-(use-modules (srfi srfi-9)
- (srfi srfi-9 gnu)
- (ice-9 q)
- (ice-9 match))
+(define-module (loopy 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!
+
+ <run-request>
+ make-run-request run-request?
+ run-request-proc run-request-when
+
+ run wrap run-wrap run-wrap-at
+
+ %current-agenda
+ start-agenda agenda-run-once))
;; @@: Using immutable agendas here, so wouldn't it make sense to
-;; replace this
+;; 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)
+ (make-agenda-intern queue prompt-tag
+ read-port-map write-port-map except-port-map
+ schedule time)
agenda?
- (queue agenda-queue))
+ (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-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)))
+ (make-agenda-intern queue prompt
+ read-port-map write-port-map except-port-map
+ schedule time))
+
+
+\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)
+ (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-time-segment-intern time queue))
+
+(define (time< time1 time2)
+ (cond ((< (car time1)
+ (car time2))
+ #t)
+ ((and (= (car time1)
+ (car time2))
+ (< (cdr time1)
+ (cdr time2)))
+ #t)
+ (else #f)))
+
+(define (time= time1 time2)
+ (and (= (car time1) (car time2))
+ (= (cdr time1) (cdr time2))))
+
+(define (time<= time1 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)
+ (make-time-delta-intern sec (or usec 0)))
+
+(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)
+ (time-carry-correct
+ (cons (+ (car time) (time-delta-sec time-delta))
+ (+ (cdr time) (time-delta-usec time-delta)))))
+
+(define (time-minus time1 time2)
+ (time-carry-correct
+ (cons (- (car time1) (car time2))
+ (- (cdr time2) (cdr time2)))))
+
+(define (time-plus time1 time2)
+ (time-carry-correct
+ (cons (+ (car time1) (car time2))
+ (+ (cdr time2) (cdr time2)))))
+
-(define* (make-agenda #:key (queue (make-q)))
- (make-agenda-intern queue))
+(define-record-type <schedule>
+ (make-schedule-intern segments)
+ schedule?
+ (segments schedule-segments set-schedule-segments!))
+
+(define* (make-schedule #:optional 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)
+ (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)
+ (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
+;;; Port handling
+;;; =============
+
+(define (make-port-mapping)
+ (make-hash-table))
+
+(define* (port-mapping-set! port-mapping port #:optional read write except)
+ "Sets port-mapping for reader / writer / exception handlers"
+ (if (not (or read write except))
+ (throw 'no-handlers-given "No handlers given for port" port))
+ (hashq-set! port-mapping port
+ `#(,read ,write ,except)))
+
+(define (port-mapping-remove! port-mapping port)
+ (hashq-remove! port-mapping port))
+
+;; TODO: This is O(n), I'm pretty sure :\
+;; ... it might be worthwhile for us to have a
+;; port-mapping record that keeps a count of how many
+;; handlers (maybe via a promise?)
+(define (port-mapping-empty? port-mapping)
+ "Is this port mapping empty?"
+ (eq? (hash-count (const #t) port-mapping) 0))
+
+(define (port-mapping-non-empty? port-mapping)
+ "Whether this port-mapping contains any elements"
+ (not (port-mapping-empty? port-mapping)))
+
+
+\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 proc #:optional when)
+ (make-run-request proc when))
+
+(define-syntax-rule (wrap body ...)
+ (lambda ()
+ body ...))
+
+(define-syntax-rule (run-wrap body ...)
+ (run (wrap body ...)))
+
+(define-syntax-rule (run-wrap-at body ... when)
+ (run (wrap body ...) when))
+
+\f
+;;; Execution of agenda, and current agenda
+;;; =======================================
(define %current-agenda (make-parameter #f))
-(define* (start-agenda agenda #:optional stop-condition)
+(define (update-agenda-from-select! agenda)
+ (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* (start-agenda agenda
+ #:key stop-condition
+ (get-time gettimeofday)
+ (handle-ports update-agenda-from-select!))
(let loop ((agenda agenda))
- (let ((new-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
(parameterize ((%current-agenda agenda))
(agenda-run-once agenda))))
- (if (and stop-condition (stop-condition))
+ (if (and stop-condition (stop-condition agenda))
'done
- (loop new-agenda)))))
+ (let* ((new-time (get-time))
+ (agenda
+ (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) new-time))))
+ ;; Update the agenda's current queue based on
+ ;; currently applicable time segments
+ (add-segments-contents-to-queue!
+ (schedule-extract-until! (agenda-schedule agenda) new-time)
+ (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 ()
+ (proc))
+ ;; TODO
+ (lambda (k) k)))
+
(let ((queue (agenda-queue agenda))
(next-queue (make-q)))
(while (not (q-empty? queue))
(let* ((proc (q-pop! queue))
- (proc-result (proc))
+ (proc-result (call-proc proc))
(enqueue
- (lambda (new-proc)
- (enq! next-queue new-proc))))
+ (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))))))))
;; @@: We might support delay-wrapped procedures here
(match proc-result
- ((? procedure? new-proc)
+ ;; TODO: replace procedure with something that indicates
+ ;; intent to run. Use a (run foo) procedure
+ ((? run-request? new-proc)
(enqueue new-proc))
- (((? procedure? new-procs) ...)
+ (((? run-request? new-procs) ...)
(for-each
(lambda (new-proc)
(enqueue new-proc))
- new-procs)))))
- ;; TODO: Selecting on ports would happen here?
+ new-procs))
+ ;; do nothing
+ (_ #f))))
+ ;; 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 / blobdiff