Damn. Sorry, I posted out of sync versions of code and output. This is
correct:
(define bstr (make-shared-bytes 509 5))
(define rx-pipe-size 16777216)
(define-values (rx-in rx-out) (make-pipe rx-pipe-size))
(define (room-in-rx-pipe? bstr)
(define avail (- rx-pipe-size (pipe-content-length rx-out)))
(displayln (format "avail: ~a" avail))
(<= (bytes-length bstr) avail))
(displayln (format "space available? ~a " (room-in-rx-pipe? bstr)))
(displayln (format "pipe content length: ~a" (pipe-content-length rx-out)))
(define num-bytes-written (write-bytes-avail* bstr rx-out))
(unless (eq? num-bytes-written (bytes-length bstr))
(displayln (format "rx buffer overflow. pipe content length: ~a, written
~a, expected ~a"
(pipe-content-length rx-out) num-bytes-written
(bytes-length bstr))))
(displayln "done")
-------- output:
avail: 16777216
space available? #t
pipe content length: 0
rx buffer overflow. pipe content length: 15, written 15, expected 509
done
On Wed, Jun 16, 2021 at 2:11 PM George Neuner <[email protected]> wrote:
>
> On 6/16/2021 1:19 PM, David Storrs wrote:
>
> I'm getting bytes off the wire and attempting to write them to a port. I
> have a check in place to verify that the pipe has free space but when I
> attempt to reports that yes, there is space, and then it writes and fails
> regardless and I'm not sure why. The following is a simplified version of
> the code but it produces the same results as the live version.
>
> I've dug through the docs on write-bytes-avail* and pipes and I'm
> scratching my head. Any thoughts?
>
> ------- code
> #lang racket
> (define bstr (make-shared-bytes 509 5))
> (define rx-pipe-size 16777216)
> (define-values (rx-in rx-out) (make-pipe rx-pipe-size))
>
> (define (room-in-rx-pipe? bstr)
> (define avail (- rx-pipe-size (pipe-content-length rx-out)))
> (displayln (format "space available: ~a" avail))
> (<= (bytes-length bstr) avail))
>
> (displayln (format "space available? ~a " (room-in-rx-pipe? bstr)))
> (define num-bytes-written (write-bytes-avail* bstr rx-out))
> (unless (eq? num-bytes-written (bytes-length bstr))
> (displayln (format "rx buffer overflow. num-bytes-written ~a, expected
> ~a"
> num-bytes-written (bytes-length bstr))))
>
> (displayln "done")
> -------- /code
>
> The output is:
>
> ------- output
> avail: 16777216
> space available? #t
> pipe content length: 0
> rx buffer overflow. pipe content length: 15, written 15, expected 509
> done
> ------- /output
>
>
>
> I'm not sure what's going on either, but your output says the pipe
> contains 15 characters/bytes and THAT will cause *write-bytes-avail** to
> fail ... it fails if there is existing buffered content. I suspect that it
> will work if you substitute *write-bytes-avail* (no *) or have
> something read from the pipe before writing to it.
>
> I've never used Racket's pipes, but this looks very much like a connect
> handshake issue.
>
> George
>
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