78 lines
2.2 KiB
Scheme
78 lines
2.2 KiB
Scheme
;;; Functional event system.
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;;; System by Olin Shivers, implementation by David Fisher
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(define-record event
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type
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(next (make-placeholder))
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((disclose e) (list "event" (event:type e))))
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;Not exported!
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(define *most-recent-event* (make-event interrupt/cont))
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(define event-lock (make-lock))
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(define (most-recent-event) *most-recent-event*)
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(define (next-event event) (placeholder-value (event:next event)))
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(define (event-type event) (event:type event))
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;Called when the interrupt actually happened.
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(define (register-interrupt type)
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(obtain-lock event-lock)
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(let ((new-event (make-event type)))
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(placeholder-set! (event:next *most-recent-event*) new-event)
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(set! *most-recent-event* new-event))
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(release-lock event-lock))
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;Wait for an event of a certain type.
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(define (wait-interrupt type pre-event)
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(let ((event (next-event pre-event)))
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(if (eq? (event-type event) type)
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event
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(wait-interrupt type event))))
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;Initialize the system.
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(define (install-event-handlers!)
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(let loop ((count 0))
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(if (< count (number-of-interrupts))
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(begin
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;we're not interested in the setter-function here:
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(low-interrupt-register
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count
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(lambda (enabled-interrupts)
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(register-interrupt count)))
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(loop (+ count 1))))))
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;;; extensions by JMG
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;;; takes list of interrupt/xxx's
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;;; blocks until one of the interrupts in the set occurs
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(define (wait-interrupt-set set pre-event)
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(let ((event (next-event pre-event)))
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(if (memq (event-type event) set)
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event
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(wait-interrupt-set set event))))
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; would need placeholder-queue exported..
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;(define (placeholder-value-set? placeholder)
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; (not (placeholder-queue placeholder)))
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(define (most-recent-event? event)
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(eq? event (most-recent-event)))
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(define (nonblockwait-interrupt type event )
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(general-nonblockwait-interrupt type event eq?))
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(define (nonblockwait-interrupt-set set event )
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(general-nonblockwait-interrupt set event memq))
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(define (general-nonblockwait-interrupt waiting-for pre-event compare?)
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(if (most-recent-event? pre-event)
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#f
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(let ((event (next-event pre-event)))
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(if (compare? (event-type event) waiting-for)
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event
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(general-nonblockwait-interrupt waiting-for event compare?)))))
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