Cached version-bits state and soft-fork reporting

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_H
6#define BITCOIN_VERSIONBITS_H
7
8#include <chain.h>
9#include <sync.h>
10
11#include <array>
12#include <map>
13#include <optional>
14#include <vector>
15
16class CChainParams;
17
18/** What block version to use for new blocks (pre versionbits) */
19inline constexpr int32_t VERSIONBITS_LAST_OLD_BLOCK_VERSION = 4;
20/** What bits to set in version for versionbits blocks */
21inline constexpr int32_t VERSIONBITS_TOP_BITS = 0x20000000UL;
22/** What bitmask determines whether versionbits is in use */
23inline constexpr int32_t VERSIONBITS_TOP_MASK = 0xE0000000UL;
24/** Total bits available for versionbits (BIP 323) */
25inline constexpr int32_t VERSIONBITS_NUM_BITS = 5;
26
27/** Opaque type for BIP9 state. See versionbits_impl.h for details. */
28enum class ThresholdState : uint8_t;
29
30// A map that gives the state for blocks whose height is a multiple of Period().
31// The map is indexed by the block's parent, however, so all keys in the map
32// will either be nullptr or a block with (height + 1) % Period() == 0.
33typedef std::map<const CBlockIndex*, ThresholdState> ThresholdConditionCache;
34
35/** Display status of an in-progress BIP9 softfork */
36struct BIP9Stats {
37    /** Length of blocks of the BIP9 signalling period */
38    uint32_t period{0};
39    /** Number of blocks with the version bit set required to activate the softfork */
40    uint32_t threshold{0};
41    /** Number of blocks elapsed since the beginning of the current period */
42    uint32_t elapsed{0};
43    /** Number of blocks with the version bit set since the beginning of the current period */
44    uint32_t count{0};
45    /** False if there are not enough blocks left in this period to pass activation threshold */
46    bool possible{false};
47};
48
49/** Detailed status of an enabled BIP9 deployment */
50struct BIP9Info {
51    /** Height at which current_state started */
52    int since{0};
53    /** String representing the current state */
54    std::string current_state{};
55    /** String representing the next block's state */
56    std::string next_state{};
57    /** For states where signalling is applicable, information about the signalling */
58    std::optional<BIP9Stats> stats;
59    /** Which blocks signalled; empty if signalling is not applicable */
60    std::vector<bool> signalling_blocks;
61    /** Height at which the deployment is active, if known. May be in the future. */
62    std::optional<int> active_since;
63};
64
65struct BIP9GBTStatus {
66    struct Info {
67        int bit;
68        uint32_t mask;
69        bool gbt_optional_rule;
70    };
71    std::map<std::string, const Info, std::less<>> signalling, locked_in, active;
72};
73
74/** BIP 9 allows multiple softforks to be deployed in parallel. We cache
75 *  per-period state for every one we implement and warning state for each
76 *  BIP 323 allowed bit. */
77class VersionBitsCache
78{
79private:
80    Mutex m_mutex;
81    std::array<ThresholdConditionCache,VERSIONBITS_NUM_BITS> m_warning_caches GUARDED_BY(m_mutex);
82    std::array<ThresholdConditionCache,Consensus::MAX_VERSION_BITS_DEPLOYMENTS> m_caches GUARDED_BY(m_mutex);
83
84public:
85    BIP9Info Info(const CBlockIndex& block_index, const Consensus::Params& params, Consensus::DeploymentPos id) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
86
87    BIP9GBTStatus GBTStatus(const CBlockIndex& block_index, const Consensus::Params& params) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
88
89    /** Get the BIP9 state for a given deployment for the block after pindexPrev. */
90    bool IsActiveAfter(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
91
92    /** Determine what nVersion a new block should use */
93    int32_t ComputeBlockVersion(const CBlockIndex* pindexPrev, const Consensus::Params& params) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
94
95    /** Check for unknown activations
96     *  Returns a vector containing the bit number used for signalling and a bool
97     *  indicating the deployment is likely to be ACTIVE, rather than merely LOCKED_IN. */
98    std::vector<std::pair<int,bool>> CheckUnknownActivations(const CBlockIndex* pindex, const CChainParams& chainparams) EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
99
100    void Clear() EXCLUSIVE_LOCKS_REQUIRED(!m_mutex);
101};
102
103#endif // BITCOIN_VERSIONBITS_H
104