1 ;;; 8sync --- Asynchronous programming for Guile
2 ;;; Copyright (C) 2015, 2016 Christopher Allan Webber <cwebber@dustycloud.org>
4 ;;; This file is part of 8sync.
6 ;;; 8sync is free software: you can redistribute it and/or modify it
7 ;;; under the terms of the GNU Lesser General Public License as
8 ;;; published by the Free Software Foundation, either version 3 of the
9 ;;; License, or (at your option) any later version.
11 ;;; 8sync is distributed in the hope that it will be useful,
12 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
13 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 ;;; GNU Lesser General Public License for more details.
16 ;;; You should have received a copy of the GNU Lesser General Public
17 ;;; License along with 8sync. If not, see <http://www.gnu.org/licenses/>.
19 (define-module (8sync agenda)
20 #:use-module (srfi srfi-1)
21 #:use-module (srfi srfi-9)
22 #:use-module (srfi srfi-9 gnu)
23 #:use-module (ice-9 q)
24 #:use-module (ice-9 match)
25 #:use-module (ice-9 receive)
26 #:use-module (ice-9 suspendable-ports)
29 agenda-queue agenda-prompt-tag
30 agenda-read-port-map agenda-write-port-map
38 make-time-segment time-segment?
39 time-segment-time time-segment-queue
41 time< time= time<= time-delta+
45 make-time-delta tdelta time-delta?
46 time-delta-sec time-delta-usec
49 make-schedule schedule?
50 schedule-add! schedule-empty?
54 schedule-segments-split schedule-extract-until!
55 add-segments-contents-to-queue!
58 make-run-request run-request?
59 run-request-proc run-request-when
61 run-it wrap wrap-apply run run-at run-delay
66 ;; used for introspecting the error, but a method for making
69 wrapped-exception-key wrapped-exception-args
70 wrapped-exception-stacks
72 print-error-and-continue
77 start-agenda agenda-run-once))
79 ;; @@: Using immutable agendas here, so wouldn't it make sense to
80 ;; replace this queue stuff with using pfds based immutable queues?
86 ;;; The agenda consists of:
87 ;;; - a queue of immediate items to handle
88 ;;; - sheduled future events to be added to a future queue
89 ;;; - a tag by which running processes can escape for some asynchronous
90 ;;; operation (from which they can be returned later)
91 ;;; - a mapping of ports to various handler procedures
93 ;;; The goal, eventually, is for this all to be immutable and functional.
94 ;;; However, we aren't there yet. Some tricky things:
95 ;;; - The schedule needs to be immutable, yet reasonably efficient.
96 ;;; - Need to use immutable queues (ijp's pfds library?)
97 ;;; - Modeling reading from ports as something repeatable,
98 ;;; and with reasonable separation from functional components?
100 (define-immutable-record-type <agenda>
101 (make-agenda-intern queue prompt-tag
102 read-port-map write-port-map
103 schedule time catch-handler pre-unwind-handler)
106 (prompt-tag agenda-prompt-tag)
107 (read-port-map agenda-read-port-map)
108 (write-port-map agenda-write-port-map)
109 (schedule agenda-schedule)
111 (catch-handler agenda-catch-handler)
112 (pre-unwind-handler agenda-pre-unwind-handler))
114 (define (make-async-prompt-tag)
115 "Make an async prompt tag for an agenda.
117 Generally done automatically for the user through (make-agenda)."
118 (make-prompt-tag "prompt"))
120 (define* (make-agenda #:key
122 (prompt (make-prompt-tag))
123 (read-port-map (make-hash-table))
124 (write-port-map (make-hash-table))
125 (schedule (make-schedule))
126 (time (gettimeofday))
128 (pre-unwind-handler print-error-and-continue))
129 ;; TODO: document arguments
130 "Make a fresh agenda."
131 (make-agenda-intern queue prompt
132 read-port-map write-port-map
134 catch-handler pre-unwind-handler))
136 (define (current-agenda-prompt)
137 "Get the prompt for the current agenda; signal an error if there isn't one."
138 (let ((current-agenda (%current-agenda)))
139 (if (not current-agenda)
142 "Can't get current agenda prompt if there's no current agenda!")
143 (agenda-prompt-tag current-agenda))))
145 ;; helper for making queues for an agenda
146 (define (list->q lst)
147 "Makes a queue composed of LST items"
155 (define (make-q* . args)
156 "Makes a queue and populates it with this invocation's ARGS"
163 ;;; This is where we handle timed events for the future
165 ;; This section totally borrows from the ideas in SICP
168 ;; NOTE: time is a cons of (seconds . microseconds)
170 (define-record-type <time-segment>
171 (make-time-segment-intern time queue)
173 (time time-segment-time)
174 (queue time-segment-queue))
176 ;; @@: This seems to be the same as srfi-18's seconds->time procedure?
177 ;; Maybe double check and switch to that? (Thanks amz3!)
179 (define (time-from-float-or-fraction time)
180 "Produce a (sec . usec) pair from TIME, a float or fraction"
181 (let* ((mixed-whole (floor time))
182 (mixed-rest (- time mixed-whole)) ; float or fraction component
184 (usec (floor (* 1000000 mixed-rest))))
185 (cons (inexact->exact sec) (inexact->exact usec))))
187 (define (time-segment-right-format time)
188 "Ensure TIME is in the right format.
190 The right format means (second . microsecond).
191 If an integer, will convert appropriately."
192 ;; TODO: add floating point / rational number support.
194 ;; time is already a cons of second and microsecnd
195 (((? integer? s) . (? integer? u)) time)
196 ;; time was just an integer (just the second)
197 ((? integer? _) (cons time 0))
198 ((or (? rational? _) (? inexact? _))
199 (time-from-float-or-fraction time))
200 (_ (throw 'invalid-time "Invalid time" time))))
202 (define* (make-time-segment time #:optional (queue (make-q)))
203 "Make a time segment of TIME and QUEUE
205 No automatic conversion is done, so you might have to
206 run (time-segment-right-format) first."
207 (make-time-segment-intern time queue))
209 (define (time< time1 time2)
210 "Check if TIME1 is less than TIME2"
211 (cond ((< (car time1)
221 (define (time= time1 time2)
222 "Check whether TIME1 and TIME2 are equivalent"
223 (and (= (car time1) (car time2))
224 (= (cdr time1) (cdr time2))))
226 (define (time<= time1 time2)
227 "Check if TIME1 is less than or equal to TIME2"
228 (or (time< time1 time2)
229 (time= time1 time2)))
232 (define-record-type <time-delta>
233 (make-time-delta-intern sec usec)
236 (usec time-delta-usec))
238 (define* (make-time-delta time)
239 "Make a <time-delta> of SEC seconds and USEC microseconds.
241 This is used primarily so the agenda can recognize RUN-REQUEST objects
242 which are meant to delay computation"
243 (match (time-segment-right-format time)
245 (make-time-delta-intern sec usec))))
247 (define tdelta make-time-delta)
249 (define (time-carry-correct time)
250 "Corrects/handles time microsecond carry.
251 Will produce (0 . 0) instead of a negative number, if needed."
252 (cond ((>= (cdr time) 1000000)
255 (- (cdr time) 1000000)))
261 (+ (cdr time) 1000000))))
264 (define (time-delta+ time time-delta)
265 "Increment a TIME by the value of TIME-DELTA"
267 (cons (+ (car time) (time-delta-sec time-delta))
268 (+ (cdr time) (time-delta-usec time-delta)))))
270 (define (time-minus time1 time2)
271 "Subtract TIME2 from TIME1"
273 (cons (- (car time1) (car time2))
274 (- (cdr time1) (cdr time2)))))
276 (define (time-plus time1 time2)
277 "Add TIME1 and TIME2"
279 (cons (+ (car time1) (car time2))
280 (+ (cdr time1) (cdr time2)))))
283 (define-record-type <schedule>
284 (make-schedule-intern segments)
286 (segments schedule-segments set-schedule-segments!))
288 (define* (make-schedule #:optional segments)
289 "Make a schedule, optionally pre-composed of SEGMENTS"
290 (make-schedule-intern (or segments '())))
292 (define (schedule-soonest-time schedule)
293 "Return a cons of (sec . usec) for next time segement, or #f if none"
294 (let ((segments (schedule-segments schedule)))
295 (if (eq? segments '())
297 (time-segment-time (car segments)))))
299 ;; TODO: This code is reasonably easy to read but it
300 ;; mutates AND is worst case of O(n) in both space and time :(
301 ;; but at least it'll be reasonably easy to refactor to
302 ;; a more functional setup?
303 (define (schedule-add! schedule time proc)
304 "Mutate SCHEDULE, adding PROC at an appropriate time segment for TIME"
305 (let ((time (time-segment-right-format time)))
306 (define (new-time-segment)
308 (make-time-segment time)))
309 (enq! (time-segment-queue new-segment) proc)
311 (define (loop segments)
312 (define (segment-equals-time? segment)
313 (time= time (time-segment-time segment)))
315 (define (segment-more-than-time? segment)
316 (time< time (time-segment-time segment)))
318 ;; We could switch this out to be more mutate'y
319 ;; and avoid the O(n) of space... is that over-optimizing?
321 ;; If we're at the end of the list, time to make a new
323 ('() (cons (new-time-segment) '()))
324 ;; If the segment's time is exactly our time, good news
325 ;; everyone! Let's append our stuff to its queue
326 (((? segment-equals-time? first) rest ...)
327 (enq! (time-segment-queue first) proc)
329 ;; If the first segment is more than our time,
330 ;; ours belongs before this one, so add it and
331 ;; start consing our way back
332 (((? segment-more-than-time? first) rest ...)
333 (cons (new-time-segment) segments))
334 ;; Otherwise, build up recursive result
336 (cons first (loop rest)))))
337 (set-schedule-segments!
339 (loop (schedule-segments schedule)))))
341 (define (schedule-empty? schedule)
342 "Check if the SCHEDULE is currently empty"
343 (eq? (schedule-segments schedule) '()))
345 (define (schedule-segments-split schedule time)
346 "Does a multiple value return of time segments before/at and after TIME"
347 (let ((time (time-segment-right-format time)))
348 (define (segment-is-now? segment)
349 (time= (time-segment-time segment) time))
350 (define (segment-is-before-now? segment)
351 (time< (time-segment-time segment) time))
353 (let loop ((segments-before '())
354 (segments-left (schedule-segments schedule)))
356 ;; end of the line, return
358 (values (reverse segments-before) '()))
360 ;; It's right now, so time to stop, but include this one in before
361 ;; but otherwise return
362 (((? segment-is-now? first) rest ...)
363 (values (reverse (cons first segments-before)) rest))
365 ;; This is prior or at now, so add it and keep going
366 (((? segment-is-before-now? first) rest ...)
367 (loop (cons first segments-before) rest))
369 ;; Otherwise it's past now, just return what we have
371 (values segments-before segments-after))))))
373 (define (schedule-extract-until! schedule time)
374 "Extract all segments until TIME from SCHEDULE, and pop old segments off"
375 (receive (segments-before segments-after)
376 (schedule-segments-split schedule time)
377 (set-schedule-segments! schedule segments-after)
380 (define (add-segments-contents-to-queue! segments queue)
383 (let ((seg-queue (time-segment-queue segment)))
384 (while (not (q-empty? seg-queue))
385 (enq! queue (deq! seg-queue)))))
390 ;;; Request to run stuff
391 ;;; ====================
393 (define-record-type <run-request>
394 (make-run-request proc when)
396 (proc run-request-proc)
397 (when run-request-when))
399 (define* (run-it proc #:optional when)
400 "Make a request to run PROC (possibly at WHEN)"
401 (make-run-request proc when))
403 (define-syntax-rule (wrap body ...)
404 "Wrap contents in a procedure"
408 (define-syntax-rule (wrap-apply body)
409 "Wrap possibly multi-value function in a procedure, applies all arguments"
414 ;; @@: Do we really want `body ...' here?
415 ;; what about just `body'?
416 (define-syntax-rule (run body ...)
417 "Run everything in BODY but wrap in a convenient procedure"
418 (make-run-request (wrap body ...) #f))
420 (define-syntax-rule (run-at body ... when)
422 (make-run-request (wrap body ...) when))
424 ;; @@: Is it okay to overload the term "delay" like this?
425 ;; Would `run-in' be better?
426 (define-syntax-rule (run-delay body ... delay-time)
427 "Run BODY at DELAY-TIME time from now"
428 (make-run-request (wrap body ...) (tdelta delay-time)))
432 ;;; Asynchronous escape to run things
433 ;;; =================================
435 (define-syntax-rule (8sync-abort-to-prompt async-request)
436 (abort-to-prompt (current-agenda-prompt)
439 ;; Async port request and run-request meta-requests
440 (define (make-async-request proc)
441 "Wrap PROC in an async-request
443 The purpose of this is to make sure that users don't accidentally
444 return the wrong thing via (8sync) and trip themselves up."
445 (cons '*async-request* proc))
447 (define (setup-async-request resume-kont async-request)
448 "Complete an async request for agenda-run-once's continuation handling"
450 (('*async-request* . async-setup-proc)
451 (async-setup-proc resume-kont))
452 ;; TODO: deliver more helpful errors depending on what the user
454 (_ (throw 'invalid-async-request
455 "Invalid request passed back via an (8sync) procedure."
458 (define-syntax-rule (8sync body ...)
459 "Run body asynchronously but ignore its result...
460 forge ahead in our current function!"
461 (8sync-abort-to-prompt
464 (list (make-run-request
465 ;; What's with returning #f to kont?
466 ;; Otherwise we sometimes get errors like
467 ;; "Zero values returned to single-valued continuation""
469 (make-run-request (lambda () body ...) #f))))))
471 ;; TODO: Rewrite when we move to this being just `sleep'.
472 (define (8sleep secs)
473 "Like sleep, but asynchronous."
474 (8sync-abort-to-prompt
477 (make-run-request (lambda () (kont #f)) (tdelta secs))))))
479 (define (8usleep usecs)
480 "Like usleep, but asynchronous."
481 (define (usecs->time-pair)
484 (let* ((sec (floor (/ usecs 1000000)))
485 (msec (- usecs (* sec 1000000))))
487 (8sync-abort-to-prompt
490 (make-run-request (lambda () (kont #f)) (tdelta usecs->time-pair))))))
492 ;; Voluntarily yield execution
493 (define (yield) ; @@: should this be define-inlinable?
494 "Voluntarily yield execution to the scheduler."
495 (8sync-abort-to-prompt
498 (make-run-request (lambda () (kont #f)) #f)))))
501 ;;; Execution of agenda, and current agenda
502 ;;; =======================================
504 (define %current-agenda (make-parameter #f))
506 (define (update-agenda-from-select! agenda)
507 "Potentially (select) on ports specified in agenda, adding items to queue.
509 Also handles sleeping when all we have to do is wait on the schedule."
510 (define (hash-keys hash)
511 (hash-map->list (lambda (k v) k) hash))
512 (define (get-wait-time)
513 ;; TODO: we need to figure this out based on whether there's anything
514 ;; in the queue, and if not, how long till the next scheduled item
515 (let ((soonest-time (schedule-soonest-time (agenda-schedule agenda))))
517 ((not (q-empty? (agenda-queue agenda)))
519 (soonest-time ; ie, the agenda is non-empty
520 (let* ((current-time (agenda-time agenda)))
521 (if (time<= soonest-time current-time)
522 ;; Well there's something due so let's select
523 ;; (this avoids a (possible?) race condition chance)
525 (time-minus soonest-time current-time))))
529 ;; TODO: support usecond wait time too
530 (match (get-wait-time)
534 (select (hash-keys (agenda-read-port-map agenda))
535 (hash-keys (agenda-write-port-map agenda))
538 (lambda (key . rest-args)
542 (_ (error "Unhandled error in select!" key rest-args))))))))
543 (define (get-procs-to-run)
544 (define (ports->procs ports port-map)
545 (lambda (initial-procs)
548 (define proc (hashq-ref port-map port))
549 ;; Now that we've selected on this port, it can be removed
550 (hashq-remove! port-map port)
555 ((read-ports write-ports except-ports) ; except-ports not used
556 ((compose (ports->procs
558 (agenda-read-port-map agenda))
561 (agenda-write-port-map agenda)))
563 (define (update-agenda)
564 (let ((procs-to-run (get-procs-to-run))
565 (q (agenda-queue agenda)))
571 (define (ports-to-select?)
572 (define (has-items? selector)
574 ;; ... we could use hash-for-each and a continuation to jump
575 ;; out with a #t at first indication of an item
576 (not (= (hash-count (const #t)
579 (or (has-items? agenda-read-port-map)
580 (has-items? agenda-write-port-map)))
582 (if (or (ports-to-select?)
583 ;; select doubles as sleep...
584 (not (schedule-empty? (agenda-schedule agenda))))
588 (define-record-type <read-request>
589 (make-read-request port proc)
591 (port read-request-port)
592 (proc read-request-proc))
594 (define-record-type <write-request>
595 (make-write-request port proc)
597 (port write-request-port)
598 (proc write-request-proc))
600 (define (agenda-handle-read-request! agenda read-request)
601 "Handle <read-request>, which is a request to add this port to the poll/select
602 on suspendable ports."
603 (hashq-set! (agenda-read-port-map agenda)
604 (read-request-port read-request)
605 (read-request-proc read-request)))
607 (define (agenda-handle-write-request! agenda write-request)
608 (hashq-set! (agenda-write-port-map agenda)
609 (write-request-port write-request)
610 (write-request-proc write-request)))
612 (define (stop-on-nothing-to-do agenda)
613 (and (q-empty? (agenda-queue agenda))
614 (schedule-empty? (agenda-schedule agenda))
615 (= 0 (hash-count (const #t) (agenda-read-port-map agenda)))
616 (= 0 (hash-count (const #t) (agenda-write-port-map agenda)))))
619 (define* (start-agenda agenda
621 ;; @@: Should we make stop-on-nothing-to-do
622 ;; the default stop-condition?
623 (stop-condition stop-on-nothing-to-do)
624 (get-time gettimeofday)
625 (handle-ports update-agenda-from-select!)
626 ;; For live hacking madness, etc
628 ;; TODO: Document fields
629 "Start up the AGENDA"
630 (install-suspendable-ports!)
631 (let loop ((agenda agenda))
633 ;; @@: Hm, maybe here would be a great place to handle
634 ;; select'ing on ports.
635 ;; We could compose over agenda-run-once and agenda-read-ports
636 (agenda-run-once agenda)))
637 ;; @@: This relies on mutation at present on the queue, in the rare
638 ;; event it's used. If we ever switch to something more immutable,
639 ;; it should return a new modified agenda instead.
641 (post-run-hook agenda))
642 (if (and stop-condition (stop-condition agenda))
645 ;; We have to update the time after ports handled, too
646 ;; because it may have changed after a select
649 ;; Adjust the agenda's time just in time
650 ;; We do this here rather than in agenda-run-once to make
651 ;; agenda-run-once's behavior fairly predictable
652 (set-field agenda (agenda-time) (get-time)))
653 (agenda-time) (get-time))))
654 ;; Update the agenda's current queue based on
655 ;; currently applicable time segments
656 (add-segments-contents-to-queue!
657 (schedule-extract-until! (agenda-schedule agenda) (agenda-time agenda))
658 (agenda-queue agenda))
662 (define (print-error-and-continue key . args)
663 "Frequently used as pre-unwind-handler for agenda"
665 ((eq? key '8sync-caught-error)
667 ((orig-key orig-args stacks)
668 (display "\n*** Caught async exception. ***\n")
669 (format (current-error-port)
670 "* Original key '~s and arguments: ~s *\n"
672 (display "* Caught stacks below (ending with original) *\n\n")
675 (display-backtrace s (current-error-port))
676 (newline (current-error-port)))
679 (format (current-error-port)
680 "\n*** Caught exception with key '~s and arguments: ~s ***\n"
682 (display-backtrace (make-stack #t 1 0)
683 (current-error-port))
684 (newline (current-error-port)))))
686 (define-syntax-rule (maybe-catch-all (catch-handler pre-unwind-handler)
688 (if (or catch-handler pre-unwind-handler)
693 (or catch-handler (lambda _ #f))
694 (or pre-unwind-handler (lambda _ #f)))
697 (define (wait-for-readable port)
698 (8sync-abort-to-prompt
701 (make-read-request port (wrap (kont #f)))))))
703 (define (wait-for-writable port)
704 (8sync-abort-to-prompt
707 (make-write-request port (wrap (kont #f)))))))
709 (define (agenda-run-once agenda)
710 "Run once through the agenda, and produce a new agenda
711 based on the results"
712 (define (call-proc proc)
714 (agenda-prompt-tag agenda)
716 (parameterize ((%current-agenda agenda)
717 ;; @@: Couldn't we just parameterize this at the start of
719 (current-read-waiter wait-for-readable)
720 (current-write-waiter wait-for-writable))
722 ((agenda-catch-handler agenda)
723 (agenda-pre-unwind-handler agenda))
725 (lambda (kont async-request)
726 (setup-async-request kont async-request))))
728 (let ((queue (agenda-queue agenda))
729 (next-queue (make-q)))
730 (while (not (q-empty? queue))
731 (let* ((proc (q-pop! queue))
732 (proc-result (call-proc proc))
734 (lambda (run-request)
735 (define (schedule-at! time proc)
736 (schedule-add! (agenda-schedule agenda) time proc))
737 (let ((request-time (run-request-when run-request)))
739 ((? time-delta? time-delta)
740 (let ((time (time-delta+ (agenda-time agenda)
742 (schedule-at! time (run-request-proc run-request))))
744 (let ((time (cons sec 0)))
745 (schedule-at! time (run-request-proc run-request))))
746 (((? integer? sec) . (? integer? usec))
747 (schedule-at! request-time (run-request-proc run-request)))
749 (enq! next-queue (run-request-proc run-request))))))))
750 (define (handle-individual result)
751 ;; @@: Could maybe optimize by switching to an explicit cond...
753 ((? run-request? new-proc)
755 ((? read-request? read-request)
756 (agenda-handle-read-request! agenda read-request))
757 ((? write-request? write-request)
758 (agenda-handle-write-request! agenda write-request))
760 ;; Remember, we don't throw an error here because procedures can
761 ;; return a run request, eg with run-it, at the end of their
762 ;; evaluation to keep looping.
763 ;; @@: Though is this really a useful feature?
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)))