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;;
;; starlet/clocks.scm
;;
;; Copyright © 2021 Thomas White <taw@bitwiz.org.uk>
;;
;; This file is part of Starlet.
;;
;; Starlet is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;;
;; This program 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 General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <http://www.gnu.org/licenses/>.
;;
(define-module (starlet clock)
#:use-module (oop goops)
#:use-module (ice-9 exceptions)
#:export (<starlet-clock>
make-clock
stop-clock!
start-clock!
reverse-clock!
<starlet-delayed-clock>
make-delayed-clock
clock-stopped?
clock-reversed?
elapsed-fraction))
(define (time-now)
(let ((a (gettimeofday)))
(+ (car a)
(/ (cdr a)
1000000))))
;; "Real" clocks are straightforward objects for measuring differences in time
;; between now and some point in the past, allowing for temporarily "pausing"
;; the clock. The time difference cannot be negative: if the start time is in
;; the future, then "time-elapsed" will return 0.
(define-class <starlet-clock> (<object>)
(start-real-time
#:init-form (time-now)
#:init-keyword #:start-time
#:getter get-start-real-time
#:setter set-start-real-time!)
(start-elapsed-time
#:init-value 0
#:getter get-start-elapsed-time
#:setter set-start-elapsed-time!)
(stopped
#:init-value #f
#:getter clock-stopped?
#:setter set-clock-stopped!)
(reversed
#:init-value #f
#:getter clock-reversed?
#:setter set-clock-reversed!))
(define (make-clock)
(make <starlet-clock>))
(define-method (time-elapsed (clock <starlet-clock>))
(if (clock-stopped? clock)
(get-start-elapsed-time clock)
(max 0
(if (clock-reversed? clock)
(- (get-start-elapsed-time clock)
(- (time-now)
(get-start-real-time clock)))
(+ (get-start-elapsed-time clock)
(- (time-now)
(get-start-real-time clock)))))))
;; Stop the clock running
(define-method (stop-clock! (clock <starlet-clock>))
(set-start-elapsed-time! clock (time-elapsed clock))
(set-clock-stopped! clock #t))
;; Start the clock running (forwards)
(define-method (start-clock! (clock <starlet-clock>))
(set-start-elapsed-time! clock (time-elapsed clock))
(set-start-real-time! clock (time-now))
(set-clock-reversed! clock #f)
(set-clock-stopped! clock #f))
;; Start the clock running, backwards
(define-method (reverse-clock! (clock <starlet-clock>))
(set-start-elapsed-time! clock (time-elapsed clock))
(set-start-real-time! clock (time-now))
(set-clock-reversed! clock #t)
(set-clock-stopped! clock #f))
;; Delayed clocks refer to a parent clock for anything to do with "real" time.
;; Note, however, that the parent clock can be another delayed clock.
(define-class <starlet-delayed-clock> (<object>)
(parent
#:init-form (error "Parent clock must be specified")
#:init-keyword #:parent
#:getter get-parent-clock)
(delay-time
#:init-form (error "Delay time must be specified")
#:init-keyword #:delay-time
#:getter get-delay-time)
(duration
#:init-value #f
#:init-keyword #:duration
#:getter get-duration))
(define-method (clock-stopped? (clock <starlet-delayed-clock>))
(clock-stopped? (get-parent-clock clock)))
(define-method (clock-reversed? (clock <starlet-delayed-clock>))
(clock-reversed? (get-parent-clock clock)))
(define-method (time-elapsed (clock <starlet-delayed-clock>))
(max 0 (- (time-elapsed (get-parent-clock clock))
(get-delay-time clock))))
(define-method (elapsed-fraction (clock <starlet-delayed-clock>))
(if (= (get-duration clock) 0)
(if (> (time-elapsed clock) 0)
1.0
0.0)
(min 1.0
(/ (time-elapsed clock)
(get-duration clock)))))
(define-method (stop-clock! (clock <starlet-delayed-clock>))
(error "Can only stop a top-level clock."))
(define-method (start-clock! (clock <starlet-delayed-clock>))
(error "Can only start a top-level clock."))
(define-method (reverse-clock! (clock <starlet-delayed-clock>))
(error "Can only reverse a top-level clock."))
(define (make-delayed-clock clock delay-time duration)
(make <starlet-delayed-clock>
#:parent clock
#:delay-time delay-time
#:duration duration))
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