validation.h

// 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 "chain.h"
#include "coins.h"
#include "protocol.h" // For CMessageHeader::MessageStartChars
#include "script/script_error.h"
#include "sync.h"
#include "versionbits.h"

#include <algorithm>
#include <cstdint>
#include <exception>
#include <map>
#include <set>
#include <string>
#include <utility>
#include <vector>

#include <atomic>

#include <boost/filesystem/path.hpp>
#include <unordered_map>

class CBlockIndex;
class CBlockTreeDB;
class CBloomFilter;
class CChainParams;
class CConnman;
class CInv;
class Config;
class CScriptCheck;
class CTxMemPool;
class CTxUndo;
class CValidationInterface;
class CValidationState;
struct ChainTxData;

struct PrecomputedTransactionData;
struct LockPoints;

#define MIN_TRANSACTION_SIZE                                                   \
    (::GetSerializeSize(CTransaction(), SER_NETWORK, PROTOCOL_VERSION))

/** Default for DEFAULT_WHITELISTRELAY. */
static const bool DEFAULT_WHITELISTRELAY = true;
/** Default for DEFAULT_WHITELISTFORCERELAY. */
static const bool DEFAULT_WHITELISTFORCERELAY = true;
/** Default for -minrelaytxfee, minimum relay fee for transactions */
static const Amount DEFAULT_MIN_RELAY_TX_FEE(1000);
//! -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 * 24 * 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 =
    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 = false;
static const unsigned int DEFAULT_BANSCORE_THRESHOLD = 100;

/** 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;

struct BlockHasher {
    size_t operator()(const uint256 &hash) const { return hash.GetCheapHash(); }
};

extern CScript COINBASE_FLAGS;
extern CCriticalSection cs_main;
extern CTxMemPool mempool;
typedef std::unordered_map<uint256, CBlockIndex *, BlockHasher> BlockMap;
extern BlockMap mapBlockIndex;
extern uint64_t nLastBlockTx;
extern uint64_t nLastBlockSize;
extern const std::string strMessageMagic;
extern CWaitableCriticalSection csBestBlock;
extern CConditionVariable cvBlockChange;
extern std::atomic_bool fImporting;
extern bool fReindex;
extern int nScriptCheckThreads;
extern bool fTxIndex;
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 CAmount 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;

/** Best header we've seen so far (used for getheaders queries' starting
 * points). */
extern CBlockIndex *pindexBestHeader;

/** Minimum disk space required - used in CheckDiskSpace() */
static const uint64_t nMinDiskSpace = 52428800;

/** 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;

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;

/**
 * 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.
 *
 * Call without cs_main held.
 *
 * @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 state.IsValid()
 */
bool ProcessNewBlock(const Config &config,
                     const std::shared_ptr<const CBlock> pblock,
                     bool fForceProcessing, bool *fNewBlock);

/**
 * Process incoming block headers.
 *
 * Call without cs_main held.
 *
 * @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[in]  chainparams The params for the chain we want to connect to
 * @param[out] ppindex If set, the pointer will be set to point to the last new
 * block index object for the given headers
 */
bool ProcessNewBlockHeaders(const Config &config,
                            const std::vector<CBlockHeader> &block,
                            CValidationState &state,
                            const CBlockIndex **ppindex = nullptr);

/** Check whether enough disk space is available for an incoming block */
bool CheckDiskSpace(uint64_t nAdditionalBytes = 0);
/** Open a block file (blk?????.dat) */
FILE *OpenBlockFile(const CDiskBlockPos &pos, bool fReadOnly = false);
/** Open an undo file (rev?????.dat) */
FILE *OpenUndoFile(const CDiskBlockPos &pos, bool fReadOnly = false);
/** Translation to a filesystem path */
boost::filesystem::path GetBlockPosFilename(const CDiskBlockPos &pos,
                                            const char *prefix);
/** Import blocks from an external file */
bool LoadExternalBlockFile(const Config &config, FILE *fileIn,
                           CDiskBlockPos *dbp = nullptr);
/** Initialize a new block tree database + block data on disk */
bool InitBlockIndex(const Config &config);
/** Load the block tree and coins database from disk */
bool LoadBlockIndex(const CChainParams &chainparams);
/** 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();
/** Format a string that describes several potential problems detected by the
 * core.
 * strFor can have three values:
 * - "rpc": get critical warnings, which should put the client in safe mode if
 * non-empty
 * - "statusbar": get all warnings
 * - "gui": get all warnings, translated (where possible) for GUI
 * This function only returns the highest priority warning of the set selected
 * by strFor.
 */
std::string GetWarnings(const std::string &strFor);
/** Retrieve a transaction (from memory pool, or from disk, if possible) */
bool GetTransaction(const Config &config, const uint256 &hash,
                    CTransactionRef &tx, uint256 &hashBlock,
                    bool fAllowSlow = false);
/** Find the best known block, and make it the tip of the block chain */
bool ActivateBestChain(
    const Config &config, CValidationState &state,
    std::shared_ptr<const CBlock> pblock = std::shared_ptr<const CBlock>());
CAmount 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, CBlockIndex *pindex);

/**
 * 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
 */
void FindFilesToPrune(std::set<int> &setFilesToPrune,
                      uint64_t nPruneAfterHeight);

/**
 *  Mark one block file as pruned.
 */
void PruneOneBlockFile(const int fileNumber);

/**
 *  Actually unlink the specified files
 */
void UnlinkPrunedFiles(const std::set<int> &setFilesToPrune);

/** Create a new block index entry for a given block hash */
CBlockIndex *InsertBlockIndex(uint256 hash);
/** 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 nPruneUpToHeight);

/** Check is UAHF has activated. */
bool IsUAHFenabled(const Config &config, const CBlockIndex *pindexPrev);

/** Check is Cash HF has activated. */
bool IsCashHFEnabled(const Config &config, const CBlockIndex *pindexPrev);

/** (try to) add transaction to memory pool
 * plTxnReplaced will be appended to with all transactions replaced from mempool
 * **/
bool AcceptToMemoryPool(const Config &config, CTxMemPool &pool,
                        CValidationState &state, const CTransactionRef &tx,
                        bool fLimitFree, bool *pfMissingInputs,
                        std::list<CTransactionRef> *plTxnReplaced = nullptr,
                        bool fOverrideMempoolLimit = false,
                        const CAmount nAbsurdFee = 0);

/** Convert CValidationState to a human-readable message for logging */
std::string FormatStateMessage(const CValidationState &state);

/** Get the BIP9 state for a given deployment at the current tip. */
ThresholdState VersionBitsTipState(const Consensus::Params &params,
                                   Consensus::DeploymentPos pos);

/** Get the block height at which the BIP9 deployment switched into the state
 * for the block building on the current tip. */
int VersionBitsTipStateSinceHeight(const Consensus::Params &params,
                                   Consensus::DeploymentPos pos);

/**
 * Count ECDSA signature operations the old-fashioned (pre-0.6) way
 * @return number of sigops this transaction's outputs will produce when spent
 * @see CTransaction::FetchInputs
 */
uint64_t GetSigOpCountWithoutP2SH(const CTransaction &tx);

/**
 * Count ECDSA signature operations in pay-to-script-hash inputs.
 *
 * @param[in] mapInputs Map of previous transactions that have outputs we're
 * spending
 * @return maximum number of sigops required to validate this transaction's
 * inputs
 * @see CTransaction::FetchInputs
 */
uint64_t GetP2SHSigOpCount(const CTransaction &tx,
                           const CCoinsViewCache &mapInputs);

/**
 * Compute total signature operation of a transaction.
 * @param[in] tx     Transaction for which we are computing the cost
 * @param[in] inputs Map of previous transactions that have outputs we're
 * spending
 * @param[out] flags Script verification flags
 * @return Total signature operation cost of tx
 */
uint64_t GetTransactionSigOpCount(const CTransaction &tx,
                                  const CCoinsViewCache &inputs, int flags);

/**
 * 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,
                 uint32_t flags, bool sigCacheStore, bool scriptCacheStore,
                 const PrecomputedTransactionData &txdata,
                 std::vector<CScriptCheck> *pvChecks = nullptr);

/** Apply the effects of this transaction on the UTXO set represented by view */
void UpdateCoins(const CTransaction &tx, CCoinsViewCache &inputs, int nHeight);
void UpdateCoins(const CTransaction &tx, CCoinsViewCache &inputs,
                 CTxUndo &txundo, int nHeight);

/** Transaction validation functions */

/** Context-independent validity checks for coinbase and non-coinbase
 * transactions */
bool CheckRegularTransaction(const CTransaction &tx, CValidationState &state,
                             bool fCheckDuplicateInputs = true);
bool CheckCoinbase(const CTransaction &tx, CValidationState &state,
                   bool fCheckDuplicateInputs = true);

namespace Consensus {

/**
 * Check whether all inputs of this transaction are valid (no double spends and
 * amounts). This does not modify the UTXO set. This does not check scripts and
 * sigs. Preconditions: tx.IsCoinBase() is false.
 */
bool CheckTxInputs(const CTransaction &tx, CValidationState &state,
                   const CCoinsViewCache &inputs, int nSpendHeight);

} // namespace Consensus

/**
 * Test whether the LockPoints height and time are still valid on the current
 * chain.
 */
bool TestLockPointValidity(const LockPoints *lp);

/**
 * Check if transaction is final per BIP 68 sequence numbers and can be included
 * in a block. Consensus critical. Takes as input a list of heights at which
 * tx's inputs (in order) confirmed.
 */
bool SequenceLocks(const CTransaction &tx, int flags,
                   std::vector<int> *prevHeights, const CBlockIndex &block);

/**
 * 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 CTransaction &tx, int flags,
                        LockPoints *lp = nullptr,
                        bool useExistingLockPoints = false);

/**
 * Closure representing one script verification.
 * Note that this stores references to the spending transaction.
 */
class CScriptCheck {
private:
    CScript scriptPubKey;
    CAmount amount;
    const CTransaction *ptxTo;
    unsigned int nIn;
    uint32_t nFlags;
    bool cacheStore;
    ScriptError error;
    PrecomputedTransactionData txdata;

public:
    CScriptCheck()
        : amount(0), ptxTo(0), nIn(0), nFlags(0), cacheStore(false),
          error(SCRIPT_ERR_UNKNOWN_ERROR), txdata() {}

    CScriptCheck(const CScript &scriptPubKeyIn, const CAmount 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(SCRIPT_ERR_UNKNOWN_ERROR), 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 WriteBlockToDisk(const CBlock &block, CDiskBlockPos &pos,
                      const CMessageHeader::MessageStartChars &messageStart);
bool ReadBlockFromDisk(CBlock &block, const CDiskBlockPos &pos,
                       const Consensus::Params &consensusParams);
bool ReadBlockFromDisk(CBlock &block, const CBlockIndex *pindex,
                       const Consensus::Params &consensusParams);

/** Functions for validating blocks and updating the block tree */

/** Context-independent validity checks */
bool CheckBlockHeader(const CBlockHeader &block, CValidationState &state,
                      const Consensus::Params &consensusParams,
                      bool fCheckPOW = true);
bool CheckBlock(const Config &Config, const CBlock &block,
                CValidationState &state,
                const Consensus::Params &consensusParams, bool fCheckPOW = true,
                bool fCheckMerkleRoot = true);

/**
 * Context dependent validity checks for non coinbase transactions. This
 * doesn't check the validity of the transaction against the UTXO set, but
 * simply characteristic that are suceptible to change over time such as feature
 * activation/deactivation and CLTV.
 */
bool ContextualCheckTransaction(const Config &config, const CTransaction &tx,
                                CValidationState &state,
                                const Consensus::Params &consensusParams,
                                int nHeight, int64_t nLockTimeCutoff);

/**
 * 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 Config &config, const CTransaction &tx, CValidationState &state,
    const Consensus::Params &consensusParams, int flags = -1);

/** 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(). */
bool ContextualCheckBlockHeader(const CBlockHeader &block,
                                CValidationState &state,
                                const Consensus::Params &consensusParams,
                                const CBlockIndex *pindexPrev,
                                int64_t nAdjustedTime);
bool ContextualCheckBlock(const Config &config, const CBlock &block,
                          CValidationState &state,
                          const Consensus::Params &consensusParams,
                          const CBlockIndex *pindexPrev);

/** Check a block is completely valid from start to finish (only works on top of
 * our current best block, with cs_main held) */
bool TestBlockValidity(const Config &config, CValidationState &state,
                       const CChainParams &chainparams, const CBlock &block,
                       CBlockIndex *pindexPrev, bool fCheckPOW = true,
                       bool fCheckMerkleRoot = true);

/** 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, const CChainParams &params);

/** RAII wrapper for VerifyDB: Verify consistency of the block and coin
 * databases */
class CVerifyDB {
public:
    CVerifyDB();
    ~CVerifyDB();
    bool VerifyDB(const Config &config, const CChainParams &chainparams,
                  CCoinsView *coinsview, int nCheckLevel, int nCheckDepth);
};

/** Find the last common block between the parameter chain and a locator. */
CBlockIndex *FindForkInGlobalIndex(const CChain &chain,
                                   const CBlockLocator &locator);

/** Mark a block as precious and reorganize. */
bool PreciousBlock(const Config &config, CValidationState &state,
                   CBlockIndex *pindex);

/** Mark a block as invalid. */
bool InvalidateBlock(const Config &config, CValidationState &state,
                     CBlockIndex *pindex);

/** Remove invalidity status from a block and its descendants. */
bool ResetBlockFailureFlags(CBlockIndex *pindex);

/** The currently-connected chain of blocks (protected by cs_main). */
extern CChain chainActive;

/** Global variable that points to the active CCoinsView (protected by cs_main)
 */
extern CCoinsViewCache *pcoinsTip;

/** Global variable that points to the active block tree (protected by cs_main)
 */
extern 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);

extern VersionBitsCache versionbitscache;

/**
 * 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 for
 * 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;
/** Transaction is already known (either in mempool or blockchain) */
static const unsigned int REJECT_ALREADY_KNOWN = 0x101;
/** Transaction conflicts with a transaction already known */
static const unsigned int REJECT_CONFLICT = 0x102;

/** Get block file info entry for one block file */
CBlockFileInfo *GetBlockFileInfo(size_t n);

/** Dump the mempool to disk. */
void DumpMempool();

/** Load the mempool from disk. */
bool LoadMempool(const Config &config);

#endif // BITCOIN_VALIDATION_H