1 /*
2 FUNCTION
3 <<tzset>>---set timezone characteristics from <[TZ]> environment variable
4
5 INDEX
6 tzset
7
8 SYNOPSIS
9 #include <time.h>
10 void tzset(void);
11
12 DESCRIPTION
13 <<tzset>> examines the <[TZ]> environment variable and sets up the three
14 external variables: <<_timezone>>, <<_daylight>>, and <<tzname>>.
15 The value of <<_timezone>> shall be the offset from the current time
16 to Universal Time.
17 The value of <<_daylight>> shall be 0 if there is no daylight savings
18 time for the current time zone, otherwise it will be non-zero.
19 The <<tzname>> array has two entries: the first is the designation of the
20 standard time period, the second is the designation of the alternate time
21 period.
22
23 The <[TZ]> environment variable is expected to be in the following POSIX
24 format (spaces inserted for clarity):
25
26 <[std]> <[offset1]> [<[dst]> [<[offset2]>] [,<[start]> [/<[time1]>], <[end]> [/<[time2]>]]]
27
28 where:
29
30 <[std]> is the designation for the standard time period (minimum 3,
31 maximum <<TZNAME_MAX>> bytes) in one of two forms:
32
33 *- quoted within angle bracket '<' '>' characters: portable numeric
34 sign or alphanumeric characters in the current locale; the
35 quoting characters are not included in the designation
36
37 *- unquoted: portable alphabetic characters in the current locale
38
39 <[offset1]> is the value to add to local standard time to get Universal Time;
40 it has the format:
41
42 [<[S]>]<[hh]>[:<[mm]>[:<[ss]>]]
43
44 where:
45
46 <[S]> is an optional numeric sign character; if negative '-', the
47 time zone is East of the International Reference
48 Meridian; else it is positive and West, and '+' may be used
49
50 <[hh]> is the required numeric hour between 0 and 24
51
52 <[mm]> is the optional numeric minute between 0 and 59
53
54 <[ss]> is the optional numeric second between 0 and 59
55
56 <[dst]> is the designation of the alternate (daylight saving or
57 summer) time period, with the same limits and forms as
58 the standard time period designation
59
60 <[offset2]> is the value to add to local alternate time to get
61 Universal Time; it has the same format as <[offset1]>
62
63 <[start]> is the date in the year that alternate time starts;
64 the form may be one of:
65 (quotes "'" around characters below are used only to distinguish literals)
66
67 <[n]> zero based Julian day (0-365), counting February 29 Leap days
68
69 'J'<[n]> one based Julian day (1-365), not counting February 29 Leap
70 days; in all years day 59 is February 28 and day 60 is March 1
71
72 'M'<[m]>'.'<[w]>'.'<[d]>
73 month <[m]> (1-12) week <[w]> (1-5) day <[d]> (0-6) where week 1 is
74 the first week in month <[m]> with day <[d]>; week 5 is the last
75 week in the month; day 0 is Sunday
76
77 <[time1]> is the optional local time that alternate time starts, in
78 the same format as <[offset1]> without any sign, and defaults
79 to 02:00:00
80
81 <[end]> is the date in the year that alternate time ends, in the same
82 forms as <[start]>
83
84 <[time2]> is the optional local time that alternate time ends, in
85 the same format as <[offset1]> without any sign, and
86 defaults to 02:00:00
87
88 Note that there is no white-space padding between fields. Also note that
89 if <[TZ]> is null, the default is Universal Time which has no daylight saving
90 time. If <[TZ]> is empty, the default EST5EDT is used.
91
92 RETURNS
93 There is no return value.
94
95 PORTABILITY
96 <<tzset>> is part of the POSIX standard.
97
98 Supporting OS subroutine required: None
99 */
100
101 #define _DEFAULT_SOURCE
102 #include <_ansi.h>
103 #include <stdio.h>
104 #include <stdlib.h>
105 #include <string.h>
106 #include <sys/types.h>
107 #include <time.h>
108 #include "local.h"
109
110 #define TZNAME_MIN 3 /* POSIX min TZ abbr size local def */
111 #define TZNAME_MAX 10 /* POSIX max TZ abbr size local def */
112
113 static char __tzname_std[TZNAME_MAX + 2];
114 static char __tzname_dst[TZNAME_MAX + 2];
115 static char *prev_tzenv = NULL;
116
117 void
_tzset_unlocked(void)118 _tzset_unlocked (void)
119 {
120 char *tzenv;
121 unsigned short hh, mm, ss, m, w, d;
122 int sign, n;
123 int i, ch;
124 long offset0, offset1;
125 __tzinfo_type *tz = __gettzinfo ();
126 static const struct __tzrule_struct default_tzrule = {'J', 0, 0, 0, 0, (time_t)0, 0L };
127
128 if ((tzenv = getenv ("TZ")) == NULL)
129 {
130 _timezone = 0;
131 _daylight = 0;
132 _tzname[0] = "GMT";
133 _tzname[1] = "GMT";
134 tz->__tzrule[0] = default_tzrule;
135 tz->__tzrule[1] = default_tzrule;
136 free(prev_tzenv);
137 prev_tzenv = NULL;
138 return;
139 }
140
141 if (prev_tzenv != NULL && strcmp(tzenv, prev_tzenv) == 0)
142 return;
143
144 free(prev_tzenv);
145 prev_tzenv = malloc (strlen(tzenv) + 1);
146 if (prev_tzenv != NULL)
147 strcpy (prev_tzenv, tzenv);
148
149 /* default to unnamed UTC in case of error */
150 _timezone = 0;
151 _daylight = 0;
152 _tzname[0] = "";
153 _tzname[1] = "";
154 tz->__tzrule[0] = default_tzrule;
155 tz->__tzrule[1] = default_tzrule;
156
157 /* ignore implementation-specific format specifier */
158 if (*tzenv == ':')
159 ++tzenv;
160
161 /* allow POSIX angle bracket < > quoted signed alphanumeric tz abbr e.g. <MESZ+0330> */
162 if (*tzenv == '<')
163 {
164 ++tzenv;
165
166 /* quit if no items, too few or too many chars, or no close quote '>' */
167 if (sscanf (tzenv, "%11[-+0-9A-Za-z]%n", __tzname_std, &n) <= 0
168 || n < TZNAME_MIN || TZNAME_MAX < n || '>' != tzenv[n])
169 return;
170
171 ++tzenv; /* bump for close quote '>' */
172 }
173 else
174 {
175 /* allow POSIX unquoted alphabetic tz abbr e.g. MESZ */
176 if (sscanf (tzenv, "%11[A-Za-z]%n", __tzname_std, &n) <= 0
177 || n < TZNAME_MIN || TZNAME_MAX < n)
178 return;
179 }
180
181 tzenv += n;
182
183 sign = 1;
184 if (*tzenv == '-')
185 {
186 sign = -1;
187 ++tzenv;
188 }
189 else if (*tzenv == '+')
190 ++tzenv;
191
192 mm = 0;
193 ss = 0;
194
195 if (sscanf (tzenv, "%hu%n:%hu%n:%hu%n", &hh, &n, &mm, &n, &ss, &n) < 1)
196 return;
197
198 offset0 = sign * (ss + SECSPERMIN * mm + SECSPERHOUR * hh);
199 tzenv += n;
200
201 /* allow POSIX angle bracket < > quoted signed alphanumeric tz abbr e.g. <MESZ+0330> */
202 if (*tzenv == '<')
203 {
204 ++tzenv;
205
206 /* quit if no items, too few or too many chars, or no close quote '>' */
207 if (sscanf (tzenv, "%11[-+0-9A-Za-z]%n", __tzname_dst, &n) <= 0 && tzenv[0] == '>')
208 { /* No dst */
209 _tzname[0] = __tzname_std;
210 _tzname[1] = _tzname[0];
211 tz->__tzrule[0].offset = offset0;
212 _timezone = offset0;
213 return;
214 }
215 else if (n < TZNAME_MIN || TZNAME_MAX < n || '>' != tzenv[n])
216 { /* error */
217 return;
218 }
219
220 ++tzenv; /* bump for close quote '>' */
221 }
222 else
223 {
224 /* allow POSIX unquoted alphabetic tz abbr e.g. MESZ */
225 if (sscanf (tzenv, "%11[A-Za-z]%n", __tzname_dst, &n) <= 0)
226 { /* No dst */
227 _tzname[0] = __tzname_std;
228 _tzname[1] = _tzname[0];
229 tz->__tzrule[0].offset = offset0;
230 _timezone = offset0;
231 return;
232 }
233 else if (n < TZNAME_MIN || TZNAME_MAX < n)
234 { /* error */
235 return;
236 }
237 }
238
239 tzenv += n;
240
241 /* otherwise we have a dst name, look for the offset */
242 sign = 1;
243 if (*tzenv == '-')
244 {
245 sign = -1;
246 ++tzenv;
247 }
248 else if (*tzenv == '+')
249 ++tzenv;
250
251 hh = 0;
252 mm = 0;
253 ss = 0;
254
255 n = 0;
256 if (sscanf (tzenv, "%hu%n:%hu%n:%hu%n", &hh, &n, &mm, &n, &ss, &n) <= 0)
257 offset1 = offset0 - 3600;
258 else
259 offset1 = sign * (ss + SECSPERMIN * mm + SECSPERHOUR * hh);
260
261 tzenv += n;
262
263 for (i = 0; i < 2; ++i)
264 {
265 if (*tzenv == ',')
266 ++tzenv;
267
268 if (*tzenv == 'M')
269 {
270 if (sscanf (tzenv, "M%hu%n.%hu%n.%hu%n", &m, &n, &w, &n, &d, &n) != 3 ||
271 m < 1 || m > 12 || w < 1 || w > 5 || d > 6)
272 return;
273
274 tz->__tzrule[i].ch = 'M';
275 tz->__tzrule[i].m = m;
276 tz->__tzrule[i].n = w;
277 tz->__tzrule[i].d = d;
278
279 tzenv += n;
280 }
281 else
282 {
283 char *end;
284 if (*tzenv == 'J')
285 {
286 ch = 'J';
287 ++tzenv;
288 }
289 else
290 ch = 'D';
291
292 d = strtoul (tzenv, &end, 10);
293
294 /* if unspecified, default to US settings */
295 /* From 1987-2006, US was M4.1.0,M10.5.0, but starting in 2007 is
296 * M3.2.0,M11.1.0 (2nd Sunday March through 1st Sunday November) */
297 if (end == tzenv)
298 {
299 if (i == 0)
300 {
301 tz->__tzrule[0].ch = 'M';
302 tz->__tzrule[0].m = 3;
303 tz->__tzrule[0].n = 2;
304 tz->__tzrule[0].d = 0;
305 }
306 else
307 {
308 tz->__tzrule[1].ch = 'M';
309 tz->__tzrule[1].m = 11;
310 tz->__tzrule[1].n = 1;
311 tz->__tzrule[1].d = 0;
312 }
313 }
314 else
315 {
316 tz->__tzrule[i].ch = ch;
317 tz->__tzrule[i].d = d;
318 }
319
320 tzenv = end;
321 }
322
323 /* default time is 02:00:00 am */
324 hh = 2;
325 mm = 0;
326 ss = 0;
327 n = 0;
328
329 if (*tzenv == '/')
330 if (sscanf (tzenv, "/%hu%n:%hu%n:%hu%n", &hh, &n, &mm, &n, &ss, &n) <= 0)
331 {
332 /* error in time format, restore tz rules to default and return */
333 tz->__tzrule[0] = default_tzrule;
334 tz->__tzrule[1] = default_tzrule;
335 return;
336 }
337
338 tz->__tzrule[i].s = ss + SECSPERMIN * mm + SECSPERHOUR * hh;
339
340 tzenv += n;
341 }
342
343 tz->__tzrule[0].offset = offset0;
344 tz->__tzrule[1].offset = offset1;
345 _tzname[0] = __tzname_std;
346 _tzname[1] = __tzname_dst;
347 __tzcalc_limits (tz->__tzyear);
348 _timezone = tz->__tzrule[0].offset;
349 _daylight = tz->__tzrule[0].offset != tz->__tzrule[1].offset;
350 }
351
352 void
tzset(void)353 tzset (void)
354 {
355 TZ_LOCK;
356 _tzset_unlocked ();
357 TZ_UNLOCK;
358 }
359
