;; Copyright (C) 2015 Christopher Allan Webber ;; This library is free software; you can redistribute it and/or ;; modify it under the terms of the GNU Lesser General Public ;; License as published by the Free Software Foundation; either ;; version 3 of the License, or (at your option) any later version. ;; ;; This library is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ;; Lesser General Public License for more details. ;; ;; You should have received a copy of the GNU Lesser General Public ;; License along with this library; if not, write to the Free Software ;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA ;; 02110-1301 USA (define-module (eightsync agenda) #:use-module (srfi srfi-1) #:use-module (srfi srfi-9) #:use-module (srfi srfi-9 gnu) #:use-module (ice-9 q) #:use-module (ice-9 match) #:use-module (ice-9 receive) #:export ( make-agenda agenda? agenda-queue agenda-prompt-tag agenda-read-port-map agenda-write-port-map agenda-except-port-map agenda-schedule make-async-prompt-tag make-time-segment time-segment? time-segment-time time-segment-queue time< time= time<= time-delta+ time-minus time-plus make-time-delta tdelta time-delta? time-delta-sec time-delta-usec make-schedule schedule? schedule-add! schedule-empty? schedule-segments schedule-soonest-time schedule-segments-split schedule-extract-until! add-segments-contents-to-queue! %sync 8sync make-run-request run-request? run-request-proc run-request-when make-port-request port-request port-request? port-request-port port-request-read port-request-write port-request-except run-it wrap run run-at run-delay %port-request %run %run-at %run-delay 8port-request 8run 8run-at 8run-delay %current-agenda start-agenda agenda-run-once)) ;; @@: Using immutable agendas here, so wouldn't it make sense to ;; replace this queue stuff with using pfds based immutable queues? ;;; Agenda definition ;;; ================= ;;; The agenda consists of: ;;; - a queue of immediate items to handle ;;; - sheduled future events to be added to a future queue ;;; - a tag by which running processes can escape for some asynchronous ;;; operation (from which they can be returned later) ;;; - a mapping of ports to various handler procedures ;;; ;;; The goal, eventually, is for this all to be immutable and functional. ;;; However, we aren't there yet. Some tricky things: ;;; - The schedule needs to be immutable, yet reasonably efficient. ;;; - Need to use immutable queues (ijp's pfds library?) ;;; - Modeling reading from ports as something repeatable, ;;; and with reasonable separation from functional components? (define-immutable-record-type (make-agenda-intern queue prompt-tag read-port-map write-port-map except-port-map schedule time) agenda? (queue agenda-queue) (prompt-tag agenda-prompt-tag) (read-port-map agenda-read-port-map) (write-port-map agenda-write-port-map) (except-port-map agenda-except-port-map) (schedule agenda-schedule) (time agenda-time)) (define (make-async-prompt-tag) "Make an async prompt tag for an agenda. Generally done automatically for the user through (make-agenda)." (make-prompt-tag "prompt")) (define* (make-agenda #:key (queue (make-q)) (prompt (make-prompt-tag)) (read-port-map (make-hash-table)) (write-port-map (make-hash-table)) (except-port-map (make-hash-table)) (schedule (make-schedule)) (time (gettimeofday))) ;; TODO: document arguments "Make a fresh agenda." (make-agenda-intern queue prompt read-port-map write-port-map except-port-map schedule time)) (define (current-agenda-prompt) "Get the prompt for the current agenda; signal an error if there isn't one." (let ((current-agenda (%current-agenda))) (if (not current-agenda) (throw 'no-current-agenda "Can't get current agenda prompt if there's no current agenda!") (agenda-prompt-tag current-agenda)))) ;;; Schedule ;;; ======== ;;; This is where we handle timed events for the future ;; This section totally borrows from the ideas in SICP ;; <3 <3 <3 ;; NOTE: time is a cons of (seconds . microseconds) (define-record-type (make-time-segment-intern time queue) time-segment? (time time-segment-time) (queue time-segment-queue)) ;; @@: This seems to be the same as srfi-18's seconds->time procedure? ;; Maybe double check and switch to that? (Thanks amz3!) (define (time-from-float-or-fraction time) "Produce a (sec . usec) pair from TIME, a float or fraction" (let* ((mixed-whole (floor time)) (mixed-rest (- time mixed-whole)) ; float or fraction component (sec mixed-whole) (usec (floor (* 1000000 mixed-rest)))) (cons (inexact->exact sec) (inexact->exact usec)))) (define (time-segment-right-format time) "Ensure TIME is in the right format. The right format means (second . microsecond). If an integer, will convert appropriately." ;; TODO: add floating point / rational number support. (match time ;; time is already a cons of second and microsecnd (((? integer? s) . (? integer? u)) time) ;; time was just an integer (just the second) ((? integer? _) (cons time 0)) ((or (? rational? _) (? inexact? _)) (time-from-float-or-fraction time)) (_ (throw 'invalid-time "Invalid time" time)))) (define* (make-time-segment time #:optional (queue (make-q))) "Make a time segment of TIME and QUEUE No automatic conversion is done, so you might have to run (time-segment-right-format) first." (make-time-segment-intern time queue)) (define (time< time1 time2) "Check if TIME1 is less than TIME2" (cond ((< (car time1) (car time2)) #t) ((and (= (car time1) (car time2)) (< (cdr time1) (cdr time2))) #t) (else #f))) (define (time= time1 time2) "Check whether TIME1 and TIME2 are equivalent" (and (= (car time1) (car time2)) (= (cdr time1) (cdr time2)))) (define (time<= time1 time2) "Check if TIME1 is less than or equal to TIME2" (or (time< time1 time2) (time= time1 time2))) (define-record-type (make-time-delta-intern sec usec) time-delta? (sec time-delta-sec) (usec time-delta-usec)) (define* (make-time-delta time) "Make a of SEC seconds and USEC microseconds. This is used primarily so the agenda can recognize RUN-REQUEST objects which are meant to delay computation" (match (time-segment-right-format time) ((sec . usec) (make-time-delta-intern sec usec)))) (define tdelta make-time-delta) (define (time-carry-correct time) "Corrects/handles time microsecond carry. Will produce (0 . 0) instead of a negative number, if needed." (cond ((>= (cdr time) 1000000) (cons (+ (car time) 1) (- (cdr time) 1000000))) ((< (cdr time) 0) (if (= (car time) 0) '(0 0) (cons (- (car time) 1) (+ (cdr time) 1000000)))) (else time))) (define (time-delta+ time time-delta) "Increment a TIME by the value of TIME-DELTA" (time-carry-correct (cons (+ (car time) (time-delta-sec time-delta)) (+ (cdr time) (time-delta-usec time-delta))))) (define (time-minus time1 time2) "Subtract TIME2 from TIME1" (time-carry-correct (cons (- (car time1) (car time2)) (- (cdr time2) (cdr time2))))) (define (time-plus time1 time2) "Add TIME1 and TIME2" (time-carry-correct (cons (+ (car time1) (car time2)) (+ (cdr time2) (cdr time2))))) (define-record-type (make-schedule-intern segments) schedule? (segments schedule-segments set-schedule-segments!)) (define* (make-schedule #:optional segments) "Make a schedule, optionally pre-composed of SEGMENTS" (make-schedule-intern (or segments '()))) (define (schedule-soonest-time schedule) "Return a cons of (sec . usec) for next time segement, or #f if none" (let ((segments (schedule-segments schedule))) (if (eq? segments '()) #f (time-segment-time (car 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! schedule time proc) "Mutate SCHEDULE, adding PROC at an appropriate time segment for TIME" (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 (new-time-segment) '())) ;; 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) "Check if the SCHEDULE is currently empty" (eq? (schedule-segments schedule) '())) (define (schedule-segments-split schedule time) "Does a multiple value return of time segments before/at and after TIME" (let ((time (time-segment-right-format time))) (define (segment-is-now? segment) (time= (time-segment-time segment) time)) (define (segment-is-before-now? segment) (time< (time-segment-time segment) time)) (let loop ((segments-before '()) (segments-left (schedule-segments schedule))) (match segments-left ;; end of the line, return ('() (values (reverse segments-before) '())) ;; It's right now, so time to stop, but include this one in before ;; but otherwise return (((? segment-is-now? first) rest ...) (values (reverse (cons first segments-before)) rest)) ;; This is prior or at now, so add it and keep going (((? segment-is-before-now? first) rest ...) (loop (cons first segments-before) rest)) ;; Otherwise it's past now, just return what we have (segments-after (values segments-before segments-after)))))) (define (schedule-extract-until! schedule time) "Extract all segments until TIME from SCHEDULE, and pop old segments off" (receive (segments-before segments-after) (schedule-segments-split schedule time) (set-schedule-segments! schedule segments-after) segments-before)) (define (add-segments-contents-to-queue! segments queue) (for-each (lambda (segment) (let ((seg-queue (time-segment-queue segment))) (while (not (q-empty? seg-queue)) (enq! queue (deq! seg-queue))))) segments)) ;;; Request to run stuff ;;; ==================== (define-record-type (make-run-request proc when) run-request? (proc run-request-proc) (when run-request-when)) (define* (run-it proc #:optional when) "Make a request to run PROC (possibly at WHEN)" (make-run-request proc when)) (define-syntax-rule (wrap body ...) "Wrap contents in a procedure" (lambda () body ...)) ;; @@: Do we really want `body ...' here? ;; what about just `body'? (define-syntax-rule (run body ...) "Run everything in BODY but wrap in a convenient procedure" (make-run-request (wrap body ...) #f)) (define-syntax-rule (run-at body ... when) "Run BODY at WHEN" (make-run-request (wrap body ...) when)) ;; @@: Is it okay to overload the term "delay" like this? ;; Would `run-in' be better? (define-syntax-rule (run-delay body ... delay-time) "Run BODY at DELAY-TIME time from now" (make-run-request (wrap body ...) (tdelta delay-time))) ;; A request to set up a port with at least one of read, write, except ;; handling processes (define-record-type (make-port-request-intern port read write except) port-request? (port port-request-port) (read port-request-read) (write port-request-write) (except port-request-except)) (define* (make-port-request port #:key read write except) (if (not (or read write except)) (throw 'no-port-handler-given "No port handler given.\n")) (make-port-request-intern port read write except)) (define port-request make-port-request) ;;; Asynchronous escape to run things ;;; ================================= ;; The future's in futures (define (make-future call-first on-success on-fail on-error) ;; TODO: add error stuff here (lambda () (let ((call-result (call-first))) ;; queue up calling the (run (on-success call-result))))) (define (agenda-on-error agenda) (const #f)) (define (agenda-on-fail agenda) (const #f)) (define* (request-future call-first on-success #:key (agenda (%current-agenda)) (on-fail (agenda-on-fail agenda)) (on-error (agenda-on-error agenda)) (when #f)) ;; TODO: error handling ;; do we need some distinction between expected, catchable errors, ;; and unexpected, uncatchable ones? Probably...? (make-run-request (make-future call-first on-success on-fail on-error) when)) (define-syntax-rule (%sync async-request) "Run BODY asynchronously at a prompt, passing args to make-future. Pronounced `eight-sync' despite the spelling. %sync was chosen because (async) was already taken and could lead to errors, and this version of asynchronous code uses a prompt, so the `a' character becomes a `%' prompt! :) The % and 8 characters kind of look similar... hence this library's name! (That, and the pun 'eight-synchronous' programming.) There are 8sync aliases if you prefer that name." (abort-to-prompt (current-agenda-prompt) async-request)) (define-syntax-rule (8sync args ...) "Alias for %sync" (%sync args ...)) ;; Async port request and run-request meta-requests (define (make-async-request proc) "Wrap PROC in an async-request The purpose of this is to make sure that users don't accidentally return the wrong thing via (8sync) and trip themselves up." (cons '*async-request* proc)) (define (setup-async-request resume-kont async-request) "Complete an async request for agenda-run-once's continuation handling" (match async-request (('*async-request* . async-setup-proc) (async-setup-proc resume-kont)) ;; TODO: deliver more helpful errors depending on what the user ;; returned (_ (throw 'invalid-async-request "Invalid request passed back via an (%sync) procedure." async-request)))) (define-syntax-rule (%run body ...) (%run-at body ... #f)) (define-syntax-rule (%run-at body ... when) (make-async-request (lambda (kont) (make-run-request (wrap (kont (begin body ...))) when)))) (define-syntax-rule (%run-delay body ... delay-time) (%run-at body ... (tdelta delay-time))) (define-syntax-rule (%port-request add-this-port port-request-args ...) (make-async-request (lambda (kont) (list (make-port-request port-request-args ...) (make-run-request kont))))) ;; TODO (define-syntax-rule (%run-with-return return body ...) (make-async-request (lambda (kont) (let ((return kont)) (lambda () body ...))))) ;; Aliases (define-syntax-rule (8run args ...) (%run args ...)) (define-syntax-rule (8run-at args ...) (%run-at args ...)) (define-syntax-rule (8run-delay args ...) (%run-delay args ...)) (define-syntax-rule (8port-request args ...) (%port-request args ...)) ;;; Execution of agenda, and current agenda ;;; ======================================= (define %current-agenda (make-parameter #f)) (define (update-agenda-from-select! agenda) "Potentially (select) on ports specified in agenda, adding items to queue" (define (hash-keys hash) (hash-map->list (lambda (k v) k) hash)) (define (get-wait-time) ;; TODO: we need to figure this out based on whether there's anything ;; in the queue, and if not, how long till the next scheduled item (let ((soonest-time (schedule-soonest-time (agenda-schedule agenda)))) (cond ((not (q-empty? (agenda-queue agenda))) (cons 0 0)) (soonest-time ; ie, the agenda is non-empty (let* ((current-time (agenda-time agenda))) (if (time<= soonest-time current-time) ;; Well there's something due so let's select ;; (this avoids a (possible?) race condition chance) (cons 0 0) (time-minus soonest-time current-time)))) (else (cons #f #f))))) (define (do-select) ;; TODO: support usecond wait time too (match (get-wait-time) ((sec . usec) (select (hash-keys (agenda-read-port-map agenda)) (hash-keys (agenda-write-port-map agenda)) (hash-keys (agenda-except-port-map agenda)) sec usec)))) (define (get-procs-to-run) (define (ports->procs ports port-map) (lambda (initial-procs) (fold (lambda (port prev) (cons (lambda () ((hash-ref port-map port) port)) prev)) initial-procs ports))) (match (do-select) ((read-ports write-ports except-ports) ;; @@: Come on, we can do better than append ;P ((compose (ports->procs read-ports (agenda-read-port-map agenda)) (ports->procs write-ports (agenda-write-port-map agenda)) (ports->procs except-ports (agenda-except-port-map agenda))) '())))) (define (update-agenda) (let ((procs-to-run (get-procs-to-run)) (q (agenda-queue agenda))) (for-each (lambda (proc) (enq! q proc)) procs-to-run)) agenda) (define (ports-to-select?) (define (has-items? selector) ;; @@: O(n) ;; ... we could use hash-for-each and a continuation to jump ;; out with a #t at first indication of an item (not (= (hash-count (const #t) (selector agenda)) 0))) (or (has-items? agenda-read-port-map) (has-items? agenda-write-port-map) (has-items? agenda-except-port-map))) (if (ports-to-select?) (update-agenda) agenda)) (define (agenda-handle-port-request! agenda port-request) "Update an agenda for a port-request" (define (handle-selector request-selector port-map-selector) (if (request-selector port-request) (hash-set! (port-map-selector agenda) (port-request-port port-request) (request-selector port-request)))) (handle-selector port-request-read agenda-read-port-map) (handle-selector port-request-write agenda-write-port-map) (handle-selector port-request-except agenda-except-port-map)) (define* (start-agenda agenda #:key stop-condition (get-time gettimeofday) (handle-ports update-agenda-from-select!)) ;; TODO: Document fields "Start up the AGENDA" (let loop ((agenda agenda)) (let ((agenda ;; @@: Hm, maybe here would be a great place to handle ;; select'ing on ports. ;; We could compose over agenda-run-once and agenda-read-ports (agenda-run-once agenda))) (if (and stop-condition (stop-condition agenda)) 'done (let* ((agenda ;; We have to update the time after ports handled, too ;; because it may have changed after a select (set-field (handle-ports ;; Adjust the agenda's time just in time ;; We do this here rather than in agenda-run-once to make ;; agenda-run-once's behavior fairly predictable (set-field agenda (agenda-time) (get-time))) (agenda-time) (get-time)))) ;; Update the agenda's current queue based on ;; currently applicable time segments (add-segments-contents-to-queue! (schedule-extract-until! (agenda-schedule agenda) (agenda-time agenda)) (agenda-queue agenda)) (loop agenda)))))) (define (agenda-run-once agenda) "Run once through the agenda, and produce a new agenda based on the results" (define (call-proc proc) (call-with-prompt (agenda-prompt-tag agenda) (lambda () (parameterize ((%current-agenda agenda)) (proc))) (lambda (kont async-request) (setup-async-request kont async-request)))) (let ((queue (agenda-queue agenda)) (next-queue (make-q))) (while (not (q-empty? queue)) (let* ((proc (q-pop! queue)) (proc-result (call-proc proc)) (enqueue (lambda (run-request) (define (schedule-at! time proc) (schedule-add! (agenda-schedule agenda) time proc)) (let ((request-time (run-request-when run-request))) (match request-time ((? time-delta? time-delta) (let ((time (time-delta+ (agenda-time agenda) time-delta))) (schedule-at! time (run-request-proc run-request)))) ((? integer? sec) (let ((time (cons sec 0))) (schedule-at! time (run-request-proc run-request)))) (((? integer? sec) . (? integer? usec)) (schedule-at! request-time (run-request-proc run-request))) (#f (enq! next-queue (run-request-proc run-request)))))))) (define (handle-individual result) (match result ((? run-request? new-proc) (enqueue new-proc)) ((? port-request? port-request) (agenda-handle-port-request! agenda port-request)) ;; do nothing (_ #f))) ;; @@: We might support delay-wrapped procedures here (match proc-result ((results ...) (for-each handle-individual results)) (one-result (handle-individual one-result))))) ;; TODO: Alternately, we could return the next-queue ;; along with changes to be added to the schedule here? ;; Return new agenda, with next queue set (set-field agenda (agenda-queue) next-queue)))