versionbits.h

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// Copyright (c) 2016-2018 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 <map>

static const int32_t VERSIONBITS_LAST_OLD_BLOCK_VERSION = 4;
static const int32_t VERSIONBITS_TOP_BITS = 0x20000000UL;
static const int32_t VERSIONBITS_TOP_MASK = 0xE0000000UL;
static const int32_t VERSIONBITS_NUM_BITS = 29;

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 one retarget period after the first retarget period with
               // STARTED blocks of which at least threshold have the associated
               // bit set in nVersion.
    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;

struct BIP9Stats {
    int period;
    int threshold;
    int elapsed;
    int count;
    bool possible;
};

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 Period(const Consensus::Params &params) const = 0;
    virtual int Threshold(const Consensus::Params &params) const = 0;

public:
    BIP9Stats GetStateStatisticsFor(const CBlockIndex *pindex,
                                    const Consensus::Params &params) const;
    ThresholdState GetStateFor(const CBlockIndex *pindexPrev,
                               const Consensus::Params &params,
                               ThresholdConditionCache &cache) const;
    int GetStateSinceHeightFor(const CBlockIndex *pindexPrev,
                               const Consensus::Params &params,
                               ThresholdConditionCache &cache) const;
};

struct VersionBitsCache {
    ThresholdConditionCache caches[Consensus::MAX_VERSION_BITS_DEPLOYMENTS];

    void Clear();
};

ThresholdState VersionBitsState(const CBlockIndex *pindexPrev,
                                const Consensus::Params &params,
                                Consensus::DeploymentPos pos,
                                VersionBitsCache &cache);
BIP9Stats VersionBitsStatistics(const CBlockIndex *pindexPrev,
                                const Consensus::Params &params,
                                Consensus::DeploymentPos pos);
int VersionBitsStateSinceHeight(const CBlockIndex *pindexPrev,
                                const Consensus::Params &params,
                                Consensus::DeploymentPos pos,
                                VersionBitsCache &cache);
uint32_t VersionBitsMask(const Consensus::Params &params,
                         Consensus::DeploymentPos pos);

#endif // BITCOIN_VERSIONBITS_H