On 6/16/2021 7:01 PM, Shu-Hung You wrote:
Out of curiosity, I wrapped David's code in a loop and tried to write
509 bytes in each iteration. From the output, it looks like CS doesn't
implement pipes using a fixed-size buffer. I'm also not sure how many
different buffers there are. I think this has something to do with
George's question.
:
Continuing in this vein, it seems that the count of bytes written starts
small and then doubles with each successive write until finished (or
until the buffer fills). I'm guessing this has to do with thread
scheduling applied to I/O ... ie. try a short write (minimum quantum),
and if it isn't finished try a longer write (longer quantum) ???
(define msg-size 15700)
(define bstr (make-bytes msg-size 42))
(define rx-pipe-size 16384)
(define-values (rx-in rx-out) (make-pipe rx-pipe-size))
(define (available?)
(- rx-pipe-size (pipe-content-length rx-out)))
(let loop ((start 0) (full? #f))
(cond
[full? (displayln "buffer full")]
[(>= start msg-size) (displayln "done")]
[else
(let ((written (write-bytes-avail* bstr rx-out start)))
(printf "written: ~a starting at ~a~n" written start)
; (printf "available: ~a~n" (available?))
(loop (+ start written) (= written 0))
)
]))
written: 15 starting at 0
written: 16 starting at 15
written: 32 starting at 31
written: 64 starting at 63
written: 128 starting at 127
written: 256 starting at 255
written: 512 starting at 511
written: 1024 starting at 1023
written: 2048 starting at 2047
written: 4096 starting at 4095
written: 7509 starting at 8191
done
With the "msg" size changed to exceed the buffer:
written: 15 starting at 0
written: 16 starting at 15
written: 32 starting at 31
written: 64 starting at 63
written: 128 starting at 127
written: 256 starting at 255
written: 512 starting at 511
written: 1024 starting at 1023
written: 2048 starting at 2047
written: 4096 starting at 4095
written: 8192 starting at 8191
written: 1 starting at 16383
written: 0 starting at 16384
buffer full
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