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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 [ # # # # : 0 : 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 : : 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
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