tzset.c

Linux下头文件time.h的实现源码

/* Copyright (C) 1991-2002,2003,2004,2007 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 Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; 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>


#define NOID
#include <timezone/tzfile.h>

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_initialized (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 void compute_change (tz_rule *rule, int year) __THROW internal_function;
static void tzset_internal (int always, int explicit)
     __THROW internal_function;

/* List of buffers containing time zone strings. */
struct tzstring_l
{
  struct tzstring_l *next;
  size_t len;  /* strlen(data) - doesn't count terminating NUL! */
  char data[0];
};

static struct tzstring_l *tzstring_list;

/* Allocate a permanent home for S.  It will never be moved or deallocated,
   but may share space with other strings.
   Don't modify the returned string. */
char *
__tzstring (const char *s)
{
  char *p;
  struct tzstring_l *t, *u, *new;
  size_t len = strlen (s);

  /* Walk the list and look for a match.  If this string is the same
     as the end of an already-allocated string, it can share space. */
  for (u = t = tzstring_list; t; u = t, t = t->next)
    if (len <= t->len)
      {
	p = &t->data[t->len - len];
	if (strcmp (s, p) == 0)
	  return p;
      }

  /* Not found; allocate a new buffer. */
  new = malloc (sizeof (struct tzstring_l) + len + 1);
  if (!new)
    return NULL;

  new->next = NULL;
  new->len = len;
  strcpy (new->data, s);

  if (u)
    u->next = new;
  else
    tzstring_list = new;

  return new->data;
}

/* Maximum length of a timezone name.  tzset_internal 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, 0);

  __libc_lock_unlock (tzset_lock);

  return __tzname_cur_max;
}

static char *old_tz;

static void
internal_function
update_vars (void)
{
  __daylight = tz_rules[0].offset != tz_rules[1].offset;
  __timezone = -tz_rules[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;
}

/* Parse the POSIX TZ-style string.  */
void
__tzset_parse_tz (tz)
     const char *tz;
{
  register size_t l;
  char *tzbuf;
  unsigned short int hh, mm, ss;
  unsigned short int whichrule;

  /* 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 = strdupa (tz);

  if (sscanf (tz, "%[^0-9,+-]", tzbuf) != 1 ||
      (l = strlen (tzbuf)) < 3)
    goto out;

  tz_rules[0].name = __tzstring (tzbuf);

  tz += l;

  /* Figure out the standard offset from UTC.  */
  if (*tz == '\0' || (*tz != '+' && *tz != '-' && !isdigit (*tz)))
    goto out;

  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:
      tz_rules[0].offset = 0;
      goto out;
    case 1:
      mm = 0;
    case 2:
      ss = 0;
    case 3:
      break;
    }
  tz_rules[0].offset *= (min (ss, 59) + (min (mm, 59) * 60) +
			 (min (hh, 24) * 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;
	      return;
	    }
	}
    }
  else
    {
      /* There is no DST.  */
      tz_rules[1].name = tz_rules[0].name;
      tz_rules[1].offset = tz_rules[0].offset;
      goto out;
    }

 done_names:
  /* 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))
	    goto out;
	  tzr->d = (unsigned short int) strtoul (tz, &end, 10);
	  if (end == tz || tzr->d > 365)
	    goto out;
	  else if (tzr->type == J1 && tzr->d == 0)
	    goto out;
	  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)
	    goto out;
	  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;
	    }
	}