Line data    Source code

       1             : // Copyright (c) 2016-2022 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 <sync.h>
      10             : 
      11             : #include <map>
      12             : 
      13             : /** What block version to use for new blocks (pre versionbits) */
      14             : static const int32_t VERSIONBITS_LAST_OLD_BLOCK_VERSION = 4;
      15             : /** What bits to set in version for versionbits blocks */
      16             : static const int32_t VERSIONBITS_TOP_BITS = 0x20000000UL;
      17             : /** What bitmask determines whether versionbits is in use */
      18             : static const int32_t VERSIONBITS_TOP_MASK = 0xE0000000UL;
      19             : /** Total bits available for versionbits */
      20             : static const int32_t VERSIONBITS_NUM_BITS = 29;
      21             : 
      22             : /** BIP 9 defines a finite-state-machine to deploy a softfork in multiple stages.
      23             :  *  State transitions happen during retarget period if conditions are met
      24             :  *  In case of reorg, transitions can go backward. Without transition, state is
      25             :  *  inherited between periods. All blocks of a period share the same state.
      26             :  */
      27             : enum class ThresholdState {
      28             :     DEFINED,   // First state that each softfork starts out as. The genesis block is by definition in this state for each deployment.
      29             :     STARTED,   // For blocks past the starttime.
      30             :     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.
      31             :     ACTIVE,    // For all blocks after the LOCKED_IN retarget period (final state)
      32             :     FAILED,    // For all blocks once the first retarget period after the timeout time is hit, if LOCKED_IN wasn't already reached (final state)
      33             : };
      34             : 
      35             : // A map that gives the state for blocks whose height is a multiple of Period().
      36             : // The map is indexed by the block's parent, however, so all keys in the map
      37             : // will either be nullptr or a block with (height + 1) % Period() == 0.
      38             : typedef std::map<const CBlockIndex*, ThresholdState> ThresholdConditionCache;
      39             : 
      40             : /** Display status of an in-progress BIP9 softfork */
      41             : struct BIP9Stats {
      42             :     /** Length of blocks of the BIP9 signalling period */
      43             :     int period;
      44             :     /** Number of blocks with the version bit set required to activate the softfork */
      45             :     int threshold;
      46             :     /** Number of blocks elapsed since the beginning of the current period */
      47             :     int elapsed;
      48             :     /** Number of blocks with the version bit set since the beginning of the current period */
      49             :     int count;
      50             :     /** False if there are not enough blocks left in this period to pass activation threshold */
      51             :     bool possible;
      52             : };
      53             : 
      54             : /**
      55             :  * Abstract class that implements BIP9-style threshold logic, and caches results.
      56             :  */
      57             : class AbstractThresholdConditionChecker {
      58             : protected:
      59             :     virtual bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const =0;
      60             :     virtual int64_t BeginTime(const Consensus::Params& params) const =0;
      61             :     virtual int64_t EndTime(const Consensus::Params& params) const =0;
      62           0 :     virtual int MinActivationHeight(const Consensus::Params& params) const { return 0; }
      63             :     virtual int Period(const Consensus::Params& params) const =0;
      64             :     virtual int Threshold(const Consensus::Params& params) const =0;
      65             : 
      66             : public:
      67             :     /** Returns the numerical statistics of an in-progress BIP9 softfork in the period including pindex
      68             :      * If provided, signalling_blocks is set to true/false based on whether each block in the period signalled
      69             :      */
      70             :     BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex, const Consensus::Params& params, std::vector<bool>* signalling_blocks = nullptr) const;
      71             :     /** Returns the state for pindex A based on parent pindexPrev B. Applies any state transition if conditions are present.
      72             :      *  Caches state from first block of period. */
      73             :     ThresholdState GetStateFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const;
      74             :     /** 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 */
      75             :     int GetStateSinceHeightFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const;
      76             : };
      77             : 
      78             : /** BIP 9 allows multiple softforks to be deployed in parallel. We cache
      79             :  *  per-period state for every one of them. */
      80           2 : class VersionBitsCache
      81             : {
      82             : private:
      83             :     Mutex m_mutex;
      84             :     ThresholdConditionCache m_caches[Consensus::MAX_VERSION_BITS_DEPLOYMENTS] GUARDED_BY(m_mutex);
      85             : 
      86             : public:
      87             :     /** Get the numerical statistics for a given deployment for the signalling period that includes pindex.
      88             :      * If provided, signalling_blocks is set to true/false based on whether each block in the period signalled
      89             :      */
      90             :     static BIP9Stats Statistics(const CBlockIndex* pindex, const Consensus::Params& params, Consensus::DeploymentPos pos, std::vector<bool>* signalling_blocks = nullptr);
      91             : 
      92             :     static uint32_t Mask(const Consensus::Params& params, Consensus::DeploymentPos pos);
      93             : 
      94             :     /** Get the BIP9 state for a given deployment for the block after pindexPrev. */
      95             :     ThresholdState State(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
      96             : 
      97             :     /** Get the block height at which the BIP9 deployment switched into the state for the block after pindexPrev. */
      98             :     int StateSinceHeight(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
      99             : 
     100             :     /** Determine what nVersion a new block should use
     101             :      */
     102             :     int32_t ComputeBlockVersion(const CBlockIndex* pindexPrev, const Consensus::Params& params) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
     103             : 
     104             :     void Clear() EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
     105             : };
     106             : 
     107             : #endif // BITCOIN_VERSIONBITS_H