/usr/share/slib/timecore.scm is in slib 3b1-5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 | ;;;; "timecore.scm" Core time conversion routines
;;; Copyright (C) 1994, 1997, 2004, 2005 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 warranty 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)
(define tms (inexact->exact
(round (- (difftime t time:year-70) tm_gmtoff))))
(let* ((secs (modulo tms 86400)) ; SECS/DAY
(days (+ (quotient tms 86400) ; SECS/DAY
(if (and (negative? tms) (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:year-70
(let ((t (current-time)))
(offset-time t (- (difftime t 0)))))
;@
(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 (difftime 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:gmtime tm)
(time:split tm 0 0 "GMT"))
;;;; Use the timezone
(define (tzrule->caltime year previous-gmt-offset
tr-month tr-week tr-day tr-time)
(define leap? (leap-year? year))
(define gmmt
(time:invert time:gmtime
(vector 0 0 0 1 (if tr-month (+ -1 tr-month) 0) year #f #f 0)))
(offset-time
gmmt
(+ tr-time previous-gmt-offset
(* 3600 24
(if tr-month
(let ((fdow (vector-ref (time:gmtime gmmt) 6)))
(case tr-week
((1 2 3 4) (+ (modulo (- tr-day fdow) 7)
(* 7 (+ -1 tr-week))))
((5)
(do ((mmax (vector-ref
(vector-ref time:days/month (if leap? 1 0))
(+ -1 tr-month)))
(d (modulo (- tr-day fdow) 7) (+ 7 d)))
((>= d mmax) (+ -7 d))))
(else (slib:error 'tzrule->caltime
"week out of range" tr-week))))
(+ tr-day
(if (and (not tr-week) (>= tr-day 60) (leap-year? year))
1 0)))))))
;@
(define (tz:params caltime tz)
(case (vector-ref tz 0)
((tz:fixed) (list 0 (vector-ref tz 3) (vector-ref tz 2)))
((tz:rule)
(let* ((year (vector-ref (time:gmtime caltime) 5))
(ttime0 (apply tzrule->caltime
year (vector-ref tz 4) (vector-ref tz 6)))
(ttime1 (apply tzrule->caltime
year (vector-ref tz 5) (vector-ref tz 7)))
(dst (if (and (not (negative? (difftime caltime ttime0)))
(negative? (difftime caltime ttime1)))
1 0)))
(list dst (vector-ref tz (+ 4 dst)) (vector-ref tz (+ 2 dst)))
;;(for-each display (list (gtime ttime0) (gtime caltime) (gtime ttime1)))
))
((tz:file) (let ((zone-spec (tzfile:get-zone-spec caltime tz)))
(list (if (vector-ref zone-spec 2) 1 0)
(- (vector-ref zone-spec 1))
(vector-ref zone-spec 0))))
(else (slib:error 'tz:params "unknown timezone type" tz))))
(define (tzfile:transition-index time zone)
(define times (difftime time time:year-70))
(and zone
(apply
(lambda (path mode-table leap-seconds transition-times transition-types)
(let ((ntrns (vector-length transition-times)))
(if (zero? ntrns) -1
(let loop ((lidx (quotient (+ 1 ntrns) 2))
(jmp (quotient (+ 1 ntrns) 4)))
(let* ((idx (max 0 (min lidx (+ -1 ntrns))))
(idx-time (vector-ref transition-times idx)))
(cond ((<= jmp 0)
(+ idx (if (>= times idx-time) 0 -1)))
((= times idx-time) idx)
((and (zero? idx) (< times idx-time)) -1)
((and (not (= idx lidx)) (not (< times idx-time))) idx)
(else
(loop ((if (< times idx-time) - +) idx jmp)
(if (= 1 jmp) 0 (quotient (+ 1 jmp) 2))))))))))
(cdr (vector->list zone)))))
(define (tzfile:get-std-spec mode-table)
(do ((type-idx 0 (+ 1 type-idx)))
((or (>= type-idx (vector-length mode-table))
(not (vector-ref (vector-ref mode-table type-idx) 2)))
(if (>= type-idx (vector-length mode-table))
(vector-ref mode-table 0)
(vector-ref mode-table type-idx)))))
(define (tzfile:get-zone-spec time zone)
(apply
(lambda (path mode-table leap-seconds transition-times transition-types)
(let ((trans-idx (tzfile:transition-index time zone)))
(if (zero? (vector-length transition-types))
(vector-ref mode-table 0)
(if (negative? trans-idx)
(tzfile:get-std-spec mode-table)
(vector-ref mode-table
(vector-ref transition-types trans-idx))))))
(cdr (vector->list zone))))
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