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
64 8sync-run 8sync-run-at 8sync-run-delay
68 ;; used for introspecting the error, but a method for making
71 wrapped-exception-key wrapped-exception-args
72 wrapped-exception-stacks
74 print-error-and-continue
79 start-agenda agenda-run-once))
81 (install-suspendable-ports!)
83 ;; @@: Using immutable agendas here, so wouldn't it make sense to
84 ;; replace this queue stuff with using pfds based immutable queues?
90 ;;; The agenda consists of:
91 ;;; - a queue of immediate items to handle
92 ;;; - sheduled future events to be added to a future queue
93 ;;; - a tag by which running processes can escape for some asynchronous
94 ;;; operation (from which they can be returned later)
95 ;;; - a mapping of ports to various handler procedures
97 ;;; The goal, eventually, is for this all to be immutable and functional.
98 ;;; However, we aren't there yet. Some tricky things:
99 ;;; - The schedule needs to be immutable, yet reasonably efficient.
100 ;;; - Need to use immutable queues (ijp's pfds library?)
101 ;;; - Modeling reading from ports as something repeatable,
102 ;;; and with reasonable separation from functional components?
104 (define-immutable-record-type <agenda>
105 (make-agenda-intern queue prompt-tag
106 read-port-map write-port-map
107 schedule time catch-handler pre-unwind-handler)
110 (prompt-tag agenda-prompt-tag)
111 (read-port-map agenda-read-port-map)
112 (write-port-map agenda-write-port-map)
113 (schedule agenda-schedule)
115 (catch-handler agenda-catch-handler)
116 (pre-unwind-handler agenda-pre-unwind-handler))
118 (define (make-async-prompt-tag)
119 "Make an async prompt tag for an agenda.
121 Generally done automatically for the user through (make-agenda)."
122 (make-prompt-tag "prompt"))
124 (define* (make-agenda #:key
126 (prompt (make-prompt-tag))
127 (read-port-map (make-hash-table))
128 (write-port-map (make-hash-table))
129 (schedule (make-schedule))
130 (time (gettimeofday))
132 (pre-unwind-handler print-error-and-continue))
133 ;; TODO: document arguments
134 "Make a fresh agenda."
135 (make-agenda-intern queue prompt
136 read-port-map write-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))))
149 ;; helper for making queues for an agenda
150 (define (list->q lst)
151 "Makes a queue composed of LST items"
159 (define (make-q* . args)
160 "Makes a queue and populates it with this invocation's ARGS"
167 ;;; This is where we handle timed events for the future
169 ;; This section totally borrows from the ideas in SICP
172 ;; NOTE: time is a cons of (seconds . microseconds)
174 (define-record-type <time-segment>
175 (make-time-segment-intern time queue)
177 (time time-segment-time)
178 (queue time-segment-queue))
180 ;; @@: This seems to be the same as srfi-18's seconds->time procedure?
181 ;; Maybe double check and switch to that? (Thanks amz3!)
183 (define (time-from-float-or-fraction time)
184 "Produce a (sec . usec) pair from TIME, a float or fraction"
185 (let* ((mixed-whole (floor time))
186 (mixed-rest (- time mixed-whole)) ; float or fraction component
188 (usec (floor (* 1000000 mixed-rest))))
189 (cons (inexact->exact sec) (inexact->exact usec))))
191 (define (time-segment-right-format time)
192 "Ensure TIME is in the right format.
194 The right format means (second . microsecond).
195 If an integer, will convert appropriately."
196 ;; TODO: add floating point / rational number support.
198 ;; time is already a cons of second and microsecnd
199 (((? integer? s) . (? integer? u)) time)
200 ;; time was just an integer (just the second)
201 ((? integer? _) (cons time 0))
202 ((or (? rational? _) (? inexact? _))
203 (time-from-float-or-fraction time))
204 (_ (throw 'invalid-time "Invalid time" time))))
206 (define* (make-time-segment time #:optional (queue (make-q)))
207 "Make a time segment of TIME and QUEUE
209 No automatic conversion is done, so you might have to
210 run (time-segment-right-format) first."
211 (make-time-segment-intern time queue))
213 (define (time< time1 time2)
214 "Check if TIME1 is less than TIME2"
215 (cond ((< (car time1)
225 (define (time= time1 time2)
226 "Check whether TIME1 and TIME2 are equivalent"
227 (and (= (car time1) (car time2))
228 (= (cdr time1) (cdr time2))))
230 (define (time<= time1 time2)
231 "Check if TIME1 is less than or equal to TIME2"
232 (or (time< time1 time2)
233 (time= time1 time2)))
236 (define-record-type <time-delta>
237 (make-time-delta-intern sec usec)
240 (usec time-delta-usec))
242 (define* (make-time-delta time)
243 "Make a <time-delta> of SEC seconds and USEC microseconds.
245 This is used primarily so the agenda can recognize RUN-REQUEST objects
246 which are meant to delay computation"
247 (match (time-segment-right-format time)
249 (make-time-delta-intern sec usec))))
251 (define tdelta make-time-delta)
253 (define (time-carry-correct time)
254 "Corrects/handles time microsecond carry.
255 Will produce (0 . 0) instead of a negative number, if needed."
256 (cond ((>= (cdr time) 1000000)
259 (- (cdr time) 1000000)))
265 (+ (cdr time) 1000000))))
268 (define (time-delta+ time time-delta)
269 "Increment a TIME by the value of TIME-DELTA"
271 (cons (+ (car time) (time-delta-sec time-delta))
272 (+ (cdr time) (time-delta-usec time-delta)))))
274 (define (time-minus time1 time2)
275 "Subtract TIME2 from TIME1"
277 (cons (- (car time1) (car time2))
278 (- (cdr time1) (cdr time2)))))
280 (define (time-plus time1 time2)
281 "Add TIME1 and TIME2"
283 (cons (+ (car time1) (car time2))
284 (+ (cdr time1) (cdr time2)))))
287 (define-record-type <schedule>
288 (make-schedule-intern segments)
290 (segments schedule-segments set-schedule-segments!))
292 (define* (make-schedule #:optional segments)
293 "Make a schedule, optionally pre-composed of SEGMENTS"
294 (make-schedule-intern (or segments '())))
296 (define (schedule-soonest-time schedule)
297 "Return a cons of (sec . usec) for next time segement, or #f if none"
298 (let ((segments (schedule-segments schedule)))
299 (if (eq? segments '())
301 (time-segment-time (car segments)))))
303 ;; TODO: This code is reasonably easy to read but it
304 ;; mutates AND is worst case of O(n) in both space and time :(
305 ;; but at least it'll be reasonably easy to refactor to
306 ;; a more functional setup?
307 (define (schedule-add! schedule time proc)
308 "Mutate SCHEDULE, adding PROC at an appropriate time segment for TIME"
309 (let ((time (time-segment-right-format time)))
310 (define (new-time-segment)
312 (make-time-segment time)))
313 (enq! (time-segment-queue new-segment) proc)
315 (define (loop segments)
316 (define (segment-equals-time? segment)
317 (time= time (time-segment-time segment)))
319 (define (segment-more-than-time? segment)
320 (time< time (time-segment-time segment)))
322 ;; We could switch this out to be more mutate'y
323 ;; and avoid the O(n) of space... is that over-optimizing?
325 ;; If we're at the end of the list, time to make a new
327 ('() (cons (new-time-segment) '()))
328 ;; If the segment's time is exactly our time, good news
329 ;; everyone! Let's append our stuff to its queue
330 (((? segment-equals-time? first) rest ...)
331 (enq! (time-segment-queue first) proc)
333 ;; If the first segment is more than our time,
334 ;; ours belongs before this one, so add it and
335 ;; start consing our way back
336 (((? segment-more-than-time? first) rest ...)
337 (cons (new-time-segment) segments))
338 ;; Otherwise, build up recursive result
340 (cons first (loop rest)))))
341 (set-schedule-segments!
343 (loop (schedule-segments schedule)))))
345 (define (schedule-empty? schedule)
346 "Check if the SCHEDULE is currently empty"
347 (eq? (schedule-segments schedule) '()))
349 (define (schedule-segments-split schedule time)
350 "Does a multiple value return of time segments before/at and after TIME"
351 (let ((time (time-segment-right-format time)))
352 (define (segment-is-now? segment)
353 (time= (time-segment-time segment) time))
354 (define (segment-is-before-now? segment)
355 (time< (time-segment-time segment) time))
357 (let loop ((segments-before '())
358 (segments-left (schedule-segments schedule)))
360 ;; end of the line, return
362 (values (reverse segments-before) '()))
364 ;; It's right now, so time to stop, but include this one in before
365 ;; but otherwise return
366 (((? segment-is-now? first) rest ...)
367 (values (reverse (cons first segments-before)) rest))
369 ;; This is prior or at now, so add it and keep going
370 (((? segment-is-before-now? first) rest ...)
371 (loop (cons first segments-before) rest))
373 ;; Otherwise it's past now, just return what we have
375 (values segments-before segments-after))))))
377 (define (schedule-extract-until! schedule time)
378 "Extract all segments until TIME from SCHEDULE, and pop old segments off"
379 (receive (segments-before segments-after)
380 (schedule-segments-split schedule time)
381 (set-schedule-segments! schedule segments-after)
384 (define (add-segments-contents-to-queue! segments queue)
387 (let ((seg-queue (time-segment-queue segment)))
388 (while (not (q-empty? seg-queue))
389 (enq! queue (deq! seg-queue)))))
394 ;;; Request to run stuff
395 ;;; ====================
397 (define-record-type <run-request>
398 (make-run-request proc when)
400 (proc run-request-proc)
401 (when run-request-when))
403 (define* (run-it proc #:optional when)
404 "Make a request to run PROC (possibly at WHEN)"
405 (make-run-request proc when))
407 (define-syntax-rule (wrap body ...)
408 "Wrap contents in a procedure"
412 (define-syntax-rule (wrap-apply body)
413 "Wrap possibly multi-value function in a procedure, applies all arguments"
418 ;; @@: Do we really want `body ...' here?
419 ;; what about just `body'?
420 (define-syntax-rule (run body ...)
421 "Run everything in BODY but wrap in a convenient procedure"
422 (make-run-request (wrap body ...) #f))
424 (define-syntax-rule (run-at body ... when)
426 (make-run-request (wrap body ...) when))
428 ;; @@: Is it okay to overload the term "delay" like this?
429 ;; Would `run-in' be better?
430 (define-syntax-rule (run-delay body ... delay-time)
431 "Run BODY at DELAY-TIME time from now"
432 (make-run-request (wrap body ...) (tdelta delay-time)))
436 ;;; Asynchronous escape to run things
437 ;;; =================================
439 (define-syntax-rule (8sync-abort-to-prompt async-request)
440 (abort-to-prompt (current-agenda-prompt)
443 ;; Async port request and run-request meta-requests
444 (define (make-async-request proc)
445 "Wrap PROC in an async-request
447 The purpose of this is to make sure that users don't accidentally
448 return the wrong thing via (8sync) and trip themselves up."
449 (cons '*async-request* proc))
451 (define (setup-async-request resume-kont async-request)
452 "Complete an async request for agenda-run-once's continuation handling"
454 (('*async-request* . async-setup-proc)
455 (async-setup-proc resume-kont))
456 ;; TODO: deliver more helpful errors depending on what the user
458 (_ (throw 'invalid-async-request
459 "Invalid request passed back via an (8sync) procedure."
462 (define-syntax-rule (8sync body ...)
463 "Run body asynchronously but ignore its result...
464 forge ahead in our current function!"
465 (8sync-abort-to-prompt
468 (list (make-run-request
469 ;; What's with returning #f to kont?
470 ;; Otherwise we sometimes get errors like
471 ;; "Zero values returned to single-valued continuation""
473 (make-run-request (lambda () body ...) #f))))))
475 ;; TODO: Rewrite when we move to this being just `sleep'.
476 (define (8sleep time)
477 (8sync-abort-to-prompt
480 (make-run-request (lambda () (kont #f)) time)))))
482 ;; Voluntarily yield execution
483 (define (yield) ; @@: should this be define-inlinable?
484 "Voluntarily yield execution to the scheduler."
485 (8sync-abort-to-prompt
488 (make-run-request (lambda () (kont #f)) #f)))))
491 ;;; Execution of agenda, and current agenda
492 ;;; =======================================
494 (define %current-agenda (make-parameter #f))
496 (define (update-agenda-from-select! agenda)
497 "Potentially (select) on ports specified in agenda, adding items to queue.
499 Also handles sleeping when all we have to do is wait on the schedule."
500 (define (hash-keys hash)
501 (hash-map->list (lambda (k v) k) hash))
502 (define (get-wait-time)
503 ;; TODO: we need to figure this out based on whether there's anything
504 ;; in the queue, and if not, how long till the next scheduled item
505 (let ((soonest-time (schedule-soonest-time (agenda-schedule agenda))))
507 ((not (q-empty? (agenda-queue agenda)))
509 (soonest-time ; ie, the agenda is non-empty
510 (let* ((current-time (agenda-time agenda)))
511 (if (time<= soonest-time current-time)
512 ;; Well there's something due so let's select
513 ;; (this avoids a (possible?) race condition chance)
515 (time-minus soonest-time current-time))))
519 ;; TODO: support usecond wait time too
520 (match (get-wait-time)
524 (select (hash-keys (agenda-read-port-map agenda))
525 (hash-keys (agenda-write-port-map agenda))
528 (lambda (key . rest-args)
532 (_ (error "Unhandled error in select!" key rest-args))))))))
533 (define (get-procs-to-run)
534 (define (ports->procs ports port-map)
535 (lambda (initial-procs)
538 (define proc (hashq-ref port-map port))
539 ;; Now that we've selected on this port, it can be removed
540 (hashq-remove! port-map port)
545 ((read-ports write-ports except-ports) ; except-ports not used
546 ((compose (ports->procs
548 (agenda-read-port-map agenda))
551 (agenda-write-port-map agenda)))
553 (define (update-agenda)
554 (let ((procs-to-run (get-procs-to-run))
555 (q (agenda-queue agenda)))
561 (define (ports-to-select?)
562 (define (has-items? selector)
564 ;; ... we could use hash-for-each and a continuation to jump
565 ;; out with a #t at first indication of an item
566 (not (= (hash-count (const #t)
569 (or (has-items? agenda-read-port-map)
570 (has-items? agenda-write-port-map)))
572 (if (or (ports-to-select?)
573 ;; select doubles as sleep...
574 (not (schedule-empty? (agenda-schedule agenda))))
578 (define-record-type <read-request>
579 (make-read-request port proc)
581 (port read-request-port)
582 (proc read-request-proc))
584 (define-record-type <write-request>
585 (make-write-request port proc)
587 (port write-request-port)
588 (proc write-request-proc))
590 (define (agenda-handle-read-request! agenda read-request)
591 "Handle <read-request>, which is a request to add this port to the poll/select
592 on suspendable ports."
593 (hashq-set! (agenda-read-port-map agenda)
594 (read-request-port read-request)
595 (read-request-proc read-request)))
597 (define (agenda-handle-write-request! agenda write-request)
598 (hashq-set! (agenda-write-port-map agenda)
599 (write-request-port write-request)
600 (write-request-proc write-request)))
602 (define (stop-on-nothing-to-do agenda)
603 (and (q-empty? (agenda-queue agenda))
604 (schedule-empty? (agenda-schedule agenda))
605 (= 0 (hash-count (const #t) (agenda-read-port-map agenda)))
606 (= 0 (hash-count (const #t) (agenda-write-port-map agenda)))))
609 (define* (start-agenda agenda
611 ;; @@: Should we make stop-on-nothing-to-do
612 ;; the default stop-condition?
613 (stop-condition stop-on-nothing-to-do)
614 (get-time gettimeofday)
615 (handle-ports update-agenda-from-select!)
616 ;; For live hacking madness, etc
618 ;; TODO: Document fields
619 "Start up the AGENDA"
620 (let loop ((agenda agenda))
622 ;; @@: Hm, maybe here would be a great place to handle
623 ;; select'ing on ports.
624 ;; We could compose over agenda-run-once and agenda-read-ports
625 (agenda-run-once agenda)))
626 ;; @@: This relies on mutation at present on the queue, in the rare
627 ;; event it's used. If we ever switch to something more immutable,
628 ;; it should return a new modified agenda instead.
630 (post-run-hook agenda))
631 (if (and stop-condition (stop-condition agenda))
634 ;; We have to update the time after ports handled, too
635 ;; because it may have changed after a select
638 ;; Adjust the agenda's time just in time
639 ;; We do this here rather than in agenda-run-once to make
640 ;; agenda-run-once's behavior fairly predictable
641 (set-field agenda (agenda-time) (get-time)))
642 (agenda-time) (get-time))))
643 ;; Update the agenda's current queue based on
644 ;; currently applicable time segments
645 (add-segments-contents-to-queue!
646 (schedule-extract-until! (agenda-schedule agenda) (agenda-time agenda))
647 (agenda-queue agenda))
651 (define (print-error-and-continue key . args)
652 "Frequently used as pre-unwind-handler for agenda"
654 ((eq? key '8sync-caught-error)
656 ((orig-key orig-args stacks)
657 (display "\n*** Caught async exception. ***\n")
658 (format (current-error-port)
659 "* Original key '~s and arguments: ~s *\n"
661 (display "* Caught stacks below (ending with original) *\n\n")
664 (display-backtrace s (current-error-port))
665 (newline (current-error-port)))
668 (format (current-error-port)
669 "\n*** Caught exception with key '~s and arguments: ~s ***\n"
671 (display-backtrace (make-stack #t 1 0)
672 (current-error-port))
673 (newline (current-error-port)))))
675 (define-syntax-rule (maybe-catch-all (catch-handler pre-unwind-handler)
677 (if (or catch-handler pre-unwind-handler)
682 (or catch-handler (lambda _ #f))
683 (or pre-unwind-handler (lambda _ #f)))
686 (define (wait-for-readable port)
687 (8sync-abort-to-prompt
690 (make-read-request port (wrap (kont #f)))))))
692 (define (wait-for-writable port)
693 (8sync-abort-to-prompt
696 (make-write-request port (wrap (kont #f)))))))
698 (define (agenda-run-once agenda)
699 "Run once through the agenda, and produce a new agenda
700 based on the results"
701 (define (call-proc proc)
703 (agenda-prompt-tag agenda)
705 (parameterize ((%current-agenda agenda)
706 ;; @@: Couldn't we just parameterize this at the start of
708 (current-read-waiter wait-for-readable)
709 (current-write-waiter wait-for-writable))
711 ((agenda-catch-handler agenda)
712 (agenda-pre-unwind-handler agenda))
714 (lambda (kont async-request)
715 (setup-async-request kont async-request))))
717 (let ((queue (agenda-queue agenda))
718 (next-queue (make-q)))
719 (while (not (q-empty? queue))
720 (let* ((proc (q-pop! queue))
721 (proc-result (call-proc proc))
723 (lambda (run-request)
724 (define (schedule-at! time proc)
725 (schedule-add! (agenda-schedule agenda) time proc))
726 (let ((request-time (run-request-when run-request)))
728 ((? time-delta? time-delta)
729 (let ((time (time-delta+ (agenda-time agenda)
731 (schedule-at! time (run-request-proc run-request))))
733 (let ((time (cons sec 0)))
734 (schedule-at! time (run-request-proc run-request))))
735 (((? integer? sec) . (? integer? usec))
736 (schedule-at! request-time (run-request-proc run-request)))
738 (enq! next-queue (run-request-proc run-request))))))))
739 (define (handle-individual result)
740 ;; @@: Could maybe optimize by switching to an explicit cond...
742 ((? run-request? new-proc)
744 ((? read-request? read-request)
745 (agenda-handle-read-request! agenda read-request))
746 ((? write-request? write-request)
747 (agenda-handle-write-request! agenda write-request))
749 ;; Remember, we don't throw an error here because procedures can
750 ;; return a run request, eg with run-it, at the end of their
751 ;; evaluation to keep looping.
752 ;; @@: Though is this really a useful feature?
754 ;; @@: We might support delay-wrapped procedures here
757 (for-each handle-individual results))
758 (one-result (handle-individual one-result)))))
759 ;; TODO: Alternately, we could return the next-queue
760 ;; along with changes to be added to the schedule here?
761 ;; Return new agenda, with next queue set
762 (set-field agenda (agenda-queue) next-queue)))