Add snapshot support tested in poolpair RPC

src/dbwrapper.h

@@ -22,6 +22,8 @@ static const std::string DEFAULT_LEVELDB_CHECKSUM = "auto";
 
 extern bool levelDBChecksum;
 
+class CStorageSnapshot;
+
 class dbwrapper_error : public std::runtime_error
 {
 public:
@@ -263,15 +265,20 @@ class CDBWrapper
 
     template <typename K, typename V>
     bool Read(const K& key, V& value) const
+    {
+        return Read(key, value, readoptions);
+    }
+
+    template <typename K, typename V>
+    bool Read(const K& key, V& value, const leveldb::ReadOptions &otherOptions) const
     {
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
         leveldb::Slice slKey(ssKey.data(), ssKey.size());
-//        leveldb::Slice slKey(SliceKey(key));
 
         std::string strValue;
-        leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
+        leveldb::Status status = pdb->Get(otherOptions, slKey, &strValue);
         if (!status.ok()) {
             if (status.IsNotFound())
                 return false;
@@ -297,16 +304,20 @@ class CDBWrapper
     }
 
     template <typename K>
-    bool Exists(const K& key) const
+    bool Exists(const K& key) const {
+        return Exists(key, readoptions);
+    }
+
+    template <typename K>
+    bool Exists(const K& key, const leveldb::ReadOptions &otherOptions) const
     {
         CDataStream ssKey(SER_DISK, CLIENT_VERSION);
         ssKey.reserve(DBWRAPPER_PREALLOC_KEY_SIZE);
         ssKey << key;
         leveldb::Slice slKey(ssKey.data(), ssKey.size());
-//        leveldb::Slice slKey(SliceKey(key));
 
         std::string strValue;
-        leveldb::Status status = pdb->Get(readoptions, slKey, &strValue);
+        leveldb::Status status = pdb->Get(otherOptions, slKey, &strValue);
         if (!status.ok()) {
             if (status.IsNotFound())
                 return false;
@@ -343,7 +354,16 @@ class CDBWrapper
 
     CDBIterator *NewIterator()
     {
-        return new CDBIterator(*this, pdb->NewIterator(iteroptions));
+        return NewIterator(readoptions);
+    }
+
+    CDBIterator *NewIterator(const leveldb::ReadOptions &readOptions)
+    {
+        return new CDBIterator(*this, pdb->NewIterator(readOptions));
+    }
+
+    [[nodiscard]] std::shared_ptr<CStorageSnapshot> GetStorageSnapshot() const {
+        return std::make_shared<CStorageSnapshot>(pdb);
     }
 
     /**
@@ -384,4 +404,30 @@ class CDBWrapper
     }
 };
 
+
+class CStorageSnapshot {
+public:
+    explicit CStorageSnapshot(leveldb::DB* db) : db(db) {
+        snapshot = db->GetSnapshot();
+    }
+
+    ~CStorageSnapshot() {
+        if (db && snapshot) {
+            db->ReleaseSnapshot(snapshot);
+        }
+    }
+
+    [[nodiscard]] const leveldb::Snapshot* GetLevelDBSnapshot() const {
+        return snapshot;
+    }
+
+    CStorageSnapshot(const CStorageSnapshot&) = delete;
+    CStorageSnapshot& operator=(const CStorageSnapshot&) = delete;
+
+private:
+    leveldb::DB* db; // Owned by pcustomcsDB
+    const leveldb::Snapshot* snapshot;
+};
+
+
 #endif // DEFI_DBWRAPPER_H

src/dfi/masternodes.cpp

@@ -782,6 +782,11 @@ CCustomCSView::CCustomCSView(CStorageKV &st)
     CheckPrefixes();
 }
 
+CCustomCSView::CCustomCSView(std::unique_ptr<CStorageLevelDB> &st, const MapKV &changed)
+    : CStorageView(new CFlushableStorageKV(st, changed)) {
+    CheckPrefixes();
+}
+
 // cache-upon-a-cache (not a copy!) constructor
 CCustomCSView::CCustomCSView(CCustomCSView &other)
     : CStorageView(new CFlushableStorageKV(other.DB())),
@@ -1394,3 +1399,11 @@ void CalcMissingRewardTempFix(CCustomCSView &mnview, const uint32_t targetHeight
         }
     }
 }
+
+std::unique_ptr<CCustomCSView> GetViewSnapshot() {
+    // Get database snapshot and flushable storage changed map
+    auto [changed, snapshotDB] = pcustomcsview->GetStorage().GetSnapshotPair();
+
+    // Create new view using snapshot and change map
+    return std::make_unique<CCustomCSView>(snapshotDB, changed);
+}

src/dfi/masternodes.h

@@ -546,10 +546,14 @@ class CCustomCSView : public CMasternodesView,
     // Increase version when underlaying tables are changed
     static constexpr const int DbVersion = 1;
 
+    // Normal constructors
     CCustomCSView();
     explicit CCustomCSView(CStorageKV &st);
 
-    // cache-upon-a-cache (not a copy!) constructor
+    // Snapshot constructor
+    explicit CCustomCSView(std::unique_ptr<CStorageLevelDB> &st, const MapKV &changed);
+
+    // Cache-upon-a-cache constructors
     CCustomCSView(CCustomCSView &other);
     CCustomCSView(CCustomCSView &other,
                   CAccountHistoryStorage *historyView,
@@ -624,6 +628,8 @@ class CCustomCSView : public CMasternodesView,
 
 std::map<CKeyID, CKey> AmISignerNow(int height, const CAnchorData::CTeam &team);
 
+std::unique_ptr<CCustomCSView> GetViewSnapshot();
+
 /** Global DB and view that holds enhanced chainstate data (should be protected by cs_main) */
 extern std::unique_ptr<CStorageLevelDB> pcustomcsDB;
 extern std::unique_ptr<CCustomCSView> pcustomcsview;