1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
4 This file is part of systemd.
6 Timezone file reading code from glibc 2.16.
8 Copyright (C) 1991-2012 Free Software Foundation, Inc.
9 Copyright 2012 Kay Sievers
11 systemd is free software; you can redistribute it and/or modify it
12 under the terms of the GNU Lesser General Public License as published by
13 the Free Software Foundation; either version 2.1 of the License, or
14 (at your option) any later version.
16 systemd is distributed in the hope that it will be useful, but
17 WITHOUT ANY WARRANTY; without even the implied warranty of
18 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 Lesser General Public License for more details.
21 You should have received a copy of the GNU Lesser General Public License
22 along with systemd; If not, see <http://www.gnu.org/licenses/>.
44 * If tzh_version is '2' or greater, the above is followed by a second instance
45 * of tzhead and a second instance of the data in which each coded transition
46 * time uses 8 rather than 4 chars, then a POSIX-TZ-environment-variable-style
47 * string for use in handling instants after the last transition time stored in
48 * the file * (with nothing between the newlines if there is no POSIX
49 * representation for such instants).
51 #define TZ_MAGIC "TZif"
53 char tzh_magic[4]; /* TZ_MAGIC */
54 char tzh_version[1]; /* '\0' or '2' as of 2005 */
55 char tzh_reserved[15]; /* reserved--must be zero */
56 char tzh_ttisgmtcnt[4]; /* coded number of trans. time flags */
57 char tzh_ttisstdcnt[4]; /* coded number of trans. time flags */
58 char tzh_leapcnt[4]; /* coded number of leap seconds */
59 char tzh_timecnt[4]; /* coded number of transition times */
60 char tzh_typecnt[4]; /* coded number of local time types */
61 char tzh_charcnt[4]; /* coded number of abbr. chars */
65 long int offset; /* Seconds east of GMT. */
66 unsigned char isdst; /* Used to set tm_isdst. */
67 unsigned char idx; /* Index into `zone_names'. */
68 unsigned char isstd; /* Transition times are in standard time. */
69 unsigned char isgmt; /* Transition times are in GMT. */
73 time_t transition; /* Time the transition takes effect. */
74 long int change; /* Seconds of correction to apply. */
77 static inline int decode(const void *ptr) {
78 return be32toh(*(int *)ptr);
81 static inline int64_t decode64(const void *ptr) {
82 return be64toh(*(int64_t *)ptr);
85 int time_get_dst(time_t date, const char *tzfile,
86 time_t *switch_cur, char **zone_cur, bool *dst_cur,
87 time_t *switch_next, int *delta_next, char **zone_next, bool *dst_next) {
88 unsigned char *type_idxs = 0;
90 struct ttinfo *types = NULL;
91 char *zone_names = NULL;
93 size_t num_isstd, num_isgmt;
103 size_t num_transitions = 0;
104 _cleanup_free_ time_t *transitions = NULL;
105 _cleanup_fclose_ FILE *f;
107 f = fopen(tzfile, "re");
111 if (fstat(fileno(f), &st) < 0)
115 if (fread((void *)&tzhead, sizeof(tzhead), 1, f) != 1 ||
116 memcmp(tzhead.tzh_magic, TZ_MAGIC, sizeof(tzhead.tzh_magic)) != 0)
119 num_transitions = (size_t)decode(tzhead.tzh_timecnt);
120 num_types = (size_t)decode(tzhead.tzh_typecnt);
121 chars = (size_t)decode(tzhead.tzh_charcnt);
122 num_leaps = (size_t)decode(tzhead.tzh_leapcnt);
123 num_isstd = (size_t)decode(tzhead.tzh_ttisstdcnt);
124 num_isgmt = (size_t)decode(tzhead.tzh_ttisgmtcnt);
126 /* For platforms with 64-bit time_t we use the new format if available. */
127 if (sizeof(time_t) == 8 && trans_width == 4 && tzhead.tzh_version[0] != '\0') {
130 /* We use the 8-byte format. */
133 /* Position the stream before the second header. */
134 to_skip = (num_transitions * (4 + 1)
137 + num_leaps * 8 + num_isstd + num_isgmt);
138 if (fseek(f, to_skip, SEEK_CUR) != 0)
144 if (num_transitions > ((SIZE_MAX - (__alignof__(struct ttinfo) - 1)) / (sizeof(time_t) + 1)))
147 total_size = num_transitions * (sizeof(time_t) + 1);
148 total_size = ((total_size + __alignof__(struct ttinfo) - 1) & ~(__alignof__(struct ttinfo) - 1));
149 types_idx = total_size;
150 if (num_leaps > (SIZE_MAX - total_size) / sizeof(struct ttinfo))
153 total_size += num_types * sizeof(struct ttinfo);
154 if (chars > SIZE_MAX - total_size)
158 if (__alignof__(struct leap) - 1 > SIZE_MAX - total_size)
161 total_size = ((total_size + __alignof__(struct leap) - 1) & ~(__alignof__(struct leap) - 1));
162 if (num_leaps > (SIZE_MAX - total_size) / sizeof(struct leap))
165 total_size += num_leaps * sizeof(struct leap);
167 if (sizeof(time_t) == 8 && trans_width == 8) {
168 off_t rem = st.st_size - ftello(f);
170 if (rem < 0 || (size_t) rem < (num_transitions * (8 + 1) + num_types * 6 + chars))
172 tzspec_len = (size_t) rem - (num_transitions * (8 + 1) + num_types * 6 + chars);
173 if (num_leaps > SIZE_MAX / 12 || tzspec_len < num_leaps * 12)
175 tzspec_len -= num_leaps * 12;
176 if (tzspec_len < num_isstd)
178 tzspec_len -= num_isstd;
179 if (tzspec_len == 0 || tzspec_len - 1 < num_isgmt)
181 tzspec_len -= num_isgmt + 1;
182 if (SIZE_MAX - total_size < tzspec_len)
186 /* leave space for additional zone_names zero terminator */
187 transitions = malloc0(total_size + tzspec_len + 1);
188 if (transitions == NULL)
191 type_idxs = (unsigned char *)transitions + (num_transitions
193 types = (struct ttinfo *)((char *)transitions + types_idx);
194 zone_names = (char *)types + num_types * sizeof(struct ttinfo);
196 if (sizeof(time_t) == 4 || trans_width == 8) {
197 if (fread(transitions, trans_width + 1, num_transitions, f) != num_transitions)
200 if (fread(transitions, 4, num_transitions, f) != num_transitions ||
201 fread(type_idxs, 1, num_transitions, f) != num_transitions)
205 /* Check for bogus indices in the data file, so we can hereafter
206 safely use type_idxs[T] as indices into `types' and never crash. */
207 for (i = 0; i < num_transitions; ++i)
208 if (type_idxs[i] >= num_types)
211 if (__BYTE_ORDER == __BIG_ENDIAN ? sizeof(time_t) == 8 && trans_width == 4
212 : sizeof(time_t) == 4 || trans_width == 4) {
213 /* Decode the transition times, stored as 4-byte integers in
214 network (big-endian) byte order. We work from the end of
215 the array so as not to clobber the next element to be
216 processed when sizeof (time_t) > 4. */
219 transitions[i] = decode((char *)transitions + i * 4);
220 } else if (__BYTE_ORDER != __BIG_ENDIAN && sizeof(time_t) == 8) {
221 /* Decode the transition times, stored as 8-byte integers in
222 network (big-endian) byte order. */
223 for (i = 0; i < num_transitions; ++i)
224 transitions[i] = decode64((char *)transitions + i * 8);
227 for (i = 0; i < num_types; ++i) {
231 if (fread(x, 1, sizeof(x), f) != sizeof(x))
234 if ((unsigned int)c > 1u)
238 if ((size_t) c > chars)
239 /* Bogus index in data file. */
242 types[i].offset = (long int)decode(x);
245 if (fread(zone_names, 1, chars, f) != chars)
248 zone_names[chars] = '\0';
250 for (i = 0; i < num_isstd; ++i) {
254 types[i].isstd = c != 0;
257 while (i < num_types)
258 types[i++].isstd = 0;
260 for (i = 0; i < num_isgmt; ++i) {
264 types[i].isgmt = c != 0;
267 while (i < num_types)
268 types[i++].isgmt = 0;
270 if (num_transitions == 0)
273 if (date < transitions[0] || date >= transitions[num_transitions - 1])
276 /* Find the first transition after TIMER, and
277 then pick the type of the transition before it. */
279 hi = num_transitions - 1;
281 /* Assume that DST is changing twice a year and guess initial
283 Half of a gregorian year has on average 365.2425 * 86400 / 2
284 = 15778476 seconds. */
285 i = (transitions[num_transitions - 1] - date) / 15778476;
286 if (i < num_transitions) {
287 i = num_transitions - 1 - i;
288 if (date < transitions[i]) {
289 if (i < 10 || date >= transitions[i - 10]) {
291 while (date < transitions[i - 1])
297 if (i + 10 >= num_transitions || date < transitions[i + 10]) {
299 while (date >= transitions[i])
308 while (lo + 1 < hi) {
310 if (date < transitions[i])
319 *switch_cur = transitions[i-1];
321 *zone_cur = strdup(&zone_names[types[type_idxs[i - 1]].idx]);
323 *dst_cur = types[type_idxs[i-1]].isdst;
326 *switch_next = transitions[i];
328 *delta_next = (types[type_idxs[i]].offset - types[type_idxs[i-1]].offset) / 60;
330 *zone_next = strdup(&zone_names[types[type_idxs[i]].idx]);
332 *dst_next = types[type_idxs[i]].isdst;