CborReader requires a ReadOnlyMemory<byte>

[chrisspre]

CborReader has only one constructor and that requires a ReadOnlyMemory

Would it not be possible to pass in a ReadOnlySpan and therefore saving a potential allocation for the client of the reader?

[bartonjs]

CborReader can't save a ReadOnlySpan<byte> as a field because it is not a ref struct.

When we built it, we felt that a class is much more usable, and that there probably weren't many scenarios where the caller would have a span versus an array (or Memory)

[chrisspre]

Thanks Jeremy. I did not realize immediately that the Reader keeps a reference to the data. But it makes sense that it does.

[bartonjs]

Yeah, in a constructor ReadOnlySpan<byte> means "I make a copy" (unless it's a ref struct) and ReadOnlyMemory<byte> means "I hold a reference". It's nicer over arrays where it was sort of arbitrary of reference vs copy.

[chrisspre]

Understood.

It might be nice in the long run (for some advanced scenarios) to have a stateless CBOR "decoder" separate from the reader that I can point at an arbitrary span and it gives me back the "token"
e.g. static int ReadInt32(ReadOnlySpan<byte> span)
For cases where I own the byte array/span, know the position of the CBOR element and don't require the reader to scan over the byte array to get to that position and track the state (depth, nesting, etc. )
I think the code for this is already in the reader but all internal (PeekSignerInteger, AdvanceDataItemCounters, ...)

[c-ohle]

I avoid such problems by using ref Span's:
static int ReadInt32(ref ReadOnlySpan<byte> span)