[API Proposal]: Convert.{From/To}HexString(utf8)

[kzrnm]

Background and motivation

Recent .NET have introduced APIs like IUtf8SpanParsable<T> and IUtf8SpanFormattable for directly reading and writing UTF-8. #81500
It would be beneficial to have similar APIs for Hex string conversions in the Convert class as well.

API Proposal

namespace System;

public static class Convert
{
        public static byte[] FromHexString(ReadOnlySpan<byte> utf8Source);
        public static OperationStatus FromHexString(ReadOnlySpan<byte> utf8Source, Span<byte> destination, out int charsConsumed, out int bytesWritten);
        public static bool TryToHexString(ReadOnlySpan<byte> source, Span<byte> utf8Destination, out int charsWritten);
        public static bool TryToHexStringLower(ReadOnlySpan<byte> source, Span<byte> utf8Destination, out int charsWritten);
}

API Usage

var helloWorld = Convert.FromHexString("48656C6C6F2C576F726C64"u8);
Console.WriteLine(Encoding.UTF8.GetString(helloWorld));

Alternative Designs

No response

Risks

Users might get confused between the input ReadOnlySpan and the output Span.

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[Tornhoof]

For base64 there is
https://learn.microsoft.com/en-us/dotnet/api/system.buffers.text.base64?view=net-9.0

That one should cover your utf8 Span needs.

[kzrnm]

@Tornhoof Hmm, I have narrow this proposal down to focus on Hex strings.

[huoyaoyuan]

I'd like to get hex casing also included. Currently only upper case is supported in ToHexString.

[kzrnm]

@huoyaoyuan Wouldn't it already be supported by TryToHexStringLower or ToHexStringLower?

[huoyaoyuan]

Wouldn't it already be supported by TryToHexStringLower or ToHexStringLower?

Just realized ToHexStringLower was included in 9.0. So the UTF-8 overloads should also include them, respectively.