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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!)))