-(use-modules (srfi srfi-9)
- (srfi srfi-9 gnu)
- (ice-9 q)
- (ice-9 match))
+(define-module (loopy agenda)
+ #:use-module (srfi srfi-9)
+ #:use-module (srfi srfi-9 gnu)
+ #:use-module (ice-9 q)
+ #:use-module (ice-9 match)
+ #:export (make-agenda
+ agenda?
+ agenda-queue agenda-prompt-tag
+ agenda-port-pmapping agenda-schedule
+
+ make-async-prompt-tag
+
+ make-time-segment
+ time-segment?
+ time-segment-time time-segment-queue
+
+ time-< time-=
+
+ make-schedule
+ schedule-add! schedule-empty?
+
+ make-port-mapping
+ port-mapping-set! port-mapping-remove!
+ port-mapping-empty? port-mapping-non-empty?
+
+ %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 queue)
+ (make-agenda-intern queue prompt-tag port-mapping schedule)
agenda?
- (queue agenda-queue))
+ (queue agenda-queue)
+ (prompt-tag agenda-prompt-tag)
+ (port-mapping agenda-port-mapping)
+ (schedule agenda-schedule))
+
+(define (make-async-prompt-tag)
+ (make-prompt-tag "prompt"))
+
+(define* (make-agenda #:key
+ (queue (make-q))
+ (prompt (make-prompt-tag))
+ (port-mapping (make-port-mapping))
+ (schedule (make-schedule)))
+ (make-agenda-intern queue prompt port-mapping schedule))
+
+
+\f
+;;; Schedule
+;;; ========
+
+;;; This is where we handle timed events for the future
+
+;; This section totally borrows from 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 %current-agenda
- (make-parameter (make-agenda (make-q))))
+(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 (make-schedule)
+ '())
+
+(define (schedule-add! time proc schedule)
+ (let ((time (time-segment-right-format time)))
+ (define (belongs-before? segments)
+ (or (null? segments)
+ (error))
+ )
+
+ ;; Find and add a schedule segment
+ (error)))
+
+(define (schedule-empty? schedule)
+ (eq? schedule '()))
+
+
+\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
+;;; Execution of agenda, and current agenda
+;;; =======================================
+
+(define %current-agenda (make-parameter #f))
(define* (start-agenda agenda #:optional stop-condition)
(let loop ((agenda agenda))
- (let ((new-agenda
- (agenda-run-once agenda)))
- (%current-agenda new-agenda)
- (if (and stop-condition (stop-condition))
+ (let ((new-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 agenda))
'done
(loop new-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))))
(match proc-result
((? procedure? new-proc)
(enqueue new-proc))
- (((? procedure? new-procs) ..)
+ (((? procedure? new-procs) ...)
(for-each
(lambda (new-proc)
(enqueue new-proc))
- new-procs)))
- ;; TODO: Selecting on ports would happen here?
- ;; Return new agenda, with next queue set
- (set-field agenda (agenda-queue) next-queue)))))
+ new-procs))
+ ;; do nothing
+ (_ #f))))
+ ;; TODO: Selecting on ports would happen here?
+ ;; Return new agenda, with next queue set
+ (set-field agenda (agenda-queue) next-queue)))
projects / 8sync.git / blobdiff