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Provides an abstraction for a managed object, known as a resource, with a fixed lifetime. This might be used to create a file port that will automatically close if unused for some amount of time.
- make-timed-resource OPENER CLOSER TIMEOUT #!optional NAMEprocedure
Returns a new timed-resource object that covers a resource with a lifetime of TIMEOUT seconds. The resource is acquired by the OPENER and released by the CLOSER. An acquired resource will be released automatically at the end of its' life.
- (procedure () *) ; returns the resource-object
- (procedure (*)) ; takes the resource-object (returned by OPENER)
- number ; seconds
- * ; prefix for the gensym of the created timed-resource
No attempt is made to serialize access to a resource, this is up to the caller; just don't share the thing.
Exceptions occurring during resource acquisition or release abort the operation. Exceptions during resource release at shutdown are just displayed but no further action is taken.
- with-timed-resource TIMED-RESOURCE ACTIONprocedure
Returns the result of invoking ACTION with the resource covered by the TIMED-RESOURCE. The acquired resource will not be released during the extent of the with-timed-resource invocation.
ACTION is a (procedure (timed-resource) *).
- timed-resource? OBJECTprocedure
Is the OBJECT a timed-resource?
- timed-resource-name TIMED-RESOURCEprocedure
Returns unique id for TIMED-RESOURCE.
- default-timed-resource-timeout SECONDSprocedure
Gets & sets the number of seconds to wait for a thread to quit.
Default is #f.
Currently only used at shutdown.
(use timed-resource srfi-4) ;; Returns a blob of random bits. ;; ;; (random-blob [BITS]) ;; BITS - the number of random bits, default is 128 (define random-blob (let ( (*tr-random-dev* (make-timed-resource ;random device (*nix only) (lambda () (open-input-file "/dev/random" #:binary)) (lambda (port) (close-output-port port)) ;open for 10 seconds 10.0)) (round-bytes (lambda (x) (fx/ (fx+ x 7) 8))) ) (lambda (#!optional (bits 128)) (with-timed-resource *tr-random-dev* (lambda (port) (u8vector->blob (read-u8vector (round-bytes bits))))) ) ) )
- Add types.
- Use compiled setup-helper (& un-hide).
- Fix for reporting an expected condition, timed-resource-closed, during shutdown.
- Moved from srfi-27 into own extension.
Copyright (C) 2010-2017 Kon Lovett. All rights reserved.
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