tx pool: Use class methods to hide raw map iterator impl details

src/txmempool.cpp

@@ -156,9 +156,9 @@ bool CTxMemPool::CalculateMemPoolAncestors(const CTxMemPoolEntry &entry, setEntr
         // GetMemPoolParents() is only valid for entries in the mempool, so we
         // iterate mapTx to find parents.
         for (unsigned int i = 0; i < tx.vin.size(); i++) {
-            txiter piter = mapTx.find(tx.vin[i].prevout.hash);
+            boost::optional<txiter> piter = GetIter(tx.vin[i].prevout.hash);
-            if (piter != mapTx.end()) {
+            if (piter) {
-                parentHashes.insert(piter);
+                parentHashes.insert(*piter);
                 if (parentHashes.size() + 1 > limitAncestorCount) {
                     errString = strprintf("too many unconfirmed parents [limit: %u]", limitAncestorCount);
                     return false;
@@ -364,13 +364,11 @@ void CTxMemPool::addUnchecked(const CTxMemPoolEntry &entry, setEntries &setAnces
     // Update transaction for any feeDelta created by PrioritiseTransaction
     // TODO: refactor so that the fee delta is calculated before inserting
     // into mapTx.
-    std::map<uint256, CAmount>::const_iterator pos = mapDeltas.find(entry.GetTx().GetHash());
+    CAmount delta{0};
-    if (pos != mapDeltas.end()) {
+    ApplyDelta(entry.GetTx().GetHash(), delta);
-        const CAmount &delta = pos->second;
     if (delta) {
             mapTx.modify(newit, update_fee_delta(delta));
     }
-    }
 
     // Update cachedInnerUsage to include contained transaction's usage.
     // (When we update the entry for in-mempool parents, memory usage will be
@@ -391,12 +389,9 @@ void CTxMemPool::addUnchecked(const CTxMemPoolEntry &entry, setEntries &setAnces
     // to clean up the mess we're leaving here.
 
     // Update ancestors with information about this tx
-    for (const uint256 &phash : setParentTransactions) {
+    for (const auto& pit : GetIterSet(setParentTransactions)) {
-        txiter pit = mapTx.find(phash);
-        if (pit != mapTx.end()) {
             UpdateParent(newit, pit, true);
     }
-    }
     UpdateAncestorsOf(true, newit, setAncestors);
     UpdateEntryForAncestors(newit, setAncestors);
 
@@ -864,6 +859,29 @@ void CTxMemPool::ClearPrioritisation(const uint256 hash)
     mapDeltas.erase(hash);
 }
 
+const CTransaction* CTxMemPool::GetConflictTx(const COutPoint& prevout) const
+{
+    const auto it = mapNextTx.find(prevout);
+    return it == mapNextTx.end() ? nullptr : it->second;
+}
+
+boost::optional<CTxMemPool::txiter> CTxMemPool::GetIter(const uint256& txid) const
+{
+    auto it = mapTx.find(txid);
+    if (it != mapTx.end()) return it;
+    return boost::optional<txiter>{};
+}
+
+CTxMemPool::setEntries CTxMemPool::GetIterSet(const std::set<uint256>& hashes) const
+{
+    CTxMemPool::setEntries ret;
+    for (const auto& h : hashes) {
+        const auto mi = GetIter(h);
+        if (mi) ret.insert(*mi);
+    }
+    return ret;
+}
+
 bool CTxMemPool::HasNoInputsOf(const CTransaction &tx) const
 {
     for (unsigned int i = 0; i < tx.vin.size(); i++)

src/txmempool.h

@@ -566,7 +566,15 @@ public:
     void ApplyDelta(const uint256 hash, CAmount &nFeeDelta) const;
     void ClearPrioritisation(const uint256 hash);
 
-public:
+    /** Get the transaction in the pool that spends the same prevout */
+    const CTransaction* GetConflictTx(const COutPoint& prevout) const EXCLUSIVE_LOCKS_REQUIRED(cs);
+
+    /** Returns an iterator to the given hash, if found */
+    boost::optional<txiter> GetIter(const uint256& txid) const EXCLUSIVE_LOCKS_REQUIRED(cs);
+
+    /** Translate a set of hashes into a set of pool iterators to avoid repeated lookups */
+    setEntries GetIterSet(const std::set<uint256>& hashes) const EXCLUSIVE_LOCKS_REQUIRED(cs);
+
     /** Remove a set of transactions from the mempool.
      *  If a transaction is in this set, then all in-mempool descendants must
      *  also be in the set, unless this transaction is being removed for being
@@ -639,7 +647,7 @@ public:
         return totalTxSize;
     }
 
-    bool exists(uint256 hash) const
+    bool exists(const uint256& hash) const
     {
         LOCK(cs);
         return (mapTx.count(hash) != 0);

src/validation.cpp

@@ -602,10 +602,8 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
     std::set<uint256> setConflicts;
     for (const CTxIn &txin : tx.vin)
     {
-        auto itConflicting = pool.mapNextTx.find(txin.prevout);
+        const CTransaction* ptxConflicting = pool.GetConflictTx(txin.prevout);
-        if (itConflicting != pool.mapNextTx.end())
+        if (ptxConflicting) {
-        {
-            const CTransaction *ptxConflicting = itConflicting->second;
             if (!setConflicts.count(ptxConflicting->GetHash()))
             {
                 // Allow opt-out of transaction replacement by setting
@@ -786,16 +784,8 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
             CFeeRate newFeeRate(nModifiedFees, nSize);
             std::set<uint256> setConflictsParents;
             const int maxDescendantsToVisit = 100;
-            CTxMemPool::setEntries setIterConflicting;
+            const CTxMemPool::setEntries setIterConflicting = pool.GetIterSet(setConflicts);
-            for (const uint256 &hashConflicting : setConflicts)
+            for (const auto& mi : setIterConflicting) {
-            {
-                CTxMemPool::txiter mi = pool.mapTx.find(hashConflicting);
-                if (mi == pool.mapTx.end())
-                    continue;
-
-                // Save these to avoid repeated lookups
-                setIterConflicting.insert(mi);
-
                 // Don't allow the replacement to reduce the feerate of the
                 // mempool.
                 //
@@ -861,13 +851,14 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
                     // Rather than check the UTXO set - potentially expensive -
                     // it's cheaper to just check if the new input refers to a
                     // tx that's in the mempool.
-                    if (pool.mapTx.find(tx.vin[j].prevout.hash) != pool.mapTx.end())
+                    if (pool.exists(tx.vin[j].prevout.hash)) {
                         return state.DoS(0, false,
                                          REJECT_NONSTANDARD, "replacement-adds-unconfirmed", false,
                                          strprintf("replacement %s adds unconfirmed input, idx %d",
                                                   hash.ToString(), j));
                     }
                 }
+            }
 
             // The replacement must pay greater fees than the transactions it
             // replaces - if we did the bandwidth used by those conflicting