Made arguments to OBTAIN-DOT-LOCK optional and supply sensible
defaults. All timings are now in seconds. Add interface procedure BREAK-DOT-LOCK. Indicate broken lock by BROKEN return value from OBTAIN-DOT-LOCK.
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@ -29,12 +29,19 @@
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;; STALE-TIME is the minimum age of a lock to be broken
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;; if #f, don't break the lock
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(define (obtain-dot-lock file-name retry-interval retry-number stale-time)
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(let ((lock-file-name (make-lock-file-name file-name)))
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(let loop ((retry-number retry-number))
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(define (obtain-dot-lock file-name . args)
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(let-optionals args ((retry-seconds 1)
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(retry-number #f)
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(stale-time 300))
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(let ((lock-file-name (make-lock-file-name file-name))
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(retry-interval (* retry-seconds 1000)))
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(let loop ((retry-number retry-number)
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(broken? #f))
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(cond
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((maybe-obtain-dot-lock file-name)
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#t)
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(if broken?
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'broken
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#t))
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((and stale-time
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(with-errno-handler
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((errno packet)
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@ -42,19 +49,23 @@
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(> (time)
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(+ (file-last-status-change (make-lock-file-name file-name))
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stale-time))))
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(with-errno-handler
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((errno packet)
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((errno/noent) 'dont-care))
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(delete-file lock-file-name))
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(loop retry-number))
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(break-dot-lock file-name)
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(loop retry-number #t))
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(else
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(sleep (+ (quotient (* retry-interval 3) 4)
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(random (quotient retry-interval 2))))
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(cond ((not retry-number)
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(loop retry-number))
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(loop retry-number broken?))
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((> retry-number 0)
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(loop (- retry-number 1)))
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(else #f)))))))
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(loop (- retry-number 1) broken?))
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(else
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#f))))))))
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(define (break-dot-lock file-name)
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(with-errno-handler
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((errno packet)
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((errno/noent) 'dont-care))
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(delete-file (make-lock-file-name file-name))))
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(define (with-dot-lock* file-name thunk)
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(dynamic-wind
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