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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 | ;; (container async-queue) -- a thread-safe asynchronous queue
;; Copyright (C) 2007 Andreas Rottmann <a dot rottmann at gmx dot at>
;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;;A asynchronous queue can be used to safely send messages from one
;;thread to another.
;;
;;; Code:
(define-module (container async-queue)
#:export (make-async-queue async-enqueue! async-dequeue!)
#:use-module (ice-9 q)
#:use-module (ice-9 threads)
#:use-module (oop goops))
(define-class <async-queue> ()
(queue #:init-form (make-q) #:getter queue)
(condv #:init-form (make-condition-variable) #:getter condv)
(mutex #:init-form (make-mutex) #:getter mutex)
(waiting-threads #:init-value 0 #:accessor waiting-threads))
(define (make-async-queue)
"Create a new asynchronous queue."
(make <async-queue>))
(define (async-enqueue! q elt)
"Enqueue @var{elt} into @var{q}."
(with-mutex (mutex q)
(enq! (queue q) elt)
(if (> (waiting-threads q) 0)
(signal-condition-variable (condv q)))))
(define (async-dequeue! q)
"Dequeue a single element from @var{q}. If the queue is empty, the
calling thread is blocked until an element is enqueued by another
thread."
(with-mutex (mutex q)
(cond ((q-empty? (queue q))
(set! (waiting-threads q) (+ (waiting-threads q) 1))
(let loop ()
(cond ((q-empty? (queue q))
(wait-condition-variable (condv q) (mutex q))
(loop))))
(set! (waiting-threads q) (- (waiting-threads q) 1))))
(deq! (queue q))))
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