115 lines
4.0 KiB
C++
115 lines
4.0 KiB
C++
// Copyright (c) 2009-2010 Satoshi Nakamoto
|
|
// Copyright (c) 2009-2014 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 "chainparams.h"
|
|
#include "primitives/block.h"
|
|
#include "uint256.h"
|
|
#include "util.h"
|
|
|
|
unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader *pblock)
|
|
{
|
|
unsigned int nProofOfWorkLimit = Params().ProofOfWorkLimit().GetCompact();
|
|
|
|
// Genesis block
|
|
if (pindexLast == NULL)
|
|
return nProofOfWorkLimit;
|
|
|
|
// Only change once per interval
|
|
if ((pindexLast->nHeight+1) % Params().Interval() != 0)
|
|
{
|
|
if (Params().AllowMinDifficultyBlocks())
|
|
{
|
|
// 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().TargetSpacing()*2)
|
|
return nProofOfWorkLimit;
|
|
else
|
|
{
|
|
// Return the last non-special-min-difficulty-rules-block
|
|
const CBlockIndex* pindex = pindexLast;
|
|
while (pindex->pprev && pindex->nHeight % Params().Interval() != 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
|
|
const CBlockIndex* pindexFirst = pindexLast;
|
|
for (int i = 0; pindexFirst && i < Params().Interval()-1; i++)
|
|
pindexFirst = pindexFirst->pprev;
|
|
assert(pindexFirst);
|
|
|
|
// Limit adjustment step
|
|
int64_t nActualTimespan = pindexLast->GetBlockTime() - pindexFirst->GetBlockTime();
|
|
LogPrintf(" nActualTimespan = %d before bounds\n", nActualTimespan);
|
|
if (nActualTimespan < Params().TargetTimespan()/4)
|
|
nActualTimespan = Params().TargetTimespan()/4;
|
|
if (nActualTimespan > Params().TargetTimespan()*4)
|
|
nActualTimespan = Params().TargetTimespan()*4;
|
|
|
|
// Retarget
|
|
arith_uint256 bnNew;
|
|
arith_uint256 bnOld;
|
|
bnNew.SetCompact(pindexLast->nBits);
|
|
bnOld = bnNew;
|
|
bnNew *= nActualTimespan;
|
|
bnNew /= Params().TargetTimespan();
|
|
|
|
if (bnNew > Params().ProofOfWorkLimit())
|
|
bnNew = Params().ProofOfWorkLimit();
|
|
|
|
/// debug print
|
|
LogPrintf("GetNextWorkRequired RETARGET\n");
|
|
LogPrintf("Params().TargetTimespan() = %d nActualTimespan = %d\n", Params().TargetTimespan(), nActualTimespan);
|
|
LogPrintf("Before: %08x %s\n", pindexLast->nBits, bnOld.ToString());
|
|
LogPrintf("After: %08x %s\n", bnNew.GetCompact(), bnNew.ToString());
|
|
|
|
return bnNew.GetCompact();
|
|
}
|
|
|
|
bool CheckProofOfWork(uint256 hash, unsigned int nBits)
|
|
{
|
|
bool fNegative;
|
|
bool fOverflow;
|
|
arith_uint256 bnTarget;
|
|
|
|
if (Params().SkipProofOfWorkCheck())
|
|
return true;
|
|
|
|
bnTarget.SetCompact(nBits, &fNegative, &fOverflow);
|
|
|
|
// Check range
|
|
if (fNegative || bnTarget == 0 || fOverflow || bnTarget > Params().ProofOfWorkLimit())
|
|
return error("CheckProofOfWork() : nBits below minimum work");
|
|
|
|
// Check proof of work matches claimed amount
|
|
if (UintToArith256(hash) > bnTarget)
|
|
return error("CheckProofOfWork() : hash doesn't match nBits");
|
|
|
|
return true;
|
|
}
|
|
|
|
arith_uint256 GetBlockProof(const CBlockIndex& block)
|
|
{
|
|
arith_uint256 bnTarget;
|
|
bool fNegative;
|
|
bool fOverflow;
|
|
bnTarget.SetCompact(block.nBits, &fNegative, &fOverflow);
|
|
if (fNegative || fOverflow || bnTarget == 0)
|
|
return 0;
|
|
// We need to compute 2**256 / (bnTarget+1), but we can't represent 2**256
|
|
// as it's too large for a arith_uint256. However, as 2**256 is at least as large
|
|
// as bnTarget+1, it is equal to ((2**256 - bnTarget - 1) / (bnTarget+1)) + 1,
|
|
// or ~bnTarget / (nTarget+1) + 1.
|
|
return (~bnTarget / (bnTarget + 1)) + 1;
|
|
}
|