JSON: Add support for Int128, UInt128 and Half

src/libraries/System.Text.Json/gen/Helpers/KnownTypeSymbols.cs

@@ -135,6 +135,15 @@ public KnownTypeSymbols(Compilation compilation)
         public INamedTypeSymbol? TimeOnlyType => GetOrResolveType("System.TimeOnly", ref _TimeOnlyType);
         private Option<INamedTypeSymbol?> _TimeOnlyType;
 
+        public INamedTypeSymbol? Int128Type => GetOrResolveType("System.Int128", ref _Int128Type);
+        private Option<INamedTypeSymbol?> _Int128Type;
+
+        public INamedTypeSymbol? UInt128Type => GetOrResolveType("System.UInt128", ref _UInt128Type);
+        private Option<INamedTypeSymbol?> _UInt128Type;
+
+        public INamedTypeSymbol? HalfType => GetOrResolveType("System.Half", ref _HalfType);
+        private Option<INamedTypeSymbol?> _HalfType;
+
         public IArrayTypeSymbol? ByteArrayType => _ByteArrayType.HasValue
             ? _ByteArrayType.Value
             : (_ByteArrayType = new(Compilation.CreateArrayTypeSymbol(Compilation.GetSpecialType(SpecialType.System_Byte), rank: 1))).Value;

src/libraries/System.Text.Json/gen/JsonSourceGenerator.Parser.cs

@@ -1494,6 +1494,9 @@ private static HashSet<ITypeSymbol> CreateBuiltInSupportTypeSet(KnownTypeSymbols
                 AddTypeIfNotNull(knownSymbols.DateTimeOffsetType);
                 AddTypeIfNotNull(knownSymbols.DateOnlyType);
                 AddTypeIfNotNull(knownSymbols.TimeOnlyType);
+                AddTypeIfNotNull(knownSymbols.Int128Type);
+                AddTypeIfNotNull(knownSymbols.UInt128Type);
+                AddTypeIfNotNull(knownSymbols.HalfType);
                 AddTypeIfNotNull(knownSymbols.GuidType);
                 AddTypeIfNotNull(knownSymbols.UriType);
                 AddTypeIfNotNull(knownSymbols.VersionType);

src/libraries/System.Text.Json/ref/System.Text.Json.netcoreapp.cs

@@ -9,6 +9,13 @@ namespace System.Text.Json.Serialization.Metadata
     public static partial class JsonMetadataServices
     {
         public static System.Text.Json.Serialization.JsonConverter<System.DateOnly> DateOnlyConverter { get { throw null; } }
+        public static System.Text.Json.Serialization.JsonConverter<System.Half> HalfConverter { get { throw null; } }
         public static System.Text.Json.Serialization.JsonConverter<System.TimeOnly> TimeOnlyConverter { get { throw null; } }
+
+#if NET7_0_OR_GREATER
+        public static System.Text.Json.Serialization.JsonConverter<System.Int128> Int128Converter { get { throw null; } }
+        [System.CLSCompliantAttribute(false)]
+        public static System.Text.Json.Serialization.JsonConverter<System.UInt128> UInt128Converter { get { throw null; } }
+#endif
     }
 }

src/libraries/System.Text.Json/src/Resources/Strings.resx

@@ -690,4 +690,13 @@
   <data name="ObjectCreationHandlingPropertyCannotAllowReferenceHandling" xml:space="preserve">
     <value>JsonObjectCreationHandling.Populate is incompatible with reference handling.</value>
   </data>
+  <data name="FormatInt128" xml:space="preserve">
+    <value>Either the JSON value is not in a supported format, or is out of bounds for an Int128.</value>
+  </data>
+  <data name="FormatUInt128" xml:space="preserve">
+    <value>Either the JSON value is not in a supported format, or is out of bounds for an UInt128.</value>
+  </data>
+  <data name="FormatHalf" xml:space="preserve">
+    <value>Either the JSON value is not in a supported format, or is out of bounds for a Half.</value>
+  </data>
 </root>

src/libraries/System.Text.Json/src/System.Text.Json.csproj

@@ -345,11 +345,17 @@ The System.Text.Json library is built-in as part of the shared framework in .NET
     <Compile Include="$(CoreLibSharedDir)System\Diagnostics\CodeAnalysis\UnconditionalSuppressMessageAttribute.cs" />
   </ItemGroup>
 
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp' and $([MSBuild]::VersionGreaterThanOrEquals('$(TargetFrameworkVersion)', '7.0'))">
+    <Compile Include="System\Text\Json\Serialization\Converters\Value\Int128Converter.cs" />
+    <Compile Include="System\Text\Json\Serialization\Converters\Value\UInt128Converter.cs" />
+  </ItemGroup>
+
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp'">
     <Compile Include="System.Text.Json.Typeforwards.netcoreapp.cs" />
     <Compile Include="System\Text\Json\Serialization\JsonSerializerOptionsUpdateHandler.cs" />
     <Compile Include="System\Text\Json\Serialization\Converters\Value\DateOnlyConverter.cs" />
     <Compile Include="System\Text\Json\Serialization\Converters\Value\TimeOnlyConverter.cs" />
+    <Compile Include="System\Text\Json\Serialization\Converters\Value\HalfConverter.cs" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETCoreApp'">

src/libraries/System.Text.Json/src/System/Text/Json/Reader/JsonReaderHelper.cs

@@ -145,6 +145,39 @@ public static bool TryGetEscapedGuid(ReadOnlySpan<byte> source, out Guid value)
             return false;
         }
 
+#if NETCOREAPP
+        public static bool TryGetFloatingPointConstant(ReadOnlySpan<byte> span, out Half value)
+        {
+            if (span.Length == 3)
+            {
+                if (span.SequenceEqual(JsonConstants.NaNValue))
+                {
+                    value = Half.NaN;
+                    return true;
+                }
+            }
+            else if (span.Length == 8)
+            {
+                if (span.SequenceEqual(JsonConstants.PositiveInfinityValue))
+                {
+                    value = Half.PositiveInfinity;
+                    return true;
+                }
+            }
+            else if (span.Length == 9)
+            {
+                if (span.SequenceEqual(JsonConstants.NegativeInfinityValue))
+                {
+                    value = Half.NegativeInfinity;
+                    return true;
+                }
+            }
+
+            value = default;
+            return false;
+        }
+#endif
+
         public static bool TryGetFloatingPointConstant(ReadOnlySpan<byte> span, out float value)
         {
             if (span.Length == 3)

src/libraries/System.Text.Json/src/System/Text/Json/Reader/Utf8JsonReader.TryGet.cs

@@ -73,6 +73,14 @@ namespace System.Text.Json
                 ThrowHelper.ThrowInvalidOperationException_ExpectedString(_tokenType);
             }
 
+            return CopyValue(utf8Destination);
+        }
+
+        internal readonly int CopyValue(Span<byte> utf8Destination)
+        {
+            Debug.Assert(_tokenType is JsonTokenType.String or JsonTokenType.PropertyName or JsonTokenType.Number);
+            Debug.Assert(_tokenType != JsonTokenType.Number || !ValueIsEscaped, "Numbers can't contain escape characters.");
+
             int bytesWritten;
 
             if (ValueIsEscaped)
@@ -129,6 +137,14 @@ namespace System.Text.Json
                 ThrowHelper.ThrowInvalidOperationException_ExpectedString(_tokenType);
             }
 
+            return CopyValue(destination);
+        }
+
+        internal readonly int CopyValue(Span<char> destination)
+        {
+            Debug.Assert(_tokenType is JsonTokenType.String or JsonTokenType.PropertyName or JsonTokenType.Number);
+            Debug.Assert(_tokenType != JsonTokenType.Number || !ValueIsEscaped, "Numbers can't contain escape characters.");
+
             scoped ReadOnlySpan<byte> unescapedSource;
             byte[]? rentedBuffer = null;
             int valueLength;

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/CharConverter.cs

@@ -12,6 +12,11 @@ internal sealed class CharConverter : JsonPrimitiveConverter<char>
 
         public override char Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
         {
+            if (reader.TokenType is not (JsonTokenType.String or JsonTokenType.PropertyName))
+            {
+                ThrowHelper.ThrowInvalidOperationException_ExpectedString(reader.TokenType);
+            }
+
             if (!JsonHelpers.IsInRangeInclusive(reader.ValueLength, 1, MaxEscapedCharacterLength))
             {
                 ThrowHelper.ThrowInvalidOperationException_ExpectedChar(reader.TokenType);

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/Value/HalfConverter.cs

@@ -0,0 +1,217 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Globalization;
+
+namespace System.Text.Json.Serialization.Converters
+{
+    internal sealed class HalfConverter : JsonPrimitiveConverter<Half>
+    {
+        private const int MaxFormatLength = 20;
+
+        public HalfConverter()
+        {
+            IsInternalConverterForNumberType = true;
+        }
+
+        public override Half Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            if (reader.TokenType != JsonTokenType.Number)
+            {
+                ThrowHelper.ThrowInvalidOperationException_ExpectedNumber(reader.TokenType);
+            }
+
+            return ReadCore(ref reader);
+        }
+
+        public override void Write(Utf8JsonWriter writer, Half value, JsonSerializerOptions options)
+        {
+            WriteCore(writer, value);
+        }
+
+        private static Half ReadCore(ref Utf8JsonReader reader)
+        {
+            Half result;
+
+            byte[]? rentedByteBuffer = null;
+            int bufferLength = reader.ValueLength;
+
+            Span<byte> byteBuffer = bufferLength <= JsonConstants.StackallocByteThreshold
+                ? stackalloc byte[JsonConstants.StackallocByteThreshold]
+                : (rentedByteBuffer = ArrayPool<byte>.Shared.Rent(bufferLength));
+
+            int written = reader.CopyValue(byteBuffer);
+            byteBuffer = byteBuffer.Slice(0, written);
+
+            bool success = TryParse(byteBuffer, out result);
+            if (rentedByteBuffer != null)
+            {
+                ArrayPool<byte>.Shared.Return(rentedByteBuffer);
+            }
+
+            if (!success)
+            {
+                ThrowHelper.ThrowFormatException(NumericType.Half);
+            }
+
+            Debug.Assert(!Half.IsNaN(result) && !Half.IsInfinity(result));
+            return result;
+        }
+
+        private static void WriteCore(Utf8JsonWriter writer, Half value)
+        {
+#if NET8_0_OR_GREATER
+            Span<byte> buffer = stackalloc byte[MaxFormatLength];
+#else
+            Span<char> buffer = stackalloc char[MaxFormatLength];
+#endif
+            Format(buffer, value, out int written);
+            writer.WriteRawValue(buffer.Slice(0, written));
+        }
+
+        internal override Half ReadAsPropertyNameCore(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            Debug.Assert(reader.TokenType == JsonTokenType.PropertyName);
+            return ReadCore(ref reader);
+        }
+
+        internal override void WriteAsPropertyNameCore(Utf8JsonWriter writer, Half value, JsonSerializerOptions options, bool isWritingExtensionDataProperty)
+        {
+#if NET8_0_OR_GREATER
+            Span<byte> buffer = stackalloc byte[MaxFormatLength];
+#else
+            Span<char> buffer = stackalloc char[MaxFormatLength];
+#endif
+            Format(buffer, value, out int written);
+            writer.WritePropertyName(buffer.Slice(0, written));
+        }
+
+        internal override Half ReadNumberWithCustomHandling(ref Utf8JsonReader reader, JsonNumberHandling handling, JsonSerializerOptions options)
+        {
+            if (reader.TokenType == JsonTokenType.String)
+            {
+                if ((JsonNumberHandling.AllowReadingFromString & handling) != 0)
+                {
+                    if (TryGetFloatingPointConstant(ref reader, out Half value))
+                    {
+                        return value;
+                    }
+
+                    return ReadCore(ref reader);
+                }
+                else if ((JsonNumberHandling.AllowNamedFloatingPointLiterals & handling) != 0)
+                {
+                    if (!TryGetFloatingPointConstant(ref reader, out Half value))
+                    {
+                        ThrowHelper.ThrowFormatException(NumericType.Half);
+                    }
+
+                    return value;
+                }
+            }
+
+            return Read(ref reader, Type, options);
+        }
+
+        internal override void WriteNumberWithCustomHandling(Utf8JsonWriter writer, Half value, JsonNumberHandling handling)
+        {
+            if ((JsonNumberHandling.WriteAsString & handling) != 0)
+            {
+#if NET8_0_OR_GREATER
+                const byte Quote = JsonConstants.Quote;
+                Span<byte> buffer = stackalloc byte[MaxFormatLength + 2];
+#else
+                const char Quote = (char)JsonConstants.Quote;
+                Span<char> buffer = stackalloc char[MaxFormatLength + 2];
+#endif
+                buffer[0] = Quote;
+                Format(buffer.Slice(1), value, out int written);
+
+                int length = written + 2;
+                buffer[length - 1] = Quote;
+                writer.WriteRawValue(buffer.Slice(0, length));
+            }
+            else if ((JsonNumberHandling.AllowNamedFloatingPointLiterals & handling) != 0)
+            {
+                WriteFloatingPointConstant(writer, value);
+            }
+            else
+            {
+                WriteCore(writer, value);
+            }
+        }
+
+        private static bool TryGetFloatingPointConstant(ref Utf8JsonReader reader, out Half value)
+        {
+            Span<byte> buffer = stackalloc byte[MaxFormatLength];
+            int written = reader.CopyValue(buffer);
+
+            return JsonReaderHelper.TryGetFloatingPointConstant(buffer.Slice(0, written), out value);
+        }
+
+        private static void WriteFloatingPointConstant(Utf8JsonWriter writer, Half value)
+        {
+            if (Half.IsNaN(value))
+            {
+                writer.WriteNumberValueAsStringUnescaped(JsonConstants.NaNValue);
+            }
+            else if (Half.IsPositiveInfinity(value))
+            {
+                writer.WriteNumberValueAsStringUnescaped(JsonConstants.PositiveInfinityValue);
+            }
+            else if (Half.IsNegativeInfinity(value))
+            {
+                writer.WriteNumberValueAsStringUnescaped(JsonConstants.NegativeInfinityValue);
+            }
+            else
+            {
+                WriteCore(writer, value);
+            }
+        }
+
+        private static bool TryParse(ReadOnlySpan<byte> buffer, out Half result)
+        {
+#if NET8_0_OR_GREATER
+            bool success = Half.TryParse(buffer, NumberStyles.Float | NumberStyles.AllowThousands, CultureInfo.InvariantCulture, out result);
+#else
+            // Half.TryFormat/TryParse(ROS<byte>) are not available on .NET 7
+            // we need to use Half.TryFormat/TryParse(ROS<char>) in that case.
+            char[]? rentedCharBuffer = null;
+
+            Span<char> charBuffer = buffer.Length <= JsonConstants.StackallocCharThreshold
+                ? stackalloc char[JsonConstants.StackallocCharThreshold]
+                : (rentedCharBuffer = ArrayPool<char>.Shared.Rent(buffer.Length));
+
+            int written = JsonReaderHelper.TranscodeHelper(buffer, charBuffer);
+
+            bool success = Half.TryParse(charBuffer, NumberStyles.Float | NumberStyles.AllowThousands, CultureInfo.InvariantCulture, out result);
+
+            if (rentedCharBuffer != null)
+            {
+                ArrayPool<char>.Shared.Return(rentedCharBuffer);
+            }
+#endif
+
+            // Half.TryParse is more lax with floating-point literals than other S.T.Json floating-point types
+            // e.g: it parses "naN" successfully. Only succeed with the exact match.
+            return success &&
+                (!Half.IsNaN(result) || buffer.SequenceEqual(JsonConstants.NaNValue)) &&
+                (!Half.IsPositiveInfinity(result) || buffer.SequenceEqual(JsonConstants.PositiveInfinityValue)) &&
+                (!Half.IsNegativeInfinity(result) || buffer.SequenceEqual(JsonConstants.NegativeInfinityValue));
+        }
+
+        private static void Format(
+#if NET8_0_OR_GREATER
+            Span<byte> destination,
+#else
+            Span<char> destination,
+#endif
+            Half value, out int written)
+        {
+            bool formattedSuccessfully = value.TryFormat(destination, out written, provider: CultureInfo.InvariantCulture);
+            Debug.Assert(formattedSuccessfully);
+        }
+    }
+}