You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
108 lines
3.8 KiB
108 lines
3.8 KiB
// Copyright (c) 2009-2010 Satoshi Nakamoto
|
|
// Copyright (c) 2009-2018 The Bitcoin Core developers
|
|
// Distributed under the MIT software license, see the accompanying
|
|
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
|
|
|
|
#include <pow.h>
|
|
|
|
#include <arith_uint256.h>
|
|
#include <chain.h>
|
|
#include <primitives/block.h>
|
|
#include <uint256.h>
|
|
|
|
unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader *pblock, const Consensus::Params& params)
|
|
{
|
|
assert(pindexLast != nullptr);
|
|
unsigned int nProofOfWorkLimit = UintToArith256(params.powLimit).GetCompact();
|
|
|
|
// Only change once per difficulty adjustment interval
|
|
if ((pindexLast->nHeight+1) % params.DifficultyAdjustmentInterval() != 0)
|
|
{
|
|
if (params.fPowAllowMinDifficultyBlocks)
|
|
{
|
|
// Special difficulty rule for testnet:
|
|
// If the new block's timestamp is more than 2* 10 minutes
|
|
// then allow mining of a min-difficulty block.
|
|
if (pblock->GetBlockTime() > pindexLast->GetBlockTime() + params.nPowTargetSpacing*2)
|
|
return nProofOfWorkLimit;
|
|
else
|
|
{
|
|
// Return the last non-special-min-difficulty-rules-block
|
|
const CBlockIndex* pindex = pindexLast;
|
|
while (pindex->pprev && pindex->nHeight % params.DifficultyAdjustmentInterval() != 0 && pindex->nBits == nProofOfWorkLimit)
|
|
pindex = pindex->pprev;
|
|
return pindex->nBits;
|
|
}
|
|
}
|
|
return pindexLast->nBits;
|
|
}
|
|
|
|
// Go back by what we want to be 14 days worth of blocks
|
|
// Litecoin: This fixes an issue where a 51% attack can change difficulty at will.
|
|
// Go back the full period unless it's the first retarget after genesis. Code courtesy of Art Forz
|
|
int blockstogoback = params.DifficultyAdjustmentInterval()-1;
|
|
if ((pindexLast->nHeight+1) != params.DifficultyAdjustmentInterval())
|
|
blockstogoback = params.DifficultyAdjustmentInterval();
|
|
|
|
// Go back by what we want to be 14 days worth of blocks
|
|
const CBlockIndex* pindexFirst = pindexLast;
|
|
for (int i = 0; pindexFirst && i < blockstogoback; i++)
|
|
pindexFirst = pindexFirst->pprev;
|
|
|
|
assert(pindexFirst);
|
|
|
|
return CalculateNextWorkRequired(pindexLast, pindexFirst->GetBlockTime(), params);
|
|
}
|
|
|
|
unsigned int CalculateNextWorkRequired(const CBlockIndex* pindexLast, int64_t nFirstBlockTime, const Consensus::Params& params)
|
|
{
|
|
if (params.fPowNoRetargeting)
|
|
return pindexLast->nBits;
|
|
|
|
// Limit adjustment step
|
|
int64_t nActualTimespan = pindexLast->GetBlockTime() - nFirstBlockTime;
|
|
if (nActualTimespan < params.nPowTargetTimespan/4)
|
|
nActualTimespan = params.nPowTargetTimespan/4;
|
|
if (nActualTimespan > params.nPowTargetTimespan*4)
|
|
nActualTimespan = params.nPowTargetTimespan*4;
|
|
|
|
// Retarget
|
|
arith_uint256 bnNew;
|
|
arith_uint256 bnOld;
|
|
bnNew.SetCompact(pindexLast->nBits);
|
|
bnOld = bnNew;
|
|
// Litecoin: intermediate uint256 can overflow by 1 bit
|
|
const arith_uint256 bnPowLimit = UintToArith256(params.powLimit);
|
|
bool fShift = bnNew.bits() > bnPowLimit.bits() - 1;
|
|
if (fShift)
|
|
bnNew >>= 1;
|
|
bnNew *= nActualTimespan;
|
|
bnNew /= params.nPowTargetTimespan;
|
|
if (fShift)
|
|
bnNew <<= 1;
|
|
|
|
if (bnNew > bnPowLimit)
|
|
bnNew = bnPowLimit;
|
|
|
|
return bnNew.GetCompact();
|
|
}
|
|
|
|
bool CheckProofOfWork(uint256 hash, unsigned int nBits, const Consensus::Params& params)
|
|
{
|
|
bool fNegative;
|
|
bool fOverflow;
|
|
arith_uint256 bnTarget;
|
|
|
|
bnTarget.SetCompact(nBits, &fNegative, &fOverflow);
|
|
|
|
// Check range
|
|
if (fNegative || bnTarget == 0 || fOverflow || bnTarget > UintToArith256(params.powLimit))
|
|
return false;
|
|
|
|
// Check proof of work matches claimed amount
|
|
if (UintToArith256(hash) > bnTarget)
|
|
return false;
|
|
|
|
return true;
|
|
}
|