Improve LevelDBStore (#3607)

* Improve `LevelDBStore`

* Added `DebuggerTypeProxy`

* Fixed up `null` for debuggerview

* revert `null` check

* Fixed test

* Reverted `DebuggerTypeProxy`

* Added caution comment to dataset classes

src/Plugins/LevelDBStore/IO/Data/LevelDB/DB.cs

@@ -11,7 +11,7 @@
 
 #nullable enable
 
-using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.IO;
 
@@ -20,14 +20,15 @@ namespace Neo.IO.Storage.LevelDB
     /// <summary>
     /// A DB is a persistent ordered map from keys to values.
     /// A DB is safe for concurrent access from multiple threads without any external synchronization.
+    /// <code>Iterating over the whole dataset can be time-consuming. Depending upon how large the dataset is.</code>
     /// </summary>
-    public class DB : LevelDBHandle
+    public class DB : LevelDBHandle, IEnumerable<KeyValuePair<byte[], byte[]>>
     {
-        private DB(IntPtr handle) : base(handle) { }
+        private DB(nint handle) : base(handle) { }
 
         protected override void FreeUnManagedObjects()
         {
-            if (Handle != IntPtr.Zero)
+            if (Handle != nint.Zero)
             {
                 Native.leveldb_close(Handle);
             }
@@ -40,7 +41,7 @@ protected override void FreeUnManagedObjects()
         /// </summary>
         public void Delete(WriteOptions options, byte[] key)
         {
-            Native.leveldb_delete(Handle, options.Handle, key, (UIntPtr)key.Length, out var error);
+            Native.leveldb_delete(Handle, options.Handle, key, (nuint)key.Length, out var error);
             NativeHelper.CheckError(error);
         }
 
@@ -50,24 +51,24 @@ public void Delete(WriteOptions options, byte[] key)
         /// </summary>
         public byte[] Get(ReadOptions options, byte[] key)
         {
-            var value = Native.leveldb_get(Handle, options.Handle, key, (UIntPtr)key.Length, out var length, out var error);
+            var value = Native.leveldb_get(Handle, options.Handle, key, (nuint)key.Length, out var length, out var error);
             try
             {
                 NativeHelper.CheckError(error);
                 return value.ToByteArray(length);
             }
             finally
             {
-                if (value != IntPtr.Zero) Native.leveldb_free(value);
+                if (value != nint.Zero) Native.leveldb_free(value);
             }
         }
 
         public bool Contains(ReadOptions options, byte[] key)
         {
-            var value = Native.leveldb_get(Handle, options.Handle, key, (UIntPtr)key.Length, out _, out var error);
+            var value = Native.leveldb_get(Handle, options.Handle, key, (nuint)key.Length, out _, out var error);
             NativeHelper.CheckError(error);
 
-            if (value != IntPtr.Zero)
+            if (value != nint.Zero)
             {
                 Native.leveldb_free(value);
                 return true;
@@ -76,12 +77,12 @@ public bool Contains(ReadOptions options, byte[] key)
             return false;
         }
 
-        public Snapshot GetSnapshot()
+        public Snapshot CreateSnapshot()
         {
             return new Snapshot(Handle);
         }
 
-        public Iterator NewIterator(ReadOptions options)
+        public Iterator CreateIterator(ReadOptions options)
         {
             return new Iterator(Native.leveldb_create_iterator(Handle, options.Handle));
         }
@@ -104,7 +105,7 @@ public static DB Open(string name, Options options)
         /// </summary>
         public void Put(WriteOptions options, byte[] key, byte[] value)
         {
-            Native.leveldb_put(Handle, options.Handle, key, (UIntPtr)key.Length, value, (UIntPtr)value.Length, out var error);
+            Native.leveldb_put(Handle, options.Handle, key, (nuint)key.Length, value, (nuint)value.Length, out var error);
             NativeHelper.CheckError(error);
         }
 
@@ -126,18 +127,14 @@ public void Write(WriteOptions options, WriteBatch write_batch)
             NativeHelper.CheckError(error);
         }
 
-        public IEnumerable<KeyValuePair<byte[], byte[]>> GetAll(Snapshot? snapshot = null)
+        public IEnumerator<KeyValuePair<byte[], byte[]>> GetEnumerator()
         {
-            using var options = new ReadOptions();
-            if (snapshot != null) options.Snapshot = snapshot;
-
-            using var iterator = NewIterator(options);
-            iterator.SeekToFirst();
-            while (iterator.Valid())
-            {
+            using var iterator = CreateIterator(ReadOptions.Default);
+            for (iterator.SeekToFirst(); iterator.Valid(); iterator.Next())
                 yield return new KeyValuePair<byte[], byte[]>(iterator.Key(), iterator.Value());
-                iterator.Next();
-            }
         }
+
+        IEnumerator IEnumerable.GetEnumerator() =>
+            GetEnumerator();
     }
 }

src/Plugins/LevelDBStore/IO/Data/LevelDB/Helper.cs

@@ -20,7 +20,7 @@ public static class Helper
     {
         public static IEnumerable<(byte[], byte[])> Seek(this DB db, ReadOptions options, byte[] prefix, SeekDirection direction)
         {
-            using Iterator it = db.NewIterator(options);
+            using Iterator it = db.CreateIterator(options);
             if (direction == SeekDirection.Forward)
             {
                 for (it.Seek(prefix); it.Valid(); it.Next())

src/Plugins/LevelDBStore/IO/Data/LevelDB/Iterator.cs

@@ -9,16 +9,14 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
-using System;
-
 namespace Neo.IO.Storage.LevelDB
 {
     /// <summary>
     /// An iterator yields a sequence of key/value pairs from a database.
     /// </summary>
     public class Iterator : LevelDBHandle
     {
-        internal Iterator(IntPtr handle) : base(handle) { }
+        internal Iterator(nint handle) : base(handle) { }
 
         private void CheckError()
         {
@@ -28,7 +26,7 @@ private void CheckError()
 
         protected override void FreeUnManagedObjects()
         {
-            if (Handle != IntPtr.Zero)
+            if (Handle != nint.Zero)
             {
                 Native.leveldb_iter_destroy(Handle);
             }
@@ -67,9 +65,9 @@ public void Prev()
         /// The iterator is Valid() after this call if the source contains
         /// an entry that comes at or past target.
         /// </summary>
-        public void Seek(byte[] target)
+        public void Seek(byte[] key)
         {
-            Native.leveldb_iter_seek(Handle, target, (UIntPtr)target.Length);
+            Native.leveldb_iter_seek(Handle, key, (nuint)key.Length);
         }
 
         public void SeekToFirst()

src/Plugins/LevelDBStore/IO/Data/LevelDB/Native.cs

@@ -17,8 +17,8 @@ namespace Neo.IO.Storage.LevelDB
 {
     public enum CompressionType : byte
     {
-        kNoCompression = 0x0,
-        kSnappyCompression = 0x1
+        NoCompression = 0x0,
+        SnappyCompression = 0x1
     }
 
     public static class Native

src/Plugins/LevelDBStore/IO/Data/LevelDB/Options.cs

@@ -126,12 +126,12 @@ public int BlockRestartInterval
         /// incompressible, the kSnappyCompression implementation will
         /// efficiently detect that and will switch to uncompressed mode.
         /// </summary>
-        public CompressionType Compression
+        public CompressionType CompressionLevel
         {
             set { Native.leveldb_options_set_compression(Handle, value); }
         }
 
-        public IntPtr FilterPolicy
+        public nint FilterPolicy
         {
             set { Native.leveldb_options_set_filter_policy(Handle, value); }
         }

src/Plugins/LevelDBStore/IO/Data/LevelDB/Snapshot.cs

@@ -9,8 +9,6 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
-using System;
-
 namespace Neo.IO.Storage.LevelDB
 {
     /// <summary>
@@ -19,16 +17,16 @@ namespace Neo.IO.Storage.LevelDB
     /// </summary>
     public class Snapshot : LevelDBHandle
     {
-        internal IntPtr _db;
+        internal nint _db;
 
-        internal Snapshot(IntPtr db) : base(Native.leveldb_create_snapshot(db))
+        internal Snapshot(nint db) : base(Native.leveldb_create_snapshot(db))
         {
             _db = db;
         }
 
         protected override void FreeUnManagedObjects()
         {
-            if (Handle != IntPtr.Zero)
+            if (Handle != nint.Zero)
             {
                 Native.leveldb_release_snapshot(_db, Handle);
             }

src/Plugins/LevelDBStore/Plugins/Storage/Snapshot.cs

@@ -11,12 +11,16 @@
 
 using Neo.IO.Storage.LevelDB;
 using Neo.Persistence;
+using System.Collections;
 using System.Collections.Generic;
 using LSnapshot = Neo.IO.Storage.LevelDB.Snapshot;
 
 namespace Neo.Plugins.Storage
 {
-    internal class Snapshot : ISnapshot
+    /// <summary>
+    /// <code>Iterating over the whole dataset can be time-consuming. Depending upon how large the dataset is.</code>
+    /// </summary>
+    internal class Snapshot : ISnapshot, IEnumerable<KeyValuePair<byte[], byte[]>>
     {
         private readonly DB _db;
         private readonly LSnapshot _snapshot;
@@ -27,7 +31,7 @@ internal class Snapshot : ISnapshot
         public Snapshot(DB db)
         {
             _db = db;
-            _snapshot = db.GetSnapshot();
+            _snapshot = db.CreateSnapshot();
             _readOptions = new ReadOptions { FillCache = false, Snapshot = _snapshot };
             _batch = new WriteBatch();
         }
@@ -76,5 +80,15 @@ public bool TryGet(byte[] key, out byte[] value)
             value = _db.Get(_readOptions, key);
             return value != null;
         }
+
+        public IEnumerator<KeyValuePair<byte[], byte[]>> GetEnumerator()
+        {
+            using var iterator = _db.CreateIterator(_readOptions);
+            for (iterator.SeekToFirst(); iterator.Valid(); iterator.Next())
+                yield return new KeyValuePair<byte[], byte[]>(iterator.Key(), iterator.Value());
+        }
+
+        IEnumerator IEnumerable.GetEnumerator() =>
+            GetEnumerator();
     }
 }

src/Plugins/LevelDBStore/Plugins/Storage/Store.cs

@@ -11,18 +11,27 @@
 
 using Neo.IO.Storage.LevelDB;
 using Neo.Persistence;
+using System.Collections;
 using System.Collections.Generic;
 
 namespace Neo.Plugins.Storage
 {
-    internal class Store : IStore
+    /// <summary>
+    /// <code>Iterating over the whole dataset can be time-consuming. Depending upon how large the dataset is.</code>
+    /// </summary>
+    internal class Store : IStore, IEnumerable<KeyValuePair<byte[], byte[]>>
     {
         private readonly DB _db;
         private readonly Options _options;
 
         public Store(string path)
         {
-            _options = new Options { CreateIfMissing = true, FilterPolicy = Native.leveldb_filterpolicy_create_bloom(15) };
+            _options = new Options
+            {
+                CreateIfMissing = true,
+                FilterPolicy = Native.leveldb_filterpolicy_create_bloom(15),
+                CompressionLevel = CompressionType.SnappyCompression,
+            };
             _db = DB.Open(path, _options);
         }
 
@@ -60,5 +69,11 @@ public bool TryGet(byte[] key, out byte[] value)
 
         public IEnumerable<(byte[], byte[])> Seek(byte[] prefix, SeekDirection direction = SeekDirection.Forward) =>
             _db.Seek(ReadOptions.Default, prefix, direction);
+
+        public IEnumerator<KeyValuePair<byte[], byte[]>> GetEnumerator() =>
+            _db.GetEnumerator();
+
+        IEnumerator IEnumerable.GetEnumerator() =>
+            GetEnumerator();
     }
 }

tests/Neo.Plugins.Storage.Tests/StoreTest.cs

@@ -10,6 +10,7 @@
 // modifications are permitted.
 
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Neo.IO.Storage.LevelDB;
 using Neo.Persistence;
 using System.IO;
 using System.Linq;
@@ -72,6 +73,20 @@ public void TestLevelDb()
             TestPersistenceRead(levelDbStore.GetStore(path_leveldb), false);
         }
 
+        [TestMethod]
+        public void TestLevelDbDatabase()
+        {
+            using var db = DB.Open(Path.GetRandomFileName(), new() { CreateIfMissing = true });
+
+            db.Put(WriteOptions.Default, [0x00, 0x00, 0x01], [0x01]);
+            db.Put(WriteOptions.Default, [0x00, 0x00, 0x02], [0x02]);
+            db.Put(WriteOptions.Default, [0x00, 0x00, 0x03], [0x03]);
+
+            CollectionAssert.AreEqual(new byte[] { 0x01, }, db.Get(ReadOptions.Default, [0x00, 0x00, 0x01]));
+            CollectionAssert.AreEqual(new byte[] { 0x02, }, db.Get(ReadOptions.Default, [0x00, 0x00, 0x02]));
+            CollectionAssert.AreEqual(new byte[] { 0x03, }, db.Get(ReadOptions.Default, [0x00, 0x00, 0x03]));
+        }
+
         [TestMethod]
         public void TestLevelDbSnapshot()
         {