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@fukamachi fukamachi/lock-pool
Created Oct 14, 2017

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Lock to allow n times to acquire
(defpackage #:lock-pool
(:use #:cl)
(:import-from #:bordeaux-threads)
(:import-from #:alexandria
#:once-only)
(:export #:lock-pool
#:make-lock-pool
#:acquire-lock-in-pool
#:release-lock-in-pool
#:with-lock-pool-held))
(in-package #:lock-pool)
(defstruct (lock-pool (:constructor %make-lock-pool))
(size 0)
(limit 0)
(lock (bt:make-recursive-lock))
(condvar (bt:make-condition-variable)))
(defun make-lock-pool (size)
(%make-lock-pool :size size))
(defun acquire-lock-in-pool (pool)
(with-slots (size limit lock condvar) pool
(bt:with-recursive-lock-held (lock)
(if (= size limit)
(progn
(bt:condition-wait condvar lock)
(acquire-lock-in-pool pool))
(incf limit)))))
(defun release-lock-in-pool (pool)
(with-slots (size limit lock condvar) pool
(when (= limit 0)
(return-from release-lock-in-pool nil))
(bt:with-recursive-lock-held (lock)
(let ((should-notify (= limit size)))
(decf limit)
(when should-notify
(bt:condition-notify condvar))
t))))
(defmacro with-lock-pool-held ((pool) &body body)
(once-only (pool)
`(progn
(acquire-lock-in-pool ,pool)
(unwind-protect (progn ,@body)
(release-lock-in-pool ,pool)))))
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