On 24-Jul-06, at 6:34 PM, Christian wrote:

Hello

Is there a way to turn a POSIX filehandle into a Gambit scheme port, or could it be added?

I'm imaging something like: (posix-fd->port 0) => returning an input-output port or (open-port (list posix-fd: 0 direction: 'input)) ;; in case one wants ;; the direction to be preserved. or similar.

There is an internal procedure for doing this. It is called ##open- predefined and you can use it like this:

(define in 1) (define out 2) (define inout 3) (define stderr (##open-predefined out '(STDERR) 2)) stderr

#<output-port #3 (STDERR)>

(display "hello\n" stderr) (force-output stderr)

hello

The third parameter of ##open-predefined is the file descriptor and the fourth optional parameter is the port settings. Note that this will only work on Unix (Windows does not use file descriptors). The special file descriptors -1, -2, -3 and -4 represent STDIN, STDOUT, STDERR and the console on Unix and Windows.

This would allow things like implement functions creating unix sockets, or maybe even UDP ports; well for the latter maybe more changes would actually be needed.

My working version of Gambit has preliminary support for UDP and RAW sockets.

Maybe I should ask (instead of the above) how one can, from a C function, read/write from/to a file descriptor without blocking the system (using the scheduler, thus possibly running other scheme code in the mean time).

One way it to use ##open-predefined and have the C code call into Scheme. Why do you need this? There is not a general solution that will work in all situations.

Marc