1 // Copyright (c) 2016-present 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_IMPL_H
6 #define BITCOIN_VERSIONBITS_IMPL_H
7 8 #include <chain.h>
9 #include <sync.h>
10 #include <versionbits.h>
11 12 /** BIP 9 defines a finite-state-machine to deploy a softfork in multiple stages.
13 * State transitions happen during retarget period if conditions are met
14 * In case of reorg, transitions can go backward. Without transition, state is
15 * inherited between periods. All blocks of a period share the same state.
16 */
17 enum class ThresholdState : uint8_t {
18 DEFINED, // First state that each softfork starts out as. The genesis block is by definition in this state for each deployment.
19 STARTED, // For blocks past the starttime.
20 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.
21 ACTIVE, // For all blocks after the LOCKED_IN retarget period (final state)
22 FAILED, // For all blocks once the first retarget period after the timeout time is hit, if LOCKED_IN wasn't already reached (final state)
23 };
24 25 /** Get a string with the state name */
26 std::string StateName(ThresholdState state);
27 28 /**
29 * Abstract class that implements BIP9-style threshold logic, and caches results.
30 */
31 class AbstractThresholdConditionChecker {
32 protected:
33 virtual bool Condition(const CBlockIndex* pindex) const =0;
34 virtual int64_t BeginTime() const =0;
35 virtual int64_t EndTime() const =0;
36 virtual int MinActivationHeight() const { return 0; }
37 virtual int Period() const =0;
38 virtual int Threshold() const =0;
39 40 public:
41 virtual ~AbstractThresholdConditionChecker() = default;
42 43 /** Returns the numerical statistics of an in-progress BIP9 softfork in the period including pindex
44 * If provided, signalling_blocks is set to true/false based on whether each block in the period signalled
45 */
46 BIP9Stats GetStateStatisticsFor(const CBlockIndex* pindex, std::vector<bool>* signalling_blocks = nullptr) const;
47 /** Returns the state for pindex A based on parent pindexPrev B. Applies any state transition if conditions are present.
48 * Caches state from first block of period. */
49 ThresholdState GetStateFor(const CBlockIndex* pindexPrev, ThresholdConditionCache& cache) const;
50 /** 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 */
51 int GetStateSinceHeightFor(const CBlockIndex* pindexPrev, ThresholdConditionCache& cache) const;
52 };
53 54 /**
55 * Class to implement versionbits logic.
56 */
57 class VersionBitsConditionChecker : public AbstractThresholdConditionChecker {
58 private:
59 const Consensus::BIP9Deployment& dep;
60 61 protected:
62 int64_t BeginTime() const override { return dep.nStartTime; }
63 int64_t EndTime() const override { return dep.nTimeout; }
64 int MinActivationHeight() const override { return dep.min_activation_height; }
65 int Period() const override { return dep.period; }
66 int Threshold() const override { return dep.threshold; }
67 68 bool Condition(const CBlockIndex* pindex) const override
69 {
70 return Condition(pindex->nVersion);
71 }
72 73 public:
74 explicit VersionBitsConditionChecker(const Consensus::BIP9Deployment& dep) : dep{dep} {}
75 explicit VersionBitsConditionChecker(const Consensus::Params& params, Consensus::DeploymentPos id) : VersionBitsConditionChecker{params.vDeployments[id]} {}
76 77 uint32_t Mask() const { return (uint32_t{1}) << dep.bit; }
78 79 bool Condition(int32_t nVersion) const
80 {
81 return (((nVersion & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS) && (nVersion & Mask()) != 0);
82 }
83 };
84 85 #endif // BITCOIN_VERSIONBITS_IMPL_H
86