Ahson Khan ahsonkhan

The default behavior of the System.Text.Json JsonSerializer and Utf8JsonWriter follows the behavior of JavascriptEncoder.Default, which means the following character sets are escaped:

Any non-ascii character
Characters required escaping based on the JSON RFC
HTML-specific ascii characters

Current Approach

The current approach involves going through the list of characters, one at a time, and check whether that character needs escaping. We special case the "null" encoder (which is the default when the user doesn't specify their own) and use a 256 byte bit-mask to indicate which character needs to be escaped. https://github.com/dotnet/corefx/blob/52d63157c78c31816b81be1599a5dacf96b5e5ca/src/System.Text.Json/src/System/Text/Json/Writer/JsonWriterHelper.Escaping.cs#L82-L109

New Approach Chosen

Motivation - Usability and Reliability:

The current writer is a ref struct, which requires passing by ref.
The use of array pool could result in reliability concerns if misused.
Async writes and state passing could be problematic.
No IBufferWriter implementation built in.

Goals:

Continue to support IBufferWriter (i.e. PipeWriter) directly
Keep ability for user to control buffering with ability to avoid data copies.

API Difference

Microsoft.Private.CoreFx.NETCoreApp-master\ref\netcoreapp3.0 vs Microsoft.Private.CoreFx.NETCoreApp-branch\ref\netcoreapp3.0

API listing follows standard diff formatting. Lines preceded by a '+' are additions and a '-' indicates removal.

Microsoft.VisualBasic
System
System.Collections.Generic
System.Collections.Immutable

BenchmarkDotNet=v0.10.14.534-nightly, OS=Windows 10.0.16299.371 (1709/FallCreatorsUpdate/Redstone3)
Intel Xeon CPU E5-1620 v2 3.70GHz, 1 CPU, 8 logical and 4 physical cores
Frequency=3604598 Hz, Resolution=277.4234 ns, Timer=TSC
.NET Core SDK=2.1.300-rtm-008823
  [Host]     : .NET Core 2.1.0-rtm-26508-02 (CoreCLR 4.6.26508.04, CoreFX 4.6.26508.03), 64bit RyuJIT
  Job-JIQQBR : .NET Core 2.1.0-rtm-26508-02 (CoreCLR 4.6.26508.04, CoreFX 4.6.26508.03), 64bit RyuJIT

InvocationCount=1024 TargetCount=5 WarmupCount=3

	// Licensed to the .NET Foundation under one or more agreements.
	// The .NET Foundation licenses this file to you under the MIT license.
	// See the LICENSE file in the project root for more information.

	using BenchmarkDotNet.Attributes;
	using MicroBenchmarks;
	using System.Collections.Generic;

	namespace System.Text.Json.Serialization.Tests
	{

	public class Rootobject
	{
	public Value value { get; set; }
	public Mentioneduser[] mentionedUsers { get; set; }
	public Collaborator[] collaborators { get; set; }
	public bool hideMeter { get; set; }
	public Collectionuserrelation[] collectionUserRelations { get; set; }
	public object mode { get; set; }
	public References references { get; set; }
	}


	// 1b) Expected output:
	{"Email":"[email protected]","Active":true,"CreatedDate":"2013-01-20T00:00:00.0000000Z","Roles":["User","Admin"]}

	// 2c) Expected output:
	{
	"Email": "[email protected]",
	"Active": true,
	"CreatedDate": "2013-01-20T00:00:00Z",
	"Roles": [

	[External Code]
	> Microsoft.Cci.Extensions.dll!Microsoft.Cci.Writers.CSharp.CSDeclarationWriter.WriteEnumValue(Microsoft.Cci.IMetadataConstant constant, Microsoft.Cci.ITypeReference constantType) Line 67 C#
	Microsoft.Cci.Extensions.dll!Microsoft.Cci.Writers.CSharp.CSDeclarationWriter.WriteMetadataConstant(Microsoft.Cci.IMetadataConstant constant, Microsoft.Cci.ITypeReference constantType) Line 258 C#
	Microsoft.Cci.Extensions.dll!Microsoft.Cci.Writers.CSharp.CSDeclarationWriter.WriteEnumValue(Microsoft.Cci.IMetadataConstant constant, Microsoft.Cci.ITypeReference constantType) Line 123 C#
	Microsoft.Cci.Extensions.dll!Microsoft.Cci.Writers.CSharp.CSDeclarationWriter.WriteMetadataConstant(Microsoft.Cci.IMetadataConstant constant, Microsoft.Cci.ITypeReference constantType) Line 258 C#
	Microsoft.Cci.Extensions.dll!Microsoft.Cci.Writers.CSharp.CSDeclarationWriter.WriteEnumValue(Microsoft.Cci.IMetadataConstant constant, Microsoft.Cci.ITypeReference constantType) Line 123 C#
	Microsoft.Cci.Extensions.dll!M

	public class ArrayBufferWriter : IBufferWriter<byte>, IDisposable
	{
	private byte[] _rentedBuffer;
	private int _written;
	private long _committed;

	private const int MinimumBufferSize = 256;

	public ArrayBufferWriter(int initialCapacity = MinimumBufferSize)
	{

	namespace System.Buffers
	{
	public class ArrayBufferWriter : IBufferWriter<byte>, IDisposable
	{
	private byte[] _rentedBuffer;
	private int _written;
	private long _committed;

	private const int MinimumBufferSize = 256;