ahsonkhan

Here are the latest results and conclusion.

Essentially, for Span specifically, calling Slice then IndexOf is just as good (if not better) than calling the IndexOf overload which removes the need to Slice.

dotnet/corefxlab#1278

(I am limiting the discussion to fast span since the conclusion doesn’t generally change for slow span)

ahsonkhan

Started by user Ahson Khan
Building in workspace C:\Program Files (x86)\Jenkins\workspace\testLinux
 > git.exe rev-parse --is-inside-work-tree # timeout=10
Fetching changes from the remote Git repository
 > git.exe config remote.origin.url https://github.com/dotnet/dotnet-ci # timeout=10
Fetching upstream changes from https://github.com/dotnet/dotnet-ci
 > git.exe --version # timeout=10
 > git.exe fetch --tags --progress https://github.com/dotnet/dotnet-ci +refs/heads/*:refs/remotes/origin/* # timeout=30
 > git.exe rev-parse "refs/remotes/origin/master^{commit}" # timeout=10
 > git.exe rev-parse "refs/remotes/origin/origin/master^{commit}" # timeout=10

ahsonkhan

namespace System.Buffers.Text {
    public static class Base64 {
        public static int ComputeDecodedLength(ReadOnlySpan<byte> source);
        public static int ComputeEncodedLength(int sourceLength);
        public static TransformationStatus Decode(ReadOnlySpan<byte> source, Span<byte> destination, out int bytesConsumed, out int bytesWritten);
        public static TransformationStatus DecodeInPlace(Span<byte> buffer, out int bytesConsumed, out int bytesWritten);
        public static TransformationStatus Encode(ReadOnlySpan<byte> source, Span<byte> destination, out int bytesConsumed, out int bytesWritten);
        public static TransformationStatus EncodeInPlace(Span<byte> buffer, int sourceLength, out int bytesWritten);
    }

ahsonkhan

public static bool TryParseInt32(ReadOnlySpan<byte> text, out int value, out int bytesConsumed)
{
    int textLength = text.Length;
    if (textLength < 1) goto FalseExit;

    int sign = 1;
    int index = default;
    int num = text[index];

ahsonkhan

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 

ahsonkhan

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

        private const int MinimumBufferSize = 256;

ahsonkhan

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)
    {

ahsonkhan

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

ahsonkhan

 	[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

ahsonkhan

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.