public override int Read(Span <byte> buffer)
{
var s = part.AsSpan().Slice((int)Position, Math.Min(buffer.Length, part.Length - (int)Position));
s.CopyTo(buffer);
Position += s.Length;
return(s.Length);
}
void ChopTrimPart(IMessagePart part)
{
var bytes0 = Guid.NewGuid().ToByteArray();
var int0 = (uint)Util.rng.Next(1000, 1000000);
var int1 = (uint)Util.rng.Next(1000, 1000000);
part.Append(bytes0);
part.Insert(int0);
part.Insert(int0);
part.Trim((UIntPtr)4);
part.Trim(out var trim);
Assert.Equal(int0, trim);
Assert.True(Util.BytesEqual(bytes0, part.AsSpan()));
part.Append(int1);
part.Append(int1);
part.Chop((UIntPtr)4);
part.Chop(out var chop);
Assert.Equal(int1, chop);
Assert.True(Util.BytesEqual(bytes0, part.AsSpan()));
}