+(define (time-= time1 time2)
+ (and (= (car time1) (car time2))
+ (= (cdr time1) (cdr time2))))
+
+(define (time-<= time1 time2)
+ (or (time-< time1 time2)
+ (time-= time1 time2)))
+
+(define-record-type <schedule>
+ (make-schedule-intern segments)
+ schedule?
+ (segments schedule-segments set-schedule-segments!))
+
+(define* (make-schedule #:optional segments)
+ (make-schedule-intern (or segments '())))
+
+;; TODO: This code is reasonably easy to read but it
+;; mutates AND is worst case of O(n) in both space and time :(
+;; but at least it'll be reasonably easy to refactor to
+;; a more functional setup?
+(define (schedule-add! time proc schedule)
+ (let ((time (time-segment-right-format time)))
+ (define (new-time-segment)
+ (let ((new-segment
+ (make-time-segment time)))
+ (enq! (time-segment-queue new-segment) proc)
+ new-segment))
+ (define (loop segments)
+ (define (segment-equals-time? segment)
+ (time-= time (time-segment-time segment)))
+
+ (define (segment-more-than-time? segment)
+ (time-< time (time-segment-time segment)))
+
+ ;; We could switch this out to be more mutate'y
+ ;; and avoid the O(n) of space... is that over-optimizing?
+ (match segments
+ ;; If we're at the end of the list, time to make a new
+ ;; segment...
+ ('() (cons (make-time-segment time) '()))
+ ;; If the segment's time is exactly our time, good news
+ ;; everyone! Let's append our stuff to its queue
+ (((? segment-equals-time? first) rest ...)
+ (enq! (time-segment-queue first) proc)
+ segments)
+ ;; If the first segment is more than our time,
+ ;; ours belongs before this one, so add it and
+ ;; start consing our way back
+ (((? segment-more-than-time? first) rest ...)
+ (cons (new-time-segment) segments))
+ ;; Otherwise, build up recursive result
+ ((first rest ... )
+ (cons first (loop rest)))))
+ (set-schedule-segments!
+ schedule
+ (loop (schedule-segments schedule)))))
+
+(define (schedule-empty? schedule)
+ (eq? (schedule-segments schedule) '()))
+
+
+\f
+;;; Port handling
+;;; =============
+
+(define (make-port-mapping)
+ (make-hash-table))
+
+(define* (port-mapping-set! port-mapping port #:optional read write except)
+ "Sets port-mapping for reader / writer / exception handlers"
+ (if (not (or read write except))
+ (throw 'no-handlers-given "No handlers given for port" port))
+ (hashq-set! port-mapping port
+ `#(,read ,write ,except)))
+
+(define (port-mapping-remove! port-mapping port)
+ (hashq-remove! port-mapping port))
+
+;; TODO: This is O(n), I'm pretty sure :\
+;; ... it might be worthwhile for us to have a
+;; port-mapping record that keeps a count of how many
+;; handlers (maybe via a promise?)
+(define (port-mapping-empty? port-mapping)
+ "Is this port mapping empty?"
+ (eq? (hash-count (const #t) port-mapping) 0))
+
+(define (port-mapping-non-empty? port-mapping)
+ "Whether this port-mapping contains any elements"
+ (not (port-mapping-empty? port-mapping)))
+
+
+\f
+;;; Execution of agenda, and current agenda
+;;; =======================================