95 lines
3.2 KiB
C++
95 lines
3.2 KiB
C++
// Copyright (c) 2009-2010 Satoshi Nakamoto
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// Copyright (c) 2009-2016 The Bitcoin Core developers
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// Distributed under the MIT software license, see the accompanying
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// file COPYING or http://www.opensource.org/licenses/mit-license.php.
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#include "pow.h"
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#include "arith_uint256.h"
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#include "chain.h"
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#include "primitives/block.h"
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#include "uint256.h"
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unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader *pblock, const Consensus::Params& params)
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{
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unsigned int nProofOfWorkLimit = UintToArith256(params.powLimit).GetCompact();
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// Genesis block
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if (pindexLast == NULL)
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return nProofOfWorkLimit;
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// Only change once per difficulty adjustment interval
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if ((pindexLast->nHeight+1) % params.DifficultyAdjustmentInterval() != 0)
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{
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if (params.fPowAllowMinDifficultyBlocks)
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{
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// Special difficulty rule for testnet:
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// If the new block's timestamp is more than 2* 10 minutes
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// then allow mining of a min-difficulty block.
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if (pblock->GetBlockTime() > pindexLast->GetBlockTime() + params.nPowTargetSpacing*2)
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return nProofOfWorkLimit;
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else
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{
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// Return the last non-special-min-difficulty-rules-block
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const CBlockIndex* pindex = pindexLast;
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while (pindex->pprev && pindex->nHeight % params.DifficultyAdjustmentInterval() != 0 && pindex->nBits == nProofOfWorkLimit)
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pindex = pindex->pprev;
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return pindex->nBits;
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}
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}
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return pindexLast->nBits;
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}
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// Go back by what we want to be 14 days worth of blocks
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int nHeightFirst = pindexLast->nHeight - (params.DifficultyAdjustmentInterval()-1);
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assert(nHeightFirst >= 0);
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const CBlockIndex* pindexFirst = pindexLast->GetAncestor(nHeightFirst);
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assert(pindexFirst);
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return CalculateNextWorkRequired(pindexLast, pindexFirst->GetBlockTime(), params);
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}
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unsigned int CalculateNextWorkRequired(const CBlockIndex* pindexLast, int64_t nFirstBlockTime, const Consensus::Params& params)
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{
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if (params.fPowNoRetargeting)
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return pindexLast->nBits;
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// Limit adjustment step
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int64_t nActualTimespan = pindexLast->GetBlockTime() - nFirstBlockTime;
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if (nActualTimespan < params.nPowTargetTimespan/4)
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nActualTimespan = params.nPowTargetTimespan/4;
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if (nActualTimespan > params.nPowTargetTimespan*4)
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nActualTimespan = params.nPowTargetTimespan*4;
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// Retarget
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const arith_uint256 bnPowLimit = UintToArith256(params.powLimit);
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arith_uint256 bnNew;
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bnNew.SetCompact(pindexLast->nBits);
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bnNew *= nActualTimespan;
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bnNew /= params.nPowTargetTimespan;
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if (bnNew > bnPowLimit)
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bnNew = bnPowLimit;
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return bnNew.GetCompact();
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}
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bool CheckProofOfWork(uint256 hash, unsigned int nBits, const Consensus::Params& params)
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{
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bool fNegative;
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bool fOverflow;
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arith_uint256 bnTarget;
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bnTarget.SetCompact(nBits, &fNegative, &fOverflow);
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// Check range
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if (fNegative || bnTarget == 0 || fOverflow || bnTarget > UintToArith256(params.powLimit))
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return false;
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// Check proof of work matches claimed amount
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if (UintToArith256(hash) > bnTarget)
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return false;
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return true;
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}
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