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; Part of Scheme 48 1.9. See file COPYING for notices and license.
; Authors: Richard Kelsey, Jonathan Rees
; Condition variables (cells for which readers block until the next write).
;
; (make-condvar [id]) -> condvar
; (condvar-has-value? condvar) -> boolean
; (condvar-value condvar) -> value
; (maybe-commit-and-wait-for-condvar condvar) -> boolean
; (condvar-set! condvar value)
(define-synchronized-record-type condvar :condvar
(really-make-condvar queue has-value? id)
(has-value? value) ; synchronize on these
condvar?
(queue condvar-queue)
(has-value? condvar-has-value? set-condvar-has-value?!)
(value condvar-value set-condvar-value!)
(id condvar-id))
(define-record-discloser :condvar
(lambda (condvar)
(if (condvar-id condvar)
(list 'condvar (condvar-id condvar))
'(condvar))))
(define (make-condvar . id-option)
(really-make-condvar (make-queue)
#f
(if (null? id-option)
#f
(car id-option))))
(define (maybe-commit-and-wait-for-condvar condvar . maybe-deadlock?)
(apply maybe-commit-and-block-on-queue (condvar-queue condvar) maybe-deadlock?))
(define (maybe-commit-and-set-condvar! condvar value)
(set-condvar-value! condvar value)
(set-condvar-has-value?! condvar #t)
(maybe-commit-and-make-ready (condvar-queue condvar)))
(define (condvar-has-waiters? condvar)
(not (thread-queue-empty? (condvar-queue condvar))))
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