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(sqlite3:with-transaction
db
(lambda ()
(condition-case
(let* ((curr-val (db:no-sync-get/default db keyname #f)))
(if curr-val
(match (db:extract-time-identifier curr-val) ;; result->timestamp, identifier
((timestamp ident)
(if (equal? ident identifier)
(cons #t timestamp) ;; this *is* my lock
(cons #f timestamp))) ;; nope, not my lock
(else (cons #f #f))) ;; nope, not my lock
(let ((curr-sec (current-seconds))
(lock-value (if identifier
(conc (current-seconds)"+"identifier)
(current-seconds))))
(sqlite3:execute db "INSERT OR REPLACE INTO no_sync_metadat (var,val) VALUES(?,?);" keyname lock-value)
(cons #t curr-sec))))
(exn (io-error) (dbfile:print-err "ERROR: i/o error with no-sync db. Check permissions, disk space etc. and try again."))
(exn (corrupt) (dbfile:print-err "ERROR: database no-sync db is corrupt. Repair it to proceed."))
(exn (busy) (dbfile:print-err "ERROR: database no-sync db is locked. Try copying to another location, remove original and copy back."))
(exn (permission)(dbfile:print-err "ERROR: database no-sync db has some permissions problem."))
(exn () ;; (status done) ;; I don't know how to detect status done but no data!
(dbfile:print-err "ERROR: Unknown error with database no-sync db message: exn="(condition->list exn)", \n"
((condition-property-accessor 'exn 'message) exn))
#f)))))
;; transaction protected lock aquisition
;; either:
;; fails returns (#f . lock-creation-time)
;; succeeds (returns (#t . lock-creation-time)
;; use (db:no-sync-del! db keyname) to release the lock
;;
(define (db:no-sync-get-lock db keyname)
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(sqlite3:with-transaction
db
(lambda ()
(condition-case
(let* ((curr-val (db:no-sync-get/default db keyname #f)))
(if curr-val
(match (db:extract-time-identifier curr-val) ;; result->timestamp, identifier
((timestamp . ident)
(cons (equal? ident identifier) timestamp))
(else (cons #f 'malformed-lock))) ;; lock malformed
(let ((curr-sec (current-seconds))
(lock-value (if identifier
(conc (current-seconds)"+"identifier)
(current-seconds))))
(sqlite3:execute db "INSERT OR REPLACE INTO no_sync_metadat (var,val) VALUES(?,?);" keyname lock-value)
(cons #t curr-sec))))
(exn (io-error) (dbfile:print-err "ERROR: i/o error with no-sync db. Check permissions, disk space etc. and try again."))
(exn (corrupt) (dbfile:print-err "ERROR: database no-sync db is corrupt. Repair it to proceed."))
(exn (busy) (dbfile:print-err "ERROR: database no-sync db is locked. Try copying to another location, remove original and copy back."))
(exn (permission)(dbfile:print-err "ERROR: database no-sync db has some permissions problem."))
(exn () ;; (status done) ;; I don't know how to detect status done but no data!
(dbfile:print-err "ERROR: Unknown error with database no-sync db message: exn="(condition->list exn)", \n"
((condition-property-accessor 'exn 'message) exn))
(cons #f #f))))))
(define (db:no-sync-check-lock db keyname identifier)
(let* ((curr-val (db:no-sync-get/default db keyname #f)))
(match (db:extract-time-identifier curr-val) ;; result->timestamp, identifier
((timestamp . ident)
(cons (equal? ident identifier) ident))
(else (cons #f 'no-lock)))))
;; get the lock, wait 0.25 seconds and verify still have it.
;; this should not be necessary given the use of transaction in
;; db:no-sync-get-lock-with-id but it does seem to be needed
;;
(define (db:no-sync-lock-and-check db keyname identifier)
(let* ((result (db:no-sync-get-lock-with-id db keyname identifier))
(gotlock (car result)))
(if gotlock
(begin
(thread-sleep! 0.25)
(db:no-sync-check-lock db keyname identifier))
result)))
;; transaction protected lock aquisition
;; either:
;; fails returns (#f . lock-creation-time)
;; succeeds (returns (#t . lock-creation-time)
;; use (db:no-sync-del! db keyname) to release the lock
;;
(define (db:no-sync-get-lock db keyname)
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