So I can write (define (make-obj stream) (define res (obj (open-output-file "out.dat"))) (define will (make-will-executor)) (will-register will res (lambda (x) (close-output-port (obj-file x)))) (thread (lambda () (let loop () (will-try-execute will) (sleep 1) (loop)))))
to make my objects? Additional threads don't hinder performance, do they? Or should I somehow figure out if the thread is already running, don't run it and use common `will' for all objects? Sat, 2 Aug 2014 07:00:04 -0500 от Robby Findler <[email protected]>: >One way is to set up a separate thread to do that. > >The reason they are not called automatically is sometimes running the >procedure passed to will-register needs to access some shared state >and so your program must be allowed to be in control of the timing of >the executor. > >In this case, it sounds like you can run the executor at any time, so >just creating a thread to close the port inside my-obj should work >fine. > >Robby > > >On Sat, Aug 2, 2014 at 6:15 AM, Roman Klochkov < [email protected] > wrote: >> Then how? >> >> Suppose I have >> (struct obj (file)) >> (define my-obj (obj (open-output-file "out.dat"))) >> >> What I have to write to close the file, when my-obj will be GC'ed? >> >> I can write >> (define will (make-will-executor)) >> (will-register will my-obj (lambda (x) (close-output-port (obj-file x)))) >> >> But as far as I understand, it will not be called until `will-execute' or >> `will-try-execute' will be manually called? >> >> Then how to call will-try-execute when GC is collecting my-obj? >> >> >> Sat, 2 Aug 2014 11:57:32 +0100 от Matthew Flatt < [email protected] >: >> >> No, use the safe "will executors" API, instead. >> >> The unsafe finalizer API is for low-level, atomic finalization. Closing a >> port can flush buffers and more, and it's not a good idea to do that in an >> unsafe atomic context. >> >>> On Aug 2, 2014, at 11:12 AM, Roman Klochkov < [email protected] > wrote: >>> >>> I have a structure, that has a filestream inside it. File have to be >>> cosed, when the structure is not used anymore (so gargbage collected). >>> >>> Is the best way to do >>> (require ffi/unsafe) >>> (register-finalizer my-obj >>> (lambda (x) (close-output-port (obj-file x)))) >>> >>> ? >>> >>> It seems doing right thing, but why `ffi/unsafe'? Is it OK, when my >>> program actually doesn't use FFI? >>> >>> >>> -- >>> Roman Klochkov >>> ____________________ >>> Racket Users list: >>> http://lists.racket-lang.org/users >> >> >> >> -- >> Roman Klochkov >> >> ____________________ >> Racket Users list: >> http://lists.racket-lang.org/users >> -- Roman Klochkov
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