refactor(cache): migrate unordered_lru_cache::get to return std::optional

Change unordered_lru_cache::get() from returning bool with an output
parameter to returning std::optional<Value> by value. This provides a
more modern API that is easier to use and less error-prone.

- Add <optional> header to unordered_lru_cache.h
- Update get() signature: bool get(key, Value&) -> std::optional<Value> get(key)
- Update all 21 call sites across 11 files to use the new API
- Maintain same copy semantics for performance (no performance impact)

Files updated:
- src/unordered_lru_cache.h
- src/llmq/quorums.cpp (5 call sites)
- src/llmq/utils.cpp (2 call sites)
- src/llmq/snapshot.cpp, signing.cpp, dkgsessionmgr.cpp, blockprocessor.cpp
- src/instantsend/db.cpp (3 call sites)
- src/evo/mnhftx.cpp, creditpool.cpp, cbtx.cpp
- src/masternode/meta.cpp

Author: PastaPastaPasta

src/evo/cbtx.cpp

@@ -86,7 +86,9 @@ auto CachedGetQcHashesQcIndexedHashes(const CBlockIndex* pindexPrev, const llmq:
             uint256 block_hash{blockIndex->GetBlockHash()};
 
             std::pair<uint256, int> qc_hash;
-            if (!qc_hashes_cached[llmqType].get(block_hash, qc_hash)) {
+            if (auto cached = qc_hashes_cached[llmqType].get(block_hash)) {
+                qc_hash = *cached;
+            } else {
                 auto [pqc, dummy_hash] = quorum_block_processor.GetMinedCommitment(llmqType, block_hash);
                 if (dummy_hash == uint256::ZERO) {
                     // this should never happen

src/evo/creditpool.cpp

@@ -70,8 +70,8 @@ static std::optional<CreditPoolDataPerBlock> GetCreditDataFromBlock(const gsl::n
     static Mutex cache_mutex;
     static Uint256LruHashMap<CreditPoolDataPerBlock> block_data_cache GUARDED_BY(cache_mutex){
         static_cast<size_t>(Params().CreditPoolPeriodBlocks()) * 2};
-    if (LOCK(cache_mutex); block_data_cache.get(block_index->GetBlockHash(), blockData)) {
-        return blockData;
+    if (LOCK(cache_mutex); auto cached = block_data_cache.get(block_index->GetBlockHash())) {
+        return *cached;
     }
 
     CBlock block;
@@ -123,8 +123,8 @@ std::optional<CCreditPool> CCreditPoolManager::GetFromCache(const CBlockIndex& b
     CCreditPool pool;
     {
         LOCK(cache_mutex);
-        if (creditPoolCache.get(block_hash, pool)) {
-            return pool;
+        if (auto cached = creditPoolCache.get(block_hash)) {
+            return *cached;
         }
     }
     if (block_index.nHeight % DISK_SNAPSHOT_PERIOD == 0) {

src/evo/mnhftx.cpp

@@ -325,8 +325,8 @@ std::optional<CMNHFManager::Signals> CMNHFManager::GetFromCache(const CBlockInde
     const uint256& blockHash = pindex->GetBlockHash();
     {
         LOCK(cs_cache);
-        if (mnhfCache.get(blockHash, signals)) {
-            return signals;
+        if (auto cached = mnhfCache.get(blockHash)) {
+            return *cached;
         }
     }
     {

src/instantsend/db.cpp

@@ -271,11 +271,14 @@ InstantSendLockPtr CInstantSendDb::GetInstantSendLockByHashInternal(const uint25
         return nullptr;
     }
 
-    InstantSendLockPtr ret;
-    if (use_cache && islockCache.get(hash, ret)) {
-        return ret;
+    if (use_cache) {
+        if (auto cached = islockCache.get(hash)) {
+            return *cached;
+        }
     }
 
+    InstantSendLockPtr ret;
+
     ret = std::make_shared<InstantSendLock>();
     bool exists = db->Read(std::make_tuple(DB_ISLOCK_BY_HASH, hash), *ret);
     if (!exists || (::SerializeHash(*ret) != hash)) {
@@ -292,13 +295,14 @@ InstantSendLockPtr CInstantSendDb::GetInstantSendLockByHashInternal(const uint25
 uint256 CInstantSendDb::GetInstantSendLockHashByTxidInternal(const uint256& txid) const
 {
     AssertLockHeld(cs_db);
+    if (auto cached = txidCache.get(txid)) {
+        return *cached;
+    }
     uint256 islockHash;
-    if (!txidCache.get(txid, islockHash)) {
-        if (!db->Read(std::make_tuple(DB_HASH_BY_TXID, txid), islockHash)) {
-            return {};
-        }
-        txidCache.insert(txid, islockHash);
+    if (!db->Read(std::make_tuple(DB_HASH_BY_TXID, txid), islockHash)) {
+        return {};
     }
+    txidCache.insert(txid, islockHash);
     return islockHash;
 }
 
@@ -311,13 +315,14 @@ InstantSendLockPtr CInstantSendDb::GetInstantSendLockByTxid(const uint256& txid)
 InstantSendLockPtr CInstantSendDb::GetInstantSendLockByInput(const COutPoint& outpoint) const
 {
     LOCK(cs_db);
+    if (auto cached = outpointCache.get(outpoint)) {
+        return GetInstantSendLockByHashInternal(*cached);
+    }
     uint256 islockHash;
-    if (!outpointCache.get(outpoint, islockHash)) {
-        if (!db->Read(std::make_tuple(DB_HASH_BY_OUTPOINT, outpoint), islockHash)) {
-            return nullptr;
-        }
-        outpointCache.insert(outpoint, islockHash);
+    if (!db->Read(std::make_tuple(DB_HASH_BY_OUTPOINT, outpoint), islockHash)) {
+        return nullptr;
     }
+    outpointCache.insert(outpoint, islockHash);
     return GetInstantSendLockByHashInternal(islockHash);
 }
 

src/llmq/blockprocessor.cpp

@@ -513,11 +513,12 @@ uint256 CQuorumBlockProcessor::GetQuorumBlockHash(const Consensus::LLMQParams& l
 
 bool CQuorumBlockProcessor::HasMinedCommitment(Consensus::LLMQType llmqType, const uint256& quorumHash) const
 {
-    bool fExists;
-    if (LOCK(minableCommitmentsCs); mapHasMinedCommitmentCache[llmqType].get(quorumHash, fExists)) {
-        return fExists;
+    if (LOCK(minableCommitmentsCs); auto cached = mapHasMinedCommitmentCache[llmqType].get(quorumHash)) {
+        return *cached;
     }
 
+    bool fExists;
+
     fExists = m_evoDb.Exists(std::make_pair(DB_MINED_COMMITMENT, std::make_pair(llmqType, quorumHash)));
 
     LOCK(minableCommitmentsCs);

src/llmq/dkgsessionmgr.cpp

@@ -149,7 +149,9 @@ MessageProcessingResult CDKGSessionManager::ProcessMessage(CNode& pfrom, bool is
         if (indexedQuorumsCache.empty()) {
             utils::InitQuorumsCache(indexedQuorumsCache);
         }
-        indexedQuorumsCache[llmqType].get(quorumHash, quorumIndex);
+        if (auto cached = indexedQuorumsCache[llmqType].get(quorumHash)) {
+            quorumIndex = *cached;
+        }
     }
 
     // No luck, try to compute

src/llmq/quorums.cpp

@@ -571,8 +571,8 @@ std::vector<CQuorumCPtr> CQuorumManager::ScanQuorums(Consensus::LLMQType llmqTyp
             }
         }
         auto& cache = scanQuorumsCache[llmqType];
-        bool fCacheExists = cache.get(pindexStore->GetBlockHash(), vecResultQuorums);
-        if (fCacheExists) {
+        if (auto cached = cache.get(pindexStore->GetBlockHash())) {
+            vecResultQuorums = *cached;
             // We have exactly what requested so just return it
             if (vecResultQuorums.size() == nCountRequested) {
                 return vecResultQuorums;
@@ -642,12 +642,15 @@ CQuorumCPtr CQuorumManager::GetQuorum(Consensus::LLMQType llmqType, const uint25
         // We cannot hold cs_quorumBaseBlockIndexCache the whole time as that creates lock-order inversion with cs_main;
         // We cannot acquire cs_main if we have cs_quorumBaseBlockIndexCache held
         const CBlockIndex* pindex;
-        if (!WITH_LOCK(cs_quorumBaseBlockIndexCache, return quorumBaseBlockIndexCache.get(quorumHash, pindex))) {
+        auto cached = WITH_LOCK(cs_quorumBaseBlockIndexCache, return quorumBaseBlockIndexCache.get(quorumHash));
+        if (!cached.has_value()) {
             pindex = WITH_LOCK(::cs_main, return m_chainstate.m_blockman.LookupBlockIndex(quorumHash));
             if (pindex) {
                 LOCK(cs_quorumBaseBlockIndexCache);
                 quorumBaseBlockIndexCache.insert(quorumHash, pindex);
             }
+        } else {
+            pindex = *cached;
         }
         return pindex;
     }();
@@ -668,9 +671,8 @@ CQuorumCPtr CQuorumManager::GetQuorum(Consensus::LLMQType llmqType, gsl::not_nul
         return nullptr;
     }
 
-    CQuorumPtr pQuorum;
-    if (LOCK(cs_map_quorums); mapQuorumsCache[llmqType].get(quorumHash, pQuorum)) {
-        return pQuorum;
+    if (LOCK(cs_map_quorums); auto cached = mapQuorumsCache[llmqType].get(quorumHash)) {
+        return *cached;
     }
 
     return BuildQuorumFromCommitment(llmqType, pQuorumBaseBlockIndex, populate_cache);
@@ -833,9 +835,12 @@ MessageProcessingResult CQuorumManager::ProcessMessage(CNode& pfrom, CConnman& c
 
         CQuorumPtr pQuorum;
         {
-            if (LOCK(cs_map_quorums); !mapQuorumsCache[request.GetLLMQType()].get(request.GetQuorumHash(), pQuorum)) {
+            LOCK(cs_map_quorums);
+            auto cached = mapQuorumsCache[request.GetLLMQType()].get(request.GetQuorumHash());
+            if (!cached.has_value()) {
                 return errorHandler("Quorum not found", 0); // Don't bump score because we asked for it
             }
+            pQuorum = *cached;
         }
 
         // Check if request has QUORUM_VERIFICATION_VECTOR data
@@ -1118,9 +1123,8 @@ void CQuorumManager::StartCleanupOldQuorumDataThread(const CBlockIndex* pIndex)
             const CBlockIndex* pindex_loop{pIndex};
             std::set<uint256> quorum_keys;
             while (pindex_loop != nullptr && pIndex->nHeight - pindex_loop->nHeight < params.max_store_depth()) {
-                uint256 quorum_key;
-                if (cache.get(pindex_loop->GetBlockHash(), quorum_key)) {
-                    quorum_keys.insert(quorum_key);
+                if (auto quorum_key = cache.get(pindex_loop->GetBlockHash())) {
+                    quorum_keys.insert(*quorum_key);
                     if (quorum_keys.size() >= static_cast<size_t>(params.keepOldKeys)) break; // extra safety belt
                 }
                 pindex_loop = pindex_loop->pprev;

src/llmq/signing.cpp

@@ -43,17 +43,16 @@ bool CRecoveredSigsDb::HasRecoveredSig(Consensus::LLMQType llmqType, const uint2
 bool CRecoveredSigsDb::HasRecoveredSigForId(Consensus::LLMQType llmqType, const uint256& id) const
 {
     auto cacheKey = std::make_pair(llmqType, id);
-    bool ret;
     {
         LOCK(cs_cache);
-        if (hasSigForIdCache.get(cacheKey, ret)) {
-            return ret;
+        if (auto cached = hasSigForIdCache.get(cacheKey)) {
+            return *cached;
         }
     }
 
 
     auto k = std::make_tuple(std::string("rs_r"), llmqType, id);
-    ret = db->Exists(k);
+    bool ret = db->Exists(k);
 
     LOCK(cs_cache);
     hasSigForIdCache.insert(cacheKey, ret);
@@ -62,16 +61,15 @@ bool CRecoveredSigsDb::HasRecoveredSigForId(Consensus::LLMQType llmqType, const
 
 bool CRecoveredSigsDb::HasRecoveredSigForSession(const uint256& signHash) const
 {
-    bool ret;
     {
         LOCK(cs_cache);
-        if (hasSigForSessionCache.get(signHash, ret)) {
-            return ret;
+        if (auto cached = hasSigForSessionCache.get(signHash)) {
+            return *cached;
         }
     }
 
     auto k = std::make_tuple(std::string("rs_s"), signHash);
-    ret = db->Exists(k);
+    bool ret = db->Exists(k);
 
     LOCK(cs_cache);
     hasSigForSessionCache.insert(signHash, ret);
@@ -80,16 +78,15 @@ bool CRecoveredSigsDb::HasRecoveredSigForSession(const uint256& signHash) const
 
 bool CRecoveredSigsDb::HasRecoveredSigForHash(const uint256& hash) const
 {
-    bool ret;
     {
         LOCK(cs_cache);
-        if (hasSigForHashCache.get(hash, ret)) {
-            return ret;
+        if (auto cached = hasSigForHashCache.get(hash)) {
+            return *cached;
         }
     }
 
     auto k = std::make_tuple(std::string("rs_h"), hash);
-    ret = db->Exists(k);
+    bool ret = db->Exists(k);
 
     LOCK(cs_cache);
     hasSigForHashCache.insert(hash, ret);

src/llmq/snapshot.cpp

@@ -352,8 +352,8 @@ std::optional<CQuorumSnapshot> CQuorumSnapshotManager::GetSnapshotForBlock(const
 
     LOCK(snapshotCacheCs);
     // try using cache before reading from disk
-    if (quorumSnapshotCache.get(snapshotHash, snapshot)) {
-        return snapshot;
+    if (auto cached = quorumSnapshotCache.get(snapshotHash)) {
+        return *cached;
     }
     if (m_evoDb.Read(std::make_pair(DB_QUORUM_SNAPSHOT, snapshotHash), snapshot)) {
         quorumSnapshotCache.insert(snapshotHash, snapshot);

src/llmq/utils.cpp

@@ -215,8 +215,8 @@ std::vector<CDeterministicMNCPtr> GetAllQuorumMembers(Consensus::LLMQType llmqTy
         }
         if (reset_cache) {
             mapQuorumMembers[llmqType].clear();
-        } else if (mapQuorumMembers[llmqType].get(pQuorumBaseBlockIndex->GetBlockHash(), quorumMembers)) {
-            return quorumMembers;
+        } else if (auto cached = mapQuorumMembers[llmqType].get(pQuorumBaseBlockIndex->GetBlockHash())) {
+            return *cached;
         }
     }
 
@@ -251,7 +251,8 @@ std::vector<CDeterministicMNCPtr> GetAllQuorumMembers(Consensus::LLMQType llmqTy
         if (reset_cache) {
             LOCK(cs_indexed_members);
             mapIndexedQuorumMembers[llmqType].clear();
-        } else if (LOCK(cs_indexed_members); mapIndexedQuorumMembers[llmqType].get(std::pair(pCycleQuorumBaseBlockIndex->GetBlockHash(), quorumIndex), quorumMembers)) {
+        } else if (LOCK(cs_indexed_members); auto cached = mapIndexedQuorumMembers[llmqType].get(std::pair(pCycleQuorumBaseBlockIndex->GetBlockHash(), quorumIndex))) {
+            quorumMembers = *cached;
             LOCK(cs_members);
             mapQuorumMembers[llmqType].insert(pQuorumBaseBlockIndex->GetBlockHash(), quorumMembers);
             return quorumMembers;