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;
139 * Decreases the reference count on @tz.
144 g_time_zone_unref (GTimeZone *tz)
146 g_assert (tz->ref_count > 0);
148 if (g_atomic_int_dec_and_test (&tz->ref_count))
150 if (tz->name != NULL)
153 g_hash_table_remove (time_zones, tz->name);
154 G_UNLOCK(time_zones);
158 g_buffer_unref (tz->zoneinfo);
162 g_slice_free (GTimeZone, tz);
170 * Increases the reference count on @tz.
172 * Returns: a new reference to @tz.
177 g_time_zone_ref (GTimeZone *tz)
179 g_assert (tz->ref_count > 0);
181 g_atomic_int_inc (&tz->ref_count);
186 /* fake zoneinfo creation (for RFC3339/ISO 8601 timezones) {{{1 */
188 * parses strings of the form 'hh' 'hhmm' or 'hh:mm' where:
193 parse_time (const gchar *time_,
196 if (*time_ < '0' || '2' < *time_)
199 *offset = 10 * 60 * 60 * (*time_++ - '0');
201 if (*time_ < '0' || '9' < *time_)
204 *offset += 60 * 60 * (*time_++ - '0');
206 if (*offset > 23 * 60 * 60)
215 if (*time_ < '0' || '5' < *time_)
218 *offset += 10 * 60 * (*time_++ - '0');
220 if (*time_ < '0' || '9' < *time_)
223 *offset += 60 * (*time_++ - '0');
225 return *time_ == '\0';
229 parse_constant_offset (const gchar *name,
239 return parse_time (name, offset);
242 if (parse_time (name, offset))
254 zone_for_constant_offset (const gchar *name)
256 const gchar fake_zoneinfo_headers[] =
257 "TZif" "2..." "...." "...." "...."
258 "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0"
259 "TZif" "2..." "...." "...." "...."
260 "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\0" "\0\0\0\1" "\0\0\0\7";
262 struct tzhead headers[2];
268 if (name == NULL || !parse_constant_offset (name, &offset))
271 offset = GINT32_TO_BE (offset);
273 fake = g_malloc (sizeof *fake);
274 memcpy (fake, fake_zoneinfo_headers, sizeof fake_zoneinfo_headers);
275 memcpy (&fake->info.tt_gmtoff, &offset, sizeof offset);
276 fake->info.tt_isdst = FALSE;
277 fake->info.tt_abbrind = 0;
278 strcpy (fake->abbr, name);
280 return g_buffer_new_take_data (fake, sizeof *fake);
283 /* Construction {{{1 */
286 * @identifier: (allow-none): a timezone identifier
288 * Creates a #GTimeZone corresponding to @identifier.
290 * @identifier can either be an RFC3339/ISO 8601 time offset or
291 * something that would pass as a valid value for the
292 * <varname>TZ</varname> environment variable (including %NULL).
294 * Valid RFC3339 time offsets are <literal>"Z"</literal> (for UTC) or
295 * <literal>"±hh:mm"</literal>. ISO 8601 additionally specifies
296 * <literal>"±hhmm"</literal> and <literal>"±hh"</literal>.
298 * The <varname>TZ</varname> environment variable typically corresponds
299 * to the name of a file in the zoneinfo database, but there are many
300 * other possibilities. Note that those other possibilities are not
301 * currently implemented, but are planned.
303 * g_time_zone_new_local() calls this function with the value of the
304 * <varname>TZ</varname> environment variable. This function itself is
305 * independent of the value of <varname>TZ</varname>, but if @identifier
306 * is %NULL then <filename>/etc/localtime</filename> will be consulted
307 * to discover the correct timezone.
310 * url='http://tools.ietf.org/html/rfc3339#section-5.6'>RFC3339
311 * §5.6</ulink> for a precise definition of valid RFC3339 time offsets
312 * (the <varname>time-offset</varname> expansion) and ISO 8601 for the
313 * full list of valid time offsets. See <ulink
314 * url='http://www.gnu.org/s/libc/manual/html_node/TZ-Variable.html'>The
315 * GNU C Library manual</ulink> for an explanation of the possible
316 * values of the <varname>TZ</varname> environment variable.
318 * You should release the return value by calling g_time_zone_unref()
319 * when you are done with it.
321 * Returns: the requested timezone
326 g_time_zone_new (const gchar *identifier)
331 if (time_zones == NULL)
332 time_zones = g_hash_table_new (g_str_hash, g_str_equal);
335 tz = g_hash_table_lookup (time_zones, identifier);
341 tz = g_slice_new0 (GTimeZone);
342 tz->name = g_strdup (identifier);
345 tz->zoneinfo = zone_for_constant_offset (identifier);
347 if (tz->zoneinfo == NULL)
351 if (identifier != NULL)
355 tzdir = getenv ("TZDIR");
357 tzdir = "/usr/share/zoneinfo";
359 filename = g_build_filename (tzdir, identifier, NULL);
362 filename = g_strdup ("/etc/localtime");
364 tz->zoneinfo = (GBuffer *) g_mapped_file_new (filename, FALSE, NULL);
368 if (tz->zoneinfo != NULL)
370 const struct tzhead *header = tz->zoneinfo->data;
371 gsize size = tz->zoneinfo->size;
373 /* we only bother to support version 2 */
374 if (size < sizeof (struct tzhead) || memcmp (header, "TZif2", 5))
376 g_buffer_unref (tz->zoneinfo);
383 /* we trust the file completely. */
384 tz->header = (const struct tzhead *)
385 (((const gchar *) (header + 1)) +
386 guint32_from_be(header->tzh_ttisgmtcnt) +
387 guint32_from_be(header->tzh_ttisstdcnt) +
388 8 * guint32_from_be(header->tzh_leapcnt) +
389 5 * guint32_from_be(header->tzh_timecnt) +
390 6 * guint32_from_be(header->tzh_typecnt) +
391 guint32_from_be(header->tzh_charcnt));
393 typecnt = guint32_from_be (tz->header->tzh_typecnt);
394 tz->timecnt = guint32_from_be (tz->header->tzh_timecnt);
395 tz->trans = (gconstpointer) (tz->header + 1);
396 tz->indices = (gconstpointer) (tz->trans + tz->timecnt);
397 tz->infos = (gconstpointer) (tz->indices + tz->timecnt);
398 tz->abbrs = (gconstpointer) (tz->infos + typecnt);
403 g_hash_table_insert (time_zones, tz->name, tz);
405 g_atomic_int_inc (&tz->ref_count);
406 G_UNLOCK (time_zones);
412 * g_time_zone_new_utc:
414 * Creates a #GTimeZone corresponding to UTC.
416 * This is equivalent to calling g_time_zone_new() with a value like
417 * "Z", "UTC", "+00", etc.
419 * You should release the return value by calling g_time_zone_unref()
420 * when you are done with it.
422 * Returns: the universal timezone
427 g_time_zone_new_utc (void)
429 return g_time_zone_new ("UTC");
433 * g_time_zone_new_local:
435 * Creates a #GTimeZone corresponding to local time.
437 * This is equivalent to calling g_time_zone_new() with the value of the
438 * <varname>TZ</varname> environment variable (including the possibility
439 * of %NULL). Changes made to <varname>TZ</varname> after the first
440 * call to this function may or may not be noticed by future calls.
442 * You should release the return value by calling g_time_zone_unref()
443 * when you are done with it.
445 * Returns: the local timezone
450 g_time_zone_new_local (void)
452 return g_time_zone_new (getenv ("TZ"));
455 /* Internal helpers {{{1 */
456 inline static const struct ttinfo *
457 interval_info (GTimeZone *tz,
461 return tz->infos + tz->indices[interval - 1];
467 interval_start (GTimeZone *tz,
471 return gint64_from_be (tz->trans[interval - 1]);
477 interval_end (GTimeZone *tz,
480 if (interval < tz->timecnt)
481 return gint64_from_be (tz->trans[interval]) - 1;
487 interval_offset (GTimeZone *tz,
490 return gint32_from_be (interval_info (tz, interval)->tt_gmtoff);
493 inline static gboolean
494 interval_isdst (GTimeZone *tz,
497 return interval_info (tz, interval)->tt_isdst;
501 interval_abbrind (GTimeZone *tz,
504 return interval_info (tz, interval)->tt_abbrind;
508 interval_local_start (GTimeZone *tz,
512 return interval_start (tz, interval) + interval_offset (tz, interval);
518 interval_local_end (GTimeZone *tz,
521 if (interval < tz->timecnt)
522 return interval_end (tz, interval) + interval_offset (tz, interval);
528 interval_valid (GTimeZone *tz,
531 return interval <= tz->timecnt;
534 /* g_time_zone_find_interval() {{{1 */
537 * g_time_zone_adjust_time:
539 * @type: the #GTimeType of @time
540 * @time: a pointer to a number of seconds since January 1, 1970
542 * Finds an interval within @tz that corresponds to the given @time,
543 * possibly adjusting @time if required to fit into an interval.
544 * The meaning of @time depends on @type.
546 * This function is similar to g_time_zone_find_interval(), with the
547 * difference that it always succeeds (by making the adjustments
550 * In any of the cases where g_time_zone_find_interval() succeeds then
551 * this function returns the same value, without modifying @time.
553 * This function may, however, modify @time in order to deal with
554 * non-existent times. If the non-existent local @time of 02:30 were
555 * requested on March 13th 2010 in Toronto then this function would
556 * adjust @time to be 03:00 and return the interval containing the
559 * Returns: the interval containing @time, never -1
564 g_time_zone_adjust_time (GTimeZone *tz,
570 if (tz->zoneinfo == NULL)
573 /* find the interval containing *time UTC
574 * TODO: this could be binary searched (or better) */
575 for (i = 0; i < tz->timecnt; i++)
576 if (*time_ <= interval_end (tz, i))
579 g_assert (interval_start (tz, i) <= *time_ && *time_ <= interval_end (tz, i));
581 if (type != G_TIME_TYPE_UNIVERSAL)
583 if (*time_ < interval_local_start (tz, i))
584 /* if time came before the start of this interval... */
588 /* if it's not in the previous interval... */
589 if (*time_ > interval_local_end (tz, i))
591 /* it doesn't exist. fast-forward it. */
593 *time_ = interval_local_start (tz, i);
597 else if (*time_ > interval_local_end (tz, i))
598 /* if time came after the end of this interval... */
602 /* if it's not in the next interval... */
603 if (*time_ < interval_local_start (tz, i))
604 /* it doesn't exist. fast-forward it. */
605 *time_ = interval_local_start (tz, i);
608 else if (interval_isdst (tz, i) != type)
609 /* it's in this interval, but dst flag doesn't match.
610 * check neighbours for a better fit. */
612 if (i && *time_ <= interval_local_end (tz, i - 1))
615 else if (i < tz->timecnt &&
616 *time_ >= interval_local_start (tz, i + 1))
625 * g_time_zone_find_interval:
627 * @type: the #GTimeType of @time_
628 * @time_: a number of seconds since January 1, 1970
630 * Finds an the interval within @tz that corresponds to the given @time_.
631 * The meaning of @time_ depends on @type.
633 * If @type is %G_TIME_TYPE_UNIVERSAL then this function will always
634 * succeed (since universal time is monotonic and continuous).
636 * Otherwise @time_ is treated is local time. The distinction between
637 * %G_TIME_TYPE_STANDARD and %G_TIME_TYPE_DAYLIGHT is ignored except in
638 * the case that the given @time_ is ambiguous. In Toronto, for example,
639 * 01:30 on November 7th 2010 occured twice (once inside of daylight
640 * savings time and the next, an hour later, outside of daylight savings
641 * time). In this case, the different value of @type would result in a
642 * different interval being returned.
644 * It is still possible for this function to fail. In Toronto, for
645 * example, 02:00 on March 14th 2010 does not exist (due to the leap
646 * forward to begin daylight savings time). -1 is returned in that
649 * Returns: the interval containing @time_, or -1 in case of failure
654 g_time_zone_find_interval (GTimeZone *tz,
660 if (tz->zoneinfo == NULL)
663 for (i = 0; i < tz->timecnt; i++)
664 if (time_ <= interval_end (tz, i))
667 if (type == G_TIME_TYPE_UNIVERSAL)
670 if (time_ < interval_local_start (tz, i))
672 if (time_ > interval_local_end (tz, --i))
676 else if (time_ > interval_local_end (tz, i))
678 if (time_ < interval_local_start (tz, ++i))
682 else if (interval_isdst (tz, i) != type)
684 if (i && time_ <= interval_local_end (tz, i - 1))
687 else if (i < tz->timecnt && time_ >= interval_local_start (tz, i + 1))
694 /* Public API accessors {{{1 */
697 * g_time_zone_get_abbreviation:
699 * @interval: an interval within the timezone
701 * Determines the time zone abbreviation to be used during a particular
702 * @interval of time in the time zone @tz.
704 * For example, in Toronto this is currently "EST" during the winter
705 * months and "EDT" during the summer months when daylight savings time
708 * Returns: the time zone abbreviation, which belongs to @tz
713 g_time_zone_get_abbreviation (GTimeZone *tz,
716 g_return_val_if_fail (interval_valid (tz, interval), NULL);
718 if (tz->header == NULL)
721 return tz->abbrs + interval_abbrind (tz, interval);
725 * g_time_zone_get_offset:
727 * @interval: an interval within the timezone
729 * Determines the offset to UTC in effect during a particular @interval
730 * of time in the time zone @tz.
732 * The offset is the number of seconds that you add to UTC time to
733 * arrive at local time for @tz (ie: negative numbers for time zones
734 * west of GMT, positive numbers for east).
736 * Returns: the number of seconds that should be added to UTC to get the
742 g_time_zone_get_offset (GTimeZone *tz,
745 g_return_val_if_fail (interval_valid (tz, interval), 0);
747 if (tz->header == NULL)
750 return interval_offset (tz, interval);
754 * g_time_zone_is_dst:
756 * @interval: an interval within the timezone
758 * Determines if daylight savings time is in effect during a particular
759 * @interval of time in the time zone @tz.
761 * Returns: %TRUE if daylight savings time is in effect
766 g_time_zone_is_dst (GTimeZone *tz,
769 g_return_val_if_fail (interval_valid (tz, interval), FALSE);
771 if (tz->header == NULL)
774 return interval_isdst (tz, interval);
778 /* vim:set foldmethod=marker: */