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90 lines
4.8 KiB
90 lines
4.8 KiB
// Copyright (c) 2016-2019 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#ifndef BITCOIN_VERSIONBITS_H
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#define BITCOIN_VERSIONBITS_H
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#include <chain.h>
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#include <map>
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/** What block version to use for new blocks (pre versionbits) */
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static const int32_t VERSIONBITS_LAST_OLD_BLOCK_VERSION = 4;
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/** What bits to set in version for versionbits blocks */
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static const int32_t VERSIONBITS_TOP_BITS = 0x20000000UL;
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/** What bitmask determines whether versionbits is in use */
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static const int32_t VERSIONBITS_TOP_MASK = 0xE0000000UL;
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/** Total bits available for versionbits */
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static const int32_t VERSIONBITS_NUM_BITS = 29;
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/** BIP 9 defines a finite-state-machine to deploy a softfork in multiple stages.
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* State transitions happen during retarget period if conditions are met
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* In case of reorg, transitions can go backward. Without transition, state is
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* inherited between periods. All blocks of a period share the same state.
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*/
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enum class ThresholdState {
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DEFINED, // First state that each softfork starts out as. The genesis block is by definition in this state for each deployment.
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STARTED, // For blocks past the starttime.
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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.
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ACTIVE, // For all blocks after the LOCKED_IN retarget period (final state)
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FAILED, // For all blocks once the first retarget period after the timeout time is hit, if LOCKED_IN wasn't already reached (final state)
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};
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// A map that gives the state for blocks whose height is a multiple of Period().
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// The map is indexed by the block's parent, however, so all keys in the map
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// will either be nullptr or a block with (height + 1) % Period() == 0.
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typedef std::map<const CBlockIndex*, ThresholdState> ThresholdConditionCache;
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/** Display status of an in-progress BIP9 softfork */
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struct BIP9Stats {
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/** Length of blocks of the BIP9 signalling period */
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int period;
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/** Number of blocks with the version bit set required to activate the softfork */
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int threshold;
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/** Number of blocks elapsed since the beginning of the current period */
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int elapsed;
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/** Number of blocks with the version bit set since the beginning of the current period */
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int count;
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/** False if there are not enough blocks left in this period to pass activation threshold */
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bool possible;
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};
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/**
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* Abstract class that implements BIP9-style threshold logic, and caches results.
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*/
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class AbstractThresholdConditionChecker {
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protected:
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virtual bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const =0;
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virtual int64_t BeginTime(const Consensus::Params& params) const =0;
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virtual int64_t EndTime(const Consensus::Params& params) const = 0;
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virtual int64_t BeginHeight(const Consensus::Params& params) const = 0;
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virtual int64_t EndHeight(const Consensus::Params& params) const = 0;
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virtual int Period(const Consensus::Params& params) const =0;
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virtual int Threshold(const Consensus::Params& params) const =0;
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public:
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/** Returns the numerical statistics of an in-progress BIP9 softfork in the current period */
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BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex, const Consensus::Params& params) const;
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/** Returns the state for pindex A based on parent pindexPrev B. Applies any state transition if conditions are present.
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* Caches state from first block of period. */
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ThresholdState GetStateFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const;
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/** 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 */
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int GetStateSinceHeightFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const;
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};
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/** BIP 9 allows multiple softforks to be deployed in parallel. We cache per-period state for every one of them
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* keyed by the bit position used to signal support. */
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struct VersionBitsCache
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{
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ThresholdConditionCache caches[Consensus::MAX_VERSION_BITS_DEPLOYMENTS];
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void Clear();
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};
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ThresholdState VersionBitsState(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos, VersionBitsCache& cache);
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BIP9Stats VersionBitsStatistics(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos);
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int VersionBitsStateSinceHeight(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos, VersionBitsCache& cache);
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uint32_t VersionBitsMask(const Consensus::Params& params, Consensus::DeploymentPos pos);
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#endif // BITCOIN_VERSIONBITS_H
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