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// Copyright (c) 2016 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 "versionbits.h"
#include "consensus/params.h"
const struct VBDeploymentInfo VersionBitsDeploymentInfo[Consensus::MAX_VERSION_BITS_DEPLOYMENTS] = {
{
/*.name =*/ "testdummy",
/*.gbt_force =*/ true,
},
{
/*.name =*/ "csv",
/*.gbt_force =*/ true,
},
{
/*.name =*/ "segwit",
/*.gbt_force =*/ true,
}
};
ThresholdState AbstractThresholdConditionChecker::GetStateFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const
{
int nPeriod = Period(params);
int nThreshold = Threshold(params);
int64_t nTimeStart = BeginTime(params);
int64_t nTimeTimeout = EndTime(params);
// Check if this deployment is always active.
if (nTimeStart == Consensus::BIP9Deployment::ALWAYS_ACTIVE) {
return THRESHOLD_ACTIVE;
}
// A block's state is always the same as that of the first of its period, so it is computed based on a pindexPrev whose height equals a multiple of nPeriod - 1.
if (pindexPrev != nullptr) {
pindexPrev = pindexPrev->GetAncestor(pindexPrev->nHeight - ((pindexPrev->nHeight + 1) % nPeriod));
}
// Walk backwards in steps of nPeriod to find a pindexPrev whose information is known
std::vector<const CBlockIndex*> vToCompute;
while (cache.count(pindexPrev) == 0) {
if (pindexPrev == nullptr) {
// The genesis block is by definition defined.
cache[pindexPrev] = THRESHOLD_DEFINED;
break;
}
if (pindexPrev->GetMedianTimePast() < nTimeStart) {
// Optimization: don't recompute down further, as we know every earlier block will be before the start time
cache[pindexPrev] = THRESHOLD_DEFINED;
break;
}
vToCompute.push_back(pindexPrev);
pindexPrev = pindexPrev->GetAncestor(pindexPrev->nHeight - nPeriod);
}
// At this point, cache[pindexPrev] is known
assert(cache.count(pindexPrev));
ThresholdState state = cache[pindexPrev];
// Now walk forward and compute the state of descendants of pindexPrev
while (!vToCompute.empty()) {
ThresholdState stateNext = state;
pindexPrev = vToCompute.back();
vToCompute.pop_back();
switch (state) {
case THRESHOLD_DEFINED: {
if (pindexPrev->GetMedianTimePast() >= nTimeTimeout) {
stateNext = THRESHOLD_FAILED;
} else if (pindexPrev->GetMedianTimePast() >= nTimeStart) {
stateNext = THRESHOLD_STARTED;
}
break;
}
case THRESHOLD_STARTED: {
if (pindexPrev->GetMedianTimePast() >= nTimeTimeout) {
stateNext = THRESHOLD_FAILED;
break;
}
// We need to count
const CBlockIndex* pindexCount = pindexPrev;
int count = 0;
for (int i = 0; i < nPeriod; i++) {
if (Condition(pindexCount, params)) {
count++;
}
pindexCount = pindexCount->pprev;
}
if (count >= nThreshold) {
stateNext = THRESHOLD_LOCKED_IN;
}
break;
}
case THRESHOLD_LOCKED_IN: {
// Always progresses into ACTIVE.
stateNext = THRESHOLD_ACTIVE;
break;
}
case THRESHOLD_FAILED:
case THRESHOLD_ACTIVE: {
// Nothing happens, these are terminal states.
break;
}
}
cache[pindexPrev] = state = stateNext;
}
return state;
}
// return the numerical statistics of blocks signalling the specified BIP9 condition in this current period
BIP9Stats AbstractThresholdConditionChecker::GetStateStatisticsFor(const CBlockIndex* pindex, const Consensus::Params& params) const
{
BIP9Stats stats = {};
stats.period = Period(params);
stats.threshold = Threshold(params);
if (pindex == nullptr)
return stats;
// Find beginning of period
const CBlockIndex* pindexEndOfPrevPeriod = pindex->GetAncestor(pindex->nHeight - ((pindex->nHeight + 1) % stats.period));
stats.elapsed = pindex->nHeight - pindexEndOfPrevPeriod->nHeight;
// Count from current block to beginning of period
int count = 0;
const CBlockIndex* currentIndex = pindex;
while (pindexEndOfPrevPeriod->nHeight != currentIndex->nHeight){
if (Condition(currentIndex, params))
count++;
currentIndex = currentIndex->pprev;
}
stats.count = count;
stats.possible = (stats.period - stats.threshold ) >= (stats.elapsed - count);
return stats;
}
int AbstractThresholdConditionChecker::GetStateSinceHeightFor(const CBlockIndex* pindexPrev, const Consensus::Params& params, ThresholdConditionCache& cache) const
{
int64_t start_time = BeginTime(params);
if (start_time == Consensus::BIP9Deployment::ALWAYS_ACTIVE) {
return 0;
}
const ThresholdState initialState = GetStateFor(pindexPrev, params, cache);
// BIP 9 about state DEFINED: "The genesis block is by definition in this state for each deployment."
if (initialState == THRESHOLD_DEFINED) {
return 0;
}
const int nPeriod = Period(params);
// A block's state is always the same as that of the first of its period, so it is computed based on a pindexPrev whose height equals a multiple of nPeriod - 1.
// To ease understanding of the following height calculation, it helps to remember that
// right now pindexPrev points to the block prior to the block that we are computing for, thus:
// if we are computing for the last block of a period, then pindexPrev points to the second to last block of the period, and
// if we are computing for the first block of a period, then pindexPrev points to the last block of the previous period.
// The parent of the genesis block is represented by nullptr.
pindexPrev = pindexPrev->GetAncestor(pindexPrev->nHeight - ((pindexPrev->nHeight + 1) % nPeriod));
const CBlockIndex* previousPeriodParent = pindexPrev->GetAncestor(pindexPrev->nHeight - nPeriod);
while (previousPeriodParent != nullptr && GetStateFor(previousPeriodParent, params, cache) == initialState) {
pindexPrev = previousPeriodParent;
previousPeriodParent = pindexPrev->GetAncestor(pindexPrev->nHeight - nPeriod);
}
// Adjust the result because right now we point to the parent block.
return pindexPrev->nHeight + 1;
}
namespace
{
/**
* Class to implement versionbits logic.
*/
class VersionBitsConditionChecker : public AbstractThresholdConditionChecker {
private:
const Consensus::DeploymentPos id;
protected:
int64_t BeginTime(const Consensus::Params& params) const override { return params.vDeployments[id].nStartTime; }
int64_t EndTime(const Consensus::Params& params) const override { return params.vDeployments[id].nTimeout; }
int Period(const Consensus::Params& params) const override { return params.nMinerConfirmationWindow; }
int Threshold(const Consensus::Params& params) const override { return params.nRuleChangeActivationThreshold; }
bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const override
{
return (((pindex->nVersion & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS) && (pindex->nVersion & Mask(params)) != 0);
}
public:
explicit VersionBitsConditionChecker(Consensus::DeploymentPos id_) : id(id_) {}
uint32_t Mask(const Consensus::Params& params) const { return ((uint32_t)1) << params.vDeployments[id].bit; }
};
} // namespace
ThresholdState VersionBitsState(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos, VersionBitsCache& cache)
{
return VersionBitsConditionChecker(pos).GetStateFor(pindexPrev, params, cache.caches[pos]);
}
BIP9Stats VersionBitsStatistics(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos)
{
return VersionBitsConditionChecker(pos).GetStateStatisticsFor(pindexPrev, params);
}
int VersionBitsStateSinceHeight(const CBlockIndex* pindexPrev, const Consensus::Params& params, Consensus::DeploymentPos pos, VersionBitsCache& cache)
{
return VersionBitsConditionChecker(pos).GetStateSinceHeightFor(pindexPrev, params, cache.caches[pos]);
}
uint32_t VersionBitsMask(const Consensus::Params& params, Consensus::DeploymentPos pos)
{
return VersionBitsConditionChecker(pos).Mask(params);
}
void VersionBitsCache::Clear()
{
for (unsigned int d = 0; d < Consensus::MAX_VERSION_BITS_DEPLOYMENTS; d++) {
caches[d].clear();
}
}
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