46 lines
1.2 KiB
Scheme
46 lines
1.2 KiB
Scheme
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;;; 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 interrupt-count)
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(let ((old-handler (vector-ref (interrupt-handlers-vector) count)))
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(set-interrupt-handler
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count
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(lambda stuff
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(register-interrupt count)
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(apply old-handler stuff)))
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(loop (+ count 1))))))
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