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Diffstat (limited to 'time.scm')
| -rw-r--r-- | time.scm | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/time.scm b/time.scm new file mode 100644 index 0000000..7ddf524 --- /dev/null +++ b/time.scm @@ -0,0 +1,158 @@ +;;;; "time.scm" Posix time conversion routines +;;; Copyright (C) 1994 Aubrey Jaffer. +; +;Permission to copy this software, to redistribute it, 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. + +(define time:daylight 0) +(define *timezone* 0) +(define time:tzname #("GMT" "GDT")) + +(define (time:tzset) + (set! time:daylight 1) + (set! *timezone* (* 5 60 60)) + (set! time:tzname #("EST" "EDT"))) + +;;; No, it doesn't do leap seconds. If you want to add it, go ahead. + +;;; 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* ((days-in-year (lambda (year) + (if (and (zero? (remainder year 4)) + (or (not (zero? (remainder year 100))) + (zero? (remainder year 400)))) + 366 365))) + (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))) ; Leap years. + (SECS/HOUR (* 60 60)) + (SECS/DAY (* SECS/HOUR 24)) + (secs (modulo t SECS/DAY)) + (days (+ (quotient t SECS/DAY) + (if (and (negative? t) (positive? secs)) -1 0)))) + (let ((tm_hour (quotient secs SECS/HOUR)) + (secs (remainder secs SECS/HOUR)) + (tm_wday (modulo (+ 4 days) 7))) ; January 1, 1970 was a Thursday. + (let loop ((tm_year 1970) + (tm_yday days)) + (let ((diy (days-in-year tm_year))) + (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 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 t) + (time:tzset) + (time:split t time:daylight *timezone* + (vector-ref time:tzname time:daylight))) + +(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 time) + (time:tzset) + (time:invert localtime time)) + +(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 time) + (time:asctime (time:localtime time))) + +(define tzset time:tzset) +(define gmtime time:gmtime) +(define localtime time:localtime) +(define mktime time:mktime) +(define asctime time:asctime) +(define ctime time:ctime) |