29 lines
915 B
Scheme
29 lines
915 B
Scheme
(define *resource-counter* 0)
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(define-record-type resource :resource
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(really-make-resource count align! lock)
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resource?
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(count resource-count)
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(align! resource-align!)
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(lock resource-lock))
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(define (make-resource align! lock)
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(set! *resource-counter* (+ *resource-counter* 1))
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(really-make-resource *resource-counter* align! lock))
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(define (with-resources-aligned resources thunk)
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(let ((locks (map resource-lock
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(sort-list resources (lambda (r1 r2)
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(< (resource-count r1)
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(resource-count r2)))))))
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(for-each obtain-lock locks)
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(for-each
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(lambda (align!) (align!))
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(map resource-align! resources))
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(let ((val (with-handler
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(lambda (cond more)
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(for-each release-lock locks)
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(more))
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thunk)))
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(for-each release-lock locks)
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val))) |