Add ByteBuffer methods getUTF8ValidatedString and readUTF8ValidatedString

[adam-fowler]

Add methods to ByteBuffer to read validated UTF8 strings

Motivation:

The current readString and getString methods of ByteBuffer do not verify that the string being read is valid UTF8. The Swift 6 standard library comes with a new initialiser String(validating:as:). This PR adds alternative methods to ByteBuffer which uses this instead of String(decoding:as:).

Modifications:

Added ByteBuffer.getUTF8ValidatedString(at:length:)
Added ByteBuffer.readUTF8ValidatedString(length:)

Result:

You can read strings from a ByteBuffer and be certain they are valid UTF8

[Lukasa]

Thanks for this! I think the API design needs a bit of a tweak.

I also wonder if we can implement an older-Swift fallback using https://developer.apple.com/documentation/swift/string/init(validatingutf8:)-208fn.

[adam-fowler]

Thanks for this! I think the API design needs a bit of a tweak.

I also wonder if we can implement an older-Swift fallback using https://developer.apple.com/documentation/swift/string/init(validatingutf8:)-208fn.

The problem with using the above function is it requires the string to be null terminated. I guess I could copy it out to a separate buffer and add the null termination.

[Lukasa]

Oh, we could do this one instead: https://developer.apple.com/documentation/swift/string/init(utf8string:)-8qmaq

[adam-fowler]

Oh, we could do this one instead: https://developer.apple.com/documentation/swift/string/init(utf8string:)-8qmaq

Which also requires a null-terminated string

[Lukasa]

Fantastic, I'm really happy with this. Thanks @adam-fowler!

[Lukasa]

Looks like there are a few compile errors in the unit tests on older Swift compilers.

[Lukasa]

FWIW, I think it's usually better to put the compiler guards inside the test function, and throw XCTSkip otherwise to mark the test as explicitly skipped.

[adam-fowler]

FWIW, I think it's usually better to put the compiler guards inside the test function, and throw XCTSkip otherwise to mark the test as explicitly skipped.

done