txmempool.cpp

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 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 <txmempool.h>

#include <chain.h>
#include <chainparams.h> // for GetConsensus.
#include <clientversion.h>
#include <config.h>
#include <consensus/consensus.h>
#include <consensus/tx_verify.h>
#include <consensus/validation.h>
#include <policy/fees.h>
#include <policy/policy.h>
#include <policy/settings.h>
#include <reverse_iterator.h>
#include <util/moneystr.h>
#include <util/system.h>
#include <util/time.h>
#include <validation.h>
#include <validationinterface.h>
#include <version.h>

#include <algorithm>

CTxMemPoolEntry::CTxMemPoolEntry(const CTransactionRef &_tx, const Amount _nFee,
                                 int64_t _nTime, unsigned int _entryHeight,
                                 bool _spendsCoinbase, int64_t _sigOpsCount,
                                 LockPoints lp)
    : tx(_tx), nFee(_nFee), nTxSize(tx->GetTotalSize()),
      nUsageSize(RecursiveDynamicUsage(tx)), nTime(_nTime),
      entryHeight(_entryHeight), spendsCoinbase(_spendsCoinbase),
      sigOpCount(_sigOpsCount), lockPoints(lp), m_epoch(0) {
    nCountWithDescendants = 1;
    nSizeWithDescendants = GetTxSize();
    nSigOpCountWithDescendants = sigOpCount;
    nModFeesWithDescendants = nFee;

    feeDelta = Amount::zero();

    nCountWithAncestors = 1;
    nSizeWithAncestors = GetTxSize();
    nModFeesWithAncestors = nFee;
    nSigOpCountWithAncestors = sigOpCount;
}

size_t CTxMemPoolEntry::GetTxVirtualSize() const {
    return GetVirtualTransactionSize(nTxSize, sigOpCount);
}

uint64_t CTxMemPoolEntry::GetVirtualSizeWithDescendants() const {
    // note this is distinct from the sum of descendants' individual virtual
    // sizes, and may be smaller.
    return GetVirtualTransactionSize(nSizeWithDescendants,
                                     nSigOpCountWithDescendants);
}

uint64_t CTxMemPoolEntry::GetVirtualSizeWithAncestors() const {
    // note this is distinct from the sum of ancestors' individual virtual
    // sizes, and may be smaller.
    return GetVirtualTransactionSize(nSizeWithAncestors,
                                     nSigOpCountWithAncestors);
}

void CTxMemPoolEntry::UpdateFeeDelta(Amount newFeeDelta) {
    nModFeesWithDescendants += newFeeDelta - feeDelta;
    nModFeesWithAncestors += newFeeDelta - feeDelta;
    feeDelta = newFeeDelta;
}

void CTxMemPoolEntry::UpdateLockPoints(const LockPoints &lp) {
    lockPoints = lp;
}

// Update the given tx for any in-mempool descendants.
// Assumes that setMemPoolChildren is correct for the given tx and all
// descendants.
void CTxMemPool::UpdateForDescendants(txiter updateIt,
                                      cacheMap &cachedDescendants,
                                      const std::set<TxId> &setExclude) {
    setEntries stageEntries, setAllDescendants;
    stageEntries = GetMemPoolChildren(updateIt);

    while (!stageEntries.empty()) {
        const txiter cit = *stageEntries.begin();
        setAllDescendants.insert(cit);
        stageEntries.erase(cit);
        const setEntries &setChildren = GetMemPoolChildren(cit);
        for (txiter childEntry : setChildren) {
            cacheMap::iterator cacheIt = cachedDescendants.find(childEntry);
            if (cacheIt != cachedDescendants.end()) {
                // We've already calculated this one, just add the entries for
                // this set but don't traverse again.
                for (txiter cacheEntry : cacheIt->second) {
                    setAllDescendants.insert(cacheEntry);
                }
            } else if (!setAllDescendants.count(childEntry)) {
                // Schedule for later processing
                stageEntries.insert(childEntry);
            }
        }
    }
    // setAllDescendants now contains all in-mempool descendants of updateIt.
    // Update and add to cached descendant map
    int64_t modifySize = 0;
    int64_t modifyCount = 0;
    Amount modifyFee = Amount::zero();
    int64_t modifySigOpCount = 0;
    for (txiter cit : setAllDescendants) {
        if (!setExclude.count(cit->GetTx().GetId())) {
            modifySize += cit->GetTxSize();
            modifyFee += cit->GetModifiedFee();
            modifyCount++;
            modifySigOpCount += cit->GetSigOpCount();
            cachedDescendants[updateIt].insert(cit);
            // Update ancestor state for each descendant
            mapTx.modify(cit,
                         update_ancestor_state(updateIt->GetTxSize(),
                                               updateIt->GetModifiedFee(), 1,
                                               updateIt->GetSigOpCount()));
        }
    }
    mapTx.modify(updateIt,
                 update_descendant_state(modifySize, modifyFee, modifyCount,
                                         modifySigOpCount));
}

// txidsToUpdate is the set of transaction hashes from a disconnected block
// which has been re-added to the mempool. For each entry, look for descendants
// that are outside txidsToUpdate, and add fee/size information for such
// descendants to the parent. For each such descendant, also update the ancestor
// state to include the parent.
void CTxMemPool::UpdateTransactionsFromBlock(
    const std::vector<TxId> &txidsToUpdate) {
    AssertLockHeld(cs);
    // For each entry in txidsToUpdate, store the set of in-mempool, but not
    // in-txidsToUpdate transactions, so that we don't have to recalculate
    // descendants when we come across a previously seen entry.
    cacheMap mapMemPoolDescendantsToUpdate;

    // Use a set for lookups into txidsToUpdate (these entries are already
    // accounted for in the state of their ancestors)
    std::set<TxId> setAlreadyIncluded(txidsToUpdate.begin(),
                                      txidsToUpdate.end());

    // Iterate in reverse, so that whenever we are looking at a transaction
    // we are sure that all in-mempool descendants have already been processed.
    // This maximizes the benefit of the descendant cache and guarantees that
    // setMemPoolChildren will be updated, an assumption made in
    // UpdateForDescendants.
    for (const TxId &txid : reverse_iterate(txidsToUpdate)) {
        // calculate children from mapNextTx
        txiter it = mapTx.find(txid);
        if (it == mapTx.end()) {
            continue;
        }

        auto iter = mapNextTx.lower_bound(COutPoint(txid, 0));
        // First calculate the children, and update setMemPoolChildren to
        // include them, and update their setMemPoolParents to include this tx.
        // we cache the in-mempool children to avoid duplicate updates
        {
            const auto epoch = GetFreshEpoch();
            for (; iter != mapNextTx.end() && iter->first->GetTxId() == txid;
                 ++iter) {
                const TxId &childTxId = iter->second->GetId();
                txiter childIter = mapTx.find(childTxId);
                assert(childIter != mapTx.end());
                // We can skip updating entries we've encountered before or that
                // are in the block (which are already accounted for).
                if (!visited(childIter) &&
                    !setAlreadyIncluded.count(childTxId)) {
                    UpdateChild(it, childIter, true);
                    UpdateParent(childIter, it, true);
                }
            }
        } // release epoch guard for UpdateForDescendants
        UpdateForDescendants(it, mapMemPoolDescendantsToUpdate,
                             setAlreadyIncluded);
    }
}

bool CTxMemPool::CalculateMemPoolAncestors(
    const CTxMemPoolEntry &entry, setEntries &setAncestors,
    uint64_t limitAncestorCount, uint64_t limitAncestorSize,
    uint64_t limitDescendantCount, uint64_t limitDescendantSize,
    std::string &errString, bool fSearchForParents /* = true */) const {
    setEntries parentHashes;
    const CTransaction &tx = entry.GetTx();

    if (fSearchForParents) {
        // Get parents of this transaction that are in the mempool
        // GetMemPoolParents() is only valid for entries in the mempool, so we
        // iterate mapTx to find parents.
        for (const CTxIn &in : tx.vin) {
            std::optional<txiter> piter = GetIter(in.prevout.GetTxId());
            if (!piter) {
                continue;
            }
            parentHashes.insert(*piter);
            if (parentHashes.size() + 1 > limitAncestorCount) {
                errString =
                    strprintf("too many unconfirmed parents [limit: %u]",
                              limitAncestorCount);
                return false;
            }
        }
    } else {
        // If we're not searching for parents, we require this to be an entry in
        // the mempool already.
        txiter it = mapTx.iterator_to(entry);
        parentHashes = GetMemPoolParents(it);
    }

    size_t totalSizeWithAncestors = entry.GetTxSize();

    while (!parentHashes.empty()) {
        txiter stageit = *parentHashes.begin();

        setAncestors.insert(stageit);
        parentHashes.erase(stageit);
        totalSizeWithAncestors += stageit->GetTxSize();

        if (stageit->GetSizeWithDescendants() + entry.GetTxSize() >
            limitDescendantSize) {
            errString = strprintf(
                "exceeds descendant size limit for tx %s [limit: %u]",
                stageit->GetTx().GetId().ToString(), limitDescendantSize);
            return false;
        }

        if (stageit->GetCountWithDescendants() + 1 > limitDescendantCount) {
            errString = strprintf("too many descendants for tx %s [limit: %u]",
                                  stageit->GetTx().GetId().ToString(),
                                  limitDescendantCount);
            return false;
        }

        if (totalSizeWithAncestors > limitAncestorSize) {
            errString = strprintf("exceeds ancestor size limit [limit: %u]",
                                  limitAncestorSize);
            return false;
        }

        const setEntries &setMemPoolParents = GetMemPoolParents(stageit);
        for (txiter phash : setMemPoolParents) {
            // If this is a new ancestor, add it.
            if (setAncestors.count(phash) == 0) {
                parentHashes.insert(phash);
            }
            if (parentHashes.size() + setAncestors.size() + 1 >
                limitAncestorCount) {
                errString =
                    strprintf("too many unconfirmed ancestors [limit: %u]",
                              limitAncestorCount);
                return false;
            }
        }
    }

    return true;
}

void CTxMemPool::UpdateAncestorsOf(bool add, txiter it,
                                   setEntries &setAncestors) {
    setEntries parentIters = GetMemPoolParents(it);
    // add or remove this tx as a child of each parent
    for (txiter piter : parentIters) {
        UpdateChild(piter, it, add);
    }
    const int64_t updateCount = (add ? 1 : -1);
    const int64_t updateSize = updateCount * it->GetTxSize();
    const int64_t updateSigOpCount = updateCount * it->GetSigOpCount();
    const Amount updateFee = updateCount * it->GetModifiedFee();
    for (txiter ancestorIt : setAncestors) {
        mapTx.modify(ancestorIt,
                     update_descendant_state(updateSize, updateFee, updateCount,
                                             updateSigOpCount));
    }
}

void CTxMemPool::UpdateEntryForAncestors(txiter it,
                                         const setEntries &setAncestors) {
    int64_t updateCount = setAncestors.size();
    int64_t updateSize = 0;
    int64_t updateSigOpsCount = 0;
    Amount updateFee = Amount::zero();

    for (txiter ancestorIt : setAncestors) {
        updateSize += ancestorIt->GetTxSize();
        updateFee += ancestorIt->GetModifiedFee();
        updateSigOpsCount += ancestorIt->GetSigOpCount();
    }
    mapTx.modify(it, update_ancestor_state(updateSize, updateFee, updateCount,
                                           updateSigOpsCount));
}

void CTxMemPool::UpdateChildrenForRemoval(txiter it) {
    const setEntries &setMemPoolChildren = GetMemPoolChildren(it);
    for (txiter updateIt : setMemPoolChildren) {
        UpdateParent(updateIt, it, false);
    }
}

void CTxMemPool::UpdateForRemoveFromMempool(const setEntries &entriesToRemove,
                                            bool updateDescendants) {
    // For each entry, walk back all ancestors and decrement size associated
    // with this transaction.
    const uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
    if (updateDescendants) {
        // updateDescendants should be true whenever we're not recursively
        // removing a tx and all its descendants, eg when a transaction is
        // confirmed in a block. Here we only update statistics and not data in
        // mapLinks (which we need to preserve until we're finished with all
        // operations that need to traverse the mempool).
        for (txiter removeIt : entriesToRemove) {
            setEntries setDescendants;
            CalculateDescendants(removeIt, setDescendants);
            setDescendants.erase(removeIt); // don't update state for self
            int64_t modifySize = -int64_t(removeIt->GetTxSize());
            Amount modifyFee = -1 * removeIt->GetModifiedFee();
            int modifySigOps = -removeIt->GetSigOpCount();
            for (txiter dit : setDescendants) {
                mapTx.modify(dit, update_ancestor_state(modifySize, modifyFee,
                                                        -1, modifySigOps));
            }
        }
    }

    for (txiter removeIt : entriesToRemove) {
        setEntries setAncestors;
        const CTxMemPoolEntry &entry = *removeIt;
        std::string dummy;
        // Since this is a tx that is already in the mempool, we can call CMPA
        // with fSearchForParents = false.  If the mempool is in a consistent
        // state, then using true or false should both be correct, though false
        // should be a bit faster.
        // However, if we happen to be in the middle of processing a reorg, then
        // the mempool can be in an inconsistent state. In this case, the set of
        // ancestors reachable via mapLinks will be the same as the set of
        // ancestors whose packages include this transaction, because when we
        // add a new transaction to the mempool in addUnchecked(), we assume it
        // has no children, and in the case of a reorg where that assumption is
        // false, the in-mempool children aren't linked to the in-block tx's
        // until UpdateTransactionsFromBlock() is called. So if we're being
        // called during a reorg, ie before UpdateTransactionsFromBlock() has
        // been called, then mapLinks[] will differ from the set of mempool
        // parents we'd calculate by searching, and it's important that we use
        // the mapLinks[] notion of ancestor transactions as the set of things
        // to update for removal.
        CalculateMemPoolAncestors(entry, setAncestors, nNoLimit, nNoLimit,
                                  nNoLimit, nNoLimit, dummy, false);
        // Note that UpdateAncestorsOf severs the child links that point to
        // removeIt in the entries for the parents of removeIt.
        UpdateAncestorsOf(false, removeIt, setAncestors);
    }
    // After updating all the ancestor sizes, we can now sever the link between
    // each transaction being removed and any mempool children (ie, update
    // setMemPoolParents for each direct child of a transaction being removed).
    for (txiter removeIt : entriesToRemove) {
        UpdateChildrenForRemoval(removeIt);
    }
}

void CTxMemPoolEntry::UpdateDescendantState(int64_t modifySize,
                                            Amount modifyFee,
                                            int64_t modifyCount,
                                            int64_t modifySigOpCount) {
    nSizeWithDescendants += modifySize;
    assert(int64_t(nSizeWithDescendants) > 0);
    nModFeesWithDescendants += modifyFee;
    nCountWithDescendants += modifyCount;
    assert(int64_t(nCountWithDescendants) > 0);
    nSigOpCountWithDescendants += modifySigOpCount;
    assert(int64_t(nSigOpCountWithDescendants) >= 0);
}

void CTxMemPoolEntry::UpdateAncestorState(int64_t modifySize, Amount modifyFee,
                                          int64_t modifyCount,
                                          int64_t modifySigOps) {
    nSizeWithAncestors += modifySize;
    assert(int64_t(nSizeWithAncestors) > 0);
    nModFeesWithAncestors += modifyFee;
    nCountWithAncestors += modifyCount;
    assert(int64_t(nCountWithAncestors) > 0);
    nSigOpCountWithAncestors += modifySigOps;
    assert(int(nSigOpCountWithAncestors) >= 0);
}

CTxMemPool::CTxMemPool()
    : nTransactionsUpdated(0), m_epoch(0), m_has_epoch_guard(false) {
    // lock free clear
    _clear();

    // Sanity checks off by default for performance, because otherwise accepting
    // transactions becomes O(N^2) where N is the number of transactions in the
    // pool
    nCheckFrequency = 0;
}

CTxMemPool::~CTxMemPool() {}

bool CTxMemPool::isSpent(const COutPoint &outpoint) const {
    LOCK(cs);
    return mapNextTx.count(outpoint);
}

unsigned int CTxMemPool::GetTransactionsUpdated() const {
    return nTransactionsUpdated;
}

void CTxMemPool::AddTransactionsUpdated(unsigned int n) {
    nTransactionsUpdated += n;
}

void CTxMemPool::addUnchecked(const CTxMemPoolEntry &entry,
                              setEntries &setAncestors) {
    // Add to memory pool without checking anything.
    // Used by AcceptToMemoryPool(), which DOES do all the appropriate checks.
    indexed_transaction_set::iterator newit = mapTx.insert(entry).first;
    mapLinks.insert(make_pair(newit, TxLinks()));

    // Update transaction for any feeDelta created by PrioritiseTransaction
    // TODO: refactor so that the fee delta is calculated before inserting into
    // mapTx.
    Amount feeDelta = Amount::zero();
    ApplyDelta(entry.GetTx().GetId(), feeDelta);
    if (feeDelta != Amount::zero()) {
        mapTx.modify(newit, update_fee_delta(feeDelta));
    }

    // Update cachedInnerUsage to include contained transaction's usage.
    // (When we update the entry for in-mempool parents, memory usage will be
    // further updated.)
    cachedInnerUsage += entry.DynamicMemoryUsage();

    const CTransaction &tx = newit->GetTx();
    std::set<TxId> setParentTransactions;
    for (const CTxIn &in : tx.vin) {
        mapNextTx.insert(std::make_pair(&in.prevout, &tx));
        setParentTransactions.insert(in.prevout.GetTxId());
    }
    // Don't bother worrying about child transactions of this one. Normal case
    // of a new transaction arriving is that there can't be any children,
    // because such children would be orphans. An exception to that is if a
    // transaction enters that used to be in a block. In that case, our
    // disconnect block logic will call UpdateTransactionsFromBlock to clean up
    // the mess we're leaving here.

    // Update ancestors with information about this tx
    for (const auto &pit : GetIterSet(setParentTransactions)) {
        UpdateParent(newit, pit, true);
    }
    UpdateAncestorsOf(true, newit, setAncestors);
    UpdateEntryForAncestors(newit, setAncestors);

    nTransactionsUpdated++;
    totalTxSize += entry.GetTxSize();

    vTxHashes.emplace_back(tx.GetHash(), newit);
    newit->vTxHashesIdx = vTxHashes.size() - 1;
}

void CTxMemPool::removeUnchecked(txiter it, MemPoolRemovalReason reason) {
    if (reason != MemPoolRemovalReason::BLOCK) {
        // Notify clients that a transaction has been removed from the mempool
        // for any reason except being included in a block. Clients interested
        // in transactions included in blocks can subscribe to the
        // BlockConnected notification.
        GetMainSignals().TransactionRemovedFromMempool(it->GetSharedTx());
    }

    for (const CTxIn &txin : it->GetTx().vin) {
        mapNextTx.erase(txin.prevout);
    }

    if (vTxHashes.size() > 1) {
        vTxHashes[it->vTxHashesIdx] = std::move(vTxHashes.back());
        vTxHashes[it->vTxHashesIdx].second->vTxHashesIdx = it->vTxHashesIdx;
        vTxHashes.pop_back();
        if (vTxHashes.size() * 2 < vTxHashes.capacity()) {
            vTxHashes.shrink_to_fit();
        }
    } else {
        vTxHashes.clear();
    }

    totalTxSize -= it->GetTxSize();
    cachedInnerUsage -= it->DynamicMemoryUsage();
    cachedInnerUsage -= memusage::DynamicUsage(mapLinks[it].parents) +
                        memusage::DynamicUsage(mapLinks[it].children);
    mapLinks.erase(it);
    mapTx.erase(it);
    nTransactionsUpdated++;
}

// Calculates descendants of entry that are not already in setDescendants, and
// adds to setDescendants. Assumes entryit is already a tx in the mempool and
// setMemPoolChildren is correct for tx and all descendants. Also assumes that
// if an entry is in setDescendants already, then all in-mempool descendants of
// it are already in setDescendants as well, so that we can save time by not
// iterating over those entries.
void CTxMemPool::CalculateDescendants(txiter entryit,
                                      setEntries &setDescendants) const {
    setEntries stage;
    if (setDescendants.count(entryit) == 0) {
        stage.insert(entryit);
    }
    // Traverse down the children of entry, only adding children that are not
    // accounted for in setDescendants already (because those children have
    // either already been walked, or will be walked in this iteration).
    while (!stage.empty()) {
        txiter it = *stage.begin();
        setDescendants.insert(it);
        stage.erase(it);

        const setEntries &setChildren = GetMemPoolChildren(it);
        for (txiter childiter : setChildren) {
            if (!setDescendants.count(childiter)) {
                stage.insert(childiter);
            }
        }
    }
}

void CTxMemPool::removeRecursive(const CTransaction &origTx,
                                 MemPoolRemovalReason reason) {
    // Remove transaction from memory pool.
    AssertLockHeld(cs);
    setEntries txToRemove;
    txiter origit = mapTx.find(origTx.GetId());
    if (origit != mapTx.end()) {
        txToRemove.insert(origit);
    } else {
        // When recursively removing but origTx isn't in the mempool be sure to
        // remove any children that are in the pool. This can happen during
        // chain re-orgs if origTx isn't re-accepted into the mempool for any
        // reason.
        for (size_t i = 0; i < origTx.vout.size(); i++) {
            auto it = mapNextTx.find(COutPoint(origTx.GetId(), i));
            if (it == mapNextTx.end()) {
                continue;
            }

            txiter nextit = mapTx.find(it->second->GetId());
            assert(nextit != mapTx.end());
            txToRemove.insert(nextit);
        }
    }

    setEntries setAllRemoves;
    for (txiter it : txToRemove) {
        CalculateDescendants(it, setAllRemoves);
    }

    RemoveStaged(setAllRemoves, false, reason);
}

void CTxMemPool::removeForReorg(const Config &config,
                                const CCoinsViewCache *pcoins,
                                unsigned int nMemPoolHeight, int flags) {
    // Remove transactions spending a coinbase which are now immature and
    // no-longer-final transactions.
    AssertLockHeld(cs);
    setEntries txToRemove;
    for (indexed_transaction_set::const_iterator it = mapTx.begin();
         it != mapTx.end(); it++) {
        const CTransaction &tx = it->GetTx();
        LockPoints lp = it->GetLockPoints();
        bool validLP = TestLockPointValidity(&lp);

        TxValidationState state;
        if (!ContextualCheckTransactionForCurrentBlock(
                config.GetChainParams().GetConsensus(), tx, state, flags) ||
            !CheckSequenceLocks(*this, tx, flags, &lp, validLP)) {
            // Note if CheckSequenceLocks fails the LockPoints may still be
            // invalid. So it's critical that we remove the tx and not depend on
            // the LockPoints.
            txToRemove.insert(it);
        } else if (it->GetSpendsCoinbase()) {
            for (const CTxIn &txin : tx.vin) {
                indexed_transaction_set::const_iterator it2 =
                    mapTx.find(txin.prevout.GetTxId());
                if (it2 != mapTx.end()) {
                    continue;
                }

                const Coin &coin = pcoins->AccessCoin(txin.prevout);
                if (nCheckFrequency != 0) {
                    assert(!coin.IsSpent());
                }

                if (coin.IsSpent() ||
                    (coin.IsCoinBase() &&
                     int64_t(nMemPoolHeight) - coin.GetHeight() <
                         COINBASE_MATURITY)) {
                    txToRemove.insert(it);
                    break;
                }
            }
        }
        if (!validLP) {
            mapTx.modify(it, update_lock_points(lp));
        }
    }
    setEntries setAllRemoves;
    for (txiter it : txToRemove) {
        CalculateDescendants(it, setAllRemoves);
    }
    RemoveStaged(setAllRemoves, false, MemPoolRemovalReason::REORG);
}

void CTxMemPool::removeConflicts(const CTransaction &tx) {
    // Remove transactions which depend on inputs of tx, recursively
    AssertLockHeld(cs);
    for (const CTxIn &txin : tx.vin) {
        auto it = mapNextTx.find(txin.prevout);
        if (it != mapNextTx.end()) {
            const CTransaction &txConflict = *it->second;
            if (txConflict != tx) {
                ClearPrioritisation(txConflict.GetId());
                removeRecursive(txConflict, MemPoolRemovalReason::CONFLICT);
            }
        }
    }
}

void CTxMemPool::removeForBlock(const std::vector<CTransactionRef> &vtx,
                                unsigned int nBlockHeight) {
    AssertLockHeld(cs);

    DisconnectedBlockTransactions disconnectpool;
    disconnectpool.addForBlock(vtx, *this);

    std::vector<const CTxMemPoolEntry *> entries;
    for (const CTransactionRef &tx :
         reverse_iterate(disconnectpool.GetQueuedTx().get<insertion_order>())) {
        const TxId &txid = tx->GetId();

        indexed_transaction_set::iterator i = mapTx.find(txid);
        if (i != mapTx.end()) {
            entries.push_back(&*i);
        }
    }

    for (const CTransactionRef &tx :
         reverse_iterate(disconnectpool.GetQueuedTx().get<insertion_order>())) {
        txiter it = mapTx.find(tx->GetId());
        if (it != mapTx.end()) {
            setEntries stage;
            stage.insert(it);
            RemoveStaged(stage, true, MemPoolRemovalReason::BLOCK);
        }
        removeConflicts(*tx);
        ClearPrioritisation(tx->GetId());
    }

    disconnectpool.clear();

    lastRollingFeeUpdate = GetTime();
    blockSinceLastRollingFeeBump = true;
}

void CTxMemPool::_clear() {
    mapLinks.clear();
    mapTx.clear();
    mapNextTx.clear();
    vTxHashes.clear();
    totalTxSize = 0;
    cachedInnerUsage = 0;
    lastRollingFeeUpdate = GetTime();
    blockSinceLastRollingFeeBump = false;
    rollingMinimumFeeRate = 0;
    ++nTransactionsUpdated;
}

void CTxMemPool::clear() {
    LOCK(cs);
    _clear();
}

static void CheckInputsAndUpdateCoins(const CTransaction &tx,
                                      CCoinsViewCache &mempoolDuplicate,
                                      const int64_t spendheight) {
    // Not used. CheckTxInputs() should always pass
    TxValidationState dummy_state;
    Amount txfee = Amount::zero();
    bool fCheckResult =
        tx.IsCoinBase() ||
        Consensus::CheckTxInputs(tx, dummy_state, mempoolDuplicate, spendheight,
                                 txfee);
    assert(fCheckResult);
    UpdateCoins(mempoolDuplicate, tx, std::numeric_limits<int>::max());
}

void CTxMemPool::check(const CCoinsViewCache *pcoins) const {
    LOCK(cs);
    if (nCheckFrequency == 0) {
        return;
    }

    if (GetRand(std::numeric_limits<uint32_t>::max()) >= nCheckFrequency) {
        return;
    }

    LogPrint(BCLog::MEMPOOL,
             "Checking mempool with %u transactions and %u inputs\n",
             (unsigned int)mapTx.size(), (unsigned int)mapNextTx.size());

    uint64_t checkTotal = 0;
    uint64_t innerUsage = 0;

    CCoinsViewCache mempoolDuplicate(const_cast<CCoinsViewCache *>(pcoins));
    const int64_t spendheight = GetSpendHeight(mempoolDuplicate);

    std::list<const CTxMemPoolEntry *> waitingOnDependants;
    for (indexed_transaction_set::const_iterator it = mapTx.begin();
         it != mapTx.end(); it++) {
        unsigned int i = 0;
        checkTotal += it->GetTxSize();
        innerUsage += it->DynamicMemoryUsage();
        const CTransaction &tx = it->GetTx();
        txlinksMap::const_iterator linksiter = mapLinks.find(it);
        assert(linksiter != mapLinks.end());
        const TxLinks &links = linksiter->second;
        innerUsage += memusage::DynamicUsage(links.parents) +
                      memusage::DynamicUsage(links.children);
        bool fDependsWait = false;
        setEntries setParentCheck;
        for (const CTxIn &txin : tx.vin) {
            // Check that every mempool transaction's inputs refer to available
            // coins, or other mempool tx's.
            indexed_transaction_set::const_iterator it2 =
                mapTx.find(txin.prevout.GetTxId());
            if (it2 != mapTx.end()) {
                const CTransaction &tx2 = it2->GetTx();
                assert(tx2.vout.size() > txin.prevout.GetN() &&
                       !tx2.vout[txin.prevout.GetN()].IsNull());
                fDependsWait = true;
                setParentCheck.insert(it2);
            } else {
                assert(pcoins->HaveCoin(txin.prevout));
            }
            // Check whether its inputs are marked in mapNextTx.
            auto it3 = mapNextTx.find(txin.prevout);
            assert(it3 != mapNextTx.end());
            assert(it3->first == &txin.prevout);
            assert(it3->second == &tx);
            i++;
        }
        assert(setParentCheck == GetMemPoolParents(it));
        // Verify ancestor state is correct.
        setEntries setAncestors;
        uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
        std::string dummy;
        CalculateMemPoolAncestors(*it, setAncestors, nNoLimit, nNoLimit,
                                  nNoLimit, nNoLimit, dummy);
        uint64_t nCountCheck = setAncestors.size() + 1;
        uint64_t nSizeCheck = it->GetTxSize();
        Amount nFeesCheck = it->GetModifiedFee();
        int64_t nSigOpCheck = it->GetSigOpCount();

        for (txiter ancestorIt : setAncestors) {
            nSizeCheck += ancestorIt->GetTxSize();
            nFeesCheck += ancestorIt->GetModifiedFee();
            nSigOpCheck += ancestorIt->GetSigOpCount();
        }

        assert(it->GetCountWithAncestors() == nCountCheck);
        assert(it->GetSizeWithAncestors() == nSizeCheck);
        assert(it->GetSigOpCountWithAncestors() == nSigOpCheck);
        assert(it->GetModFeesWithAncestors() == nFeesCheck);

        // Check children against mapNextTx
        CTxMemPool::setEntries setChildrenCheck;
        auto iter = mapNextTx.lower_bound(COutPoint(it->GetTx().GetId(), 0));
        uint64_t child_sizes = 0;
        int64_t child_sigop_counts = 0;
        for (; iter != mapNextTx.end() &&
               iter->first->GetTxId() == it->GetTx().GetId();
             ++iter) {
            txiter childit = mapTx.find(iter->second->GetId());
            // mapNextTx points to in-mempool transactions
            assert(childit != mapTx.end());
            if (setChildrenCheck.insert(childit).second) {
                child_sizes += childit->GetTxSize();
                child_sigop_counts += childit->GetSigOpCount();
            }
        }
        assert(setChildrenCheck == GetMemPoolChildren(it));
        // Also check to make sure size is greater than sum with immediate
        // children. Just a sanity check, not definitive that this calc is
        // correct...
        assert(it->GetSizeWithDescendants() >= child_sizes + it->GetTxSize());
        assert(it->GetSigOpCountWithDescendants() >=
               child_sigop_counts + it->GetSigOpCount());

        if (fDependsWait) {
            waitingOnDependants.push_back(&(*it));
        } else {
            CheckInputsAndUpdateCoins(tx, mempoolDuplicate, spendheight);
        }
    }

    unsigned int stepsSinceLastRemove = 0;
    while (!waitingOnDependants.empty()) {
        const CTxMemPoolEntry *entry = waitingOnDependants.front();
        waitingOnDependants.pop_front();
        if (!mempoolDuplicate.HaveInputs(entry->GetTx())) {
            waitingOnDependants.push_back(entry);
            stepsSinceLastRemove++;
            assert(stepsSinceLastRemove < waitingOnDependants.size());
        } else {
            CheckInputsAndUpdateCoins(entry->GetTx(), mempoolDuplicate,
                                      spendheight);
            stepsSinceLastRemove = 0;
        }
    }

    for (auto it = mapNextTx.cbegin(); it != mapNextTx.cend(); it++) {
        const TxId &txid = it->second->GetId();
        indexed_transaction_set::const_iterator it2 = mapTx.find(txid);
        const CTransaction &tx = it2->GetTx();
        assert(it2 != mapTx.end());
        assert(&tx == it->second);
    }

    assert(totalTxSize == checkTotal);
    assert(innerUsage == cachedInnerUsage);
}

bool CTxMemPool::CompareDepthAndScore(const TxId &txida, const TxId &txidb) {
    LOCK(cs);
    indexed_transaction_set::const_iterator i = mapTx.find(txida);
    if (i == mapTx.end()) {
        return false;
    }
    indexed_transaction_set::const_iterator j = mapTx.find(txidb);
    if (j == mapTx.end()) {
        return true;
    }
    uint64_t counta = i->GetCountWithAncestors();
    uint64_t countb = j->GetCountWithAncestors();
    if (counta == countb) {
        return CompareTxMemPoolEntryByScore()(*i, *j);
    }
    return counta < countb;
}

namespace {
class DepthAndScoreComparator {
public:
    bool
    operator()(const CTxMemPool::indexed_transaction_set::const_iterator &a,
               const CTxMemPool::indexed_transaction_set::const_iterator &b) {
        uint64_t counta = a->GetCountWithAncestors();
        uint64_t countb = b->GetCountWithAncestors();
        if (counta == countb) {
            return CompareTxMemPoolEntryByScore()(*a, *b);
        }
        return counta < countb;
    }
};
} // namespace

std::vector<CTxMemPool::indexed_transaction_set::const_iterator>
CTxMemPool::GetSortedDepthAndScore() const {
    std::vector<indexed_transaction_set::const_iterator> iters;
    AssertLockHeld(cs);

    iters.reserve(mapTx.size());
    for (indexed_transaction_set::iterator mi = mapTx.begin();
         mi != mapTx.end(); ++mi) {
        iters.push_back(mi);
    }

    std::sort(iters.begin(), iters.end(), DepthAndScoreComparator());
    return iters;
}

void CTxMemPool::queryHashes(std::vector<uint256> &vtxid) const {
    LOCK(cs);
    auto iters = GetSortedDepthAndScore();

    vtxid.clear();
    vtxid.reserve(mapTx.size());

    for (auto it : iters) {
        vtxid.push_back(it->GetTx().GetId());
    }
}

static TxMempoolInfo
GetInfo(CTxMemPool::indexed_transaction_set::const_iterator it) {
    return TxMempoolInfo{it->GetSharedTx(), it->GetTime(), it->GetFee(),
                         it->GetTxSize(), it->GetModifiedFee() - it->GetFee()};
}

std::vector<TxMempoolInfo> CTxMemPool::infoAll() const {
    LOCK(cs);
    auto iters = GetSortedDepthAndScore();

    std::vector<TxMempoolInfo> ret;
    ret.reserve(mapTx.size());
    for (auto it : iters) {
        ret.push_back(GetInfo(it));
    }

    return ret;
}

CTransactionRef CTxMemPool::get(const TxId &txid) const {
    LOCK(cs);
    indexed_transaction_set::const_iterator i = mapTx.find(txid);
    if (i == mapTx.end()) {
        return nullptr;
    }

    return i->GetSharedTx();
}

TxMempoolInfo CTxMemPool::info(const TxId &txid) const {
    LOCK(cs);
    indexed_transaction_set::const_iterator i = mapTx.find(txid);
    if (i == mapTx.end()) {
        return TxMempoolInfo();
    }

    return GetInfo(i);
}

CFeeRate CTxMemPool::estimateFee() const {
    LOCK(cs);

    uint64_t maxMempoolSize =
        gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
    // minerPolicy uses recent blocks to figure out a reasonable fee.  This
    // may disagree with the rollingMinimumFeerate under certain scenarios
    // where the mempool  increases rapidly, or blocks are being mined which
    // do not contain propagated transactions.
    return std::max(::minRelayTxFee, GetMinFee(maxMempoolSize));
}

void CTxMemPool::PrioritiseTransaction(const TxId &txid,
                                       const Amount nFeeDelta) {
    {
        LOCK(cs);
        Amount &delta = mapDeltas[txid];
        delta += nFeeDelta;
        txiter it = mapTx.find(txid);
        if (it != mapTx.end()) {
            mapTx.modify(it, update_fee_delta(delta));
            // Now update all ancestors' modified fees with descendants
            setEntries setAncestors;
            uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
            std::string dummy;
            CalculateMemPoolAncestors(*it, setAncestors, nNoLimit, nNoLimit,
                                      nNoLimit, nNoLimit, dummy, false);
            for (txiter ancestorIt : setAncestors) {
                mapTx.modify(ancestorIt,
                             update_descendant_state(0, nFeeDelta, 0, 0));
            }

            // Now update all descendants' modified fees with ancestors
            setEntries setDescendants;
            CalculateDescendants(it, setDescendants);
            setDescendants.erase(it);
            for (txiter descendantIt : setDescendants) {
                mapTx.modify(descendantIt,
                             update_ancestor_state(0, nFeeDelta, 0, 0));
            }
            ++nTransactionsUpdated;
        }
    }
    LogPrintf("PrioritiseTransaction: %s fee += %s\n", txid.ToString(),
              FormatMoney(nFeeDelta));
}

void CTxMemPool::ApplyDelta(const TxId &txid, Amount &nFeeDelta) const {
    LOCK(cs);
    std::map<TxId, Amount>::const_iterator pos = mapDeltas.find(txid);
    if (pos == mapDeltas.end()) {
        return;
    }

    nFeeDelta += pos->second;
}

void CTxMemPool::ClearPrioritisation(const TxId &txid) {
    LOCK(cs);
    mapDeltas.erase(txid);
}

const CTransaction *CTxMemPool::GetConflictTx(const COutPoint &prevout) const {
    const auto it = mapNextTx.find(prevout);
    return it == mapNextTx.end() ? nullptr : it->second;
}

std::optional<CTxMemPool::txiter> CTxMemPool::GetIter(const TxId &txid) const {
    auto it = mapTx.find(txid);
    if (it != mapTx.end()) {
        return it;
    }
    return std::optional<txiter>{std::nullopt};
}

CTxMemPool::setEntries
CTxMemPool::GetIterSet(const std::set<TxId> &txids) const {
    CTxMemPool::setEntries ret;
    for (const auto &txid : txids) {
        const auto mi = GetIter(txid);
        if (mi) {
            ret.insert(*mi);
        }
    }
    return ret;
}

bool CTxMemPool::HasNoInputsOf(const CTransaction &tx) const {
    for (const CTxIn &in : tx.vin) {
        if (exists(in.prevout.GetTxId())) {
            return false;
        }
    }

    return true;
}

CCoinsViewMemPool::CCoinsViewMemPool(CCoinsView *baseIn,
                                     const CTxMemPool &mempoolIn)
    : CCoinsViewBacked(baseIn), mempool(mempoolIn) {}

bool CCoinsViewMemPool::GetCoin(const COutPoint &outpoint, Coin &coin) const {
    // If an entry in the mempool exists, always return that one, as it's
    // guaranteed to never conflict with the underlying cache, and it cannot
    // have pruned entries (as it contains full) transactions. First checking
    // the underlying cache risks returning a pruned entry instead.
    CTransactionRef ptx = mempool.get(outpoint.GetTxId());
    if (ptx) {
        if (outpoint.GetN() < ptx->vout.size()) {
            coin = Coin(ptx->vout[outpoint.GetN()], MEMPOOL_HEIGHT, false);
            return true;
        }
        return false;
    }
    return base->GetCoin(outpoint, coin);
}

size_t CTxMemPool::DynamicMemoryUsage() const {
    LOCK(cs);
    // Estimate the overhead of mapTx to be 12 pointers + an allocation, as no
    // exact formula for boost::multi_index_contained is implemented.
    return memusage::MallocUsage(sizeof(CTxMemPoolEntry) +
                                 12 * sizeof(void *)) *
               mapTx.size() +
           memusage::DynamicUsage(mapNextTx) +
           memusage::DynamicUsage(mapDeltas) +
           memusage::DynamicUsage(mapLinks) +
           memusage::DynamicUsage(vTxHashes) + cachedInnerUsage;
}

void CTxMemPool::RemoveStaged(setEntries &stage, bool updateDescendants,
                              MemPoolRemovalReason reason) {
    AssertLockHeld(cs);
    UpdateForRemoveFromMempool(stage, updateDescendants);
    for (txiter it : stage) {
        removeUnchecked(it, reason);
    }
}

int CTxMemPool::Expire(std::chrono::seconds time) {
    AssertLockHeld(cs);
    indexed_transaction_set::index<entry_time>::type::iterator it =
        mapTx.get<entry_time>().begin();
    setEntries toremove;
    while (it != mapTx.get<entry_time>().end() && it->GetTime() < time) {
        toremove.insert(mapTx.project<0>(it));
        it++;
    }

    setEntries stage;
    for (txiter removeit : toremove) {
        CalculateDescendants(removeit, stage);
    }

    RemoveStaged(stage, false, MemPoolRemovalReason::EXPIRY);
    return stage.size();
}

void CTxMemPool::LimitSize(size_t limit, std::chrono::seconds age) {
    int expired = Expire(GetTime<std::chrono::seconds>() - age);
    if (expired != 0) {
        LogPrint(BCLog::MEMPOOL,
                 "Expired %i transactions from the memory pool\n", expired);
    }

    std::vector<COutPoint> vNoSpendsRemaining;
    TrimToSize(limit, &vNoSpendsRemaining);
    for (const COutPoint &removed : vNoSpendsRemaining) {
        ::ChainstateActive().CoinsTip().Uncache(removed);
    }
}

void CTxMemPool::addUnchecked(const CTxMemPoolEntry &entry) {
    setEntries setAncestors;
    uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
    std::string dummy;
    CalculateMemPoolAncestors(entry, setAncestors, nNoLimit, nNoLimit, nNoLimit,
                              nNoLimit, dummy);
    return addUnchecked(entry, setAncestors);
}

void CTxMemPool::UpdateChild(txiter entry, txiter child, bool add) {
    setEntries s;
    if (add && mapLinks[entry].children.insert(child).second) {
        cachedInnerUsage += memusage::IncrementalDynamicUsage(s);
    } else if (!add && mapLinks[entry].children.erase(child)) {
        cachedInnerUsage -= memusage::IncrementalDynamicUsage(s);
    }
}

void CTxMemPool::UpdateParent(txiter entry, txiter parent, bool add) {
    setEntries s;
    if (add && mapLinks[entry].parents.insert(parent).second) {
        cachedInnerUsage += memusage::IncrementalDynamicUsage(s);
    } else if (!add && mapLinks[entry].parents.erase(parent)) {
        cachedInnerUsage -= memusage::IncrementalDynamicUsage(s);
    }
}

const CTxMemPool::setEntries &
CTxMemPool::GetMemPoolParents(txiter entry) const {
    assert(entry != mapTx.end());
    txlinksMap::const_iterator it = mapLinks.find(entry);
    assert(it != mapLinks.end());
    return it->second.parents;
}

const CTxMemPool::setEntries &
CTxMemPool::GetMemPoolChildren(txiter entry) const {
    assert(entry != mapTx.end());
    txlinksMap::const_iterator it = mapLinks.find(entry);
    assert(it != mapLinks.end());
    return it->second.children;
}

CFeeRate CTxMemPool::GetMinFee(size_t sizelimit) const {
    LOCK(cs);
    if (!blockSinceLastRollingFeeBump || rollingMinimumFeeRate == 0) {
        return CFeeRate(int64_t(ceill(rollingMinimumFeeRate)) * SATOSHI);
    }

    int64_t time = GetTime();
    if (time > lastRollingFeeUpdate + 10) {
        double halflife = ROLLING_FEE_HALFLIFE;
        if (DynamicMemoryUsage() < sizelimit / 4) {
            halflife /= 4;
        } else if (DynamicMemoryUsage() < sizelimit / 2) {
            halflife /= 2;
        }

        rollingMinimumFeeRate =
            rollingMinimumFeeRate /
            pow(2.0, (time - lastRollingFeeUpdate) / halflife);
        lastRollingFeeUpdate = time;
    }
    return CFeeRate(int64_t(ceill(rollingMinimumFeeRate)) * SATOSHI);
}

void CTxMemPool::trackPackageRemoved(const CFeeRate &rate) {
    AssertLockHeld(cs);
    if ((rate.GetFeePerK() / SATOSHI) > rollingMinimumFeeRate) {
        rollingMinimumFeeRate = rate.GetFeePerK() / SATOSHI;
        blockSinceLastRollingFeeBump = false;
    }
}

void CTxMemPool::TrimToSize(size_t sizelimit,
                            std::vector<COutPoint> *pvNoSpendsRemaining) {
    AssertLockHeld(cs);

    unsigned nTxnRemoved = 0;
    CFeeRate maxFeeRateRemoved(Amount::zero());
    while (!mapTx.empty() && DynamicMemoryUsage() > sizelimit) {
        indexed_transaction_set::index<descendant_score>::type::iterator it =
            mapTx.get<descendant_score>().begin();

        // We set the new mempool min fee to the feerate of the removed set,
        // plus the "minimum reasonable fee rate" (ie some value under which we
        // consider txn to have 0 fee). This way, we don't allow txn to enter
        // mempool with feerate equal to txn which were removed with no block in
        // between.
        CFeeRate removed(it->GetModFeesWithDescendants(),
                         it->GetVirtualSizeWithDescendants());
        removed += MEMPOOL_FULL_FEE_INCREMENT;

        trackPackageRemoved(removed);
        maxFeeRateRemoved = std::max(maxFeeRateRemoved, removed);

        setEntries stage;
        CalculateDescendants(mapTx.project<0>(it), stage);
        nTxnRemoved += stage.size();

        std::vector<CTransaction> txn;
        if (pvNoSpendsRemaining) {
            txn.reserve(stage.size());
            for (txiter iter : stage) {
                txn.push_back(iter->GetTx());
            }
        }
        RemoveStaged(stage, false, MemPoolRemovalReason::SIZELIMIT);
        if (pvNoSpendsRemaining) {
            for (const CTransaction &tx : txn) {
                for (const CTxIn &txin : tx.vin) {
                    if (exists(txin.prevout.GetTxId())) {
                        continue;
                    }
                    pvNoSpendsRemaining->push_back(txin.prevout);
                }
            }
        }
    }

    if (maxFeeRateRemoved > CFeeRate(Amount::zero())) {
        LogPrint(BCLog::MEMPOOL,
                 "Removed %u txn, rolling minimum fee bumped to %s\n",
                 nTxnRemoved, maxFeeRateRemoved.ToString());
    }
}

uint64_t CTxMemPool::CalculateDescendantMaximum(txiter entry) const {
    // find parent with highest descendant count
    std::vector<txiter> candidates;
    setEntries counted;
    candidates.push_back(entry);
    uint64_t maximum = 0;
    while (candidates.size()) {
        txiter candidate = candidates.back();
        candidates.pop_back();
        if (!counted.insert(candidate).second) {
            continue;
        }
        const setEntries &parents = GetMemPoolParents(candidate);
        if (parents.size() == 0) {
            maximum = std::max(maximum, candidate->GetCountWithDescendants());
        } else {
            for (txiter i : parents) {
                candidates.push_back(i);
            }
        }
    }
    return maximum;
}

void CTxMemPool::GetTransactionAncestry(const TxId &txid, size_t &ancestors,
                                        size_t &descendants) const {
    LOCK(cs);
    auto it = mapTx.find(txid);
    ancestors = descendants = 0;
    if (it != mapTx.end()) {
        ancestors = it->GetCountWithAncestors();
        descendants = CalculateDescendantMaximum(it);
    }
}

bool CTxMemPool::IsLoaded() const {
    LOCK(cs);
    return m_is_loaded;
}

void CTxMemPool::SetIsLoaded(bool loaded) {
    LOCK(cs);
    m_is_loaded = loaded;
}

static const size_t MAX_DISCONNECTED_TX_POOL_SIZE = 20 * DEFAULT_MAX_BLOCK_SIZE;

void DisconnectedBlockTransactions::addForBlock(
    const std::vector<CTransactionRef> &vtx, CTxMemPool &pool) {
    AssertLockHeld(pool.cs);
    for (const auto &tx : reverse_iterate(vtx)) {
        // If we already added it, just skip.
        auto it = queuedTx.find(tx->GetId());
        if (it != queuedTx.end()) {
            continue;
        }

        // Insert the transaction into the pool.
        addTransaction(tx);

        // Fill in the set of parents.
        std::unordered_set<TxId, SaltedTxIdHasher> parents;
        for (const CTxIn &in : tx->vin) {
            parents.insert(in.prevout.GetTxId());
        }

        // In order to make sure we keep things in topological order, we check
        // if we already know of the parent of the current transaction. If so,
        // we remove them from the set and then add them back.
        while (parents.size() > 0) {
            std::unordered_set<TxId, SaltedTxIdHasher> worklist(
                std::move(parents));
            parents.clear();

            for (const TxId &txid : worklist) {
                // If we do not have that txid in the set, nothing needs to be
                // done.
                auto pit = queuedTx.find(txid);
                if (pit == queuedTx.end()) {
                    continue;
                }

                // We have parent in our set, we reinsert them at the right
                // position.
                const CTransactionRef ptx = *pit;
                queuedTx.erase(pit);
                queuedTx.insert(ptx);

                // And we make sure ancestors are covered.
                for (const CTxIn &in : ptx->vin) {
                    parents.insert(in.prevout.GetTxId());
                }
            }
        }
    }

    // Keep the size under control.
    while (DynamicMemoryUsage() > MAX_DISCONNECTED_TX_POOL_SIZE) {
        // Drop the earliest entry, and remove its children from the
        // mempool.
        auto it = queuedTx.get<insertion_order>().begin();
        pool.removeRecursive(**it, MemPoolRemovalReason::REORG);
        removeEntry(it);
    }
}

void DisconnectedBlockTransactions::importMempool(CTxMemPool &pool) {
    AssertLockHeld(pool.cs);
    // addForBlock's algorithm sorts a vector of transactions back into
    // topological order. We use it in a separate object to create a valid
    // ordering of all mempool transactions, which we then splice in front of
    // the current queuedTx. This results in a valid sequence of transactions to
    // be reprocessed in updateMempoolForReorg.

    // We create vtx in order of the entry_time index to facilitate for
    // addForBlocks (which iterates in reverse order), as vtx probably end in
    // the correct ordering for queuedTx.
    std::vector<CTransactionRef> vtx;

    vtx.reserve(pool.mapTx.size());
    for (const CTxMemPoolEntry &e : pool.mapTx.get<entry_time>()) {
        vtx.push_back(e.GetSharedTx());
    }
    pool.clear();

    // Use addForBlocks to sort the transactions and then splice them in front
    // of queuedTx
    DisconnectedBlockTransactions orderedTxnPool;
    orderedTxnPool.addForBlock(vtx, pool);
    cachedInnerUsage += orderedTxnPool.cachedInnerUsage;
    queuedTx.get<insertion_order>().splice(
        queuedTx.get<insertion_order>().begin(),
        orderedTxnPool.queuedTx.get<insertion_order>());

    // We limit memory usage because we can't know if more blocks will be
    // disconnected
    while (DynamicMemoryUsage() > MAX_DISCONNECTED_TX_POOL_SIZE) {
        // Drop the earliest entry which, by definition, has no children
        removeEntry(queuedTx.get<insertion_order>().begin());
    }
}

void DisconnectedBlockTransactions::updateMempoolForReorg(const Config &config,
                                                          bool fAddToMempool,
                                                          CTxMemPool &pool) {
    AssertLockHeld(cs_main);
    AssertLockHeld(pool.cs);
    std::vector<TxId> txidsUpdate;

    // disconnectpool's insertion_order index sorts the entries from oldest to
    // newest, but the oldest entry will be the last tx from the latest mined
    // block that was disconnected.
    // Iterate disconnectpool in reverse, so that we add transactions back to
    // the mempool starting with the earliest transaction that had been
    // previously seen in a block.
    for (const CTransactionRef &tx :
         reverse_iterate(queuedTx.get<insertion_order>())) {
        // ignore validation errors in resurrected transactions
        TxValidationState stateDummy;
        if (!fAddToMempool || tx->IsCoinBase() ||
            !AcceptToMemoryPool(config, pool, stateDummy, tx,
                                true /* bypass_limits */,
                                Amount::zero() /* nAbsurdFee */)) {
            // If the transaction doesn't make it in to the mempool, remove any
            // transactions that depend on it (which would now be orphans).
            pool.removeRecursive(*tx, MemPoolRemovalReason::REORG);
        } else if (pool.exists(tx->GetId())) {
            txidsUpdate.push_back(tx->GetId());
        }
    }

    queuedTx.clear();

    // AcceptToMemoryPool/addUnchecked all assume that new mempool entries have
    // no in-mempool children, which is generally not true when adding
    // previously-confirmed transactions back to the mempool.
    // UpdateTransactionsFromBlock finds descendants of any transactions in the
    // disconnectpool that were added back and cleans up the mempool state.
    pool.UpdateTransactionsFromBlock(txidsUpdate);

    // We also need to remove any now-immature transactions
    pool.removeForReorg(config, &::ChainstateActive().CoinsTip(),
                        ::ChainActive().Tip()->nHeight + 1,
                        STANDARD_LOCKTIME_VERIFY_FLAGS);

    // Re-limit mempool size, in case we added any transactions
    pool.LimitSize(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) *
                       1000000,
                   std::chrono::hours{
                       gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY)});
}

CTxMemPool::EpochGuard CTxMemPool::GetFreshEpoch() const {
    return EpochGuard(*this);
}

CTxMemPool::EpochGuard::EpochGuard(const CTxMemPool &in) : pool(in) {
    assert(!pool.m_has_epoch_guard);
    ++pool.m_epoch;
    pool.m_has_epoch_guard = true;
}

CTxMemPool::EpochGuard::~EpochGuard() {
    // prevents stale results being used
    ++pool.m_epoch;
    pool.m_has_epoch_guard = false;
}