text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2016 The Bitcoin Core developers
  // Copyright (c) 2017 The Bitcoin developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef BITCOIN_VALIDATION_H
  #define BITCOIN_VALIDATION_H
  
  #if defined(HAVE_CONFIG_H)
  #include <config/bitcoin-config.h>
  #endif
  
  #include <amount.h>
  #include <blockfileinfo.h>
  #include <coins.h>
  #include <consensus/consensus.h>
  #include <flatfile.h>
  #include <fs.h>
  #include <protocol.h> // For CMessageHeader::MessageMagic
  #include <script/script_error.h>
  #include <sync.h>
  #include <versionbits.h>
  
  #include <algorithm>
  #include <atomic>
  #include <cstdint>
  #include <exception>
  #include <map>
  #include <set>
  #include <string>
  #include <utility>
  #include <vector>
  
  class arith_uint256;
  
  class CBlockIndex;
  class CBlockTreeDB;
  class CChainParams;
  class CChain;
  class CCoinsViewDB;
  class CConnman;
  class CInv;
  class Config;
  class CScriptCheck;
  class CTxMemPool;
  class CTxUndo;
  class CValidationState;
  
  struct FlatFilePos;
  struct ChainTxData;
  struct PrecomputedTransactionData;
  struct LockPoints;
  
  namespace Consensus {
  struct Params;
  }
  
  #define MIN_TRANSACTION_SIZE                                                   \
      (::GetSerializeSize(CTransaction(), SER_NETWORK, PROTOCOL_VERSION))
  
  /** Default for -whitelistrelay. */
  static const bool DEFAULT_WHITELISTRELAY = true;
  /** Default for -whitelistforcerelay. */
  static const bool DEFAULT_WHITELISTFORCERELAY = true;
  /** Default for -minrelaytxfee, minimum relay fee for transactions */
  static const Amount DEFAULT_MIN_RELAY_TX_FEE_PER_KB(1000 * SATOSHI);
  /** Default for -excessutxocharge for transactions transactions */
  static const Amount DEFAULT_UTXO_FEE = Amount::zero();
  //! -maxtxfee default
  static const Amount DEFAULT_TRANSACTION_MAXFEE(COIN / 10);
  //! Discourage users to set fees higher than this amount (in satoshis) per kB
  static const Amount HIGH_TX_FEE_PER_KB(COIN / 100);
  /**
   * -maxtxfee will warn if called with a higher fee than this amount (in satoshis
   */
  static const Amount HIGH_MAX_TX_FEE(100 * HIGH_TX_FEE_PER_KB);
  /** Default for -limitancestorcount, max number of in-mempool ancestors */
  static const unsigned int DEFAULT_ANCESTOR_LIMIT = 25;
  /** Default for -limitancestorsize, maximum kilobytes of tx + all in-mempool
   * ancestors */
  static const unsigned int DEFAULT_ANCESTOR_SIZE_LIMIT = 101;
  /** Default for -limitdescendantcount, max number of in-mempool descendants */
  static const unsigned int DEFAULT_DESCENDANT_LIMIT = 25;
  /** Default for -limitdescendantsize, maximum kilobytes of in-mempool
   * descendants */
  static const unsigned int DEFAULT_DESCENDANT_SIZE_LIMIT = 101;
  /** Default for -mempoolexpiry, expiration time for mempool transactions in
   * hours */
  static const unsigned int DEFAULT_MEMPOOL_EXPIRY = 336;
  /** The maximum size of a blk?????.dat file (since 0.8) */
  static const unsigned int MAX_BLOCKFILE_SIZE = 0x8000000; // 128 MiB
  /** The pre-allocation chunk size for blk?????.dat files (since 0.8) */
  static const unsigned int BLOCKFILE_CHUNK_SIZE = 0x1000000; // 16 MiB
  /** The pre-allocation chunk size for rev?????.dat files (since 0.8) */
  static const unsigned int UNDOFILE_CHUNK_SIZE = 0x100000; // 1 MiB
  
  /** Maximum number of script-checking threads allowed */
  static const int MAX_SCRIPTCHECK_THREADS = 16;
  /** -par default (number of script-checking threads, 0 = auto) */
  static const int DEFAULT_SCRIPTCHECK_THREADS = 0;
  /**
   * Number of blocks that can be requested at any given time from a single peer.
   */
  static const int MAX_BLOCKS_IN_TRANSIT_PER_PEER = 16;
  /**
   * Timeout in seconds during which a peer must stall block download progress
   * before being disconnected.
   */
  static const unsigned int BLOCK_STALLING_TIMEOUT = 2;
  /**
   * Number of headers sent in one getheaders result. We rely on the assumption
   * that if a peer sends less than this number, we reached its tip. Changing this
   * value is a protocol upgrade.
   */
  static const unsigned int MAX_HEADERS_RESULTS = 2000;
  /**
   * Maximum depth of blocks we're willing to serve as compact blocks to peers
   * when requested. For older blocks, a regular BLOCK response will be sent.
   */
  static const int MAX_CMPCTBLOCK_DEPTH = 5;
  /**
   * Maximum depth of blocks we're willing to respond to GETBLOCKTXN requests for.
   */
  static const int MAX_BLOCKTXN_DEPTH = 10;
  /**
   * Size of the "block download window": how far ahead of our current height do
   * we fetch ? Larger windows tolerate larger download speed differences between
   * peer, but increase the potential degree of disordering of blocks on disk
   * (which make reindexing and in the future perhaps pruning harder). We'll
   * probably want to make this a per-peer adaptive value at some point.
   */
  static const unsigned int BLOCK_DOWNLOAD_WINDOW = 1024;
  /** Time to wait (in seconds) between writing blocks/block index to disk. */
  static const unsigned int DATABASE_WRITE_INTERVAL = 60 * 60;
  /** Time to wait (in seconds) between flushing chainstate to disk. */
  static const unsigned int DATABASE_FLUSH_INTERVAL = 24 * 60 * 60;
  /** Maximum length of reject messages. */
  static const unsigned int MAX_REJECT_MESSAGE_LENGTH = 111;
  /** Average delay between local address broadcasts in seconds. */
  static const unsigned int AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL = 24 * 60 * 60;
  /** Average delay between peer address broadcasts in seconds. */
  static const unsigned int AVG_ADDRESS_BROADCAST_INTERVAL = 30;
  /**
   * Average delay between trickled inventory transmissions in seconds.
   * Blocks and whitelisted receivers bypass this, outbound peers get half this
   * delay.
   */
  static const unsigned int INVENTORY_BROADCAST_INTERVAL = 5;
  /**
   * Maximum number of inventory items to send per transmission.
   * Limits the impact of low-fee transaction floods.
   */
  static const unsigned int INVENTORY_BROADCAST_MAX_PER_MB =
      7 * INVENTORY_BROADCAST_INTERVAL;
  /** Average delay between feefilter broadcasts in seconds. */
  static const unsigned int AVG_FEEFILTER_BROADCAST_INTERVAL = 10 * 60;
  /** Maximum feefilter broadcast delay after significant change. */
  static const unsigned int MAX_FEEFILTER_CHANGE_DELAY = 5 * 60;
  /** Block download timeout base, expressed in millionths of the block interval
   * (i.e. 10 min) */
  static const int64_t BLOCK_DOWNLOAD_TIMEOUT_BASE = 1000000;
  /**
   * Additional block download timeout per parallel downloading peer (i.e. 5 min)
   */
  static const int64_t BLOCK_DOWNLOAD_TIMEOUT_PER_PEER = 500000;
  
  static const unsigned int DEFAULT_LIMITFREERELAY = 0;
  static const bool DEFAULT_RELAYPRIORITY = true;
  static const int64_t DEFAULT_MAX_TIP_AGE = 24 * 60 * 60;
  /**
   * Maximum age of our tip in seconds for us to be considered current for fee
   * estimation.
   */
  static const int64_t MAX_FEE_ESTIMATION_TIP_AGE = 3 * 60 * 60;
  
  /** Default for -permitbaremultisig */
  static const bool DEFAULT_PERMIT_BAREMULTISIG = true;
  static const bool DEFAULT_CHECKPOINTS_ENABLED = true;
  static const bool DEFAULT_TXINDEX = true;
  static const unsigned int DEFAULT_BANSCORE_THRESHOLD = 100;
  
  /** Default for -persistmempool */
  static const bool DEFAULT_PERSIST_MEMPOOL = true;
  /** Default for using fee filter */
  static const bool DEFAULT_FEEFILTER = true;
  
  /**
   * Maximum number of headers to announce when relaying blocks with headers
   * message.
   */
  static const unsigned int MAX_BLOCKS_TO_ANNOUNCE = 8;
  
  /** Maximum number of unconnecting headers announcements before DoS score */
  static const int MAX_UNCONNECTING_HEADERS = 10;
  
  static const bool DEFAULT_PEERBLOOMFILTERS = true;
  
  /** Default for -stopatheight */
  static const int DEFAULT_STOPATHEIGHT = 0;
  /** Default for -maxreorgdepth */
  static const int DEFAULT_MAX_REORG_DEPTH = 10;
  /**
   * Default for -finalizationdelay
   * This is the minimum time between a block header reception and the block
   * finalization.
   * This value should be >> block propagation and validation time
   */
  static const int64_t DEFAULT_MIN_FINALIZATION_DELAY = 2 * 60 * 60;
  
  extern CScript COINBASE_FLAGS;
  extern CCriticalSection cs_main;
  extern CTxMemPool g_mempool;
  extern uint64_t nLastBlockTx;
  extern uint64_t nLastBlockSize;
  extern const std::string strMessageMagic;
  extern Mutex g_best_block_mutex;
  extern std::condition_variable g_best_block_cv;
  extern uint256 g_best_block;
  extern std::atomic_bool fImporting;
  extern std::atomic_bool fReindex;
  extern int nScriptCheckThreads;
  extern bool fIsBareMultisigStd;
  extern bool fRequireStandard;
  extern bool fCheckBlockIndex;
  extern bool fCheckpointsEnabled;
  extern size_t nCoinCacheUsage;
  
  /**
   * A fee rate smaller than this is considered zero fee (for relaying, mining and
   * transaction creation)
   */
  extern CFeeRate minRelayTxFee;
  /**
   * Absolute maximum transaction fee (in satoshis) used by wallet and mempool
   * (rejects high fee in sendrawtransaction)
   */
  extern Amount maxTxFee;
  /**
   * If the tip is older than this (in seconds), the node is considered to be in
   * initial block download.
   */
  extern int64_t nMaxTipAge;
  
  /**
   * Block hash whose ancestors we will assume to have valid scripts without
   * checking them.
   */
  extern uint256 hashAssumeValid;
  
  /**
   * Minimum work we will assume exists on some valid chain.
   */
  extern arith_uint256 nMinimumChainWork;
  
  /** Minimum disk space required - used in CheckDiskSpace() */
  static const uint64_t nMinDiskSpace = 52428800;
  
  /**
   * Best header we've seen so far (used for getheaders queries' starting points).
   */
  extern CBlockIndex *pindexBestHeader;
  
  /** Pruning-related variables and constants */
  /** True if any block files have ever been pruned. */
  extern bool fHavePruned;
  /** True if we're running in -prune mode. */
  extern bool fPruneMode;
  /** Number of MiB of block files that we're trying to stay below. */
  extern uint64_t nPruneTarget;
  /** Block files containing a block-height within MIN_BLOCKS_TO_KEEP of
   * chainActive.Tip() will not be pruned. */
  static const unsigned int MIN_BLOCKS_TO_KEEP = 288;
  /** Minimum blocks required to signal NODE_NETWORK_LIMITED */
  static const unsigned int NODE_NETWORK_LIMITED_MIN_BLOCKS = 288;
  
  static const signed int DEFAULT_CHECKBLOCKS = 6;
  static const unsigned int DEFAULT_CHECKLEVEL = 3;
  
  /**
   * Require that user allocate at least 550MB for block & undo files (blk???.dat
   * and rev???.dat)
   * At 1MB per block, 288 blocks = 288MB.
   * Add 15% for Undo data = 331MB
   * Add 20% for Orphan block rate = 397MB
   * We want the low water mark after pruning to be at least 397 MB and since we
   * prune in full block file chunks, we need the high water mark which triggers
   * the prune to be one 128MB block file + added 15% undo data = 147MB greater
   * for a total of 545MB. Setting the target to > than 550MB will make it likely
   * we can respect the target.
   */
  static const uint64_t MIN_DISK_SPACE_FOR_BLOCK_FILES = 550 * 1024 * 1024;
  
  class BlockValidationOptions {
  private:
      uint64_t excessiveBlockSize;
      bool checkPoW : 1;
      bool checkMerkleRoot : 1;
  
  public:
      // Do full validation by default
      BlockValidationOptions(const Config &config);
      BlockValidationOptions(uint64_t _excessiveBlockSize, bool _checkPow = true,
                             bool _checkMerkleRoot = true)
          : excessiveBlockSize(_excessiveBlockSize), checkPoW(_checkPow),
            checkMerkleRoot(_checkMerkleRoot) {}
  
      BlockValidationOptions withCheckPoW(bool _checkPoW = true) const {
          BlockValidationOptions ret = *this;
          ret.checkPoW = _checkPoW;
          return ret;
      }
  
      BlockValidationOptions
      withCheckMerkleRoot(bool _checkMerkleRoot = true) const {
          BlockValidationOptions ret = *this;
          ret.checkMerkleRoot = _checkMerkleRoot;
          return ret;
      }
  
      bool shouldValidatePoW() const { return checkPoW; }
      bool shouldValidateMerkleRoot() const { return checkMerkleRoot; }
      uint64_t getExcessiveBlockSize() const { return excessiveBlockSize; }
  };
  
  /**
   * Process an incoming block. This only returns after the best known valid
   * block is made active. Note that it does not, however, guarantee that the
   * specific block passed to it has been checked for validity!
   *
   * If you want to *possibly* get feedback on whether pblock is valid, you must
   * install a CValidationInterface (see validationinterface.h) - this will have
   * its BlockChecked method called whenever *any* block completes validation.
   *
   * Note that we guarantee that either the proof-of-work is valid on pblock, or
   * (and possibly also) BlockChecked will have been called.
   *
   * May not be called in a validationinterface callback.
   *
   * @param[in]   config  The global config.
   * @param[in]   pblock  The block we want to process.
   * @param[in]   fForceProcessing Process this block even if unrequested; used
   * for non-network block sources and whitelisted peers.
   * @param[out]  fNewBlock A boolean which is set to indicate if the block was
   *                        first received via this call.
   * @return True if the block is accepted as a valid block.
   */
  bool ProcessNewBlock(const Config &config,
                       const std::shared_ptr<const CBlock> pblock,
                       bool fForceProcessing, bool *fNewBlock)
      LOCKS_EXCLUDED(cs_main);
  
  /**
   * Process incoming block headers.
   *
   * May not be called in a validationinterface callback.
   *
   * @param[in]  config        The config.
   * @param[in]  block         The block headers themselves.
   * @param[out] state         This may be set to an Error state if any error
   *                           occurred processing them.
   * @param[out] ppindex       If set, the pointer will be set to point to the
   *                           last new block index object for the given headers.
   * @param[out] first_invalid First header that fails validation, if one exists.
   * @return True if block headers were accepted as valid.
   */
  bool ProcessNewBlockHeaders(const Config &config,
                              const std::vector<CBlockHeader> &block,
                              CValidationState &state,
                              const CBlockIndex **ppindex = nullptr,
                              CBlockHeader *first_invalid = nullptr)
      LOCKS_EXCLUDED(cs_main);
  
  /**
   * Open a block file (blk?????.dat).
   */
  FILE *OpenBlockFile(const FlatFilePos &pos, bool fReadOnly = false);
  
  /**
   * Translation to a filesystem path.
   */
  fs::path GetBlockPosFilename(const FlatFilePos &pos);
  
  /**
   * Import blocks from an external file.
   */
  bool LoadExternalBlockFile(const Config &config, FILE *fileIn,
                             FlatFilePos *dbp = nullptr);
  
  /**
   * Ensures we have a genesis block in the block tree, possibly writing one to
   * disk.
   */
  bool LoadGenesisBlock(const CChainParams &chainparams);
  
  /**
   * Load the block tree and coins database from disk, initializing state if we're
   * running with -reindex.
   */
  bool LoadBlockIndex(const Config &config) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /**
   * Update the chain tip based on database information.
   */
  bool LoadChainTip(const Config &config) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /**
   * Unload database information.
   */
  void UnloadBlockIndex();
  
  /**
   * Run an instance of the script checking thread.
   */
  void ThreadScriptCheck();
  
  /**
   * Check whether we are doing an initial block download (synchronizing from disk
   * or network)
   */
  bool IsInitialBlockDownload();
  
  /**
   * Retrieve a transaction (from memory pool, or from disk, if possible).
   */
  bool GetTransaction(const Consensus::Params &params, const TxId &txid,
                      CTransactionRef &tx, uint256 &hashBlock,
                      bool fAllowSlow = false, CBlockIndex *blockIndex = nullptr);
  
  bool GetTransaction(const Config &config, const TxId &txid, CTransactionRef &tx,
                      uint256 &hashBlock, bool fAllowSlow = false,
                      CBlockIndex *blockIndex = nullptr);
  
  /**
   * Find the best known block, and make it the tip of the block chain
   *
   * May not be called with cs_main held. May not be called in a
   * validationinterface callback.
   */
  bool ActivateBestChain(
      const Config &config, CValidationState &state,
      std::shared_ptr<const CBlock> pblock = std::shared_ptr<const CBlock>());
  Amount GetBlockSubsidy(int nHeight, const Consensus::Params &consensusParams);
  
  /**
   * Guess verification progress (as a fraction between 0.0=genesis and
   * 1.0=current tip).
   */
  double GuessVerificationProgress(const ChainTxData &data,
                                   const CBlockIndex *pindex);
  
  /**
   * Calculate the amount of disk space the block & undo files currently use.
   */
  uint64_t CalculateCurrentUsage();
  
  /**
   * Mark one block file as pruned.
   */
  void PruneOneBlockFile(const int fileNumber);
  
  /**
   * Actually unlink the specified files
   */
  void UnlinkPrunedFiles(const std::set<int> &setFilesToPrune);
  
  /** Flush all state, indexes and buffers to disk. */
  void FlushStateToDisk();
  /** Prune block files and flush state to disk. */
  void PruneAndFlush();
  /** Prune block files up to a given height */
  void PruneBlockFilesManual(int nManualPruneHeight);
  
  /**
   * (try to) add transaction to memory pool
   */
  bool AcceptToMemoryPool(const Config &config, CTxMemPool &pool,
                          CValidationState &state, const CTransactionRef &tx,
                          bool fLimitFree, bool *pfMissingInputs,
                          bool fOverrideMempoolLimit = false,
                          const Amount nAbsurdFee = Amount::zero(),
                          bool test_accept = false)
      EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /** Convert CValidationState to a human-readable message for logging */
  std::string FormatStateMessage(const CValidationState &state);
  
  /**
   * 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 sigCacheStore/scriptCacheStore 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.
   */
  bool CheckInputs(const CTransaction &tx, CValidationState &state,
                   const CCoinsViewCache &view, bool fScriptChecks,
                   const uint32_t flags, bool sigCacheStore,
                   bool scriptCacheStore,
                   const PrecomputedTransactionData &txdata,
                   std::vector<CScriptCheck> *pvChecks = nullptr);
  
  /**
   * Mark all the coins corresponding to a given transaction inputs as spent.
   */
  void SpendCoins(CCoinsViewCache &view, const CTransaction &tx, CTxUndo &txundo,
                  int nHeight);
  
  /**
   * Apply the effects of this transaction on the UTXO set represented by view.
   */
  void UpdateCoins(CCoinsViewCache &view, const CTransaction &tx, int nHeight);
  void UpdateCoins(CCoinsViewCache &view, const CTransaction &tx, CTxUndo &txundo,
                   int nHeight);
  
  /**
   * Test whether the LockPoints height and time are still valid on the current
   * chain.
   */
  bool TestLockPointValidity(const LockPoints *lp)
      EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /**
   * Check if transaction will be BIP 68 final in the next block to be created.
   *
   * Simulates calling SequenceLocks() with data from the tip of the current
   * active chain. Optionally stores in LockPoints the resulting height and time
   * calculated and the hash of the block needed for calculation or skips the
   * calculation and uses the LockPoints passed in for evaluation. The LockPoints
   * should not be considered valid if CheckSequenceLocks returns false.
   *
   * See consensus/consensus.h for flag definitions.
   */
  bool CheckSequenceLocks(const CTxMemPool &pool, const CTransaction &tx,
                          int flags, LockPoints *lp = nullptr,
                          bool useExistingLockPoints = false)
      EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /**
   * Closure representing one script verification.
   * Note that this stores references to the spending transaction.
   */
  class CScriptCheck {
  private:
      CScript scriptPubKey;
      Amount amount;
      const CTransaction *ptxTo;
      unsigned int nIn;
      uint32_t nFlags;
      bool cacheStore;
      ScriptError error;
      PrecomputedTransactionData txdata;
  
  public:
      CScriptCheck()
          : amount(), ptxTo(nullptr), nIn(0), nFlags(0), cacheStore(false),
            error(ScriptError::UNKNOWN), txdata() {}
  
      CScriptCheck(const CScript &scriptPubKeyIn, const Amount amountIn,
                   const CTransaction &txToIn, unsigned int nInIn,
                   uint32_t nFlagsIn, bool cacheIn,
                   const PrecomputedTransactionData &txdataIn)
          : scriptPubKey(scriptPubKeyIn), amount(amountIn), ptxTo(&txToIn),
            nIn(nInIn), nFlags(nFlagsIn), cacheStore(cacheIn),
            error(ScriptError::UNKNOWN), txdata(txdataIn) {}
  
      bool operator()();
  
      void swap(CScriptCheck &check) {
          scriptPubKey.swap(check.scriptPubKey);
          std::swap(ptxTo, check.ptxTo);
          std::swap(amount, check.amount);
          std::swap(nIn, check.nIn);
          std::swap(nFlags, check.nFlags);
          std::swap(cacheStore, check.cacheStore);
          std::swap(error, check.error);
          std::swap(txdata, check.txdata);
      }
  
      ScriptError GetScriptError() const { return error; }
  };
  
  /** Functions for disk access for blocks */
  bool ReadBlockFromDisk(CBlock &block, const FlatFilePos &pos,
                         const Consensus::Params &params);
  bool ReadBlockFromDisk(CBlock &block, const CBlockIndex *pindex,
                         const Consensus::Params &params);
  
  /** Functions for validating blocks and updating the block tree */
  
  /**
   * Context-independent validity checks.
   *
   * Returns true if the provided block is valid (has valid header,
   * transactions are valid, block is a valid size, etc.)
   */
  bool CheckBlock(const CBlock &block, CValidationState &state,
                  const Consensus::Params &params,
                  BlockValidationOptions validationOptions);
  
  /**
   * This is a variant of ContextualCheckTransaction which computes the contextual
   * check for a transaction based on the chain tip.
   *
   * See consensus/consensus.h for flag definitions.
   */
  bool ContextualCheckTransactionForCurrentBlock(const Consensus::Params &params,
                                                 const CTransaction &tx,
                                                 CValidationState &state,
                                                 int flags = -1);
  
  /**
   * Check a block is completely valid from start to finish (only works on top of
   * our current best block)
   */
  bool TestBlockValidity(CValidationState &state, const CChainParams &params,
                         const CBlock &block, CBlockIndex *pindexPrev,
                         BlockValidationOptions validationOptions)
      EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /**
   * When there are blocks in the active chain with missing data, rewind the
   * chainstate and remove them from the block index.
   */
  bool RewindBlockIndex(const Config &config);
  
  /**
   * RAII wrapper for VerifyDB: Verify consistency of the block and coin
   * databases.
   */
  class CVerifyDB {
  public:
      CVerifyDB();
      ~CVerifyDB();
      bool VerifyDB(const Config &config, CCoinsView *coinsview, int nCheckLevel,
                    int nCheckDepth);
  };
  
  /** Replay blocks that aren't fully applied to the database. */
  bool ReplayBlocks(const Consensus::Params &params, CCoinsView *view);
  
  /** Find the last common block between the parameter chain and a locator. */
  CBlockIndex *FindForkInGlobalIndex(const CChain &chain,
                                     const CBlockLocator &locator)
      EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /**
   * Mark a block as precious and reorganize.
   *
   * May not be called in a validationinterface callback.
   */
  bool PreciousBlock(const Config &config, CValidationState &state,
                     CBlockIndex *pindex) LOCKS_EXCLUDED(cs_main);
  
  /**
   * Mark a block as finalized.
   * A finalized block can not be reorged in any way.
   */
  bool FinalizeBlockAndInvalidate(const Config &config, CValidationState &state,
                                  CBlockIndex *pindex);
  
  /** Mark a block as invalid. */
  bool InvalidateBlock(const Config &config, CValidationState &state,
                       CBlockIndex *pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /** Park a block. */
  bool ParkBlock(const Config &config, CValidationState &state,
                 CBlockIndex *pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /** Remove invalidity status from a block and its descendants. */
  void ResetBlockFailureFlags(CBlockIndex *pindex)
      EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /** Remove parked status from a block and its descendants. */
  void UnparkBlockAndChildren(CBlockIndex *pindex)
      EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /** Remove parked status from a block. */
  void UnparkBlock(CBlockIndex *pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /**
   * Retrieve the topmost finalized block.
   */
  const CBlockIndex *GetFinalizedBlock() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /**
   * Checks if a block is finalized.
   */
  bool IsBlockFinalized(const CBlockIndex *pindex)
      EXCLUSIVE_LOCKS_REQUIRED(cs_main);
  
  /** The currently-connected chain of blocks (protected by cs_main). */
  extern CChain &chainActive;
  
  /**
   * Global variable that points to the coins database (protected by cs_main)
   */
  extern std::unique_ptr<CCoinsViewDB> pcoinsdbview;
  
  /**
   * Global variable that points to the active CCoinsView (protected by cs_main)
   */
  extern std::unique_ptr<CCoinsViewCache> pcoinsTip;
  
  /**
   * Global variable that points to the active block tree (protected by cs_main)
   */
  extern std::unique_ptr<CBlockTreeDB> pblocktree;
  
  /**
   * Return the spend height, which is one more than the inputs.GetBestBlock().
   * While checking, GetBestBlock() refers to the parent block. (protected by
   * cs_main)
   * This is also true for mempool checks.
   */
  int GetSpendHeight(const CCoinsViewCache &inputs);
  
  /**
   * Determine what nVersion a new block should use.
   */
  int32_t ComputeBlockVersion(const CBlockIndex *pindexPrev,
                              const Consensus::Params &params);
  
  /**
   * Reject codes greater or equal to this can be returned by AcceptToMemPool or
   * AcceptBlock for blocks/transactions, to signal internal conditions. They
   * cannot and should not be sent over the P2P network.
   */
  static const unsigned int REJECT_INTERNAL = 0x100;
  /** Too high fee. Can not be triggered by P2P transactions */
  static const unsigned int REJECT_HIGHFEE = 0x100;
  /** Block conflicts with a transaction already known */
  static const unsigned int REJECT_AGAINST_FINALIZED = 0x103;
  
  /** Get block file info entry for one block file */
  CBlockFileInfo *GetBlockFileInfo(size_t n);
  
  /** Dump the mempool to disk. */
  bool DumpMempool(const CTxMemPool &pool);
  
  /** Load the mempool from disk. */
  bool LoadMempool(const Config &config, CTxMemPool &pool);
  
  bool AbortNode(const std::string &strMessage, const std::string &userMessage = "");
  
  void AlertNotify(const std::string &strMessage);
  #endif // BITCOIN_VALIDATION_H
  