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;;;; "psxtime.scm" Posix time conversion routines
;;; Copyright (C) 1994, 1997 Aubrey Jaffer
;
;Permission to copy this software, to modify it, to redistribute it,
;to distribute modified versions, and to use it for any purpose is
;granted, subject to the following restrictions and understandings.
;
;1. Any copy made of this software must include this copyright notice
;in full.
;
;2. I have made no warrantee or representation that the operation of
;this software will be error-free, and I am under no obligation to
;provide any services, by way of maintenance, update, or otherwise.
;
;3. In conjunction with products arising from the use of this
;material, there shall be no use of my name in any advertising,
;promotional, or sales literature without prior written consent in
;each case.
;;; No, it doesn't do leap seconds.
(define time:days/month
'#(#(31 28 31 30 31 30 31 31 30 31 30 31) ; Normal years.
#(31 29 31 30 31 30 31 31 30 31 30 31)))
(define (leap-year? year)
(and (zero? (remainder year 4))
(or (not (zero? (remainder year 100)))
(zero? (remainder year 400))))) ; Leap years.
;;; Returns the `struct tm' representation of T,
;;; offset TM_GMTOFF seconds east of UCT.
(define (time:split t tm_isdst tm_gmtoff tm_zone)
(set! t (difftime t tm_gmtoff))
(let* ((secs (modulo t 86400)) ; SECS/DAY
(days (+ (quotient t 86400) ; SECS/DAY
(if (and (negative? t) (positive? secs)) -1 0))))
(let ((tm_hour (quotient secs 3600))
(secs (remainder secs 3600))
(tm_wday (modulo (+ 4 days) 7))) ; January 1, 1970 was a Thursday.
(let loop ((tm_year 1970)
(tm_yday days))
(let ((diy (if (leap-year? tm_year) 366 365)))
(cond
((negative? tm_yday) (loop (+ -1 tm_year) (+ tm_yday diy)))
((>= tm_yday diy) (loop (+ 1 tm_year) (- tm_yday diy)))
(else
(let* ((mv (vector-ref time:days/month (- diy 365))))
(do ((tm_mon 0 (+ 1 tm_mon))
(tm_mday tm_yday (- tm_mday (vector-ref mv tm_mon))))
((< tm_mday (vector-ref mv tm_mon))
(vector
(remainder secs 60) ; Seconds. [0-61] (2 leap seconds)
(quotient secs 60) ; Minutes. [0-59]
tm_hour ; Hours. [0-23]
(+ tm_mday 1) ; Day. [1-31]
tm_mon ; Month. [0-11]
(- tm_year 1900) ; Year - 1900.
tm_wday ; Day of week. [0-6]
tm_yday ; Days in year. [0-365]
tm_isdst ; DST. [-1/0/1]
tm_gmtoff ; Seconds west of UTC.
tm_zone ; Timezone abbreviation.
)))))))))))
(define (time:gmtime t)
(time:split t 0 0 "GMT"))
(define (time:localtime caltime . tz)
(require 'time-zone)
(set! tz (if (null? tz) (tzset) (car tz)))
(apply time:split caltime (tz:params caltime tz)))
(define time:year-70
(let* ((t (current-time)))
(offset-time (offset-time t (- (difftime t 0))) (* -70 32140800))))
(define (time:invert decoder target)
(let* ((times '#(1 60 3600 86400 2678400 32140800))
(trough ; rough time for target
(do ((i 5 (+ i -1))
(trough time:year-70
(offset-time trough (* (vector-ref target i)
(vector-ref times i)))))
((negative? i) trough))))
;;; (print 'trough trough 'target target)
(let loop ((guess trough)
(j 0)
(guess-tm (decoder trough)))
;;; (print 'guess guess 'guess-tm guess-tm)
(do ((i 5 (+ i -1))
(rough time:year-70
(offset-time rough (* (vector-ref guess-tm i)
(vector-ref times i))))
(sign (let ((d (- (vector-ref target 5)
(vector-ref guess-tm 5))))
(and (not (zero? d)) d))
(or sign
(let ((d (- (vector-ref target i)
(vector-ref guess-tm i))))
(and (not (zero? d)) d)))))
((negative? i)
(let* ((distance (abs (- trough rough))))
(cond ((and (zero? distance) sign)
;;; (print "trying to jump")
(set! distance (if (negative? sign) -86400 86400)))
((and sign (negative? sign)) (set! distance (- distance))))
(set! guess (offset-time guess distance))
;;; (print 'distance distance 'sign sign)
(cond ((zero? distance) guess)
((> j 5) #f) ;to prevent inf loops.
(else
(loop guess
(+ 1 j)
(decoder guess))))))))))
(define (time:mktime univtime . tz)
(require 'time-zone)
(set! tz (if (null? tz) (tzset) (car tz)))
(+ (gmktime univtime) (tz:std-offset tz)))
(define (time:gmktime univtime)
(time:invert time:gmtime univtime))
(define (time:asctime decoded)
(let ((days '#("Sun" "Mon" "Tue" "Wed" "Thu" "Fri" "Sat"))
(months '#("Jan" "Feb" "Mar" "Apr" "May" "Jun"
"Jul" "Aug" "Sep" "Oct" "Nov" "Dec"))
(number->2digits
(lambda (n ch)
(set! n (number->string n))
(if (= 1 (string-length n))
(string-append ch n)
n))))
(string-append
(vector-ref days (vector-ref decoded 6)) " "
(vector-ref months (vector-ref decoded 4)) " "
(number->2digits (vector-ref decoded 3) " ") " "
(number->2digits (vector-ref decoded 2) "0") ":"
(number->2digits (vector-ref decoded 1) "0") ":"
(number->2digits (vector-ref decoded 0) "0") " "
(number->string (+ 1900 (vector-ref decoded 5)))
(string #\newline))))
(define (time:ctime . args)
(time:asctime (apply time:localtime args)))
(define (time:gtime time)
(time:asctime (time:gmtime time)))
;;; GMT Local -- take optional 2nd TZ arg
(define gmtime time:gmtime) (define localtime time:localtime)
(define gmktime time:gmktime) (define mktime time:mktime)
(define gtime time:gtime) (define ctime time:ctime)
(define asctime time:asctime)
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