versionbits.h

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// 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>

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 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;

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 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:
    BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex, const Consensus::Params& params, std::vector<bool>* signalling_blocks = nullptr) 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;
};

class VersionBitsCache
{
private:
    Mutex m_mutex;
    ThresholdConditionCache m_caches[Consensus::MAX_VERSION_BITS_DEPLOYMENTS] GUARDED_BY(m_mutex);

public:
    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);

    ThresholdState State(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

    int StateSinceHeight(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);

    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