Merge pull request #6843 from chrisdunelm/csharp_wrapper_primitive_opts

C#: Optimize parsing of some primitive and wrapper types

csharp/src/Google.Protobuf.Test/WellKnownTypes/WrappersTest.cs

@@ -386,7 +386,7 @@ namespace Google.Protobuf.WellKnownTypes
         }
 
         [Test]
-        public void UnknownFieldInWrapper()
+        public void UnknownFieldInWrapperInt32FastPath()
         {
             var stream = new MemoryStream();
             var output = new CodedOutputStream(stream);
@@ -395,19 +395,96 @@ namespace Google.Protobuf.WellKnownTypes
             var valueTag = WireFormat.MakeTag(Int32Value.ValueFieldNumber, WireFormat.WireType.Varint);
 
             output.WriteTag(wrapperTag);
-            output.WriteLength(4); // unknownTag + value 5 + valueType + value 6, each 1 byte
+            // Wrapper message is just long enough - 6 bytes - to use the wrapper fast-path.
+            output.WriteLength(6); // unknownTag + value 5 + valueType, each 1 byte, + value 65536, 3 bytes
             output.WriteTag(unknownTag);
             output.WriteInt32((int) valueTag); // Sneakily "pretend" it's a tag when it's really a value
             output.WriteTag(valueTag);
+            output.WriteInt32(65536);
+            
+            output.Flush();
+            Assert.AreEqual(8, stream.Length); // tag (1 byte) + length (1 byte) + message (6 bytes)
+            stream.Position = 0;
+
+            var message = TestWellKnownTypes.Parser.ParseFrom(stream);
+            Assert.AreEqual(65536, message.Int32Field);
+        }
+
+        [Test]
+        public void UnknownFieldInWrapperInt32SlowPath()
+        {
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            var wrapperTag = WireFormat.MakeTag(TestWellKnownTypes.Int32FieldFieldNumber, WireFormat.WireType.LengthDelimited);
+            var unknownTag = WireFormat.MakeTag(15, WireFormat.WireType.Varint);
+            var valueTag = WireFormat.MakeTag(Int32Value.ValueFieldNumber, WireFormat.WireType.Varint);
+
+            output.WriteTag(wrapperTag);
+            // Wrapper message is too short to be used on the wrapper fast-path.
+            output.WriteLength(4); // unknownTag + value 5 + valueType + value 6, each 1 byte
+            output.WriteTag(unknownTag);
+            output.WriteInt32((int)valueTag); // Sneakily "pretend" it's a tag when it's really a value
+            output.WriteTag(valueTag);
             output.WriteInt32(6);
 
             output.Flush();
+            Assert.Less(stream.Length, 8); // tag (1 byte) + length (1 byte) + message
             stream.Position = 0;
 
             var message = TestWellKnownTypes.Parser.ParseFrom(stream);
             Assert.AreEqual(6, message.Int32Field);
         }
 
+        [Test]
+        public void UnknownFieldInWrapperInt64FastPath()
+        {
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            var wrapperTag = WireFormat.MakeTag(TestWellKnownTypes.Int64FieldFieldNumber, WireFormat.WireType.LengthDelimited);
+            var unknownTag = WireFormat.MakeTag(15, WireFormat.WireType.Varint);
+            var valueTag = WireFormat.MakeTag(Int64Value.ValueFieldNumber, WireFormat.WireType.Varint);
+
+            output.WriteTag(wrapperTag);
+            // Wrapper message is just long enough - 10 bytes - to use the wrapper fast-path.
+            output.WriteLength(11); // unknownTag + value 5 + valueType, each 1 byte, + value 0xfffffffffffff, 8 bytes
+            output.WriteTag(unknownTag);
+            output.WriteInt64((int)valueTag); // Sneakily "pretend" it's a tag when it's really a value
+            output.WriteTag(valueTag);
+            output.WriteInt64(0xfffffffffffffL);
+
+            output.Flush();
+            Assert.AreEqual(13, stream.Length); // tag (1 byte) + length (1 byte) + message (11 bytes)
+            stream.Position = 0;
+
+            var message = TestWellKnownTypes.Parser.ParseFrom(stream);
+            Assert.AreEqual(0xfffffffffffffL, message.Int64Field);
+        }
+
+        [Test]
+        public void UnknownFieldInWrapperInt64SlowPath()
+        {
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            var wrapperTag = WireFormat.MakeTag(TestWellKnownTypes.Int64FieldFieldNumber, WireFormat.WireType.LengthDelimited);
+            var unknownTag = WireFormat.MakeTag(15, WireFormat.WireType.Varint);
+            var valueTag = WireFormat.MakeTag(Int64Value.ValueFieldNumber, WireFormat.WireType.Varint);
+
+            output.WriteTag(wrapperTag);
+            // Wrapper message is too short to be used on the wrapper fast-path.
+            output.WriteLength(4); // unknownTag + value 5 + valueType + value 6, each 1 byte
+            output.WriteTag(unknownTag);
+            output.WriteInt64((int)valueTag); // Sneakily "pretend" it's a tag when it's really a value
+            output.WriteTag(valueTag);
+            output.WriteInt64(6);
+
+            output.Flush();
+            Assert.Less(stream.Length, 12); // tag (1 byte) + length (1 byte) + message
+            stream.Position = 0;
+
+            var message = TestWellKnownTypes.Parser.ParseFrom(stream);
+            Assert.AreEqual(6L, message.Int64Field);
+        }
+
         [Test]
         public void ClearWithReflection()
         {

csharp/src/Google.Protobuf/FieldCodec.cs

@@ -507,7 +507,7 @@ namespace Google.Protobuf
         {
             var nestedCodec = WrapperCodecs.GetCodec<T>();
             return new FieldCodec<T?>(
-                input => WrapperCodecs.Read<T>(input, nestedCodec),
+                WrapperCodecs.GetReader<T>(),
                 (output, value) => WrapperCodecs.Write<T>(output, value.Value, nestedCodec),
                 (CodedInputStream i, ref T? v) => v = WrapperCodecs.Read<T>(i, nestedCodec),
                 (ref T? v, T? v2) => { if (v2.HasValue) { v = v2; } return v.HasValue; },
@@ -539,6 +539,25 @@ namespace Google.Protobuf
                 { typeof(ByteString), ForBytes(WireFormat.MakeTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.LengthDelimited)) }
             };
 
+            private static readonly Dictionary<System.Type, object> Readers = new Dictionary<System.Type, object>
+            {
+                // TODO: Provide more optimized readers.
+                { typeof(bool), (Func<CodedInputStream, bool?>)CodedInputStream.ReadBoolWrapper },
+                { typeof(int), (Func<CodedInputStream, int?>)CodedInputStream.ReadInt32Wrapper },
+                { typeof(long), (Func<CodedInputStream, long?>)CodedInputStream.ReadInt64Wrapper },
+                { typeof(uint), (Func<CodedInputStream, uint?>)CodedInputStream.ReadUInt32Wrapper },
+                { typeof(ulong), (Func<CodedInputStream, ulong?>)CodedInputStream.ReadUInt64Wrapper },
+                { typeof(float), BitConverter.IsLittleEndian ?
+                    (Func<CodedInputStream, float?>)CodedInputStream.ReadFloatWrapperLittleEndian :
+                    (Func<CodedInputStream, float?>)CodedInputStream.ReadFloatWrapperSlow },
+                { typeof(double), BitConverter.IsLittleEndian ?
+                    (Func<CodedInputStream, double?>)CodedInputStream.ReadDoubleWrapperLittleEndian :
+                    (Func<CodedInputStream, double?>)CodedInputStream.ReadDoubleWrapperSlow },
+                // `string` and `ByteString` less performance-sensitive. Do not implement for now.
+                { typeof(string), null },
+                { typeof(ByteString), null },
+            };
+
             /// <summary>
             /// Returns a field codec which effectively wraps a value of type T in a message.
             ///
@@ -553,6 +572,23 @@ namespace Google.Protobuf
                 return (FieldCodec<T>) value;
             }
 
+            internal static Func<CodedInputStream, T?> GetReader<T>() where T : struct
+            {
+                object value;
+                if (!Readers.TryGetValue(typeof(T), out value))
+                {
+                    throw new InvalidOperationException("Invalid type argument requested for wrapper reader: " + typeof(T));
+                }
+                if (value == null)
+                {
+                    // Return default unoptimized reader for the wrapper type.
+                    var nestedCoded = GetCodec<T>();
+                    return input => Read<T>(input, nestedCoded);
+                }
+                // Return optimized read for the wrapper type.
+                return (Func<CodedInputStream, T?>)value;
+            }
+
             internal static T Read<T>(CodedInputStream input, FieldCodec<T> codec)
             {
                 int length = input.ReadLength();