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Block on remove if Q is empty

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This commit is contained in:
Justin Ethier 2019-06-26 18:45:04 -04:00
parent 0b4803a7ef
commit 2e60569dd0
1 changed files with 15 additions and 19 deletions
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34
libs/cyclone/shared-queue.sld
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@ -29,7 +29,6 @@
queue-add!
%queue-add! ;; DEBUG
queue-remove!
%queue-remove! ;; DEBUG
queue-clear!
queue-size
queue-capacity
@ -50,13 +49,13 @@
;if start == end after an add, then vector is full, need to resize
(define-record-type <queue>
(%make-queue store start end lock)
(%make-queue store start end lock cv)
queue?
(store q:store q:set-store!)
(start q:start q:set-start!)
(end q:end q:set-end!)
(lock q:lock q:set-lock!)
;(empty-lock q:empty-lock q:set-empty-lock!)
(cv q:cv q:set-cv!)
)
(define (make-queue)
@ -66,7 +65,7 @@
0
0
(make-mutex)
;(make-mutex)
(make-condition-variable)
)))
(define (queue . elems)
@ -94,6 +93,7 @@
(mutex-lock! (q:lock q))
(%queue-add! q obj)
(mutex-unlock! (q:lock q))
(condition-variable-signal! (q:cv q))
)
(define (%queue-resize! q)
@ -115,23 +115,19 @@
)
(define (queue-remove! q)
(let ((result #f))
(let loop ()
(mutex-lock! (q:lock q))
(set! result (%queue-remove! q))
(mutex-unlock! (q:lock q))
result))
;- queue-remove! - remove item (when to block? would be nice if we can block until an item becomes available)
; maybe block by default, but have an optional timeout
(define (%queue-remove! q)
(cond
((= (q:start q) (q:end q))
(write "queue is already empty"))
(else
(let ((result (vector-ref (q:store q) (q:start q))))
(q:set-start! q (inc (q:start q) (vector-length (q:store q))))
result)))
)
(cond
((= (q:start q) (q:end q))
;; Wait for CV, indicating data is ready
(mutex-unlock! (q:lock q) (q:cv q))
(loop))
(else
(let ((result (vector-ref (q:store q) (q:start q))))
(q:set-start! q (inc (q:start q) (vector-length (q:store q))))
(mutex-unlock! (q:lock q))
result)))))
(define (queue-clear! q)
(mutex-lock! (q:lock q))