Nullable storage classes (#3718)

* Nullable storage

* Fix ut

* Complete ut

src/Neo/Persistence/IReadOnlyStoreView.cs

@@ -9,8 +9,11 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+#nullable enable
+
 using Neo.SmartContract;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 
 namespace Neo.Persistence
 {
@@ -41,6 +44,6 @@ public interface IReadOnlyStoreView
         /// <param name="key">The key to get.</param>
         /// <param name="item">The entry if found, null otherwise.</param>
         /// <returns>True if the entry exists, false otherwise.</returns>
-        bool TryGet(StorageKey key, out StorageItem item);
+        bool TryGet(StorageKey key, [NotNullWhen(true)] out StorageItem? item);
     }
 }

src/Neo/Persistence/ISnapshot.cs

@@ -9,6 +9,8 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+#nullable enable
+
 using System;
 
 namespace Neo.Persistence

src/Neo/Persistence/IStore.cs

@@ -9,6 +9,8 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+#nullable enable
+
 using System;
 
 namespace Neo.Persistence

src/Neo/Persistence/IStoreProvider.cs

@@ -9,6 +9,8 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+#nullable enable
+
 namespace Neo.Persistence
 {
     /// <summary>

src/Neo/Persistence/MemoryStoreProvider.cs

@@ -9,6 +9,8 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+#nullable enable
+
 namespace Neo.Persistence
 {
     public class MemoryStoreProvider : IStoreProvider

src/Neo/Persistence/ReadOnlyStoreView.cs

@@ -9,22 +9,25 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+#nullable enable
+
 using Neo.SmartContract;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 
 namespace Neo.Persistence
 {
     public class ReadOnlyStoreView : IReadOnlyStoreView
     {
-        private readonly IReadOnlyStore store;
+        private readonly IReadOnlyStore _store;
 
         public ReadOnlyStoreView(IReadOnlyStore store)
         {
-            this.store = store;
+            _store = store;
         }
 
         /// <inheritdoc/>
-        public bool Contains(StorageKey key) => store.Contains(key.ToArray());
+        public bool Contains(StorageKey key) => _store.Contains(key.ToArray());
 
         /// <inheritdoc/>
         public StorageItem this[StorageKey key]
@@ -38,11 +41,16 @@ public StorageItem this[StorageKey key]
         }
 
         /// <inheritdoc/>
-        public bool TryGet(StorageKey key, out StorageItem item)
+        public bool TryGet(StorageKey key, [NotNullWhen(true)] out StorageItem? item)
         {
-            var ok = store.TryGet(key.ToArray(), out byte[] value);
-            item = ok ? new StorageItem(value) : null;
-            return ok;
+            if (_store.TryGet(key.ToArray(), out var value))
+            {
+                item = new StorageItem(value);
+                return true;
+            }
+
+            item = null;
+            return false;
         }
     }
 }

src/Neo/Persistence/StoreFactory.cs

@@ -9,36 +9,38 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+#nullable enable
+
 using System.Collections.Generic;
 
 namespace Neo.Persistence
 {
     public static class StoreFactory
     {
-        private static readonly Dictionary<string, IStoreProvider> providers = new();
+        private static readonly Dictionary<string, IStoreProvider> s_providers = [];
 
         static StoreFactory()
         {
             var memProvider = new MemoryStoreProvider();
             RegisterProvider(memProvider);
 
             // Default cases
-            providers.Add("", memProvider);
+            s_providers.Add("", memProvider);
         }
 
         public static void RegisterProvider(IStoreProvider provider)
         {
-            providers.Add(provider.Name, provider);
+            s_providers.Add(provider.Name, provider);
         }
 
         /// <summary>
         /// Get store provider by name
         /// </summary>
         /// <param name="name">Name</param>
         /// <returns>Store provider</returns>
-        public static IStoreProvider GetStoreProvider(string name)
+        public static IStoreProvider? GetStoreProvider(string name)
         {
-            if (providers.TryGetValue(name, out var provider))
+            if (s_providers.TryGetValue(name, out var provider))
             {
                 return provider;
             }
@@ -54,7 +56,7 @@ public static IStoreProvider GetStoreProvider(string name)
         /// <returns>The storage engine.</returns>
         public static IStore GetStore(string storageProvider, string path)
         {
-            return providers[storageProvider].GetStore(path);
+            return s_providers[storageProvider].GetStore(path);
         }
     }
 }

src/Neo/SmartContract/KeyBuilder.cs

@@ -9,6 +9,8 @@
 // Redistribution and use in source and binary forms with or without
 // modifications are permitted.
 
+#nullable enable
+
 using Neo.IO;
 using System;
 using System.Buffers.Binary;
@@ -22,7 +24,7 @@ namespace Neo.SmartContract
     /// </summary>
     public class KeyBuilder
     {
-        private readonly MemoryStream stream;
+        private readonly MemoryStream _stream;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="KeyBuilder"/> class.
@@ -35,9 +37,9 @@ public KeyBuilder(int id, byte prefix, int keySizeHint = ApplicationEngine.MaxSt
             Span<byte> data = stackalloc byte[sizeof(int)];
             BinaryPrimitives.WriteInt32LittleEndian(data, id);
 
-            stream = new(keySizeHint);
-            stream.Write(data);
-            stream.WriteByte(prefix);
+            _stream = new(keySizeHint);
+            _stream.Write(data);
+            _stream.WriteByte(prefix);
         }
 
         /// <summary>
@@ -48,7 +50,7 @@ public KeyBuilder(int id, byte prefix, int keySizeHint = ApplicationEngine.MaxSt
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public KeyBuilder Add(byte key)
         {
-            stream.WriteByte(key);
+            _stream.WriteByte(key);
             return this;
         }
 
@@ -60,7 +62,7 @@ public KeyBuilder Add(byte key)
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public KeyBuilder Add(ReadOnlySpan<byte> key)
         {
-            stream.Write(key);
+            _stream.Write(key);
             return this;
         }
 
@@ -95,7 +97,7 @@ public KeyBuilder Add(ReadOnlySpan<byte> key)
         /// <returns>A reference to this instance after the add operation has completed.</returns>
         public KeyBuilder Add(ISerializable key)
         {
-            using (BinaryWriter writer = new(stream, Utility.StrictUTF8, true))
+            using (BinaryWriter writer = new(_stream, Utility.StrictUTF8, true))
             {
                 key.Serialize(writer);
                 writer.Flush();
@@ -165,18 +167,15 @@ public KeyBuilder AddBigEndian(ulong key)
         /// <returns>The storage key.</returns>
         public byte[] ToArray()
         {
-            using (stream)
+            using (_stream)
             {
-                return stream.ToArray();
+                return _stream.ToArray();
             }
         }
 
         public static implicit operator StorageKey(KeyBuilder builder)
         {
-            using (builder.stream)
-            {
-                return new StorageKey(builder.stream.ToArray());
-            }
+            return new StorageKey(builder.ToArray());
         }
     }
 }