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 print-error-and-continue
71 start-agenda agenda-run-once))
73 ;; @@: Using immutable agendas here, so wouldn't it make sense to
74 ;; replace this queue stuff with using pfds based immutable queues?
80 ;;; The agenda consists of:
81 ;;; - a queue of immediate items to handle
82 ;;; - sheduled future events to be added to a future queue
83 ;;; - a tag by which running processes can escape for some asynchronous
84 ;;; operation (from which they can be returned later)
85 ;;; - a mapping of ports to various handler procedures
87 ;;; The goal, eventually, is for this all to be immutable and functional.
88 ;;; However, we aren't there yet. Some tricky things:
89 ;;; - The schedule needs to be immutable, yet reasonably efficient.
90 ;;; - Need to use immutable queues (ijp's pfds library?)
91 ;;; - Modeling reading from ports as something repeatable,
92 ;;; and with reasonable separation from functional components?
94 (define-immutable-record-type <agenda>
95 (make-agenda-intern queue prompt-tag
96 read-port-map write-port-map except-port-map
97 schedule time catch-handler pre-unwind-handler)
100 (prompt-tag agenda-prompt-tag)
101 (read-port-map agenda-read-port-map)
102 (write-port-map agenda-write-port-map)
103 (except-port-map agenda-except-port-map)
104 (schedule agenda-schedule)
106 (catch-handler agenda-catch-handler)
107 (pre-unwind-handler agenda-pre-unwind-handler))
109 (define (make-async-prompt-tag)
110 "Make an async prompt tag for an agenda.
112 Generally done automatically for the user through (make-agenda)."
113 (make-prompt-tag "prompt"))
115 (define* (make-agenda #:key
117 (prompt (make-prompt-tag))
118 (read-port-map (make-hash-table))
119 (write-port-map (make-hash-table))
120 (except-port-map (make-hash-table))
121 (schedule (make-schedule))
122 (time (gettimeofday))
124 (pre-unwind-handler #f))
125 ;; TODO: document arguments
126 "Make a fresh agenda."
127 (make-agenda-intern queue prompt
128 read-port-map write-port-map except-port-map
130 catch-handler pre-unwind-handler))
132 (define (current-agenda-prompt)
133 "Get the prompt for the current agenda; signal an error if there isn't one."
134 (let ((current-agenda (%current-agenda)))
135 (if (not current-agenda)
138 "Can't get current agenda prompt if there's no current agenda!")
139 (agenda-prompt-tag current-agenda))))
146 ;;; This is where we handle timed events for the future
148 ;; This section totally borrows from the ideas in SICP
151 ;; NOTE: time is a cons of (seconds . microseconds)
153 (define-record-type <time-segment>
154 (make-time-segment-intern time queue)
156 (time time-segment-time)
157 (queue time-segment-queue))
159 ;; @@: This seems to be the same as srfi-18's seconds->time procedure?
160 ;; Maybe double check and switch to that? (Thanks amz3!)
162 (define (time-from-float-or-fraction time)
163 "Produce a (sec . usec) pair from TIME, a float or fraction"
164 (let* ((mixed-whole (floor time))
165 (mixed-rest (- time mixed-whole)) ; float or fraction component
167 (usec (floor (* 1000000 mixed-rest))))
168 (cons (inexact->exact sec) (inexact->exact usec))))
170 (define (time-segment-right-format time)
171 "Ensure TIME is in the right format.
173 The right format means (second . microsecond).
174 If an integer, will convert appropriately."
175 ;; TODO: add floating point / rational number support.
177 ;; time is already a cons of second and microsecnd
178 (((? integer? s) . (? integer? u)) time)
179 ;; time was just an integer (just the second)
180 ((? integer? _) (cons time 0))
181 ((or (? rational? _) (? inexact? _))
182 (time-from-float-or-fraction time))
183 (_ (throw 'invalid-time "Invalid time" time))))
185 (define* (make-time-segment time #:optional (queue (make-q)))
186 "Make a time segment of TIME and QUEUE
188 No automatic conversion is done, so you might have to
189 run (time-segment-right-format) first."
190 (make-time-segment-intern time queue))
192 (define (time< time1 time2)
193 "Check if TIME1 is less than TIME2"
194 (cond ((< (car time1)
204 (define (time= time1 time2)
205 "Check whether TIME1 and TIME2 are equivalent"
206 (and (= (car time1) (car time2))
207 (= (cdr time1) (cdr time2))))
209 (define (time<= time1 time2)
210 "Check if TIME1 is less than or equal to TIME2"
211 (or (time< time1 time2)
212 (time= time1 time2)))
215 (define-record-type <time-delta>
216 (make-time-delta-intern sec usec)
219 (usec time-delta-usec))
221 (define* (make-time-delta time)
222 "Make a <time-delta> of SEC seconds and USEC microseconds.
224 This is used primarily so the agenda can recognize RUN-REQUEST objects
225 which are meant to delay computation"
226 (match (time-segment-right-format time)
228 (make-time-delta-intern sec usec))))
230 (define tdelta make-time-delta)
232 (define (time-carry-correct time)
233 "Corrects/handles time microsecond carry.
234 Will produce (0 . 0) instead of a negative number, if needed."
235 (cond ((>= (cdr time) 1000000)
238 (- (cdr time) 1000000)))
244 (+ (cdr time) 1000000))))
247 (define (time-delta+ time time-delta)
248 "Increment a TIME by the value of TIME-DELTA"
250 (cons (+ (car time) (time-delta-sec time-delta))
251 (+ (cdr time) (time-delta-usec time-delta)))))
253 (define (time-minus time1 time2)
254 "Subtract TIME2 from TIME1"
256 (cons (- (car time1) (car time2))
257 (- (cdr time1) (cdr time2)))))
259 (define (time-plus time1 time2)
260 "Add TIME1 and TIME2"
262 (cons (+ (car time1) (car time2))
263 (+ (cdr time1) (cdr time2)))))
266 (define-record-type <schedule>
267 (make-schedule-intern segments)
269 (segments schedule-segments set-schedule-segments!))
271 (define* (make-schedule #:optional segments)
272 "Make a schedule, optionally pre-composed of SEGMENTS"
273 (make-schedule-intern (or segments '())))
275 (define (schedule-soonest-time schedule)
276 "Return a cons of (sec . usec) for next time segement, or #f if none"
277 (let ((segments (schedule-segments schedule)))
278 (if (eq? segments '())
280 (time-segment-time (car segments)))))
282 ;; TODO: This code is reasonably easy to read but it
283 ;; mutates AND is worst case of O(n) in both space and time :(
284 ;; but at least it'll be reasonably easy to refactor to
285 ;; a more functional setup?
286 (define (schedule-add! schedule time proc)
287 "Mutate SCHEDULE, adding PROC at an appropriate time segment for TIME"
288 (let ((time (time-segment-right-format time)))
289 (define (new-time-segment)
291 (make-time-segment time)))
292 (enq! (time-segment-queue new-segment) proc)
294 (define (loop segments)
295 (define (segment-equals-time? segment)
296 (time= time (time-segment-time segment)))
298 (define (segment-more-than-time? segment)
299 (time< time (time-segment-time segment)))
301 ;; We could switch this out to be more mutate'y
302 ;; and avoid the O(n) of space... is that over-optimizing?
304 ;; If we're at the end of the list, time to make a new
306 ('() (cons (new-time-segment) '()))
307 ;; If the segment's time is exactly our time, good news
308 ;; everyone! Let's append our stuff to its queue
309 (((? segment-equals-time? first) rest ...)
310 (enq! (time-segment-queue first) proc)
312 ;; If the first segment is more than our time,
313 ;; ours belongs before this one, so add it and
314 ;; start consing our way back
315 (((? segment-more-than-time? first) rest ...)
316 (cons (new-time-segment) segments))
317 ;; Otherwise, build up recursive result
319 (cons first (loop rest)))))
320 (set-schedule-segments!
322 (loop (schedule-segments schedule)))))
324 (define (schedule-empty? schedule)
325 "Check if the SCHEDULE is currently empty"
326 (eq? (schedule-segments schedule) '()))
328 (define (schedule-segments-split schedule time)
329 "Does a multiple value return of time segments before/at and after TIME"
330 (let ((time (time-segment-right-format time)))
331 (define (segment-is-now? segment)
332 (time= (time-segment-time segment) time))
333 (define (segment-is-before-now? segment)
334 (time< (time-segment-time segment) time))
336 (let loop ((segments-before '())
337 (segments-left (schedule-segments schedule)))
339 ;; end of the line, return
341 (values (reverse segments-before) '()))
343 ;; It's right now, so time to stop, but include this one in before
344 ;; but otherwise return
345 (((? segment-is-now? first) rest ...)
346 (values (reverse (cons first segments-before)) rest))
348 ;; This is prior or at now, so add it and keep going
349 (((? segment-is-before-now? first) rest ...)
350 (loop (cons first segments-before) rest))
352 ;; Otherwise it's past now, just return what we have
354 (values segments-before segments-after))))))
356 (define (schedule-extract-until! schedule time)
357 "Extract all segments until TIME from SCHEDULE, and pop old segments off"
358 (receive (segments-before segments-after)
359 (schedule-segments-split schedule time)
360 (set-schedule-segments! schedule segments-after)
363 (define (add-segments-contents-to-queue! segments queue)
366 (let ((seg-queue (time-segment-queue segment)))
367 (while (not (q-empty? seg-queue))
368 (enq! queue (deq! seg-queue)))))
373 ;;; Request to run stuff
374 ;;; ====================
376 (define-record-type <run-request>
377 (make-run-request proc when)
379 (proc run-request-proc)
380 (when run-request-when))
382 (define* (run-it proc #:optional when)
383 "Make a request to run PROC (possibly at WHEN)"
384 (make-run-request proc when))
386 (define-syntax-rule (wrap body ...)
387 "Wrap contents in a procedure"
391 (define-syntax-rule (wrap-apply body)
392 "Wrap possibly multi-value function in a procedure, applies all arguments"
397 ;; @@: Do we really want `body ...' here?
398 ;; what about just `body'?
399 (define-syntax-rule (run body ...)
400 "Run everything in BODY but wrap in a convenient procedure"
401 (make-run-request (wrap body ...) #f))
403 (define-syntax-rule (run-at body ... when)
405 (make-run-request (wrap body ...) when))
407 ;; @@: Is it okay to overload the term "delay" like this?
408 ;; Would `run-in' be better?
409 (define-syntax-rule (run-delay body ... delay-time)
410 "Run BODY at DELAY-TIME time from now"
411 (make-run-request (wrap body ...) (tdelta delay-time)))
414 ;; A request to set up a port with at least one of read, write, except
415 ;; handling processes
417 (define-record-type <port-request>
418 (make-port-request-intern port read write except)
420 (port port-request-port)
421 (read port-request-read)
422 (write port-request-write)
423 (except port-request-except))
425 (define* (make-port-request port #:key read write except)
426 (if (not (or read write except))
427 (throw 'no-port-handler-given "No port handler given.\n"))
428 (make-port-request-intern port read write except))
430 (define port-request make-port-request)
434 ;;; Asynchronous escape to run things
435 ;;; =================================
437 (define (agenda-on-error agenda)
440 (define (agenda-on-fail agenda)
443 (define-syntax-rule (%8sync async-request)
444 "Run BODY asynchronously at a prompt, passing args to make-future.
446 Runs things asynchronously (8synchronously?)"
447 (abort-to-prompt (current-agenda-prompt)
450 ;; Async port request and run-request meta-requests
451 (define (make-async-request proc)
452 "Wrap PROC in an async-request
454 The purpose of this is to make sure that users don't accidentally
455 return the wrong thing via (%8sync) and trip themselves up."
456 (cons '*async-request* proc))
458 (define (setup-async-request resume-kont async-request)
459 "Complete an async request for agenda-run-once's continuation handling"
461 (('*async-request* . async-setup-proc)
462 (async-setup-proc resume-kont))
463 ;; TODO: deliver more helpful errors depending on what the user
465 (_ (throw 'invalid-async-request
466 "Invalid request passed back via an (%8sync) procedure."
469 (define-syntax-rule (%run body ...)
470 (%run-at body ... #f))
472 (define-syntax-rule (%run-at body ... when)
481 (define-syntax-rule (%run-delay body ... delay-time)
482 (%run-at body ... (tdelta delay-time)))
484 (define-syntax-rule (%port-request add-this-port port-request-args ...)
487 (list (make-port-request port-request-args ...)
488 (make-run-request kont)))))
491 (define-syntax-rule (%run-with-return return body ...)
500 ;;; Execution of agenda, and current agenda
501 ;;; =======================================
503 (define %current-agenda (make-parameter #f))
505 (define (update-agenda-from-select! agenda)
506 "Potentially (select) on ports specified in agenda, adding items to queue"
507 (define (hash-keys hash)
508 (hash-map->list (lambda (k v) k) hash))
509 (define (get-wait-time)
510 ;; TODO: we need to figure this out based on whether there's anything
511 ;; in the queue, and if not, how long till the next scheduled item
512 (let ((soonest-time (schedule-soonest-time (agenda-schedule agenda))))
514 ((not (q-empty? (agenda-queue agenda)))
516 (soonest-time ; ie, the agenda is non-empty
517 (let* ((current-time (agenda-time agenda)))
518 (if (time<= soonest-time current-time)
519 ;; Well there's something due so let's select
520 ;; (this avoids a (possible?) race condition chance)
522 (time-minus soonest-time current-time))))
526 ;; TODO: support usecond wait time too
527 (match (get-wait-time)
531 (select (hash-keys (agenda-read-port-map agenda))
532 (hash-keys (agenda-write-port-map agenda))
533 (hash-keys (agenda-except-port-map agenda))
535 (lambda (key . rest-args)
539 (_ (error "Unhandled error in select!" key rest-args))))))))
540 (define (get-procs-to-run)
541 (define (ports->procs ports port-map)
542 (lambda (initial-procs)
546 ((hash-ref port-map port) port))
551 ((read-ports write-ports except-ports)
552 ;; @@: Come on, we can do better than append ;P
553 ((compose (ports->procs
555 (agenda-read-port-map agenda))
558 (agenda-write-port-map agenda))
561 (agenda-except-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)
581 (has-items? agenda-except-port-map)))
583 (if (ports-to-select?)
587 (define (agenda-handle-port-request! agenda port-request)
588 "Update an agenda for a port-request"
589 (define (handle-selector request-selector port-map-selector)
590 (if (request-selector port-request)
591 (hash-set! (port-map-selector agenda)
592 (port-request-port port-request)
593 (request-selector port-request))))
594 (handle-selector port-request-read agenda-read-port-map)
595 (handle-selector port-request-write agenda-write-port-map)
596 (handle-selector port-request-except agenda-except-port-map))
599 (define* (start-agenda agenda
601 (get-time gettimeofday)
602 (handle-ports update-agenda-from-select!))
603 ;; TODO: Document fields
604 "Start up the AGENDA"
605 (let loop ((agenda agenda))
607 ;; @@: Hm, maybe here would be a great place to handle
608 ;; select'ing on ports.
609 ;; We could compose over agenda-run-once and agenda-read-ports
610 (agenda-run-once agenda)))
611 (if (and stop-condition (stop-condition agenda))
614 ;; We have to update the time after ports handled, too
615 ;; because it may have changed after a select
618 ;; Adjust the agenda's time just in time
619 ;; We do this here rather than in agenda-run-once to make
620 ;; agenda-run-once's behavior fairly predictable
621 (set-field agenda (agenda-time) (get-time)))
622 (agenda-time) (get-time))))
623 ;; Update the agenda's current queue based on
624 ;; currently applicable time segments
625 (add-segments-contents-to-queue!
626 (schedule-extract-until! (agenda-schedule agenda) (agenda-time agenda))
627 (agenda-queue agenda))
630 (define (print-error-and-continue . args)
631 "Frequently used as pre-unwind-handler for agenda"
632 (format (current-error-port) "\n*** Caught exception with arguments: ~s ***\n"
634 (display-backtrace (make-stack #t 1 0)
635 (current-error-port))
636 (newline (current-error-port)))
638 (define-syntax-rule (maybe-catch-all (catch-handler pre-unwind-handler)
640 (if (or catch-handler pre-unwind-handler)
645 (or catch-handler (lambda _ #f))
646 (or pre-unwind-handler (lambda _ #f)))
649 (define (agenda-run-once agenda)
650 "Run once through the agenda, and produce a new agenda
651 based on the results"
652 (define (call-proc proc)
654 (agenda-prompt-tag agenda)
656 (parameterize ((%current-agenda agenda))
658 ((agenda-catch-handler agenda)
659 (agenda-pre-unwind-handler agenda))
661 (lambda (kont async-request)
662 (setup-async-request kont async-request))))
664 (let ((queue (agenda-queue agenda))
665 (next-queue (make-q)))
666 (while (not (q-empty? queue))
667 (let* ((proc (q-pop! queue))
668 (proc-result (call-proc proc))
670 (lambda (run-request)
671 (define (schedule-at! time proc)
672 (schedule-add! (agenda-schedule agenda) time proc))
673 (let ((request-time (run-request-when run-request)))
675 ((? time-delta? time-delta)
676 (let ((time (time-delta+ (agenda-time agenda)
678 (schedule-at! time (run-request-proc run-request))))
680 (let ((time (cons sec 0)))
681 (schedule-at! time (run-request-proc run-request))))
682 (((? integer? sec) . (? integer? usec))
683 (schedule-at! request-time (run-request-proc run-request)))
685 (enq! next-queue (run-request-proc run-request))))))))
686 (define (handle-individual result)
688 ((? run-request? new-proc)
690 ((? port-request? port-request)
691 (agenda-handle-port-request! agenda port-request))
694 ;; @@: We might support delay-wrapped procedures here
697 (for-each handle-individual results))
698 (one-result (handle-individual one-result)))))
699 ;; TODO: Alternately, we could return the next-queue
700 ;; along with changes to be added to the schedule here?
701 ;; Return new agenda, with next queue set
702 (set-field agenda (agenda-queue) next-queue)))