summaryrefslogtreecommitdiffstats
path: root/psxtime.scm
blob: 9d94b869746476715f8071b86b829eacf04bb16b (plain)
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
;;;; "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)