aboutsummaryrefslogtreecommitdiffstats
path: root/tzfile.scm
blob: 2f3c2d01e3f44ddf74b694888ce48fd6b2665845 (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
; "tzfile.scm", Read sysV style (binary) timezone file.
; Copyright (c) 1997 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.

(require 'byte)

(define tzfile:vicinity (make-vicinity "/usr/lib/zoneinfo/"))

(define (tzfile:read-long port)
  (let ((hibyte (read-byte port)))
    (do ((idx 3 (+ -1 idx))
	 (val (if (> hibyte 127) (+ #x-100 hibyte) hibyte)
	      (+ (ash val 8) (read-byte port))))
	((zero? idx) val))))
(define (tzfile:read-longs len port)
  (define ra (make-vector len 0))
  (do ((idx 0 (+ 1 idx)))
      ((>= idx len) ra)
    (vector-set! ra idx (tzfile:read-long port))))

(define (tzfile:read-bool port)
  (let ((c (read-char port)))
    (if (eof-object? c) c (if (zero? (char->integer c)) #f #t))))

(define (tzfile:read path)
  (define null (integer->char 0))
  (call-with-input-file path
    (lambda (port)
      (do ((idx 0 (+ 1 idx)))		;reserved.
	  ((>= idx 20))
	(read-char port))
      (let* ((ttisgmtcnt (tzfile:read-long port))
	     (ttisstdcnt (tzfile:read-long port))
	     (leapcnt (tzfile:read-long port))
	     (timecnt (tzfile:read-long port))
	     (typecnt (tzfile:read-long port))
	     (charcnt (tzfile:read-long port))
	     (transition-times (tzfile:read-longs timecnt port))
	     (transition-types
	      (do ((ra (make-vector timecnt 0))
		   (idx 0 (+ 1 idx)))
		  ((>= idx timecnt) ra)
		(vector-set! ra idx (read-byte port))))
	     ;;(printf "  typecnt = %d\n" typecnt)
	     (mode-table (do ((tt (make-vector typecnt #f))
			      (idx 0 (+ 1 idx)))
			     ((>= idx typecnt) tt)
			   (let* ((gmt-offset (tzfile:read-long port))
				  (isdst (tzfile:read-bool port))
				  (abbrev-index (read-byte port)))
			     (vector-set! tt idx
					  (vector abbrev-index gmt-offset
						  isdst #f #f)))))
	     ;;(printf "  %d bytes of abbreviations:\n" charcnt)
	     (abbrevs (do ((ra (make-bytes charcnt 0))
			   (idx 0 (+ 1 idx)))
			  ((>= idx charcnt) ra)
			(string-set! ra idx (read-char port))))
	     (leap-seconds (tzfile:read-longs (* 2 leapcnt) port)))
	(cond ((not (or (eqv? 0 ttisstdcnt) (eqv? typecnt ttisstdcnt)))
	       (slib:warn 'tzfile:read "format error" ttisstdcnt typecnt)))
	(cond ((not (or (eqv? 0 ttisgmtcnt) (eqv? typecnt ttisgmtcnt)))
	       (slib:warn 'tzfile:read "format error" ttisgmtcnt typecnt)))
	;;(printf " reading %d transition attributes\n" ttisstdcnt)
	(do ((idx 0 (+ 1 idx)))
	    ((>= idx ttisstdcnt))
	  (vector-set! (vector-ref mode-table idx) 3 (tzfile:read-bool port)))
	;;(printf " reading %d transition attributes\n" ttisgmtcnt)
	(do ((idx 0 (+ 1 idx)))
	    ((>= idx ttisgmtcnt))
	  (vector-set! (vector-ref mode-table idx) 4 (tzfile:read-bool port)))
	(cond ((not (eof-object? (peek-char port)))
	       (slib:warn 'tzfile:read "bytes left at end")))
	(do ((idx 0 (+ 1 idx)))
	    ((>= idx ttisstdcnt))
	  (let ((rec (vector-ref mode-table idx)))
	    (vector-set!
	     rec 0 (let loop ((pos (vector-ref rec 0)))
		     (cond ((>= pos (string-length abbrevs))
			    (slib:warn 'tzfile:read "format error" abbrevs) #f)
			   ((char=? null (string-ref abbrevs pos))
			    (substring abbrevs (vector-ref rec 0) pos))
			   (else (loop (+ 1 pos))))))))
	(list path mode-table leap-seconds transition-times transition-types)
	))))

(define (tzfile:transition-index time zone)
  (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 (ash (+ 1 ntrns) -1))
			   (jmp (ash (+ 1 ntrns) -2)))
		  (let* ((idx (max 0 (min lidx (+ -1 ntrns))))
			 (idx-time (vector-ref transition-times idx)))
		    (cond ((<= jmp 0)
			   (+ idx (if (>= time idx-time) 0 -1)))
			  ((= time idx-time) idx)
			  ((and (zero? idx) (< time idx-time)) -1)
			  ((and (not (= idx lidx)) (not (< time idx-time))) idx)
			  (else
			   (loop ((if (< time idx-time) - +) idx jmp)
				 (if (= 1 jmp) 0 (ash (+ 1 jmp) -1))))))))))
	(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))))