Re: %default-port-conversion-strategy and string ports

[ludo@gnu.org (Ludovic Courtès)]

Hi David,

Ports in Guile can be used to write characters, or bytes, or both.  In
particular, every port (including string ports, void ports, etc.) has an
“encoding”, which is actually only used for textual I/O.

Conversely, an R6RS port is either textual or binary, but not both.

IMO, one advantage of mixed text/binary ports is to allow things like this:

  scheme@(guile-user)> (define (string->utf16 s)
                         (let ((p (with-fluids ((%default-port-encoding "UTF-16BE"))
                                    (open-input-string s))))
                           (get-bytevector-all p)))
  scheme@(guile-user)> (string->utf16 "hello")
  $4 = #vu8(0 104 0 101 0 108 0 108 0 111)
  scheme@(guile-user)> (use-modules(rnrs bytevectors))
  scheme@(guile-user)> (utf16->string $4)
  $5 = "hello"

Thanks,
Ludo’.