[API Proposal]: Add Int128 and UInt128 BitConverter.GetBytes support

[ctigrisht]

Background and motivation

Get the underlying bytes of 128 bit integers for use in binary serialization and others

API Proposal

EDIT:
Signatures for the methods:

namespace System;

public static partial class BitConverter
{
    public static byte[] GetBytes(Int128 value);
    public static Int128 ToInt128(ReadOnlySpan<byte> value);
    public static Int128 ToInt128(byte[] value, int startIndex);
    public static bool TryWriteBytes(Span<byte> destination, Int128 value);

    public static byte[] GetBytes(UInt128 value);
    public static UInt128 ToUInt128(ReadOnlySpan<byte> value);
    public static UInt128 ToUInt128(byte[] value, int startIndex);
    public static bool TryWriteBytes(Span<byte> destination, UInt128 value);
}

API Usage

public void Example(Int128 value)
{
    var bytes = BitConverter.GetBytes(value);
    var newValue = BitConverter.ToInt128(bytes, 0);
}

Alternative Designs

No response

Risks

No response

[dotnet-issue-labeler]

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[ghost]

Tagging subscribers to this area: @dotnet/area-system-numerics
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Issue Details

---

Background and motivation

Get the underlying bytes of 128 bit integers for use in binary serialization and others

API Proposal

// check usage

API Usage

public void Example(Int128 value)
{
    var bytes = BitConverter.GetBytes(value);
    var newValue = BitConverter.ToInt128(bytes, 0);
}

Alternative Designs

No response

Risks

No response

Author:	ctigrisht
Assignees:	-
Labels:	api-suggestion, area-System.Numerics, untriaged
Milestone:	-

[tannergooding]

@ctigrisht can you please add the API proposal containing the full signature of both APIs being asked for here?

Once that's done, I can mark this ready for review.

[ctigrisht]

@tannergooding

There you go :)
I also added it to the original post

byte[] GetBytes(Int128 value);
Int128 ToInt128(ReadOnlySpan<byte> value);
Int128 ToInt128(byte[] value, int startIndex);

byte[] GetBytes(UInt128 value);
UInt128 ToUInt128(ReadOnlySpan<byte> value);
UInt128 ToUInt128(byte[] value, int startIndex);

[tannergooding]

Thanks!

I tweaked it just slightly further to be in the format that API review expects (we require the namespace, class, and full signature to be displayed).

I also ensured that TryWriteBytes was included as that will be required for parity with what is exposed for other types.

namespace System;

public static partial class BitConverter
{
    public static byte[] GetBytes(Int128 value);
    public static Int128 ToInt128(ReadOnlySpan<byte> value);
    public static Int128 ToInt128(byte[] value, int startIndex);
    public static bool TryWriteBytes(Span<byte> destination, Int128 value);

    public static byte[] GetBytes(UInt128 value);
    public static UInt128 ToUInt128(ReadOnlySpan<byte> value);
    public static UInt128 ToUInt128(byte[] value, int startIndex);
    public static bool TryWriteBytes(Span<byte> destination, UInt128 value);
}

[ctigrisht]

@tannergooding Thanks! My bad, I've never done this before so I was unsure of the format.

[bartonjs]

Looks good as proposed.

namespace System;

public static partial class BitConverter
{
    public static byte[] GetBytes(Int128 value);
    public static Int128 ToInt128(ReadOnlySpan<byte> value);
    public static Int128 ToInt128(byte[] value, int startIndex);
    public static bool TryWriteBytes(Span<byte> destination, Int128 value);

    public static byte[] GetBytes(UInt128 value);
    public static UInt128 ToUInt128(ReadOnlySpan<byte> value);
    public static UInt128 ToUInt128(byte[] value, int startIndex);
    public static bool TryWriteBytes(Span<byte> destination, UInt128 value);
}