RFC4122 compatible binary representation for GUID

[huoyaoyuan]

Background and Motivation

Previous discussions: #23868 #29523
Currently, the Guid type uses "MS quirk" binary representation. It's hard to use it to communicate with RFC4122 compatible (all-BigEndian) representations.

Proposed API

namespace System
{
    public struct Guid
    {
        public Guid(byte[]);
        public Guid(ReadOnlySpan<byte>);
+        public static Guid FromBigEndian(ReadOnlySpan<byte>);

        public byte[] ToByteArray();
+        public byte[] ToBigEndianByteArray();

        public bool TryWriteBytes(Span<byte>);
+        public bool TryWriteBigEndianBytes(Span<byte>);
    }
}

Usage Examples

Guid guid = new Guid("00112233-4455-6677-8899-aabbccddeeff");
var bytes = guid.ToBigEndianByteArray();
// Gets an array encodes bytes in the same order of string representation

Alternative Designs

Use a new type duplicates the api surface of Guid.

Risks

People may get confused about which representation to use.

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[AaronRobinsonMSFT]

@GrabYourPitchforks I think you previously had some thoughts in this area. Perspective on this proposal?

[ghost]

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Issue Details

---

Background and Motivation

Previous discussions: #23868 #29523
Currently, the Guid type uses "MS quirk" binary representation. It's hard to use it to communicate with RFC4122 compatible (all-BigEndian) representations.

Proposed API

namespace System
{
    public struct Guid
    {
        public Guid(byte[]);
        public Guid(ReadOnlySpan<byte>);
+        public static Guid FromBigEndian(ReadOnlySpan<byte>);

        public byte[] ToByteArray();
+        public byte[] ToBigEndianByteArray();

        public bool TryWriteBytes(Span<byte>);
+        public bool TryWriteBigEndianBytes(Span<byte>);
    }
}

Usage Examples

Guid guid = new Guid("00112233-4455-6677-8899-aabbccddeeff");
var bytes = guid.ToBigEndianByteArray();
// Gets an array encodes bytes in the same order of string representation

Alternative Designs

Use a new type duplicates the api surface of Guid.

Risks

People may get confused about which representation to use.

Author:	huoyaoyuan
Assignees:	-
Labels:	api-suggestion, area-System.Runtime, untriaged
Milestone:	-

[GrabYourPitchforks]

IMO this direction solves the heartache I had with #23868. It's not adding new GUID factories, so it shouldn't contribute to significant consumer confusion. It's just allowing users to control how the structure is converted to / from a binary blob.

[danmoseley]

@GrabYourPitchforks based on your comment above, should we mark as ready for review?

[tannergooding]

I wonder if users are going to expect a TryWriteBigEndian API to match RFC4122 when the format of Guid itself is the Microsoft representation.

Having the name TryWriteRfc4122Bytes might be a "better" name in some sense due to that. Having a BigEndian API without a corresponding LittleEndian API is another concern.

[huoyaoyuan]

Should the name be discussed during API review? I'm somehow OK with Rfc4122 in the name, but generally I haven't seen spec ids mentioned much in .NET APIs.

My original idea was mentioning "RFC4122 compatible" and "Microsoft OLE compatible" in xml doc.

[huoyaoyuan]

Closed in favor of #86798.