internal static unsafe Guid Read(ref ProtoReader.State state)
{
// note: we can't use a stackalloc-span here because the compiler doesn't trust
// state, which is a ref-local (and can store spans), not to store it; since we *don't*
// do that, we can be evil
byte *ptr = stackalloc byte[MAX_LENGTH];
var available = state.ReadBytes(new Span <byte>(ptr, MAX_LENGTH));
char standardFormat;
switch (available.Length)
{
case 0:
return(Guid.Empty);
case 16: // treat as big-endian bytes
// expand those bytes to hex, backwards so we don't overwrite live data
int write = 32;
for (int i = 15; i >= 0; i--)
{
var val = ptr[i];
ptr[--write] = ToHex(val & 0b1111);
ptr[--write] = ToHex((val >> 4) & 0b1111);
}
available = new Span <byte>(ptr, 32);
standardFormat = 'N';
break;
case 32: // no hyphens
standardFormat = 'N';
break;
case 36: // hyphens
standardFormat = 'D';
break;
default:
ThrowHelper.Format($"Unexpected Guid length: {available.Length}");
return(default);
}
if (!(Utf8Parser.TryParse(available, out Guid guid, out int bytes, standardFormat) && bytes == available.Length))
{
ThrowHelper.Format($"Failed to read Guid: '{Encoding.UTF8.GetString(ptr, available.Length)}'");
}
return(guid);