2 * Copyright © 2010 Codethink Limited
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the licence, or (at your option) any later version.
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this library; if not, write to the
16 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 * Boston, MA 02111-1307, USA.
19 * Author: Ryan Lortie <desrt@desrt.ca>
24 #include "gtimezone.h"
30 #include "gmappedfile.h"
31 #include "gtestutils.h"
32 #include "gfileutils.h"
33 #include "gstrfuncs.h"
41 * @short_description: A structure representing a time zone
42 * @see_also: #GDateTime
44 * #GTimeZone is a structure that represents a time zone, at no
45 * particular point in time. It is refcounted and immutable.
47 * A time zone contains a number of intervals. Each interval has
48 * an abbreviation to describe it, an offet to UTC and a flag indicating
49 * if the daylight savings time is in effect during that interval. A
50 * time zone always has at least one interval -- interval 0.
52 * Every UTC time is contained within exactly one interval, but a given
53 * local time may be contained within zero, one or two intervals (due to
54 * incontinuities associated with daylight savings time).
56 * An interval may refer to a specific period of time (eg: the duration
57 * of daylight savings time during 2010) or it may refer to many periods
58 * of time that share the same properties (eg: all periods of daylight
59 * savings time). It is also possible (usually for political reasons)
60 * that some properties (like the abbreviation) change between intervals
61 * without other properties changing.
63 * #GTimeZone is available since GLib 2.26.
69 * #GDateTime is an opaque structure whose members cannot be accessed
75 /* zoneinfo file format {{{1 */
78 typedef struct { gchar bytes[8]; } gint64_be;
79 typedef struct { gchar bytes[4]; } gint32_be;
80 typedef struct { gchar bytes[4]; } guint32_be;
82 static inline gint64 gint64_from_be (const gint64_be be) {
83 gint64 tmp; memcpy (&tmp, &be, sizeof tmp); return GINT64_FROM_BE (tmp);
86 static inline gint32 gint32_from_be (const gint32_be be) {
87 gint32 tmp; memcpy (&tmp, &be, sizeof tmp); return GINT32_FROM_BE (tmp);
90 static inline guint32 guint32_from_be (const guint32_be be) {
91 guint32 tmp; memcpy (&tmp, &be, sizeof tmp); return GUINT32_FROM_BE (tmp);
98 guchar tzh_reserved[15];
100 guint32_be tzh_ttisgmtcnt;
101 guint32_be tzh_ttisstdcnt;
102 guint32_be tzh_leapcnt;
103 guint32_be tzh_timecnt;
104 guint32_be tzh_typecnt;
105 guint32_be tzh_charcnt;
115 /* GTimeZone structure and lifecycle {{{1 */
122 const struct tzhead *header;
123 const struct ttinfo *infos;
124 const gint64_be *trans;
125 const guint8 *indices;
132 G_LOCK_DEFINE_STATIC (time_zones);
133 static GHashTable/*<string?, GTimeZone>*/ *time_zones;
136 g_str_hash0 (gconstpointer data)
138 return data ? g_str_hash (data) : 0;
142 g_str_equal0 (gconstpointer a,
151 return g_str_equal (a, b);
158 * Decreases the reference count on @tz.
163 g_time_zone_unref (GTimeZone *tz)
165 g_assert (tz->ref_count > 0);
167 if (g_atomic_int_dec_and_test (&tz->ref_count))
170 g_hash_table_remove (time_zones, tz->name);
171 G_UNLOCK(time_zones);
174 g_buffer_unref (tz->zoneinfo);
178 g_slice_free (GTimeZone, tz);
186 * Increases the reference count on @tz.
188 * Returns: a new reference to @tz.
193 g_time_zone_ref (GTimeZone *tz)
195 g_assert (tz->ref_count > 0);
197 g_atomic_int_inc (&tz->ref_count);
202 /* fake zoneinfo creation (for RFC3339/ISO 8601 timezones) {{{1 */
204 * parses strings of the form 'hh' 'hhmm' or 'hh:mm' where:
209 parse_time (const gchar *time,
212 if (*time < '0' || '2' < *time)
215 *offset = 10 * 60 * 60 * (*time++ - '0');
217 if (*time < '0' || '9' < *time)
220 *offset += 60 * 60 * (*time++ - '0');
222 if (*offset > 23 * 60 * 60)
231 if (*time < '0' || '5' < *time)
234 *offset += 10 * 60 * (*time++ - '0');
236 if (*time < '0' || '9' < *time)
239 *offset += 60 * (*time++ - '0');
241 return *time == '\0';
245 parse_constant_offset (const gchar *name,
255 return parse_time (name, offset);
258 if (parse_time (name, offset))
270 zone_for_constant_offset (const gchar *name)
272 const gchar fake_zoneinfo_headers[] =
273 "TZif" "2..." "...." "...." "...."
274 "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0"
275 "TZif" "2..." "...." "...." "...."
276 "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\1" "\0\0\0\7";
278 struct tzhead headers[2];
284 if (name == NULL || !parse_constant_offset (name, &offset))
287 offset = GINT32_TO_BE (offset);
289 fake = g_malloc (sizeof *fake);
290 memcpy (fake, fake_zoneinfo_headers, sizeof fake_zoneinfo_headers);
291 memcpy (&fake->info.tt_gmtoff, &offset, sizeof offset);
292 fake->info.tt_isdst = FALSE;
293 fake->info.tt_abbrind = 0;
294 strcpy (fake->abbr, name);
296 return g_buffer_new_take_data (fake, sizeof *fake);
299 /* Construction {{{1 */
302 * @identifier: (allow-none): a timezone identifier
304 * Creates a #GTimeZone corresponding to @identifier.
306 * @identifier can either be an RFC3339/ISO 8601 time offset or
307 * something that would pass as a valid value for the
308 * <varname>TZ</varname> environment variable (including %NULL).
310 * Valid RFC3339 time offsets are <literal>"Z"</literal> (for UTC) or
311 * <literal>"±hh:mm"</literal>. ISO 8601 additionally specifies
312 * <literal>"±hhmm"</literal> and <literal>"±hh"</literal>.
314 * The <varname>TZ</varname> environment variable typically corresponds
315 * to the name of a file in the zoneinfo database, but there are many
316 * other possibilities. Note that those other possibilities are not
317 * currently implemented, but are planned.
319 * g_time_zone_new_local() calls this function with the value of the
320 * <varname>TZ</varname> environment variable. This function itself is
321 * independent of the value of <varname>TZ</varname>, but if @identifier
322 * is %NULL then <filename>/etc/localtime</filename> will be consulted
323 * to discover the correct timezone.
326 * url='http://tools.ietf.org/html/rfc3339#section-5.6'>RFC3339
327 * §5.6</ulink> for a precise definition of valid RFC3339 time offsets
328 * (the <varname>time-offset</varname> expansion) and ISO 8601 for the
329 * full list of valid time offsets. See <ulink
330 * url='http://www.gnu.org/s/libc/manual/html_node/TZ-Variable.html'>The
331 * GNU C Library manual</ulink> for an explanation of the possible
332 * values of the <varname>TZ</varname> environment variable.
334 * You should release the return value by calling g_time_zone_unref()
335 * when you are done with it.
337 * Returns: the requested timezone
342 g_time_zone_new (const gchar *identifier)
347 if (time_zones == NULL)
348 time_zones = g_hash_table_new (g_str_hash0,
351 tz = g_hash_table_lookup (time_zones, identifier);
354 tz = g_slice_new0 (GTimeZone);
355 tz->name = g_strdup (identifier);
358 tz->zoneinfo = zone_for_constant_offset (identifier);
360 if (tz->zoneinfo == NULL)
364 if (identifier != NULL)
368 tzdir = getenv ("TZDIR");
370 tzdir = "/usr/share/zoneinfo";
372 filename = g_build_filename (tzdir, identifier, NULL);
375 filename = g_strdup ("/etc/localtime");
377 tz->zoneinfo = (GBuffer *) g_mapped_file_new (filename, FALSE, NULL);
381 if (tz->zoneinfo != NULL)
383 const struct tzhead *header = tz->zoneinfo->data;
384 gsize size = tz->zoneinfo->size;
386 /* we only bother to support version 2 */
387 if (size < sizeof (struct tzhead) || memcmp (header, "TZif2", 5))
389 g_buffer_unref (tz->zoneinfo);
396 /* we trust the file completely. */
397 tz->header = (const struct tzhead *)
398 (((const gchar *) (header + 1)) +
399 guint32_from_be(header->tzh_ttisgmtcnt) +
400 guint32_from_be(header->tzh_ttisstdcnt) +
401 8 * guint32_from_be(header->tzh_leapcnt) +
402 5 * guint32_from_be(header->tzh_timecnt) +
403 6 * guint32_from_be(header->tzh_typecnt) +
404 guint32_from_be(header->tzh_charcnt));
406 typecnt = guint32_from_be (tz->header->tzh_typecnt);
407 tz->timecnt = guint32_from_be (tz->header->tzh_timecnt);
408 tz->trans = (gconstpointer) (tz->header + 1);
409 tz->indices = (gconstpointer) (tz->trans + tz->timecnt);
410 tz->infos = (gconstpointer) (tz->indices + tz->timecnt);
411 tz->abbrs = (gconstpointer) (tz->infos + typecnt);
415 g_hash_table_insert (time_zones, tz->name, tz);
417 g_atomic_int_inc (&tz->ref_count);
418 G_UNLOCK (time_zones);
424 * g_time_zone_new_utc:
426 * Creates a #GTimeZone corresponding to UTC.
428 * This is equivalent to calling g_time_zone_new() with a value like
429 * "Z", "UTC", "+00", etc.
431 * You should release the return value by calling g_time_zone_unref()
432 * when you are done with it.
434 * Returns: the universal timezone
439 g_time_zone_new_utc (void)
441 return g_time_zone_new ("UTC");
445 * g_time_zone_new_local:
447 * Creates a #GTimeZone corresponding to local time.
449 * This is equivalent to calling g_time_zone_new() with the value of the
450 * <varname>TZ</varname> environment variable (including the possibility
451 * of %NULL). Changes made to <varname>TZ</varname> after the first
452 * call to this function may or may not be noticed by future calls.
454 * You should release the return value by calling g_time_zone_unref()
455 * when you are done with it.
457 * Returns: the local timezone
462 g_time_zone_new_local (void)
464 return g_time_zone_new (getenv ("TZ"));
467 /* Internal helpers {{{1 */
468 inline static const struct ttinfo *
469 interval_info (GTimeZone *tz,
473 return tz->infos + tz->indices[interval - 1];
479 interval_start (GTimeZone *tz,
483 return gint64_from_be (tz->trans[interval - 1]);
489 interval_end (GTimeZone *tz,
492 if (interval < tz->timecnt)
493 return gint64_from_be (tz->trans[interval]) - 1;
499 interval_offset (GTimeZone *tz,
502 return gint32_from_be (interval_info (tz, interval)->tt_gmtoff);
505 inline static gboolean
506 interval_isdst (GTimeZone *tz,
509 return interval_info (tz, interval)->tt_isdst;
513 interval_abbrind (GTimeZone *tz,
516 return interval_info (tz, interval)->tt_abbrind;
520 interval_local_start (GTimeZone *tz,
524 return interval_start (tz, interval) + interval_offset (tz, interval);
530 interval_local_end (GTimeZone *tz,
533 if (interval < tz->timecnt)
534 return interval_end (tz, interval) + interval_offset (tz, interval);
540 interval_valid (GTimeZone *tz,
543 return interval <= tz->timecnt;
546 /* g_time_zone_find_interval() {{{1 */
549 * g_time_zone_adjust_time:
551 * @type: the #GTimeType of @time
552 * @time: a pointer to a number of seconds since January 1, 1970
554 * Finds an interval within @tz that corresponds to the given @time,
555 * possibly adjusting @time if required to fit into an interval.
556 * The meaning of @time depends on @type.
558 * This function is similar to g_time_zone_find_interval(), with the
559 * difference that it always succeeds (by making the adjustments
562 * In any of the cases where g_time_zone_find_interval() succeeds then
563 * this function returns the same value, without modifying @time.
565 * This function may, however, modify @time in order to deal with
566 * non-existent times. If the non-existent local @time of 02:30 were
567 * requested on March 13th 2010 in Toronto then this function would
568 * adjust @time to be 03:00 and return the interval containing the
571 * Returns: the interval containing @time, never -1
576 g_time_zone_adjust_time (GTimeZone *tz,
582 if (tz->zoneinfo == NULL)
585 /* find the interval containing *time UTC
586 * TODO: this could be binary searched (or better) */
587 for (i = 0; i < tz->timecnt; i++)
588 if (*time <= interval_end (tz, i))
591 g_assert (interval_start (tz, i) <= *time && *time <= interval_end (tz, i));
593 if (type != G_TIME_TYPE_UNIVERSAL)
595 if (*time < interval_local_start (tz, i))
596 /* if time came before the start of this interval... */
600 /* if it's not in the previous interval... */
601 if (*time > interval_local_end (tz, i))
603 /* it doesn't exist. fast-forward it. */
605 *time = interval_local_start (tz, i);
609 else if (*time > interval_local_end (tz, i))
610 /* if time came after the end of this interval... */
614 /* if it's not in the next interval... */
615 if (*time < interval_local_start (tz, i))
616 /* it doesn't exist. fast-forward it. */
617 *time = interval_local_start (tz, i);
620 else if (interval_isdst (tz, i) != type)
621 /* it's in this interval, but dst flag doesn't match.
622 * check neighbours for a better fit. */
624 if (i && *time <= interval_local_end (tz, i - 1))
627 else if (i < tz->timecnt &&
628 *time >= interval_local_start (tz, i + 1))
637 * g_time_zone_find_interval:
639 * @type: the #GTimeType of @time
640 * @time: a number of seconds since January 1, 1970
642 * Finds an the interval within @tz that corresponds to the given @time.
643 * The meaning of @time depends on @type.
645 * If @type is %G_TIME_TYPE_UNIVERSAL then this function will always
646 * succeed (since universal time is monotonic and continuous).
648 * Otherwise @time is treated is local time. The distinction between
649 * %G_TIME_TYPE_STANDARD and %G_TIME_TYPE_DAYLIGHT is ignored except in
650 * the case that the given @time is ambiguous. In Toronto, for example,
651 * 01:30 on November 7th 2010 occured twice (once inside of daylight
652 * savings time and the next, an hour later, outside of daylight savings
653 * time). In this case, the different value of @type would result in a
654 * different interval being returned.
656 * It is still possible for this function to fail. In Toronto, for
657 * example, 02:00 on March 14th 2010 does not exist (due to the leap
658 * forward to begin daylight savings time). -1 is returned in that
661 * Returns: the interval containing @time, or -1 in case of failure
666 g_time_zone_find_interval (GTimeZone *tz,
672 if (tz->zoneinfo == NULL)
675 for (i = 0; i < tz->timecnt; i++)
676 if (time <= interval_end (tz, i))
679 if (type == G_TIME_TYPE_UNIVERSAL)
682 if (time < interval_local_start (tz, i))
684 if (time > interval_local_end (tz, --i))
688 else if (time > interval_local_end (tz, i))
690 if (time < interval_local_start (tz, ++i))
694 else if (interval_isdst (tz, i) != type)
696 if (i && time <= interval_local_end (tz, i - 1))
699 else if (i < tz->timecnt && time >= interval_local_start (tz, i + 1))
706 /* Public API accessors {{{1 */
709 * g_time_zone_get_abbreviation:
711 * @interval: an interval within the timezone
713 * Determines the time zone abbreviation to be used during a particular
714 * @interval of time in the time zone @tz.
716 * For example, in Toronto this is currently "EST" during the winter
717 * months and "EDT" during the summer months when daylight savings time
720 * Returns: the time zone abbreviation, which belongs to @tz
725 g_time_zone_get_abbreviation (GTimeZone *tz,
728 g_return_val_if_fail (interval_valid (tz, interval), NULL);
730 if (tz->header == NULL)
733 return tz->abbrs + interval_abbrind (tz, interval);
737 * g_time_zone_get_offset:
739 * @interval: an interval within the timezone
741 * Determines the offset to UTC in effect during a particular @interval
742 * of time in the time zone @tz.
744 * The offset is the number of seconds that you add to UTC time to
745 * arrive at local time for @tz (ie: negative numbers for time zones
746 * west of GMT, positive numbers for east).
748 * Returns: the number of seconds that should be added to UTC to get the
754 g_time_zone_get_offset (GTimeZone *tz,
757 g_return_val_if_fail (interval_valid (tz, interval), 0);
759 if (tz->header == NULL)
762 return interval_offset (tz, interval);
766 * g_time_zone_is_dst:
768 * @interval: an interval within the timezone
770 * Determines if daylight savings time is in effect during a particular
771 * @interval of time in the time zone @tz.
773 * Returns: %TRUE if daylight savings time is in effect
778 g_time_zone_is_dst (GTimeZone *tz,
781 g_return_val_if_fail (interval_valid (tz, interval), FALSE);
783 if (tz->header == NULL)
786 return interval_isdst (tz, interval);
790 /* vim:set foldmethod=marker: */