1  // Copyright (c) 2009-2010 Satoshi Nakamoto
  2  // Copyright (c) 2009-present The Bitcoin Core developers
  3  // Distributed under the MIT software license, see the accompanying
  4  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  5  
  6  #ifndef BITCOIN_CONSENSUS_PARAMS_H
  7  #define BITCOIN_CONSENSUS_PARAMS_H
  8  
  9  #include <script/verify_flags.h>
 10  #include <uint256.h>
 11  
 12  #include <array>
 13  #include <chrono>
 14  #include <limits>
 15  #include <map>
 16  #include <vector>
 17  
 18  namespace Consensus {
 19  
 20  /**
 21   * A buried deployment is one where the height of the activation has been hardcoded into
 22   * the client implementation long after the consensus change has activated. See BIP 90.
 23   */
 24  enum BuriedDeployment : int16_t {
 25      // buried deployments get negative values to avoid overlap with DeploymentPos
 26      DEPLOYMENT_HEIGHTINCB = std::numeric_limits<int16_t>::min(),
 27      DEPLOYMENT_CLTV,
 28      DEPLOYMENT_DERSIG,
 29      DEPLOYMENT_CSV,
 30      DEPLOYMENT_SEGWIT,
 31  };
 32  constexpr bool ValidDeployment(BuriedDeployment dep) { return dep <= DEPLOYMENT_SEGWIT; }
 33  
 34  enum DeploymentPos : uint16_t {
 35      DEPLOYMENT_TESTDUMMY,
 36      DEPLOYMENT_TAPROOT, // Deployment of Schnorr/Taproot (BIPs 340-342)
 37      // NOTE: Also add new deployments to VersionBitsDeploymentInfo in deploymentinfo.cpp
 38      MAX_VERSION_BITS_DEPLOYMENTS
 39  };
 40  constexpr bool ValidDeployment(DeploymentPos dep) { return dep < MAX_VERSION_BITS_DEPLOYMENTS; }
 41  
 42  /**
 43   * Struct for each individual consensus rule change using BIP9.
 44   */
 45  struct BIP9Deployment {
 46      /** Bit position to select the particular bit in nVersion. */
 47      int bit{28};
 48      /** Start MedianTime for version bits miner confirmation. Can be a date in the past */
 49      int64_t nStartTime{NEVER_ACTIVE};
 50      /** Timeout/expiry MedianTime for the deployment attempt. */
 51      int64_t nTimeout{NEVER_ACTIVE};
 52      /** If lock in occurs, delay activation until at least this block
 53       *  height.  Note that activation will only occur on a retarget
 54       *  boundary.
 55       */
 56      int min_activation_height{0};
 57      /** Period of blocks to check signalling in (usually retarget period, ie params.DifficultyAdjustmentInterval()) */
 58      uint32_t period{2016};
 59      /**
 60       * Minimum blocks including miner confirmation of the total of 2016 blocks in a retargeting period,
 61       * which is also used for BIP9 deployments.
 62       * Examples: 1916 for 95%, 1512 for testchains.
 63       */
 64      uint32_t threshold{1916};
 65  
 66      /** Constant for nTimeout very far in the future. */
 67      static constexpr int64_t NO_TIMEOUT = std::numeric_limits<int64_t>::max();
 68  
 69      /** Special value for nStartTime indicating that the deployment is always active.
 70       *  This is useful for testing, as it means tests don't need to deal with the activation
 71       *  process (which takes at least 3 BIP9 intervals). Only tests that specifically test the
 72       *  behaviour during activation cannot use this. */
 73      static constexpr int64_t ALWAYS_ACTIVE = -1;
 74  
 75      /** Special value for nStartTime indicating that the deployment is never active.
 76       *  This is useful for integrating the code changes for a new feature
 77       *  prior to deploying it on some or all networks. */
 78      static constexpr int64_t NEVER_ACTIVE = -2;
 79  };
 80  
 81  /**
 82   * Parameters that influence chain consensus.
 83   */
 84  struct Params {
 85      uint256 hashGenesisBlock;
 86      int nSubsidyHalvingInterval;
 87      /**
 88       * Hashes of blocks that
 89       * - are known to be consensus valid, and
 90       * - buried in the chain, and
 91       * - fail if the default script verify flags are applied.
 92       */
 93      std::map<uint256, script_verify_flags> script_flag_exceptions;
 94      /** Block height and hash at which BIP34 becomes active */
 95      int BIP34Height;
 96      uint256 BIP34Hash;
 97      /** Block height at which BIP65 becomes active */
 98      int BIP65Height;
 99      /** Block height at which BIP66 becomes active */
100      int BIP66Height;
101      /** Block height at which CSV (BIP68, BIP112 and BIP113) becomes active */
102      int CSVHeight;
103      /** Block height at which Segwit (BIP141, BIP143 and BIP147) becomes active.
104       * Note that segwit v0 script rules are enforced on all blocks except the
105       * BIP 16 exception blocks. */
106      int SegwitHeight;
107      /** Don't warn about unknown BIP 9 activations below this height.
108       * This prevents us from warning about the CSV and segwit activations. */
109      int MinBIP9WarningHeight;
110      std::array<BIP9Deployment,MAX_VERSION_BITS_DEPLOYMENTS> vDeployments;
111      /** Proof of work parameters */
112      uint256 powLimit;
113      bool fPowAllowMinDifficultyBlocks;
114      /**
115        * Enforce BIP94 timewarp attack mitigation. On testnet4 this also enforces
116        * the block storm mitigation.
117        */
118      bool enforce_BIP94;
119      bool fPowNoRetargeting;
120      int64_t nPowTargetSpacing;
121      int64_t nPowTargetTimespan;
122      std::chrono::seconds PowTargetSpacing() const
123      {
124          return std::chrono::seconds{nPowTargetSpacing};
125      }
126      int64_t DifficultyAdjustmentInterval() const { return nPowTargetTimespan / nPowTargetSpacing; }
127      /** The best chain should have at least this much work */
128      uint256 nMinimumChainWork;
129      /** By default assume that the signatures in ancestors of this block are valid */
130      uint256 defaultAssumeValid;
131  
132      /**
133       * If true, witness commitments contain a payload equal to a Bitcoin Script solution
134       * to the signet challenge. See BIP325.
135       */
136      bool signet_blocks{false};
137      std::vector<uint8_t> signet_challenge;
138  
139      int DeploymentHeight(BuriedDeployment dep) const
140      {
141          switch (dep) {
142          case DEPLOYMENT_HEIGHTINCB:
143              return BIP34Height;
144          case DEPLOYMENT_CLTV:
145              return BIP65Height;
146          case DEPLOYMENT_DERSIG:
147              return BIP66Height;
148          case DEPLOYMENT_CSV:
149              return CSVHeight;
150          case DEPLOYMENT_SEGWIT:
151              return SegwitHeight;
152          } // no default case, so the compiler can warn about missing cases
153          return std::numeric_limits<int>::max();
154      }
155  };
156  
157  } // namespace Consensus
158  
159  #endif // BITCOIN_CONSENSUS_PARAMS_H