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#       1                 :            : // Copyright (c) 2016-2019 The Bitcoin Core developers
#       2                 :            : // Distributed under the MIT software license, see the accompanying
#       3                 :            : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
#       4                 :            : 
#       5                 :            : #ifndef BITCOIN_VERSIONBITS_H
#       6                 :            : #define BITCOIN_VERSIONBITS_H
#       7                 :            : 
#       8                 :            : #include <chain.h>
#       9                 :            : #include <map>
#      10                 :            : 
#      11                 :            : /** What block version to use for new blocks (pre versionbits) */
#      12                 :            : static const int32_t VERSIONBITS_LAST_OLD_BLOCK_VERSION = 4;
#      13                 :            : /** What bits to set in version for versionbits blocks */
#      14                 :            : static const int32_t VERSIONBITS_TOP_BITS = 0x20000000UL;
#      15                 :            : /** What bitmask determines whether versionbits is in use */
#      16                 :            : static const int32_t VERSIONBITS_TOP_MASK = 0xE0000000UL;
#      17                 :            : /** Total bits available for versionbits */
#      18                 :            : static const int32_t VERSIONBITS_NUM_BITS = 29;
#      19                 :            : 
#      20                 :            : /** BIP 9 defines a finite-state-machine to deploy a softfork in multiple stages.
#      21                 :            :  *  State transitions happen during retarget period if conditions are met
#      22                 :            :  *  In case of reorg, transitions can go backward. Without transition, state is
#      23                 :            :  *  inherited between periods. All blocks of a period share the same state.
#      24                 :            :  */
#      25                 :            : enum class ThresholdState {
#      26                 :            :     DEFINED,   // First state that each softfork starts out as. The genesis block is by definition in this state for each deployment.
#      27                 :            :     STARTED,   // For blocks past the starttime.
#      28                 :            :     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.
#      29                 :            :     ACTIVE,    // For all blocks after the LOCKED_IN retarget period (final state)
#      30                 :            :     FAILED,    // For all blocks once the first retarget period after the timeout time is hit, if LOCKED_IN wasn't already reached (final state)
#      31                 :            : };
#      32                 :            : 
#      33                 :            : // A map that gives the state for blocks whose height is a multiple of Period().
#      34                 :            : // The map is indexed by the block's parent, however, so all keys in the map
#      35                 :            : // will either be nullptr or a block with (height + 1) % Period() == 0.
#      36                 :            : typedef std::map<const CBlockIndex*, ThresholdState> ThresholdConditionCache;
#      37                 :            : 
#      38                 :            : /** Display status of an in-progress BIP9 softfork */
#      39                 :            : struct BIP9Stats {
#      40                 :            :     /** Length of blocks of the BIP9 signalling period */
#      41                 :            :     int period;
#      42                 :            :     /** Number of blocks with the version bit set required to activate the softfork */
#      43                 :            :     int threshold;
#      44                 :            :     /** Number of blocks elapsed since the beginning of the current period */
#      45                 :            :     int elapsed;
#      46                 :            :     /** Number of blocks with the version bit set since the beginning of the current period */
#      47                 :            :     int count;
#      48                 :            :     /** False if there are not enough blocks left in this period to pass activation threshold */
#      49                 :            :     bool possible;
#      50                 :            : };
#      51                 :            : 
#      52                 :            : /**
#      53                 :            :  * Abstract class that implements BIP9-style threshold logic, and caches results.
#      54                 :            :  */
#      55                 :            : class AbstractThresholdConditionChecker {
#      56                 :            : protected:
#      57                 :            :     virtual bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const =0;
#      58                 :            :     virtual int64_t BeginTime(const Consensus::Params& params) const =0;
#      59                 :            :     virtual int64_t EndTime(const Consensus::Params& params) const =0;
#      60                 :    1969131 :     virtual int MinActivationHeight(const Consensus::Params& params) const { return 0; }
#      61                 :            :     virtual int Period(const Consensus::Params& params) const =0;
#      62                 :            :     virtual int Threshold(const Consensus::Params& params) const =0;
#      63                 :            : 
#      64                 :            : public:
#      65                 :            :     /** Returns the numerical statistics of an in-progress BIP9 softfork in the current period */
#      66                 :            :     BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex, const Consensus::Params& params) const;
#      67                 :            :     /** Returns the state for pindex A based on parent pindexPrev B. Applies any state transition if conditions are present.
#      68                 :            :      *  Caches state from first block of period. */
#      69                 :            :     ThresholdState GetStateFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const;
#      70                 :            :     /** 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 */
#      71                 :            :     int GetStateSinceHeightFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const;
#      72                 :            : };
#      73                 :            : 
#      74                 :            : /** BIP 9 allows multiple softforks to be deployed in parallel. We cache per-period state for every one of them
#      75                 :            :  *  keyed by the bit position used to signal support. */
#      76                 :            : struct VersionBitsCache
#      77                 :            : {
#      78                 :            :     ThresholdConditionCache caches[Consensus::MAX_VERSION_BITS_DEPLOYMENTS];
#      79                 :            : 
#      80                 :            :     void Clear();
#      81                 :            : };
#      82                 :            : 
#      83                 :            : /** Get the BIP9 state for a given deployment at the current tip. */
#      84                 :            : ThresholdState VersionBitsState(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos, VersionBitsCache& cache);
#      85                 :            : /** Get the numerical statistics for the BIP9 state for a given deployment at the current tip. */
#      86                 :            : BIP9Stats VersionBitsStatistics(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos);
#      87                 :            : /** Get the block height at which the BIP9 deployment switched into the state for the block building on the current tip. */
#      88                 :            : int VersionBitsStateSinceHeight(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos, VersionBitsCache& cache);
#      89                 :            : uint32_t VersionBitsMask(const Consensus::Params& params, Consensus::DeploymentPos pos);
#      90                 :            : 
#      91                 :            : #endif // BITCOIN_VERSIONBITS_H