+++ /dev/null
-;; Copyright (C) 2015 Christopher Allan Webber <cwebber@dustycloud.org>
-
-;; 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 (<agenda>
- 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
-
- <time-segment>
- make-time-segment time-segment?
- time-segment-time time-segment-queue
-
- time< time= time<= time-delta+
- time-minus time-plus
-
- <time-delta>
- make-time-delta tdelta time-delta?
- time-delta-sec time-delta-usec
-
- <schedule>
- 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
-
- <run-request>
- make-run-request run-request?
- run-request-proc run-request-when
-
- <port-request>
- 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?
-
-\f
-;;; 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 <agenda>
- (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))))
-
-
-\f
-;;; 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 <time-segment>
- (make-time-segment-intern time queue)
- time-segment?
- (time time-segment-time)
- (queue time-segment-queue))
-
-(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))
- (_ (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 <time-delta>
- (make-time-delta-intern sec usec)
- time-delta?
- (sec time-delta-sec)
- (usec time-delta-usec))
-
-(define* (make-time-delta sec #:optional (usec 0))
- "Make a <time-delta> of SEC seconds and USEC microseconds.
-
-This is used primarily so the agenda can recognize RUN-REQUEST objects
-which are meant "
- (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 <schedule>
- (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))
-
-
-\f
-;;; Request to run stuff
-;;; ====================
-
-(define-record-type <run-request>
- (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 <port-request>
- (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)
-
-
-\f
-;;; 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 ...))
-
-
-\f
-;;; 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)))
godir=$(libdir)/guile/2.0/ccache
SOURCES = \
- 8sync/agenda.scm
+ eightsync/agenda.scm
TESTS = \
--- /dev/null
+;; Copyright (C) 2015 Christopher Allan Webber <cwebber@dustycloud.org>
+
+;; 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 (<agenda>
+ 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
+
+ <time-segment>
+ make-time-segment time-segment?
+ time-segment-time time-segment-queue
+
+ time< time= time<= time-delta+
+ time-minus time-plus
+
+ <time-delta>
+ make-time-delta tdelta time-delta?
+ time-delta-sec time-delta-usec
+
+ <schedule>
+ 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
+
+ <run-request>
+ make-run-request run-request?
+ run-request-proc run-request-when
+
+ <port-request>
+ 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?
+
+\f
+;;; 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 <agenda>
+ (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))))
+
+
+\f
+;;; 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 <time-segment>
+ (make-time-segment-intern time queue)
+ time-segment?
+ (time time-segment-time)
+ (queue time-segment-queue))
+
+(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))
+ (_ (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 <time-delta>
+ (make-time-delta-intern sec usec)
+ time-delta?
+ (sec time-delta-sec)
+ (usec time-delta-usec))
+
+(define* (make-time-delta sec #:optional (usec 0))
+ "Make a <time-delta> of SEC seconds and USEC microseconds.
+
+This is used primarily so the agenda can recognize RUN-REQUEST objects
+which are meant "
+ (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 <schedule>
+ (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))
+
+
+\f
+;;; Request to run stuff
+;;; ====================
+
+(define-record-type <run-request>
+ (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 <port-request>
+ (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)
+
+
+\f
+;;; 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 ...))
+
+
+\f
+;;; 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)))
projects / 8sync.git / commitdiff