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(define-module (guix-build-coordinator utils timeout)
#:use-module (ice-9 exceptions)
#:use-module (ice-9 suspendable-ports)
#:use-module ((ice-9 ports internal) #:select (port-poll))
#:export (&port-timeout
&port-read-timeout
&port-write-timeout
port-timeout-error?
port-read-timeout-error?
port-write-timeout-error?
with-port-timeouts))
(define &port-timeout
(make-exception-type '&port-timeout
&external-error
'(port)))
(define make-port-timeout-error
(record-constructor &port-timeout))
(define port-timeout-error?
(record-predicate &port-timeout))
(define &port-read-timeout
(make-exception-type '&port-read-timeout
&port-timeout
'()))
(define make-port-read-timeout-error
(record-constructor &port-read-timeout))
(define port-read-timeout-error?
(record-predicate &port-read-timeout))
(define &port-write-timeout
(make-exception-type '&port-write-timeout
&port-timeout
'()))
(define make-port-write-timeout-error
(record-constructor &port-write-timeout))
(define port-write-timeout-error?
(record-predicate &port-write-timeout))
(define* (with-port-timeouts thunk #:key timeout)
;; When the GC runs, it restarts the poll syscall, but the timeout remains
;; unchanged! When the timeout is longer than the time between the syscall
;; restarting, I think this renders the timeout useless. Therefore, this
;; code uses a short timeout, and repeatedly calls poll while watching the
;; clock to see if it has timed out overall.
(define poll-timeout-ms 200)
(define (wait port mode)
(let ((timeout-internal
(+ (get-internal-real-time)
(* internal-time-units-per-second timeout))))
(let loop ((poll-value
(port-poll port mode poll-timeout-ms)))
(if (= poll-value 0)
(if (> (get-internal-real-time)
timeout-internal)
(raise-exception
(if (string=? mode "r")
(make-port-read-timeout-error port)
(make-port-write-timeout-error port)))
(loop (port-poll port mode poll-timeout-ms)))
poll-value))))
(parameterize
((current-read-waiter
(lambda (port)
(wait port "r")))
(current-write-waiter
(lambda (port)
(wait port "w"))))
(thunk)))
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