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+;;;; "process.scm", Multi-Processing for Scheme
+;;; Copyright (C) 1992, 1993 Aubrey Jaffer.
+;
+;Permission to copy this software, to redistribute it, and to use it
+;for any purpose is granted, subject to the following restrictions and
+;understandings.
+;
+;1. Any copy made of this software must include this copyright notice
+;in full.
+;
+;2. I have made no warrantee or representation that the operation of
+;this software will be error-free, and I am under no obligation to
+;provide any services, by way of maintenance, update, or otherwise.
+;
+;3. In conjunction with products arising from the use of this
+;material, there shall be no use of my name in any advertising,
+;promotional, or sales literature without prior written consent in
+;each case.
+
+(require 'full-continuation)
+(require 'queue)
+
+(define (add-process! thunk1)
+ (cond ((procedure? thunk1)
+ (defer-ints)
+ (enqueue! process:queue thunk1)
+ (allow-ints))
+ (else (slib:error "add-process!: wrong type argument " thunk1))))
+
+(define (process:schedule!)
+ (defer-ints)
+ (cond ((queue-empty? process:queue) (allow-ints)
+ 'still-running)
+ (else (call-with-current-continuation
+ (lambda (cont)
+ (enqueue! process:queue cont)
+ (let ((proc (dequeue! process:queue)))
+ (allow-ints)
+ (proc 'run))
+ (kill-process!))))))
+
+(define (kill-process!)
+ (defer-ints)
+ (cond ((queue-empty? process:queue) (allow-ints)
+ (slib:exit))
+ (else (let ((proc (dequeue! process:queue)))
+ (allow-ints)
+ (proc 'run))
+ (kill-process!))))
+
+(define ints-disabled #f)
+(define alarm-deferred #f)
+
+(define (defer-ints) (set! ints-disabled #t))
+
+(define (allow-ints)
+ (set! ints-disabled #f)
+ (cond (alarm-deferred
+ (set! alarm-deferred #f)
+ (alarm-interrupt))))
+
+;;; Make THE process queue.
+(define process:queue (make-queue))
+
+(define (alarm-interrupt)
+ (alarm 1)
+ (if ints-disabled (set! alarm-deferred #t)
+ (process:schedule!)))