glibc/time/tzset.c
1995-02-18 01:27:10 +00:00

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/* Copyright (C) 1991, 1992, 1993, 1994, 1995 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., 675 Mass Ave,
Cambridge, MA 02139, USA. */
#include <ansidecl.h>
#include <localeinfo.h>
#include <ctype.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_lengths[2][12];
#define NOID
#include "tzfile.h"
extern int __use_tzfile;
extern void EXFUN(__tzfile_read, (CONST char *file));
extern void EXFUN(__tzfile_default, (char *std AND char *dst AND
long int stdoff AND long int dstoff));
extern int EXFUN(__tzfile_compute, (time_t, struct tm));
#ifndef HAVE_WEAK_SYMBOLS
#define __tzname tzname
#define __daylight daylight
#define __timezone timezone
#else
weak_alias (__tzname, tzname)
weak_alias (__daylight, daylight)
weak_alias (__timezone, timezone)
#endif
char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
int __daylight = 0;
long int __timezone = 0L;
#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
{
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];
int __tzset_run = 0;
/* Interpret the TZ envariable. */
void
DEFUN_VOID(__tzset)
{
register CONST char *tz;
register size_t l;
unsigned short int hh, mm, ss;
unsigned short int whichrule;
/* Free old storage. */
if (tz_rules[0].name != NULL && *tz_rules[0].name != '\0')
free((PTR) tz_rules[0].name);
if (tz_rules[1].name != NULL && *tz_rules[1].name != '\0' &&
tz_rules[1].name != tz_rules[0].name)
free((PTR) tz_rules[1].name);
tz = getenv("TZ");
if (tz != NULL && *tz == ':')
{
__tzfile_read(tz + 1);
if (__use_tzfile)
{
__tzset_run = 1;
return;
}
else
tz = NULL;
}
if (tz == NULL || *tz == '\0')
tz = _time_info->tz;
if (tz == NULL || *tz == '\0')
{
__tzfile_read((char *) NULL);
if (!__use_tzfile)
{
size_t len = strlen(_time_info->ut0) + 1;
tz_rules[0].name = (char *) malloc(len);
if (tz_rules[0].name == NULL)
return;
tz_rules[1].name = (char *) malloc(len);
if (tz_rules[1].name == NULL)
return;
memcpy((PTR) tz_rules[0].name, _time_info->ut0, len);
memcpy((PTR) tz_rules[1].name, _time_info->ut0, len);
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;
}
__tzset_run = 1;
return;
}
/* Clear out old state and reset to unnamed GMT. */
memset (tz_rules, 0, sizeof tz_rules);
tz_rules[0].name = tz_rules[1].name = (char *) "";
/* Get the standard timezone name. */
tz_rules[0].name = (char *) malloc (strlen (tz) + 1);
if (tz_rules[0].name == NULL)
/* Don't set __tzset_run so we will try again. */
return;
if (sscanf(tz, "%[^0-9,+-]", tz_rules[0].name) != 1 ||
(l = strlen(tz_rules[0].name)) < 3)
{
free (tz_rules[0].name);
tz_rules[0].name = (char *) "";
return;
}
{
char *n = realloc ((PTR) tz_rules[0].name, l + 1);
if (n != NULL)
tz_rules[0].name = n;
}
tz += l;
/* Figure out the standard offset from GMT. */
if (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit(*tz)))
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:
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, 12) * 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 = malloc (strlen(tz) + 1);
if (n != NULL)
{
tz_rules[1].name = n;
if (sscanf(tz, "%[^0-9,+-]", tz_rules[1].name) != 1 ||
(l = strlen(tz_rules[1].name)) < 3)
{
free (n);
tz_rules[1].name = (char *) "";
goto done_names; /* Punt on name, set up the offsets. */
}
n = realloc ((PTR) tz_rules[1].name, l + 1);
if (n != NULL)
tz_rules[1].name = 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, 12) * (60 * 60)));
break;
}
for (l = 0; l < 3; ++l)
{
while (isdigit (*tz))
++tz;
if (l < 2 && *tz == ':')
++tz;
}
done_names:
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)
{
__tzset_run = 1;
return;
}
}
/* Figure out the standard <-> DST rules. */
for (whichrule = 0; whichrule < 2; ++whichrule)
{
register tz_rule *tzr = &tz_rules[whichrule];
if (*tz == ',')
{
++tz;
if (*tz == '\0')
return;
}
/* 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;
}
__tzset_run = 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. */
long int __tzname_cur_max;
long int
DEFUN_VOID(__tzname_max)
{
if (! __tzset_run)
__tzset ();
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
DEFUN(compute_change, (rule, year), tz_rule *rule AND 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. */
{
register int i, d, m1, yy0, yy1, yy2, dow;
/* First add SECSPERDAY for each day in months before M. */
for (i = 0; i < rule->m - 1; ++i)
t += __mon_lengths[__isleap (year)][i] * 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 >= __mon_lengths[__isleap (year)][rule->m - 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. */
int
DEFUN(__tz_compute, (timer, tm),
time_t timer AND const struct tm *tm)
{
if (! __tzset_run)
__tzset ();
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 ? 1 : 0].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;
}
weak_alias (__tzset, tzset)