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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2019 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 <chain.h>
#include <tinyformat.h>
#include <util/time.h>
std::string CBlockFileInfo::ToString() const
{
return strprintf("CBlockFileInfo(blocks=%u, size=%u, heights=%u...%u, time=%s...%s)", nBlocks, nSize, nHeightFirst, nHeightLast, FormatISO8601Date(nTimeFirst), FormatISO8601Date(nTimeLast));
}
std::string CBlockIndex::ToString() const
{
return strprintf("CBlockIndex(pprev=%p, nHeight=%d, merkle=%s, hashBlock=%s)",
pprev, nHeight, hashMerkleRoot.ToString(), GetBlockHash().ToString());
}
void CChain::SetTip(CBlockIndex& block)
{
CBlockIndex* pindex = █
vChain.resize(pindex->nHeight + 1);
while (pindex && vChain[pindex->nHeight] != pindex) {
vChain[pindex->nHeight] = pindex;
pindex = pindex->pprev;
}
}
std::vector<uint256> LocatorEntries(const CBlockIndex* index)
{
int step = 1;
std::vector<uint256> have;
if (index == nullptr) return have;
have.reserve(32);
while (index) {
have.emplace_back(index->GetBlockHash());
if (index->nHeight == 0) break;
// Exponentially larger steps back, plus the genesis block.
int height = std::max(index->nHeight - step, 0);
// Use skiplist.
index = index->GetAncestor(height);
if (have.size() > 10) step *= 2;
}
return have;
}
CBlockLocator GetLocator(const CBlockIndex* index)
{
return CBlockLocator{LocatorEntries(index)};
}
CBlockLocator CChain::GetLocator() const
{
return ::GetLocator(Tip());
}
const CBlockIndex *CChain::FindFork(const CBlockIndex *pindex) const {
if (pindex == nullptr) {
return nullptr;
}
if (pindex->nHeight > Height())
pindex = pindex->GetAncestor(Height());
while (pindex && !Contains(pindex))
pindex = pindex->pprev;
return pindex;
}
CBlockIndex* CChain::FindEarliestAtLeast(int64_t nTime, int height) const
{
std::pair<int64_t, int> blockparams = std::make_pair(nTime, height);
std::vector<CBlockIndex*>::const_iterator lower = std::lower_bound(vChain.begin(), vChain.end(), blockparams,
[](CBlockIndex* pBlock, const std::pair<int64_t, int>& blockparams) -> bool { return pBlock->GetBlockTimeMax() < blockparams.first || pBlock->nHeight < blockparams.second; });
return (lower == vChain.end() ? nullptr : *lower);
}
/** Turn the lowest '1' bit in the binary representation of a number into a '0'. */
int static inline InvertLowestOne(int n) { return n & (n - 1); }
/** Compute what height to jump back to with the CBlockIndex::pskip pointer. */
int static inline GetSkipHeight(int height) {
if (height < 2)
return 0;
// Determine which height to jump back to. Any number strictly lower than height is acceptable,
// but the following expression seems to perform well in simulations (max 110 steps to go back
// up to 2**18 blocks).
return (height & 1) ? InvertLowestOne(InvertLowestOne(height - 1)) + 1 : InvertLowestOne(height);
}
const CBlockIndex* CBlockIndex::GetAncestor(int height) const
{
if (height > nHeight || height < 0) {
return nullptr;
}
const CBlockIndex* pindexWalk = this;
int heightWalk = nHeight;
while (heightWalk > height) {
int heightSkip = GetSkipHeight(heightWalk);
int heightSkipPrev = GetSkipHeight(heightWalk - 1);
if (pindexWalk->pskip != nullptr &&
(heightSkip == height ||
(heightSkip > height && !(heightSkipPrev < heightSkip - 2 &&
heightSkipPrev >= height)))) {
// Only follow pskip if pprev->pskip isn't better than pskip->pprev.
pindexWalk = pindexWalk->pskip;
heightWalk = heightSkip;
} else {
assert(pindexWalk->pprev);
pindexWalk = pindexWalk->pprev;
heightWalk--;
}
}
return pindexWalk;
}
CBlockIndex* CBlockIndex::GetAncestor(int height)
{
return const_cast<CBlockIndex*>(static_cast<const CBlockIndex*>(this)->GetAncestor(height));
}
void CBlockIndex::BuildSkip()
{
if (pprev)
pskip = pprev->GetAncestor(GetSkipHeight(nHeight));
}
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 an 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 / (bnTarget+1) + 1.
return (~bnTarget / (bnTarget + 1)) + 1;
}
int64_t GetBlockProofEquivalentTime(const CBlockIndex& to, const CBlockIndex& from, const CBlockIndex& tip, const Consensus::Params& params)
{
arith_uint256 r;
int sign = 1;
if (to.nChainWork > from.nChainWork) {
r = to.nChainWork - from.nChainWork;
} else {
r = from.nChainWork - to.nChainWork;
sign = -1;
}
r = r * arith_uint256(params.nPowTargetSpacing) / GetBlockProof(tip);
if (r.bits() > 63) {
return sign * std::numeric_limits<int64_t>::max();
}
return sign * int64_t(r.GetLow64());
}
/** Find the last common ancestor two blocks have.
* Both pa and pb must be non-nullptr. */
const CBlockIndex* LastCommonAncestor(const CBlockIndex* pa, const CBlockIndex* pb) {
if (pa->nHeight > pb->nHeight) {
pa = pa->GetAncestor(pb->nHeight);
} else if (pb->nHeight > pa->nHeight) {
pb = pb->GetAncestor(pa->nHeight);
}
while (pa != pb && pa && pb) {
pa = pa->pprev;
pb = pb->pprev;
}
// Eventually all chain branches meet at the genesis block.
assert(pa == pb);
return pa;
}
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