Line data    Source code

       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 one retarget period after the first retarget period with STARTED blocks of which at least threshold have the associated bit set in nVersion.
      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     6464324 : 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             :     virtual int Period(const Consensus::Params& params) const =0;
      61             :     virtual int Threshold(const Consensus::Params& params) const =0;
      62             : 
      63             : public:
      64             :     /** Returns the numerical statistics of an in-progress BIP9 softfork in the current period */
      65             :     BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex, const Consensus::Params& params) const;
      66             :     /** Returns the state for pindex A based on parent pindexPrev B. Applies any state transition if conditions are present.
      67             :      *  Caches state from first block of period. */
      68             :     ThresholdState GetStateFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const;
      69             :     /** 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 */
      70             :     int GetStateSinceHeightFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const;
      71             : };
      72             : 
      73             : /** BIP 9 allows multiple softforks to be deployed in parallel. We cache per-period state for every one of them
      74             :  *  keyed by the bit position used to signal support. */
      75        2560 : struct VersionBitsCache
      76             : {
      77             :     ThresholdConditionCache caches[Consensus::MAX_VERSION_BITS_DEPLOYMENTS];
      78             : 
      79             :     void Clear();
      80             : };
      81             : 
      82             : ThresholdState VersionBitsState(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos, VersionBitsCache& cache);
      83             : BIP9Stats VersionBitsStatistics(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos);
      84             : int VersionBitsStateSinceHeight(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos, VersionBitsCache& cache);
      85             : uint32_t VersionBitsMask(const Consensus::Params& params, Consensus::DeploymentPos pos);
      86             : 
      87             : #endif // BITCOIN_VERSIONBITS_H