_NUM_BITS; b++) {
          warningcache[b].clear();
      }
  
      for (BlockMap::value_type& entry : mapBlockIndex) {
          delete entry.second;
      }
      mapBlockIndex.clear();
      fHavePruned = false;
  }
  
  bool LoadBlockIndex(const CChainParams& chainparams)
  {
      // Load block index from databases
      bool needs_init = fReindex;
      if (!fReindex) {
          bool ret = LoadBlockIndexDB(chainparams);
          if (!ret) return false;
          needs_init = mapBlockIndex.empty();
      }
  
      if (needs_init) {
          // Everything here is for *new* reindex/DBs. Thus, though
          // LoadBlockIndexDB may have set fReindex if we shut down
          // mid-reindex previously, we don't check fReindex and
          // instead only check it prior to LoadBlockIndexDB to set
          // needs_init.
  
          LogPrintf("Initializing databases...\n");
          // Use the provided setting for -txindex in the new database
          fTxIndex = gArgs.GetBoolArg("-txindex", DEFAULT_TXINDEX);
          pblocktree->WriteFlag("txindex", fTxIndex);
      }
      return true;
  }
  
  bool LoadGenesisBlock(const CChainParams& chainparams)
  {
      LOCK(cs_main);
  
      // Check whether we're already initialized by checking for genesis in
      // mapBlockIndex. Note that we can't use chainActive here, since it is
      // set based on the coins db, not the block index db, which is the only
      // thing loaded at this point.
      if (mapBlockIndex.count(chainparams.GenesisBlock().GetHash()))
          return true;
  
      try {
          CBlock &block = const_cast<CBlock&>(chainparams.GenesisBlock());
          // Start new block file
          unsigned int nBlockSize = ::GetSerializeSize(block, SER_DISK, CLIENT_VERSION);
          CDiskBlockPos blockPos;
          CValidationState state;
          if (!FindBlockPos(state, blockPos, nBlockSize+8, 0, block.GetBlockTime()))
              return error("%s: FindBlockPos failed", __func__);
          if (!WriteBlockToDisk(block, blockPos, chainparams.MessageStart()))
              return error("%s: writing genesis block to disk failed", __func__);
          CBlockIndex *pindex = AddToBlockIndex(block);
          if (!ReceivedBlockTransactions(block, state, pindex, blockPos, chainparams.GetConsensus()))
              return error("%s: genesis block not accepted", __func__);
      } catch (const std::runtime_error& e) {
          return error("%s: failed to write genesis block: %s", __func__, e.what());
      }
  
      return true;
  }
  
  bool LoadExternalBlockFile(const CChainParams& chainparams, FILE* fileIn, CDiskBlockPos *dbp)
  {
      // Map of disk positions for blocks with unknown parent (only used for reindex)
      static std::multimap<uint256, CDiskBlockPos> mapBlocksUnknownParent;
      int64_t nStart = GetTimeMillis();
  
      int nLoaded = 0;
      try {
          // This takes over fileIn and calls fclose() on it in the CBufferedFile destructor
          CBufferedFile blkdat(fileIn, 2*MAX_BLOCK_SERIALIZED_SIZE, MAX_BLOCK_SERIALIZED_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[CMessageHeader::MESSAGE_START_SIZE];
                  blkdat.FindByte(chainparams.MessageStart()[0]);
                  nRewind = blkdat.GetPos()+1;
                  blkdat >> FLATDATA(buf);
                  if (memcmp(buf, chainparams.MessageStart(), CMessageHeader::MESSAGE_START_SIZE))
                      continue;
                  // read size
                  blkdat >> nSize;
                  if (nSize < 80 || nSize > MAX_BLOCK_SERIALIZED_SIZE)
                      continue;
              } catch (const std::exception&) {
                  // no valid block header found; don't complain
                  break;
              }
              try {
                  // read block
                  uint64_t nBlockPos = blkdat.GetPos();
                  if (dbp)
                      dbp->nPos = nBlockPos;
                  blkdat.SetLimit(nBlockPos + nSize);
                  blkdat.SetPos(nBlockPos);
                  std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
                  CBlock& block = *pblock;
                  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(BCLog::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(pblock, state, chainparams, nullptr, true, dbp, nullptr))
                          nLoaded++;
                      if (state.IsError())
                          break;
                  } else if (hash != chainparams.GetConsensus().hashGenesisBlock && mapBlockIndex[hash]->nHeight % 1000 == 0) {
                      LogPrint(BCLog::REINDEX, "Block Import: already had block %s at height %d\n", hash.ToString(), mapBlockIndex[hash]->nHeight);
                  }
  
                  // Activate the genesis block so normal node progress can continue
                  if (hash == chainparams.GetConsensus().hashGenesisBlock) {
                      CValidationState state;
                      if (!ActivateBestChain(state, chainparams)) {
                          break;
                      }
                  }
  
                  NotifyHeaderTip();
  
                  // Recursively process earlier encountered successors of this block
                  std::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;
                          std::shared_ptr<CBlock> pblockrecursive = std::make_shared<CBlock>();
                          if (ReadBlockFromDisk(*pblockrecursive, it->second, chainparams.GetConsensus()))
                          {
                              LogPrint(BCLog::REINDEX, "%s: Processing out of order child %s of %s\n", __func__, pblockrecursive->GetHash().ToString(),
                                      head.ToString());
                              LOCK(cs_main);
                              CValidationState dummy;
                              if (AcceptBlock(pblockrecursive, dummy, chainparams, nullptr, true, &it->second, nullptr))
                              {
                                  nLoaded++;
                                  queue.push_back(pblockrecursive->GetHash());
                              }
                          }
                          range.first++;
                          mapBlocksUnknownParent.erase(it);
                          NotifyHeaderTip();
                      }
                  }
              } catch (const std::exception& e) {
                  LogPrintf("%s: Deserialize or I/O error - %s\n", __func__, e.what());
              }
          }
      } catch (const std::runtime_error& e) {
          AbortNode(std::string("System error: ") + e.what());
      }
      if (nLoaded > 0)
          LogPrintf("Loaded %i blocks from external file in %dms\n", nLoaded, GetTimeMillis() - nStart);
      return nLoaded > 0;
  }
  
  void static CheckBlockIndex(const Consensus::Params& consensusParams)
  {
      if (!fCheckBlockIndex) {
          return;
      }
  
      LOCK(cs_main);
  
      // During a reindex, we read the genesis block and call CheckBlockIndex before ActivateBestChain,
      // so we have the genesis block in mapBlockIndex but no active chain.  (A few of the tests when
      // iterating the block tree require that chainActive has been initialized.)
      if (chainActive.Height() < 0) {
          assert(mapBlockIndex.size() <= 1);
          return;
      }
  
      // Build forward-pointing map of the entire block tree.
      std::multimap<CBlockIndex*,CBlockIndex*> forward;
      for (BlockMap::iterator it = mapBlockIndex.begin(); it != mapBlockIndex.end(); it++) {
          forward.insert(std::make_pair(it->second->pprev, it->second));
      }
  
      assert(forward.size() == mapBlockIndex.size());
  
      std::pair<std::multimap<CBlockIndex*,CBlockIndex*>::iterator,std::multimap<CBlockIndex*,CBlockIndex*>::iterator> rangeGenesis = forward.equal_range(nullptr);
      CBlockIndex *pindex = rangeGenesis.first->second;
      rangeGenesis.first++;
      assert(rangeGenesis.first == rangeGenesis.second); // There is only one index entry with parent nullptr.
  
      // 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 = nullptr; // Oldest ancestor of pindex which is invalid.
      CBlockIndex* pindexFirstMissing = nullptr; // Oldest ancestor of pindex which does not have BLOCK_HAVE_DATA.
      CBlockIndex* pindexFirstNeverProcessed = nullptr; // Oldest ancestor of pindex for which nTx == 0.
      CBlockIndex* pindexFirstNotTreeValid = nullptr; // Oldest ancestor of pindex which does not have BLOCK_VALID_TREE (regardless of being valid or not).
      CBlockIndex* pindexFirstNotTransactionsValid = nullptr; // Oldest ancestor of pindex which does not have BLOCK_VALID_TRANSACTIONS (regardless of being valid or not).
      CBlockIndex* pindexFirstNotChainValid = nullptr; // Oldest ancestor of pindex which does not have BLOCK_VALID_CHAIN (regardless of being valid or not).
      CBlockIndex* pindexFirstNotScriptsValid = nullptr; // Oldest ancestor of pindex which does not have BLOCK_VALID_SCRIPTS (regardless of being valid or not).
      while (pindex != nullptr) {
          nNodes++;
          if (pindexFirstInvalid == nullptr && pindex->nStatus & BLOCK_FAILED_VALID) pindexFirstInvalid = pindex;
          if (pindexFirstMissing == nullptr && !(pindex->nStatus & BLOCK_HAVE_DATA)) pindexFirstMissing = pindex;
          if (pindexFirstNeverProcessed == nullptr && pindex->nTx == 0) pindexFirstNeverProcessed = pindex;
          if (pindex->pprev != nullptr && pindexFirstNotTreeValid == nullptr && (pindex->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_TREE) pindexFirstNotTreeValid = pindex;
          if (pindex->pprev != nullptr && pindexFirstNotTransactionsValid == nullptr && (pindex->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_TRANSACTIONS) pindexFirstNotTransactionsValid = pindex;
          if (pindex->pprev != nullptr && pindexFirstNotChainValid == nullptr && (pindex->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_CHAIN) pindexFirstNotChainValid = pindex;
          if (pindex->pprev != nullptr && pindexFirstNotScriptsValid == nullptr && (pindex->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_SCRIPTS) pindexFirstNotScriptsValid = pindex;
  
          // Begin: actual consistency checks.
          if (pindex->pprev == nullptr) {
              // 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 positive for blocks that aren't linked (negative is used for preciousblock)
          // 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 != nullptr) == (pindex->nChainTx == 0)); // nChainTx != 0 is used to signal that all parent blocks have been processed (but may have been pruned).
          assert((pindexFirstNotTransactionsValid != nullptr) == (pindex->nChainTx == 0));
          assert(pindex->nHeight == nHeight); // nHeight must be consistent.
          assert(pindex->pprev == nullptr || 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 == nullptr); // All mapBlockIndex entries must at least be TREE valid
          if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_TREE) assert(pindexFirstNotTreeValid == nullptr); // TREE valid implies all parents are TREE valid
          if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_CHAIN) assert(pindexFirstNotChainValid == nullptr); // CHAIN valid implies all parents are CHAIN valid
          if ((pindex->nStatus & BLOCK_VALID_MASK) >= BLOCK_VALID_SCRIPTS) assert(pindexFirstNotScriptsValid == nullptr); // SCRIPTS valid implies all parents are SCRIPTS valid
          if (pindexFirstInvalid == nullptr) {
              // 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 == nullptr) {
              if (pindexFirstInvalid == nullptr) {
                  // 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 == nullptr || 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 != nullptr && pindexFirstInvalid == nullptr) {
              // 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 == nullptr) assert(!foundInUnlinked); // We aren't missing data for any parent -- cannot be in mapBlocksUnlinked.
          if (pindex->pprev && (pindex->nStatus & BLOCK_HAVE_DATA) && pindexFirstNeverProcessed == nullptr && pindexFirstMissing != nullptr) {
              // 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 == nullptr) {
                      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 = nullptr;
              if (pindex == pindexFirstMissing) pindexFirstMissing = nullptr;
              if (pindex == pindexFirstNeverProcessed) pindexFirstNeverProcessed = nullptr;
              if (pindex == pindexFirstNotTreeValid) pindexFirstNotTreeValid = nullptr;
              if (pindex == pindexFirstNotTransactionsValid) pindexFirstNotTransactionsValid = nullptr;
              if (pindex == pindexFirstNotChainValid) pindexFirstNotChainValid = nullptr;
              if (pindex == pindexFirstNotScriptsValid) pindexFirstNotScriptsValid = nullptr;
              // 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());
  }
  
  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));
  }
  
  CBlockFileInfo* GetBlockFileInfo(size_t n)
  {
      return &vinfoBlockFile.at(n);
  }
  
  ThresholdState VersionBitsTipState(const Consensus::Params& params, Consensus::DeploymentPos pos)
  {
      LOCK(cs_main);
      return VersionBitsState(chainActive.Tip(), params, pos, versionbitscache);
  }
  
  BIP9Stats VersionBitsTipStatistics(const Consensus::Params& params, Consensus::DeploymentPos pos)
  {
      LOCK(cs_main);
      return VersionBitsStatistics(chainActive.Tip(), params, pos);
  }
  
  int VersionBitsTipStateSinceHeight(const Consensus::Params& params, Consensus::DeploymentPos pos)
  {
      LOCK(cs_main);
      return VersionBitsStateSinceHeight(chainActive.Tip(), params, pos, versionbitscache);
  }
  
  static const uint64_t MEMPOOL_DUMP_VERSION = 1;
  
  bool LoadMempool(void)
  {
      const CChainParams& chainparams = Params();
      int64_t nExpiryTimeout = gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60;
      FILE* filestr = fsbridge::fopen(GetDataDir() / "mempool.dat", "rb");
      CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
      if (file.IsNull()) {
          LogPrintf("Failed to open mempool file from disk. Continuing anyway.\n");
          return false;
      }
  
      int64_t count = 0;
      int64_t skipped = 0;
      int64_t failed = 0;
      int64_t nNow = GetTime();
  
      try {
          uint64_t version;
          file >> version;
          if (version != MEMPOOL_DUMP_VERSION) {
              return false;
          }
          uint64_t num;
          file >> num;
          while (num--) {
              CTransactionRef tx;
              int64_t nTime;
              int64_t nFeeDelta;
              file >> tx;
              file >> nTime;
              file >> nFeeDelta;
  
              CAmount amountdelta = nFeeDelta;
              if (amountdelta) {
                  mempool.PrioritiseTransaction(tx->GetHash(), amountdelta);
              }
              CValidationState state;
              if (nTime + nExpiryTimeout > nNow) {
                  LOCK(cs_main);
                  AcceptToMemoryPoolWithTime(chainparams, mempool, state, tx, true, nullptr, nTime, nullptr, false, 0);
                  if (state.IsValid()) {
                      ++count;
                  } else {
                      ++failed;
                  }
              } else {
                  ++skipped;
              }
              if (ShutdownRequested())
                  return false;
          }
          std::map<uint256, CAmount> mapDeltas;
          file >> mapDeltas;
  
          for (const auto& i : mapDeltas) {
              mempool.PrioritiseTransaction(i.first, i.second);
          }
      } catch (const std::exception& e) {
          LogPrintf("Failed to deserialize mempool data on disk: %s. Continuing anyway.\n", e.what());
          return false;
      }
  
      LogPrintf("Imported mempool transactions from disk: %i successes, %i failed, %i expired\n", count, failed, skipped);
      return true;
  }
  
  void DumpMempool(void)
  {
      int64_t start = GetTimeMicros();
  
      std::map<uint256, CAmount> mapDeltas;
      std::vector<TxMempoolInfo> vinfo;
  
      {
          LOCK(mempool.cs);
          for (const auto &i : mempool.mapDeltas) {
              mapDeltas[i.first] = i.second;
          }
          vinfo = mempool.infoAll();
      }
  
      int64_t mid = GetTimeMicros();
  
      try {
          FILE* filestr = fsbridge::fopen(GetDataDir() / "mempool.dat.new", "wb");
          if (!filestr) {
              return;
          }
  
          CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
  
          uint64_t version = MEMPOOL_DUMP_VERSION;
          file << version;
  
          file << (uint64_t)vinfo.size();
          for (const auto& i : vinfo) {
              file << *(i.tx);
              file << (int64_t)i.nTime;
              file << (int64_t)i.nFeeDelta;
              mapDeltas.erase(i.tx->GetHash());
          }
  
          file << mapDeltas;
          FileCommit(file.Get());
          file.fclose();
          RenameOver(GetDataDir() / "mempool.dat.new", GetDataDir() / "mempool.dat");
          int64_t last = GetTimeMicros();
          LogPrintf("Dumped mempool: %gs to copy, %gs to dump\n", (mid-start)*0.000001, (last-mid)*0.000001);
      } catch (const std::exception& e) {
          LogPrintf("Failed to dump mempool: %s. Continuing anyway.\n", e.what());
      }
  }
  
  //! Guess how far we are in the verification process at the given block index
  double GuessVerificationProgress(const ChainTxData& data, CBlockIndex *pindex) {
      if (pindex == nullptr)
          return 0.0;
  
      int64_t nNow = time(nullptr);
  
      double fTxTotal;
  
      if (pindex->nChainTx <= data.nTxCount) {
          fTxTotal = data.nTxCount + (nNow - data.nTime) * data.dTxRate;
      } else {
          fTxTotal = pindex->nChainTx + (nNow - pindex->GetBlockTime()) * data.dTxRate;
      }
  
      return pindex->nChainTx / fTxTotal;
  }
  
  class CMainCleanup
  {
  public:
      CMainCleanup() {}
      ~CMainCleanup() {
          // block headers
          BlockMap::iterator it1 = mapBlockIndex.begin();
          for (; it1 != mapBlockIndex.end(); it1++)
              delete (*it1).second;
          mapBlockIndex.clear();
      }
  } instance_of_cmaincleanup;
  