Partial cleanup of SpanExtensionsLab

[ahsonkhan]

Working towards - #1314 / #1292

• Move to System.Binary

  • public static T Read(this ReadOnlySpan slice) where T : struct;
  • public static T Read(this Span slice) where T : struct;
  • public static bool TryRead(this ReadOnlySpan slice, out T value) where T : struct;
  • public static bool TryRead(this Span slice, out T value) where T : struct;
  • public static bool TryWrite(this Span slice, T value) where T : struct;
  • public static void Write(this Span slice, T value) where T : struct;

• Moved to SpanExtensions: (PR Adding Span.StartsWith corefx#17322)

  • public static bool StartsWith(this ReadOnlySpan bytes, ReadOnlySpan slice);
  • public static bool StartsWith(this ReadOnlySpan items, ReadOnlySpan slice) where T : struct, IEquatable;

• Move to BuffersExtension in experimental

  • public static int IndexOf(this ReadOnlySpan buffer, byte value0, byte value1);
  • public static int IndexOf(this ReadOnlySpan buffer, byte value0, byte value1, byte value2);
  • public static int IndexOf(this Span buffer, byte value0, byte value1);
  • public static int IndexOf(this Span buffer, byte value0, byte value1, byte value2);
  • public static int SequentialIndexOf(this ReadOnlySpan span, byte value);
  • public static int SequentialIndexOf(this Span span, byte value);
  • public static bool TryIndicesOf(this ReadOnlySpan buffer, byte value, Span indices, out int numberOfIndices);
  • public static bool TryIndicesOf(this Span buffer, byte value, Span indices, out int numberOfIndices);

• Remove (this should be on ArraySegment)

  • public static ArraySegment Slice(this ArraySegment source, int count);

• Delete:

  • public static bool StartsWith(this ReadOnlySpan str, ReadOnlySpan value);

NOTE:
Moving the following to System.Buffers.Experimental\System\Buffers\BufferExtensions.cs causes System.IO.Pipelines to take a dependency on System.Buffers.Experimental.

    - public static int IndexOf(this ReadOnlySpan<byte> buffer, byte value0, byte value1);
    - public static int IndexOf(this ReadOnlySpan<byte> buffer, byte value0, byte value1, byte value2);
    - public static int IndexOf(this Span<byte> buffer, byte value0, byte value1);
    - public static int IndexOf(this Span<byte> buffer, byte value0, byte value1, byte value2);

The IndexOf with multiple byte values are used in ReadCursorOperations.Seek, here:
https://github.com/aspnet/KestrelHttpServer/blob/f6e5e74d9551df57effda19c856352608374cee7/src/Microsoft.AspNetCore.Server.Kestrel/Internal/Http/KestrelHttpParser.cs#L273

This function is implemented here:

corefxlab/src/System.IO.Pipelines/ReadCursorOperations.cs

Line 32 in 3bd0ffd

public static int Seek(ReadCursor begin, ReadCursor end, out ReadCursor result, byte byte0, byte byte1)

What should we do about this dependency? This is the only that System.IO.Pipelines depends on Buffers.Experimental.
If we remove those Seek overloads (and the one reference to it in kestrel), we could remove this dependency.

Edit:
Adding back IndexOf overloads to SpanExtensionsLab (in Buffes.Primitives). Will remove them once they are ported over to corefx (in System.Memory.dll).

[davidfowl]

Moving the following to System.Buffers.Experimental\System\Buffers\BufferExtensions.cs causes System.IO.Pipelines to take a dependency on System.Buffers.Experimental.

I'm not a fan of this. Move those methods to corefx proper before breaking this package.

[KrzysztofCwalina]

Yeah, if the APIs are used by pipelines, and we know they have benefits, we should just have them in SpanExtensions. BTW, I think it would be ok to move the APIs to SpanExtensions without proving they have benefits (perf) and measure later.

Otherwise the PR looks good.

[KrzysztofCwalina]

Looks good. Thanks!

[KrzysztofCwalina]

Ah, I think I merged Ben's rename and now there is a conflict. @ahsonkhan, could you please resolve and then just merge? Thanks.

[ahsonkhan]

@KrzysztofCwalina, resolved the conflicts.