// Copyright (c) 2016-2022 The Bitcoin Core developers // Distributed under the MIT software license, see the accompanying // file COPYING or http://www.opensource.org/licenses/mit-license.php. #ifndef BITCOIN_VERSIONBITS_H #define BITCOIN_VERSIONBITS_H #include <chain.h> #include <sync.h> #include <map> /** What block version to use for new blocks (pre versionbits) */ static const int32_t VERSIONBITS_LAST_OLD_BLOCK_VERSION = 4; /** What bits to set in version for versionbits blocks */ static const int32_t VERSIONBITS_TOP_BITS = 0x20000000UL; /** What bitmask determines whether versionbits is in use */ static const int32_t VERSIONBITS_TOP_MASK = 0xE0000000UL; /** Total bits available for versionbits */ static const int32_t VERSIONBITS_NUM_BITS = 29; /** BIP 9 defines a finite-state-machine to deploy a softfork in multiple stages. * State transitions happen during retarget period if conditions are met * In case of reorg, transitions can go backward. Without transition, state is * inherited between periods. All blocks of a period share the same state. */ enum class ThresholdState { DEFINED, // First state that each softfork starts out as. The genesis block is by definition in this state for each deployment. STARTED, // For blocks past the starttime. LOCKED_IN, // For at least one retarget period after the first retarget period with STARTED blocks of which at least threshold have the associated bit set in nVersion, until min_activation_height is reached. ACTIVE, // For all blocks after the LOCKED_IN retarget period (final state) FAILED, // For all blocks once the first retarget period after the timeout time is hit, if LOCKED_IN wasn't already reached (final state) }; // A map that gives the state for blocks whose height is a multiple of Period(). // The map is indexed by the block's parent, however, so all keys in the map // will either be nullptr or a block with (height + 1) % Period() == 0. typedef std::map<const CBlockIndex*, ThresholdState> ThresholdConditionCache; /** Display status of an in-progress BIP9 softfork */ struct BIP9Stats { /** Length of blocks of the BIP9 signalling period */ int period; /** Number of blocks with the version bit set required to activate the softfork */ int threshold; /** Number of blocks elapsed since the beginning of the current period */ int elapsed; /** Number of blocks with the version bit set since the beginning of the current period */ int count; /** False if there are not enough blocks left in this period to pass activation threshold */ bool possible; }; /** * Abstract class that implements BIP9-style threshold logic, and caches results. */ class AbstractThresholdConditionChecker { protected: virtual bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const =0; virtual int64_t BeginTime(const Consensus::Params& params) const =0; virtual int64_t EndTime(const Consensus::Params& params) const =0; virtual int MinActivationHeight(const Consensus::Params& params) const { return 0; } virtual int Period(const Consensus::Params& params) const =0; virtual int Threshold(const Consensus::Params& params) const =0; public: /** Returns the numerical statistics of an in-progress BIP9 softfork in the period including pindex * If provided, signalling_blocks is set to true/false based on whether each block in the period signalled */ BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex, const Consensus::Params& params, std::vector<bool>* signalling_blocks = nullptr) const; /** Returns the state for pindex A based on parent pindexPrev B. Applies any state transition if conditions are present. * Caches state from first block of period. */ ThresholdState GetStateFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const; /** Returns the height since when the ThresholdState has started for pindex A based on parent pindexPrev B, all blocks of a period share the same */ int GetStateSinceHeightFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const; }; /** BIP 9 allows multiple softforks to be deployed in parallel. We cache * per-period state for every one of them. */ class VersionBitsCache { private: Mutex m_mutex; ThresholdConditionCache m_caches[Consensus::MAX_VERSION_BITS_DEPLOYMENTS] GUARDED_BY(m_mutex); public: /** Get the numerical statistics for a given deployment for the signalling period that includes pindex. * If provided, signalling_blocks is set to true/false based on whether each block in the period signalled */ static BIP9Stats Statistics(const CBlockIndex* pindex, const Consensus::Params& params, Consensus::DeploymentPos pos, std::vector<bool>* signalling_blocks = nullptr); static uint32_t Mask(const Consensus::Params& params, Consensus::DeploymentPos pos); /** Get the BIP9 state for a given deployment for the block after pindexPrev. */ ThresholdState State(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex); /** Get the block height at which the BIP9 deployment switched into the state for the block after pindexPrev. */ int StateSinceHeight(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex); /** Determine what nVersion a new block should use */ int32_t ComputeBlockVersion(const CBlockIndex* pindexPrev, const Consensus::Params& params) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex); void Clear() EXCLUSIVE_LOCKS_REQUIRED(!m_mutex); }; #endif // BITCOIN_VERSIONBITS_H