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pow.cpp
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pow.cpp
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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2014 The Bitcoin developers
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include "pow.h"
#include "chain.h"
#include "chainparams.h"
#include "main.h"
#include "primitives/block.h"
#include "uint256.h"
#include "util.h"
#include <math.h>
// Lux modified: find last block index up to pindex
const CBlockIndex* GetLastBlockIndex(const CBlockIndex* pindex, bool fProofOfStake)
{
while (pindex && pindex->pprev && (pindex->IsProofOfStake() != fProofOfStake))
pindex = pindex->pprev;
return pindex;
}
unsigned int GetNextWorkRequired(const CBlockIndex* pindexLast, const CBlockHeader* pblock, bool fProofOfStake)
{
int64_t nTargetSpacing = 120;
int64_t nTargetTimespan = 30 * 60;
uint256 bnTargetLimit(Params().ProofOfWorkLimit());
if(fProofOfStake) {
bnTargetLimit = GetProofOfStakeLimit(pindexLast->nHeight);
}
if (pindexLast == nullptr) // Lux Modified
return bnTargetLimit.GetCompact();
const CBlockIndex* pindexPrev = GetLastBlockIndex(pindexLast, fProofOfStake);
if (pindexPrev->pprev == nullptr)
return bnTargetLimit.GetCompact(); // first block
const CBlockIndex* pindexPrevPrev = GetLastBlockIndex(pindexPrev->pprev, fProofOfStake);
if (pindexPrevPrev->pprev == nullptr)
return bnTargetLimit.GetCompact(); // second block
int64_t nActualSpacing = pindexPrev->GetBlockTime() - pindexPrevPrev->GetBlockTime();
if (nActualSpacing < 0)
nActualSpacing = nTargetSpacing;
// ppcoin: target change every block
// ppcoin: retarget with exponential moving toward target spacing
uint256 bnNew;
bnNew.SetCompact(pindexPrev->nBits); // Replaced pindexLast to avoid bugs
int64_t nInterval = nTargetTimespan / nTargetSpacing;
bnNew *= ((nInterval - 1) * nTargetSpacing + nActualSpacing + nActualSpacing);
bnNew /= ((nInterval + 1) * nTargetSpacing);
if (bnNew <= 0 || bnNew > bnTargetLimit)
bnNew = bnTargetLimit;
return bnNew.GetCompact();
}
bool CheckProofOfWork(uint256 hash, unsigned int nBits)
{
bool fNegative;
bool fOverflow;
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 (hash > bnTarget)
return error("CheckProofOfWork() : hash doesn't match nBits");
return true;
}
uint256 GetBlockProof(const CBlockIndex& block)
{
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 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;
}