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 (local_timezone);
133 static GTimeZone *local_timezone;
135 G_LOCK_DEFINE_STATIC (time_zones);
136 static GHashTable/*<string?, GTimeZone>*/ *time_zones;
142 * Decreases the reference count on @tz.
147 g_time_zone_unref (GTimeZone *tz)
149 g_assert (tz->ref_count > 0);
151 if (g_atomic_int_dec_and_test (&tz->ref_count))
153 if G_UNLIKELY (tz == local_timezone)
155 g_critical ("The last reference on the local timezone was just "
156 "dropped, but GTimeZone itself still owns one. This "
157 "means that g_time_zone_unref() was called too many "
158 "times. Restoring the refcount to 1.");
160 /* We don't want to just inc this back again since if there
161 * are refcounting bugs in the code then maybe we are already
162 * at -1 and inc will just take us back to 0. Set to 1 to be
169 if (tz->name != NULL)
172 g_hash_table_remove (time_zones, tz->name);
173 G_UNLOCK(time_zones);
177 g_buffer_unref (tz->zoneinfo);
181 g_slice_free (GTimeZone, tz);
189 * Increases the reference count on @tz.
191 * Returns: a new reference to @tz.
196 g_time_zone_ref (GTimeZone *tz)
198 g_assert (tz->ref_count > 0);
200 g_atomic_int_inc (&tz->ref_count);
205 /* fake zoneinfo creation (for RFC3339/ISO 8601 timezones) {{{1 */
207 * parses strings of the form 'hh' 'hhmm' or 'hh:mm' where:
212 parse_time (const gchar *time_,
215 if (*time_ < '0' || '2' < *time_)
218 *offset = 10 * 60 * 60 * (*time_++ - '0');
220 if (*time_ < '0' || '9' < *time_)
223 *offset += 60 * 60 * (*time_++ - '0');
225 if (*offset > 23 * 60 * 60)
234 if (*time_ < '0' || '5' < *time_)
237 *offset += 10 * 60 * (*time_++ - '0');
239 if (*time_ < '0' || '9' < *time_)
242 *offset += 60 * (*time_++ - '0');
244 return *time_ == '\0';
248 parse_constant_offset (const gchar *name,
258 return parse_time (name, offset);
261 if (parse_time (name, offset))
273 zone_for_constant_offset (const gchar *name)
275 const gchar fake_zoneinfo_headers[] =
276 "TZif" "2..." "...." "...." "...."
277 "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0"
278 "TZif" "2..." "...." "...." "...."
279 "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\1" "\0\0\0\7";
281 struct tzhead headers[2];
287 if (name == NULL || !parse_constant_offset (name, &offset))
290 offset = GINT32_TO_BE (offset);
292 fake = g_malloc (sizeof *fake);
293 memcpy (fake, fake_zoneinfo_headers, sizeof fake_zoneinfo_headers);
294 memcpy (&fake->info.tt_gmtoff, &offset, sizeof offset);
295 fake->info.tt_isdst = FALSE;
296 fake->info.tt_abbrind = 0;
297 strcpy (fake->abbr, name);
299 return g_buffer_new_take_data (fake, sizeof *fake);
302 /* Construction {{{1 */
305 * @identifier: (allow-none): a timezone identifier
307 * Creates a #GTimeZone corresponding to @identifier.
309 * @identifier can either be an RFC3339/ISO 8601 time offset or
310 * something that would pass as a valid value for the
311 * <varname>TZ</varname> environment variable (including %NULL).
313 * Valid RFC3339 time offsets are <literal>"Z"</literal> (for UTC) or
314 * <literal>"±hh:mm"</literal>. ISO 8601 additionally specifies
315 * <literal>"±hhmm"</literal> and <literal>"±hh"</literal>.
317 * The <varname>TZ</varname> environment variable typically corresponds
318 * to the name of a file in the zoneinfo database, but there are many
319 * other possibilities. Note that those other possibilities are not
320 * currently implemented, but are planned.
322 * g_time_zone_new_local() calls this function with the value of the
323 * <varname>TZ</varname> environment variable. This function itself is
324 * independent of the value of <varname>TZ</varname>, but if @identifier
325 * is %NULL then <filename>/etc/localtime</filename> will be consulted
326 * to discover the correct timezone.
329 * url='http://tools.ietf.org/html/rfc3339#section-5.6'>RFC3339
330 * §5.6</ulink> for a precise definition of valid RFC3339 time offsets
331 * (the <varname>time-offset</varname> expansion) and ISO 8601 for the
332 * full list of valid time offsets. See <ulink
333 * url='http://www.gnu.org/s/libc/manual/html_node/TZ-Variable.html'>The
334 * GNU C Library manual</ulink> for an explanation of the possible
335 * values of the <varname>TZ</varname> environment variable.
337 * You should release the return value by calling g_time_zone_unref()
338 * when you are done with it.
340 * Returns: the requested timezone
345 g_time_zone_new (const gchar *identifier)
350 if (time_zones == NULL)
351 time_zones = g_hash_table_new (g_str_hash, g_str_equal);
354 tz = g_hash_table_lookup (time_zones, identifier);
360 tz = g_slice_new0 (GTimeZone);
361 tz->name = g_strdup (identifier);
364 tz->zoneinfo = zone_for_constant_offset (identifier);
366 if (tz->zoneinfo == NULL)
370 if (identifier != NULL)
374 tzdir = getenv ("TZDIR");
376 tzdir = "/usr/share/zoneinfo";
378 filename = g_build_filename (tzdir, identifier, NULL);
381 filename = g_strdup ("/etc/localtime");
383 tz->zoneinfo = (GBuffer *) g_mapped_file_new (filename, FALSE, NULL);
387 if (tz->zoneinfo != NULL)
389 const struct tzhead *header = tz->zoneinfo->data;
390 gsize size = tz->zoneinfo->size;
392 /* we only bother to support version 2 */
393 if (size < sizeof (struct tzhead) || memcmp (header, "TZif2", 5))
395 g_buffer_unref (tz->zoneinfo);
402 /* we trust the file completely. */
403 tz->header = (const struct tzhead *)
404 (((const gchar *) (header + 1)) +
405 guint32_from_be(header->tzh_ttisgmtcnt) +
406 guint32_from_be(header->tzh_ttisstdcnt) +
407 8 * guint32_from_be(header->tzh_leapcnt) +
408 5 * guint32_from_be(header->tzh_timecnt) +
409 6 * guint32_from_be(header->tzh_typecnt) +
410 guint32_from_be(header->tzh_charcnt));
412 typecnt = guint32_from_be (tz->header->tzh_typecnt);
413 tz->timecnt = guint32_from_be (tz->header->tzh_timecnt);
414 tz->trans = (gconstpointer) (tz->header + 1);
415 tz->indices = (gconstpointer) (tz->trans + tz->timecnt);
416 tz->infos = (gconstpointer) (tz->indices + tz->timecnt);
417 tz->abbrs = (gconstpointer) (tz->infos + typecnt);
422 g_hash_table_insert (time_zones, tz->name, tz);
424 g_atomic_int_inc (&tz->ref_count);
425 G_UNLOCK (time_zones);
431 * g_time_zone_new_utc:
433 * Creates a #GTimeZone corresponding to UTC.
435 * This is equivalent to calling g_time_zone_new() with a value like
436 * "Z", "UTC", "+00", etc.
438 * You should release the return value by calling g_time_zone_unref()
439 * when you are done with it.
441 * Returns: the universal timezone
446 g_time_zone_new_utc (void)
448 return g_time_zone_new ("UTC");
452 * g_time_zone_new_local:
454 * Creates a #GTimeZone corresponding to local time.
456 * This is equivalent to calling g_time_zone_new() with the value of the
457 * <varname>TZ</varname> environment variable (including the possibility
458 * of %NULL). Changes made to <varname>TZ</varname> after the first
459 * call to this function may or may not be noticed by future calls.
461 * You should release the return value by calling g_time_zone_unref()
462 * when you are done with it.
464 * Returns: the local timezone
469 g_time_zone_new_local (void)
473 G_LOCK (local_timezone);
474 if (local_timezone == NULL)
475 local_timezone = g_time_zone_new (getenv ("TZ"));
477 result = g_time_zone_ref (local_timezone);
478 G_UNLOCK (local_timezone);
484 * g_time_zone_refresh_local:
486 * Notifies #GTimeZone that the local timezone may have changed.
488 * In response, #GTimeZone will drop its cache of the local time zone.
489 * No existing #GTimeZone will be modified and no #GDateTime will change
490 * its timezone but future calls to g_time_zone_new_local() will start
491 * returning the new timezone.
493 * #GTimeZone does no monitoring of the local timezone on its own, which
494 * is why you have to call this function to notify it of the change.
496 * If you use #GTimeZoneMonitor to watch for changes then this function
497 * will automatically be called for you.
500 g_time_zone_refresh_local (void)
502 GTimeZone *drop_this_ref = NULL;
504 G_LOCK (local_timezone);
505 drop_this_ref = local_timezone;
506 local_timezone = NULL;
507 G_UNLOCK (local_timezone);
510 g_time_zone_unref (drop_this_ref);
513 /* Internal helpers {{{1 */
514 inline static const struct ttinfo *
515 interval_info (GTimeZone *tz,
519 return tz->infos + tz->indices[interval - 1];
525 interval_start (GTimeZone *tz,
529 return gint64_from_be (tz->trans[interval - 1]);
535 interval_end (GTimeZone *tz,
538 if (interval < tz->timecnt)
539 return gint64_from_be (tz->trans[interval]) - 1;
545 interval_offset (GTimeZone *tz,
548 return gint32_from_be (interval_info (tz, interval)->tt_gmtoff);
551 inline static gboolean
552 interval_isdst (GTimeZone *tz,
555 return interval_info (tz, interval)->tt_isdst;
559 interval_abbrind (GTimeZone *tz,
562 return interval_info (tz, interval)->tt_abbrind;
566 interval_local_start (GTimeZone *tz,
570 return interval_start (tz, interval) + interval_offset (tz, interval);
576 interval_local_end (GTimeZone *tz,
579 if (interval < tz->timecnt)
580 return interval_end (tz, interval) + interval_offset (tz, interval);
586 interval_valid (GTimeZone *tz,
589 return interval <= tz->timecnt;
592 /* g_time_zone_find_interval() {{{1 */
595 * g_time_zone_adjust_time:
597 * @type: the #GTimeType of @time
598 * @time: a pointer to a number of seconds since January 1, 1970
600 * Finds an interval within @tz that corresponds to the given @time,
601 * possibly adjusting @time if required to fit into an interval.
602 * The meaning of @time depends on @type.
604 * This function is similar to g_time_zone_find_interval(), with the
605 * difference that it always succeeds (by making the adjustments
608 * In any of the cases where g_time_zone_find_interval() succeeds then
609 * this function returns the same value, without modifying @time.
611 * This function may, however, modify @time in order to deal with
612 * non-existent times. If the non-existent local @time of 02:30 were
613 * requested on March 13th 2010 in Toronto then this function would
614 * adjust @time to be 03:00 and return the interval containing the
617 * Returns: the interval containing @time, never -1
622 g_time_zone_adjust_time (GTimeZone *tz,
628 if (tz->zoneinfo == NULL)
631 /* find the interval containing *time UTC
632 * TODO: this could be binary searched (or better) */
633 for (i = 0; i < tz->timecnt; i++)
634 if (*time_ <= interval_end (tz, i))
637 g_assert (interval_start (tz, i) <= *time_ && *time_ <= interval_end (tz, i));
639 if (type != G_TIME_TYPE_UNIVERSAL)
641 if (*time_ < interval_local_start (tz, i))
642 /* if time came before the start of this interval... */
646 /* if it's not in the previous interval... */
647 if (*time_ > interval_local_end (tz, i))
649 /* it doesn't exist. fast-forward it. */
651 *time_ = interval_local_start (tz, i);
655 else if (*time_ > interval_local_end (tz, i))
656 /* if time came after the end of this interval... */
660 /* if it's not in the next interval... */
661 if (*time_ < interval_local_start (tz, i))
662 /* it doesn't exist. fast-forward it. */
663 *time_ = interval_local_start (tz, i);
666 else if (interval_isdst (tz, i) != type)
667 /* it's in this interval, but dst flag doesn't match.
668 * check neighbours for a better fit. */
670 if (i && *time_ <= interval_local_end (tz, i - 1))
673 else if (i < tz->timecnt &&
674 *time_ >= interval_local_start (tz, i + 1))
683 * g_time_zone_find_interval:
685 * @type: the #GTimeType of @time_
686 * @time_: a number of seconds since January 1, 1970
688 * Finds an the interval within @tz that corresponds to the given @time_.
689 * The meaning of @time_ depends on @type.
691 * If @type is %G_TIME_TYPE_UNIVERSAL then this function will always
692 * succeed (since universal time is monotonic and continuous).
694 * Otherwise @time_ is treated is local time. The distinction between
695 * %G_TIME_TYPE_STANDARD and %G_TIME_TYPE_DAYLIGHT is ignored except in
696 * the case that the given @time_ is ambiguous. In Toronto, for example,
697 * 01:30 on November 7th 2010 occured twice (once inside of daylight
698 * savings time and the next, an hour later, outside of daylight savings
699 * time). In this case, the different value of @type would result in a
700 * different interval being returned.
702 * It is still possible for this function to fail. In Toronto, for
703 * example, 02:00 on March 14th 2010 does not exist (due to the leap
704 * forward to begin daylight savings time). -1 is returned in that
707 * Returns: the interval containing @time_, or -1 in case of failure
712 g_time_zone_find_interval (GTimeZone *tz,
718 if (tz->zoneinfo == NULL)
721 for (i = 0; i < tz->timecnt; i++)
722 if (time_ <= interval_end (tz, i))
725 if (type == G_TIME_TYPE_UNIVERSAL)
728 if (time_ < interval_local_start (tz, i))
730 if (time_ > interval_local_end (tz, --i))
734 else if (time_ > interval_local_end (tz, i))
736 if (time_ < interval_local_start (tz, ++i))
740 else if (interval_isdst (tz, i) != type)
742 if (i && time_ <= interval_local_end (tz, i - 1))
745 else if (i < tz->timecnt && time_ >= interval_local_start (tz, i + 1))
752 /* Public API accessors {{{1 */
755 * g_time_zone_get_abbreviation:
757 * @interval: an interval within the timezone
759 * Determines the time zone abbreviation to be used during a particular
760 * @interval of time in the time zone @tz.
762 * For example, in Toronto this is currently "EST" during the winter
763 * months and "EDT" during the summer months when daylight savings time
766 * Returns: the time zone abbreviation, which belongs to @tz
771 g_time_zone_get_abbreviation (GTimeZone *tz,
774 g_return_val_if_fail (interval_valid (tz, interval), NULL);
776 if (tz->header == NULL)
779 return tz->abbrs + interval_abbrind (tz, interval);
783 * g_time_zone_get_offset:
785 * @interval: an interval within the timezone
787 * Determines the offset to UTC in effect during a particular @interval
788 * of time in the time zone @tz.
790 * The offset is the number of seconds that you add to UTC time to
791 * arrive at local time for @tz (ie: negative numbers for time zones
792 * west of GMT, positive numbers for east).
794 * Returns: the number of seconds that should be added to UTC to get the
800 g_time_zone_get_offset (GTimeZone *tz,
803 g_return_val_if_fail (interval_valid (tz, interval), 0);
805 if (tz->header == NULL)
808 return interval_offset (tz, interval);
812 * g_time_zone_is_dst:
814 * @interval: an interval within the timezone
816 * Determines if daylight savings time is in effect during a particular
817 * @interval of time in the time zone @tz.
819 * Returns: %TRUE if daylight savings time is in effect
824 g_time_zone_is_dst (GTimeZone *tz,
827 g_return_val_if_fail (interval_valid (tz, interval), FALSE);
829 if (tz->header == NULL)
832 return interval_isdst (tz, interval);
836 /* vim:set foldmethod=marker: */