Support for ring buffers or buffer-spanning messages

[dcsommer]

I've been reading through the API of untrusted and it seems great for parsing network messages in general, but there are a few edge cases I'm wondering how to handle and it seems there may be a slight gap in the API. Sometimes a logical message (e.g. a TCP frame) can be split across multiple packets and end up in different buffers. These buffers are typically chained together in some kind of ring buffer structure. I don't see a way to nicely splice together multiple slices and handle them as a contiguous Input.

Also, in network applications, handling partially received data is the norm. For instance, a single packet may include 1 complete message and half of the next. Using Input::read_all() would return incomplete_read if a packet doesn't contain exactly whole messages. So, it seems using Reader::new() directly would be the way to go, but the documentation of that function discourages its direct use.

[briansmith]

I'm open to doing this, but somebody else would need to do the design, initial implementation, and tests. Then I could try changing webpki to support such non-contiguous inputs, which might be pretty useful. (That would probably require changing ring's signature public key parser to support such non-contiguous inputs too.)