> Scheme Request for Implementation 181,
> "Custom ports,"
> by John Cowan,

LGTM. Thanks for writing this up. Props for re-using R6RS interfaces.

Two questions:

- How are error situations handled? If my reading is correct, the
user-supplied read! and write! procedures should return zero
(bytes/characters read/written) on error. Presumably they can also raise
an exception if they want to.

- What about object ports (i.e. ports where the fundamental unit or
reading/writing is an arbitrary Scheme object, not a character or a
byte) - too complex for this SRFI?