1 ;; Copyright (C) 2015 Christopher Allan Webber <cwebber@dustycloud.org>
3 ;; This library is free software; you can redistribute it and/or
4 ;; modify it under the terms of the GNU Lesser General Public
5 ;; License as published by the Free Software Foundation; either
6 ;; version 3 of the License, or (at your option) any later version.
8 ;; This library is distributed in the hope that it will be useful,
9 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
10 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 ;; Lesser General Public License for more details.
13 ;; You should have received a copy of the GNU Lesser General Public
14 ;; License along with this library; if not, write to the Free Software
15 ;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
18 (define-module (eightsync agenda)
19 #:use-module (srfi srfi-1)
20 #:use-module (srfi srfi-9)
21 #:use-module (srfi srfi-9 gnu)
22 #:use-module (ice-9 q)
23 #:use-module (ice-9 match)
24 #:use-module (ice-9 receive)
27 agenda-queue agenda-prompt-tag
28 agenda-read-port-map agenda-write-port-map agenda-except-port-map
34 make-time-segment time-segment?
35 time-segment-time time-segment-queue
37 time< time= time<= time-delta+
41 make-time-delta tdelta time-delta?
42 time-delta-sec time-delta-usec
45 make-schedule schedule?
46 schedule-add! schedule-empty?
50 schedule-segments-split schedule-extract-until!
51 add-segments-contents-to-queue!
56 make-run-request run-request?
57 run-request-proc run-request-when
60 make-port-request port-request port-request?
62 port-request-read port-request-write port-request-except
64 run-it wrap wrap-apply run run-at run-delay
66 %port-request %run %run-at %run-delay
68 catch-8sync catch-%8sync
70 ;; used for introspecting the error, but a method for making
73 wrapped-exception-key wrapped-exception-args
74 wrapped-exception-stacks
76 print-error-and-continue
79 start-agenda agenda-run-once))
81 ;; @@: Using immutable agendas here, so wouldn't it make sense to
82 ;; replace this queue stuff with using pfds based immutable queues?
88 ;;; The agenda consists of:
89 ;;; - a queue of immediate items to handle
90 ;;; - sheduled future events to be added to a future queue
91 ;;; - a tag by which running processes can escape for some asynchronous
92 ;;; operation (from which they can be returned later)
93 ;;; - a mapping of ports to various handler procedures
95 ;;; The goal, eventually, is for this all to be immutable and functional.
96 ;;; However, we aren't there yet. Some tricky things:
97 ;;; - The schedule needs to be immutable, yet reasonably efficient.
98 ;;; - Need to use immutable queues (ijp's pfds library?)
99 ;;; - Modeling reading from ports as something repeatable,
100 ;;; and with reasonable separation from functional components?
102 (define-immutable-record-type <agenda>
103 (make-agenda-intern queue prompt-tag
104 read-port-map write-port-map except-port-map
105 schedule time catch-handler pre-unwind-handler)
108 (prompt-tag agenda-prompt-tag)
109 (read-port-map agenda-read-port-map)
110 (write-port-map agenda-write-port-map)
111 (except-port-map agenda-except-port-map)
112 (schedule agenda-schedule)
114 (catch-handler agenda-catch-handler)
115 (pre-unwind-handler agenda-pre-unwind-handler))
117 (define (make-async-prompt-tag)
118 "Make an async prompt tag for an agenda.
120 Generally done automatically for the user through (make-agenda)."
121 (make-prompt-tag "prompt"))
123 (define* (make-agenda #:key
125 (prompt (make-prompt-tag))
126 (read-port-map (make-hash-table))
127 (write-port-map (make-hash-table))
128 (except-port-map (make-hash-table))
129 (schedule (make-schedule))
130 (time (gettimeofday))
132 (pre-unwind-handler #f))
133 ;; TODO: document arguments
134 "Make a fresh agenda."
135 (make-agenda-intern queue prompt
136 read-port-map write-port-map except-port-map
138 catch-handler pre-unwind-handler))
140 (define (current-agenda-prompt)
141 "Get the prompt for the current agenda; signal an error if there isn't one."
142 (let ((current-agenda (%current-agenda)))
143 (if (not current-agenda)
146 "Can't get current agenda prompt if there's no current agenda!")
147 (agenda-prompt-tag current-agenda))))
154 ;;; This is where we handle timed events for the future
156 ;; This section totally borrows from the ideas in SICP
159 ;; NOTE: time is a cons of (seconds . microseconds)
161 (define-record-type <time-segment>
162 (make-time-segment-intern time queue)
164 (time time-segment-time)
165 (queue time-segment-queue))
167 ;; @@: This seems to be the same as srfi-18's seconds->time procedure?
168 ;; Maybe double check and switch to that? (Thanks amz3!)
170 (define (time-from-float-or-fraction time)
171 "Produce a (sec . usec) pair from TIME, a float or fraction"
172 (let* ((mixed-whole (floor time))
173 (mixed-rest (- time mixed-whole)) ; float or fraction component
175 (usec (floor (* 1000000 mixed-rest))))
176 (cons (inexact->exact sec) (inexact->exact usec))))
178 (define (time-segment-right-format time)
179 "Ensure TIME is in the right format.
181 The right format means (second . microsecond).
182 If an integer, will convert appropriately."
183 ;; TODO: add floating point / rational number support.
185 ;; time is already a cons of second and microsecnd
186 (((? integer? s) . (? integer? u)) time)
187 ;; time was just an integer (just the second)
188 ((? integer? _) (cons time 0))
189 ((or (? rational? _) (? inexact? _))
190 (time-from-float-or-fraction time))
191 (_ (throw 'invalid-time "Invalid time" time))))
193 (define* (make-time-segment time #:optional (queue (make-q)))
194 "Make a time segment of TIME and QUEUE
196 No automatic conversion is done, so you might have to
197 run (time-segment-right-format) first."
198 (make-time-segment-intern time queue))
200 (define (time< time1 time2)
201 "Check if TIME1 is less than TIME2"
202 (cond ((< (car time1)
212 (define (time= time1 time2)
213 "Check whether TIME1 and TIME2 are equivalent"
214 (and (= (car time1) (car time2))
215 (= (cdr time1) (cdr time2))))
217 (define (time<= time1 time2)
218 "Check if TIME1 is less than or equal to TIME2"
219 (or (time< time1 time2)
220 (time= time1 time2)))
223 (define-record-type <time-delta>
224 (make-time-delta-intern sec usec)
227 (usec time-delta-usec))
229 (define* (make-time-delta time)
230 "Make a <time-delta> of SEC seconds and USEC microseconds.
232 This is used primarily so the agenda can recognize RUN-REQUEST objects
233 which are meant to delay computation"
234 (match (time-segment-right-format time)
236 (make-time-delta-intern sec usec))))
238 (define tdelta make-time-delta)
240 (define (time-carry-correct time)
241 "Corrects/handles time microsecond carry.
242 Will produce (0 . 0) instead of a negative number, if needed."
243 (cond ((>= (cdr time) 1000000)
246 (- (cdr time) 1000000)))
252 (+ (cdr time) 1000000))))
255 (define (time-delta+ time time-delta)
256 "Increment a TIME by the value of TIME-DELTA"
258 (cons (+ (car time) (time-delta-sec time-delta))
259 (+ (cdr time) (time-delta-usec time-delta)))))
261 (define (time-minus time1 time2)
262 "Subtract TIME2 from TIME1"
264 (cons (- (car time1) (car time2))
265 (- (cdr time1) (cdr time2)))))
267 (define (time-plus time1 time2)
268 "Add TIME1 and TIME2"
270 (cons (+ (car time1) (car time2))
271 (+ (cdr time1) (cdr time2)))))
274 (define-record-type <schedule>
275 (make-schedule-intern segments)
277 (segments schedule-segments set-schedule-segments!))
279 (define* (make-schedule #:optional segments)
280 "Make a schedule, optionally pre-composed of SEGMENTS"
281 (make-schedule-intern (or segments '())))
283 (define (schedule-soonest-time schedule)
284 "Return a cons of (sec . usec) for next time segement, or #f if none"
285 (let ((segments (schedule-segments schedule)))
286 (if (eq? segments '())
288 (time-segment-time (car segments)))))
290 ;; TODO: This code is reasonably easy to read but it
291 ;; mutates AND is worst case of O(n) in both space and time :(
292 ;; but at least it'll be reasonably easy to refactor to
293 ;; a more functional setup?
294 (define (schedule-add! schedule time proc)
295 "Mutate SCHEDULE, adding PROC at an appropriate time segment for TIME"
296 (let ((time (time-segment-right-format time)))
297 (define (new-time-segment)
299 (make-time-segment time)))
300 (enq! (time-segment-queue new-segment) proc)
302 (define (loop segments)
303 (define (segment-equals-time? segment)
304 (time= time (time-segment-time segment)))
306 (define (segment-more-than-time? segment)
307 (time< time (time-segment-time segment)))
309 ;; We could switch this out to be more mutate'y
310 ;; and avoid the O(n) of space... is that over-optimizing?
312 ;; If we're at the end of the list, time to make a new
314 ('() (cons (new-time-segment) '()))
315 ;; If the segment's time is exactly our time, good news
316 ;; everyone! Let's append our stuff to its queue
317 (((? segment-equals-time? first) rest ...)
318 (enq! (time-segment-queue first) proc)
320 ;; If the first segment is more than our time,
321 ;; ours belongs before this one, so add it and
322 ;; start consing our way back
323 (((? segment-more-than-time? first) rest ...)
324 (cons (new-time-segment) segments))
325 ;; Otherwise, build up recursive result
327 (cons first (loop rest)))))
328 (set-schedule-segments!
330 (loop (schedule-segments schedule)))))
332 (define (schedule-empty? schedule)
333 "Check if the SCHEDULE is currently empty"
334 (eq? (schedule-segments schedule) '()))
336 (define (schedule-segments-split schedule time)
337 "Does a multiple value return of time segments before/at and after TIME"
338 (let ((time (time-segment-right-format time)))
339 (define (segment-is-now? segment)
340 (time= (time-segment-time segment) time))
341 (define (segment-is-before-now? segment)
342 (time< (time-segment-time segment) time))
344 (let loop ((segments-before '())
345 (segments-left (schedule-segments schedule)))
347 ;; end of the line, return
349 (values (reverse segments-before) '()))
351 ;; It's right now, so time to stop, but include this one in before
352 ;; but otherwise return
353 (((? segment-is-now? first) rest ...)
354 (values (reverse (cons first segments-before)) rest))
356 ;; This is prior or at now, so add it and keep going
357 (((? segment-is-before-now? first) rest ...)
358 (loop (cons first segments-before) rest))
360 ;; Otherwise it's past now, just return what we have
362 (values segments-before segments-after))))))
364 (define (schedule-extract-until! schedule time)
365 "Extract all segments until TIME from SCHEDULE, and pop old segments off"
366 (receive (segments-before segments-after)
367 (schedule-segments-split schedule time)
368 (set-schedule-segments! schedule segments-after)
371 (define (add-segments-contents-to-queue! segments queue)
374 (let ((seg-queue (time-segment-queue segment)))
375 (while (not (q-empty? seg-queue))
376 (enq! queue (deq! seg-queue)))))
381 ;;; Request to run stuff
382 ;;; ====================
384 (define-record-type <run-request>
385 (make-run-request proc when)
387 (proc run-request-proc)
388 (when run-request-when))
390 (define* (run-it proc #:optional when)
391 "Make a request to run PROC (possibly at WHEN)"
392 (make-run-request proc when))
394 (define-syntax-rule (wrap body ...)
395 "Wrap contents in a procedure"
399 (define-syntax-rule (wrap-apply body)
400 "Wrap possibly multi-value function in a procedure, applies all arguments"
405 ;; @@: Do we really want `body ...' here?
406 ;; what about just `body'?
407 (define-syntax-rule (run body ...)
408 "Run everything in BODY but wrap in a convenient procedure"
409 (make-run-request (wrap body ...) #f))
411 (define-syntax-rule (run-at body ... when)
413 (make-run-request (wrap body ...) when))
415 ;; @@: Is it okay to overload the term "delay" like this?
416 ;; Would `run-in' be better?
417 (define-syntax-rule (run-delay body ... delay-time)
418 "Run BODY at DELAY-TIME time from now"
419 (make-run-request (wrap body ...) (tdelta delay-time)))
422 ;; A request to set up a port with at least one of read, write, except
423 ;; handling processes
425 (define-record-type <port-request>
426 (make-port-request-intern port read write except)
428 (port port-request-port)
429 (read port-request-read)
430 (write port-request-write)
431 (except port-request-except))
433 (define* (make-port-request port #:key read write except)
434 (if (not (or read write except))
435 (throw 'no-port-handler-given "No port handler given.\n"))
436 (make-port-request-intern port read write except))
438 (define port-request make-port-request)
442 ;;; Asynchronous escape to run things
443 ;;; =================================
445 (define (agenda-on-error agenda)
448 (define (agenda-on-fail agenda)
451 (define-syntax-rule (%8sync async-request)
452 "Run BODY asynchronously at a prompt, passing args to make-future.
454 Runs things asynchronously (8synchronously?)"
455 (propagate-%async-exceptions
456 (abort-to-prompt (current-agenda-prompt)
459 ;; Async port request and run-request meta-requests
460 (define (make-async-request proc)
461 "Wrap PROC in an async-request
463 The purpose of this is to make sure that users don't accidentally
464 return the wrong thing via (%8sync) and trip themselves up."
465 (cons '*async-request* proc))
467 (define (setup-async-request resume-kont async-request)
468 "Complete an async request for agenda-run-once's continuation handling"
470 (('*async-request* . async-setup-proc)
471 (async-setup-proc resume-kont))
472 ;; TODO: deliver more helpful errors depending on what the user
474 (_ (throw 'invalid-async-request
475 "Invalid request passed back via an (%8sync) procedure."
478 (define-record-type <wrapped-exception>
479 (make-wrapped-exception key args stacks)
481 (key wrapped-exception-key)
482 (args wrapped-exception-args)
483 (stacks wrapped-exception-stacks))
485 (define-syntax-rule (propagate-%async-exceptions body)
486 (let ((body-result body))
487 (if (wrapped-exception? body-result)
488 (throw '8sync-caught-error
489 (wrapped-exception-key body-result)
490 (wrapped-exception-args body-result)
491 (wrapped-exception-stacks body-result))
494 (define-syntax-rule (%run body ...)
495 (%run-at body ... #f))
497 (define-syntax-rule (%run-at body ... when)
498 ;; Send an asynchronous request to apply a continuation to the
499 ;; following function, then handle that as a request to the agenda
502 ;; We're making a run request
504 ;; Wrapping the following execution to run...
506 ;; Once we get the result from the inner part, we'll resume
507 ;; this continuation, but first
508 ;; @@: Is this running immediately, or queueing the result
509 ;; after evaluation for the next agenda tick? It looks
510 ;; like evaluating immediately. Is that what we want?
512 ;; Any unhandled errors are caught
513 (let ((exception-stack #f))
515 ;; Run the actual code the user requested
518 ;; If something bad happened and we didn't catch it,
519 ;; we'll wrap it up in such a way that the continuation
523 ((eq? key '8sync-caught-error)
525 ((orig-key orig-args orig-stacks)
526 (make-wrapped-exception
528 (cons exception-stack orig-stacks)))))
530 (make-wrapped-exception key args
531 (list exception-stack)))))
533 (set! exception-stack (make-stack #t 1 0)))))))
536 (define-syntax-rule (%run-delay body ... delay-time)
537 (%run-at body ... (tdelta delay-time)))
539 (define-syntax-rule (%port-request add-this-port port-request-args ...)
542 (list (make-port-request port-request-args ...)
543 (make-run-request kont)))))
546 (define-syntax-rule (%run-with-return return body ...)
553 (define-syntax-rule (catch-8sync exp (handler-key handler) ...)
554 (catch '8sync-caught-error
557 (lambda (_ orig-key orig-args orig-stacks)
559 ((or (eq? handler-key #t)
560 (eq? orig-key handler-key))
561 (apply handler orig-stacks orig-args)) ...
562 (else (raise '8sync-caught-error
563 orig-key orig-args orig-stacks))))))
566 (define-syntax-rule (catch-%8sync rest ...)
567 (catch-8sync rest ...))
571 ;;; Execution of agenda, and current agenda
572 ;;; =======================================
574 (define %current-agenda (make-parameter #f))
576 (define (update-agenda-from-select! agenda)
577 "Potentially (select) on ports specified in agenda, adding items to queue"
578 (define (hash-keys hash)
579 (hash-map->list (lambda (k v) k) hash))
580 (define (get-wait-time)
581 ;; TODO: we need to figure this out based on whether there's anything
582 ;; in the queue, and if not, how long till the next scheduled item
583 (let ((soonest-time (schedule-soonest-time (agenda-schedule agenda))))
585 ((not (q-empty? (agenda-queue agenda)))
587 (soonest-time ; ie, the agenda is non-empty
588 (let* ((current-time (agenda-time agenda)))
589 (if (time<= soonest-time current-time)
590 ;; Well there's something due so let's select
591 ;; (this avoids a (possible?) race condition chance)
593 (time-minus soonest-time current-time))))
597 ;; TODO: support usecond wait time too
598 (match (get-wait-time)
602 (select (hash-keys (agenda-read-port-map agenda))
603 (hash-keys (agenda-write-port-map agenda))
604 (hash-keys (agenda-except-port-map agenda))
606 (lambda (key . rest-args)
610 (_ (error "Unhandled error in select!" key rest-args))))))))
611 (define (get-procs-to-run)
612 (define (ports->procs ports port-map)
613 (lambda (initial-procs)
617 ((hash-ref port-map port) port))
622 ((read-ports write-ports except-ports)
623 ;; @@: Come on, we can do better than append ;P
624 ((compose (ports->procs
626 (agenda-read-port-map agenda))
629 (agenda-write-port-map agenda))
632 (agenda-except-port-map agenda)))
634 (define (update-agenda)
635 (let ((procs-to-run (get-procs-to-run))
636 (q (agenda-queue agenda)))
642 (define (ports-to-select?)
643 (define (has-items? selector)
645 ;; ... we could use hash-for-each and a continuation to jump
646 ;; out with a #t at first indication of an item
647 (not (= (hash-count (const #t)
650 (or (has-items? agenda-read-port-map)
651 (has-items? agenda-write-port-map)
652 (has-items? agenda-except-port-map)))
654 (if (ports-to-select?)
658 (define (agenda-handle-port-request! agenda port-request)
659 "Update an agenda for a port-request"
660 (define (handle-selector request-selector port-map-selector)
661 (if (request-selector port-request)
662 (hash-set! (port-map-selector agenda)
663 (port-request-port port-request)
664 (request-selector port-request))))
665 (handle-selector port-request-read agenda-read-port-map)
666 (handle-selector port-request-write agenda-write-port-map)
667 (handle-selector port-request-except agenda-except-port-map))
670 (define* (start-agenda agenda
672 (get-time gettimeofday)
673 (handle-ports update-agenda-from-select!))
674 ;; TODO: Document fields
675 "Start up the AGENDA"
676 (let loop ((agenda agenda))
678 ;; @@: Hm, maybe here would be a great place to handle
679 ;; select'ing on ports.
680 ;; We could compose over agenda-run-once and agenda-read-ports
681 (agenda-run-once agenda)))
682 (if (and stop-condition (stop-condition agenda))
685 ;; We have to update the time after ports handled, too
686 ;; because it may have changed after a select
689 ;; Adjust the agenda's time just in time
690 ;; We do this here rather than in agenda-run-once to make
691 ;; agenda-run-once's behavior fairly predictable
692 (set-field agenda (agenda-time) (get-time)))
693 (agenda-time) (get-time))))
694 ;; Update the agenda's current queue based on
695 ;; currently applicable time segments
696 (add-segments-contents-to-queue!
697 (schedule-extract-until! (agenda-schedule agenda) (agenda-time agenda))
698 (agenda-queue agenda))
701 (define (print-error-and-continue . args)
702 "Frequently used as pre-unwind-handler for agenda"
703 (format (current-error-port) "\n*** Caught exception with arguments: ~s ***\n"
705 (display-backtrace (make-stack #t 1 0)
706 (current-error-port))
707 (newline (current-error-port)))
709 (define-syntax-rule (maybe-catch-all (catch-handler pre-unwind-handler)
711 (if (or catch-handler pre-unwind-handler)
716 (or catch-handler (lambda _ #f))
717 (or pre-unwind-handler (lambda _ #f)))
720 (define (agenda-run-once agenda)
721 "Run once through the agenda, and produce a new agenda
722 based on the results"
723 (define (call-proc proc)
725 (agenda-prompt-tag agenda)
727 (parameterize ((%current-agenda agenda))
729 ((agenda-catch-handler agenda)
730 (agenda-pre-unwind-handler agenda))
732 (lambda (kont async-request)
733 (setup-async-request kont async-request))))
735 (let ((queue (agenda-queue agenda))
736 (next-queue (make-q)))
737 (while (not (q-empty? queue))
738 (let* ((proc (q-pop! queue))
739 (proc-result (call-proc proc))
741 (lambda (run-request)
742 (define (schedule-at! time proc)
743 (schedule-add! (agenda-schedule agenda) time proc))
744 (let ((request-time (run-request-when run-request)))
746 ((? time-delta? time-delta)
747 (let ((time (time-delta+ (agenda-time agenda)
749 (schedule-at! time (run-request-proc run-request))))
751 (let ((time (cons sec 0)))
752 (schedule-at! time (run-request-proc run-request))))
753 (((? integer? sec) . (? integer? usec))
754 (schedule-at! request-time (run-request-proc run-request)))
756 (enq! next-queue (run-request-proc run-request))))))))
757 (define (handle-individual result)
759 ((? run-request? new-proc)
761 ((? port-request? port-request)
762 (agenda-handle-port-request! agenda port-request))
765 ;; @@: We might support delay-wrapped procedures here
768 (for-each handle-individual results))
769 (one-result (handle-individual one-result)))))
770 ;; TODO: Alternately, we could return the next-queue
771 ;; along with changes to be added to the schedule here?
772 ;; Return new agenda, with next queue set
773 (set-field agenda (agenda-queue) next-queue)))