glibc/time/tzset.c

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/* Copyright (C) 1991,92,93,94,95,96,97,98 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <ctype.h>
#include <errno.h>
#include <bits/libc-lock.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
/* Defined in mktime.c. */
extern const unsigned short int __mon_yday[2][13];
/* Defined in localtime.c. */
extern struct tm _tmbuf;
#define NOID
#include <timezone/tzfile.h>
extern int __use_tzfile;
extern void __tzfile_read __P ((const char *file));
extern int __tzfile_compute __P ((time_t timer, int use_localtime,
long int *leap_correct, int *leap_hit));
extern void __tzfile_default __P ((const char *std, const char *dst,
long int stdoff, long int dstoff));
extern char *__tzstring __P ((const char *string));
char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
int __daylight = 0;
long int __timezone = 0L;
weak_alias (__tzname, tzname)
weak_alias (__daylight, daylight)
weak_alias (__timezone, timezone)
/* This locks all the state variables in tzfile.c and this file. */
__libc_lock_define (static, tzset_lock)
#define min(a, b) ((a) < (b) ? (a) : (b))
#define max(a, b) ((a) > (b) ? (a) : (b))
#define sign(x) ((x) < 0 ? -1 : 1)
/* This structure contains all the information about a
timezone given in the POSIX standard TZ envariable. */
typedef struct
{
const char *name;
/* When to change. */
enum { J0, J1, M } type; /* Interpretation of: */
unsigned short int m, n, d; /* Month, week, day. */
unsigned int secs; /* Time of day. */
long int offset; /* Seconds east of GMT (west if < 0). */
/* We cache the computed time of change for a
given year so we don't have to recompute it. */
time_t change; /* When to change to this zone. */
int computed_for; /* Year above is computed for. */
} tz_rule;
/* tz_rules[0] is standard, tz_rules[1] is daylight. */
static tz_rule tz_rules[2];
static int compute_change __P ((tz_rule *rule, int year)) internal_function;
static int tz_compute __P ((time_t timer, const struct tm *tm))
internal_function;
static void tzset_internal __P ((int always)) internal_function;
/* Header for a list of buffers containing time zone strings. */
struct tzstring_head
{
struct tzstring_head *next;
/* The buffer itself immediately follows the header.
The buffer contains zero or more (possibly overlapping) strings.
The last string is followed by 2 '\0's instead of the usual 1. */
};
/* First in a list of buffers containing time zone strings.
All the buffers but the last are read-only. */
static struct
{
struct tzstring_head head;
char data[48];
} tzstring_list;
/* Size of the last buffer in the list, not counting its header. */
static size_t tzstring_last_buffer_size = sizeof tzstring_list.data;
/* Allocate a time zone string with given contents.
The string will never be moved or deallocated.
However, its contents may be shared with other such strings. */
char *
__tzstring (string)
const char *string;
{
struct tzstring_head *h = &tzstring_list.head;
size_t needed;
char *p;
/* Look through time zone string list for a duplicate of this one. */
for (h = &tzstring_list.head; ; h = h->next)
{
for (p = (char *) (h + 1); p[0] | p[1]; ++p)
if (strcmp (p, string) == 0)
return p;
if (! h->next)
break;
}
/* No duplicate was found. Copy to the end of this buffer if there's room;
otherwise, append a large-enough new buffer to the list and use it. */
++p;
needed = strlen (string) + 2; /* Need 2 trailing '\0's after last string. */
if ((size_t) ((char *) (h + 1) + tzstring_last_buffer_size - p) < needed)
{
size_t buffer_size = tzstring_last_buffer_size;
while ((buffer_size *= 2) < needed)
continue;
if (! (h = h->next = malloc (sizeof *h + buffer_size)))
return NULL;
h->next = NULL;
tzstring_last_buffer_size = buffer_size;
p = (char *) (h + 1);
}
return strncpy (p, string, needed);
}
static char *old_tz = NULL;
/* Interpret the TZ envariable. */
static void
internal_function
tzset_internal (always)
int always;
{
static int is_initialized = 0;
register const char *tz;
register size_t l;
char *tzbuf;
unsigned short int hh, mm, ss;
unsigned short int whichrule;
if (is_initialized && !always)
return;
is_initialized = 1;
/* Examine the TZ environment variable. */
tz = getenv ("TZ");
if (tz == NULL)
/* No user specification; use the site-wide default. */
tz = TZDEFAULT;
else if (*tz == '\0')
/* User specified the empty string; use UTC explicitly. */
tz = "Universal";
/* A leading colon means "implementation defined syntax".
We ignore the colon and always use the same algorithm:
try a data file, and if none exists parse the 1003.1 syntax. */
if (tz && *tz == ':')
++tz;
/* Check whether the value changes since the last run. */
if (old_tz != NULL && tz != NULL && strcmp (tz, old_tz) == 0)
/* No change, simply return. */
return;
tz_rules[0].name = NULL;
tz_rules[1].name = NULL;
/* Save the value of `tz'. */
if (old_tz != NULL)
free (old_tz);
old_tz = tz ? __strdup (tz) : NULL;
/* Try to read a data file. */
__tzfile_read (tz);
if (__use_tzfile)
return;
/* No data file found. Default to UTC if nothing specified. */
if (tz == NULL || *tz == '\0')
{
tz_rules[0].name = tz_rules[1].name = "UTC";
tz_rules[0].type = tz_rules[1].type = J0;
tz_rules[0].m = tz_rules[0].n = tz_rules[0].d = 0;
tz_rules[1].m = tz_rules[1].n = tz_rules[1].d = 0;
tz_rules[0].secs = tz_rules[1].secs = 0;
tz_rules[0].offset = tz_rules[1].offset = 0L;
tz_rules[0].change = tz_rules[1].change = (time_t) -1;
tz_rules[0].computed_for = tz_rules[1].computed_for = 0;
return;
}
/* Clear out old state and reset to unnamed UTC. */
memset (tz_rules, 0, sizeof tz_rules);
tz_rules[0].name = tz_rules[1].name = "";
/* Get the standard timezone name. */
tzbuf = malloc (strlen (tz) + 1);
if (! tzbuf)
{
/* Clear the old tz name so we will try again. */
free (old_tz);
old_tz = NULL;
return;
}
if (sscanf (tz, "%[^0-9,+-]", tzbuf) != 1 ||
(l = strlen (tzbuf)) < 3)
{
free (tzbuf);
return;
}
tz_rules[0].name = __tzstring (tzbuf);
tz += l;
/* Figure out the standard offset from UTC. */
if (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit (*tz)))
{
free (tzbuf);
return;
}
if (*tz == '-' || *tz == '+')
tz_rules[0].offset = *tz++ == '-' ? 1L : -1L;
else
tz_rules[0].offset = -1L;
switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
{
default:
free (tzbuf);
return;
case 1:
mm = 0;
case 2:
ss = 0;
case 3:
break;
}
tz_rules[0].offset *= (min (ss, 59) + (min (mm, 59) * 60) +
(min (hh, 23) * 60 * 60));
for (l = 0; l < 3; ++l)
{
while (isdigit(*tz))
++tz;
if (l < 2 && *tz == ':')
++tz;
}
/* Get the DST timezone name (if any). */
if (*tz != '\0')
{
char *n = tzbuf + strlen (tzbuf) + 1;
if (sscanf (tz, "%[^0-9,+-]", n) != 1 ||
(l = strlen (n)) < 3)
goto done_names; /* Punt on name, set up the offsets. */
tz_rules[1].name = __tzstring (n);
tz += l;
/* Figure out the DST offset from GMT. */
if (*tz == '-' || *tz == '+')
tz_rules[1].offset = *tz++ == '-' ? 1L : -1L;
else
tz_rules[1].offset = -1L;
switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
{
default:
/* Default to one hour later than standard time. */
tz_rules[1].offset = tz_rules[0].offset + (60 * 60);
break;
case 1:
mm = 0;
case 2:
ss = 0;
case 3:
tz_rules[1].offset *= (min (ss, 59) + (min (mm, 59) * 60) +
(min (hh, 23) * (60 * 60)));
break;
}
for (l = 0; l < 3; ++l)
{
while (isdigit (*tz))
++tz;
if (l < 2 && *tz == ':')
++tz;
}
if (*tz == '\0' || (tz[0] == ',' && tz[1] == '\0'))
{
/* There is no rule. See if there is a default rule file. */
__tzfile_default (tz_rules[0].name, tz_rules[1].name,
tz_rules[0].offset, tz_rules[1].offset);
if (__use_tzfile)
{
free (old_tz);
old_tz = NULL;
free (tzbuf);
return;
}
}
}
else
{
/* There is no DST. */
tz_rules[1].name = tz_rules[0].name;
free (tzbuf);
return;
}
done_names:
free (tzbuf);
/* Figure out the standard <-> DST rules. */
for (whichrule = 0; whichrule < 2; ++whichrule)
{
register tz_rule *tzr = &tz_rules[whichrule];
/* Ignore comma to support string following the incorrect
specification in early POSIX.1 printings. */
tz += *tz == ',';
/* Get the date of the change. */
if (*tz == 'J' || isdigit (*tz))
{
char *end;
tzr->type = *tz == 'J' ? J1 : J0;
if (tzr->type == J1 && !isdigit (*++tz))
return;
tzr->d = (unsigned short int) strtoul (tz, &end, 10);
if (end == tz || tzr->d > 365)
return;
else if (tzr->type == J1 && tzr->d == 0)
return;
tz = end;
}
else if (*tz == 'M')
{
int n;
tzr->type = M;
if (sscanf (tz, "M%hu.%hu.%hu%n",
&tzr->m, &tzr->n, &tzr->d, &n) != 3 ||
tzr->m < 1 || tzr->m > 12 ||
tzr->n < 1 || tzr->n > 5 || tzr->d > 6)
return;
tz += n;
}
else if (*tz == '\0')
{
/* United States Federal Law, the equivalent of "M4.1.0,M10.5.0". */
tzr->type = M;
if (tzr == &tz_rules[0])
{
tzr->m = 4;
tzr->n = 1;
tzr->d = 0;
}
else
{
tzr->m = 10;
tzr->n = 5;
tzr->d = 0;
}
}
else
return;
if (*tz != '\0' && *tz != '/' && *tz != ',')
return;
else if (*tz == '/')
{
/* Get the time of day of the change. */
++tz;
if (*tz == '\0')
return;
switch (sscanf (tz, "%hu:%hu:%hu", &hh, &mm, &ss))
{
default:
hh = 2; /* Default to 2:00 AM. */
case 1:
mm = 0;
case 2:
ss = 0;
case 3:
break;
}
for (l = 0; l < 3; ++l)
{
while (isdigit (*tz))
++tz;
if (l < 2 && *tz == ':')
++tz;
}
tzr->secs = (hh * 60 * 60) + (mm * 60) + ss;
}
else
/* Default to 2:00 AM. */
tzr->secs = 2 * 60 * 60;
tzr->computed_for = -1;
}
}
/* Maximum length of a timezone name. __tz_compute keeps this up to date
(never decreasing it) when ! __use_tzfile.
tzfile.c keeps it up to date when __use_tzfile. */
size_t __tzname_cur_max;
long int
__tzname_max ()
{
__libc_lock_lock (tzset_lock);
tzset_internal (0);
__libc_lock_unlock (tzset_lock);
return __tzname_cur_max;
}
/* Figure out the exact time (as a time_t) in YEAR
when the change described by RULE will occur and
put it in RULE->change, saving YEAR in RULE->computed_for.
Return nonzero if successful, zero on failure. */
static int
internal_function
compute_change (rule, year)
tz_rule *rule;
int year;
{
register time_t t;
int y;
if (year != -1 && rule->computed_for == year)
/* Operations on times in 1969 will be slower. Oh well. */
return 1;
/* First set T to January 1st, 0:00:00 GMT in YEAR. */
t = 0;
for (y = 1970; y < year; ++y)
t += SECSPERDAY * (__isleap (y) ? 366 : 365);
switch (rule->type)
{
case J1:
/* Jn - Julian day, 1 == January 1, 60 == March 1 even in leap years.
In non-leap years, or if the day number is 59 or less, just
add SECSPERDAY times the day number-1 to the time of
January 1, midnight, to get the day. */
t += (rule->d - 1) * SECSPERDAY;
if (rule->d >= 60 && __isleap (year))
t += SECSPERDAY;
break;
case J0:
/* n - Day of year.
Just add SECSPERDAY times the day number to the time of Jan 1st. */
t += rule->d * SECSPERDAY;
break;
case M:
/* Mm.n.d - Nth "Dth day" of month M. */
{
unsigned int i;
int d, m1, yy0, yy1, yy2, dow;
const unsigned short int *myday =
&__mon_yday[__isleap (year)][rule->m];
/* First add SECSPERDAY for each day in months before M. */
t += myday[-1] * SECSPERDAY;
/* Use Zeller's Congruence to get day-of-week of first day of month. */
m1 = (rule->m + 9) % 12 + 1;
yy0 = (rule->m <= 2) ? (year - 1) : year;
yy1 = yy0 / 100;
yy2 = yy0 % 100;
dow = ((26 * m1 - 2) / 10 + 1 + yy2 + yy2 / 4 + yy1 / 4 - 2 * yy1) % 7;
if (dow < 0)
dow += 7;
/* DOW is the day-of-week of the first day of the month. Get the
day-of-month (zero-origin) of the first DOW day of the month. */
d = rule->d - dow;
if (d < 0)
d += 7;
for (i = 1; i < rule->n; ++i)
{
if (d + 7 >= (int) myday[0] - myday[-1])
break;
d += 7;
}
/* D is the day-of-month (zero-origin) of the day we want. */
t += d * SECSPERDAY;
}
break;
}
/* T is now the Epoch-relative time of 0:00:00 GMT on the day we want.
Just add the time of day and local offset from GMT, and we're done. */
rule->change = t - rule->offset + rule->secs;
rule->computed_for = year;
return 1;
}
/* Figure out the correct timezone for *TIMER and TM (which must be the same)
and set `__tzname', `__timezone', and `__daylight' accordingly.
Return nonzero on success, zero on failure. */
static int
internal_function
tz_compute (timer, tm)
time_t timer;
const struct tm *tm;
{
if (! compute_change (&tz_rules[0], 1900 + tm->tm_year) ||
! compute_change (&tz_rules[1], 1900 + tm->tm_year))
return 0;
__daylight = timer >= tz_rules[0].change && timer < tz_rules[1].change;
__timezone = -tz_rules[__daylight].offset;
__tzname[0] = (char *) tz_rules[0].name;
__tzname[1] = (char *) tz_rules[1].name;
{
/* Keep __tzname_cur_max up to date. */
size_t len0 = strlen (__tzname[0]);
size_t len1 = strlen (__tzname[1]);
if (len0 > __tzname_cur_max)
__tzname_cur_max = len0;
if (len1 > __tzname_cur_max)
__tzname_cur_max = len1;
}
return 1;
}
/* Reinterpret the TZ environment variable and set `tzname'. */
#undef tzset
void
__tzset (void)
{
__libc_lock_lock (tzset_lock);
tzset_internal (1);
if (!__use_tzfile)
{
/* Set `tzname'. */
__tzname[0] = (char *) tz_rules[0].name;
__tzname[1] = (char *) tz_rules[1].name;
}
__libc_lock_unlock (tzset_lock);
}
weak_alias (__tzset, tzset)
/* Return the `struct tm' representation of *TIMER in the local timezone.
Use local time if USE_LOCALTIME is nonzero, UTC otherwise. */
struct tm *
__tz_convert (const time_t *timer, int use_localtime, struct tm *tp)
{
long int leap_correction;
int leap_extra_secs;
if (timer == NULL)
{
__set_errno (EINVAL);
return NULL;
}
__libc_lock_lock (tzset_lock);
/* Update internal database according to current TZ setting.
POSIX.1 8.3.7.2 says that localtime_r is not required to set tzname.
This is a good idea since this allows at least a bit more parallelism.
By analogy we apply the same rule to gmtime_r. */
tzset_internal (tp == &_tmbuf);
if (__use_tzfile)
{
if (! __tzfile_compute (*timer, use_localtime,
&leap_correction, &leap_extra_secs))
tp = NULL;
}
else
{
if (! (__offtime (timer, 0, tp) && tz_compute (*timer, tp)))
tp = NULL;
leap_correction = 0L;
leap_extra_secs = 0;
}
if (tp)
{
if (use_localtime)
{
tp->tm_isdst = __daylight;
tp->tm_zone = __tzname[__daylight];
tp->tm_gmtoff = -__timezone;
}
else
{
tp->tm_isdst = 0;
tp->tm_zone = "GMT";
tp->tm_gmtoff = 0L;
}
if (__offtime (timer, tp->tm_gmtoff - leap_correction, tp))
tp->tm_sec += leap_extra_secs;
else
tp = NULL;
}
__libc_lock_unlock (tzset_lock);
return tp;
}