glibc/time/tzfile.c

/* Copyright (C) 1991, 1992, 1993 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 <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <limits.h>

#define	NOID
#include <tzfile.h>

#ifndef	HAVE_GNU_LD
#define	__tzname	tzname
#define	__daylight	daylight
#define	__timezone	timezone
#endif

int __use_tzfile = 0;

struct ttinfo
  {
    long int offset;		/* Seconds east of GMT.  */
    unsigned char isdst;	/* Used to set tm_isdst.  */
    unsigned char idx;		/* Index into `zone_names'.  */
    unsigned char isstd;	/* Transition times are standard time.  */
  };

struct leap
  {
    time_t transition;		/* Time the transition takes effect.  */
    long int change;		/* Seconds of correction to apply.  */
  };

static void compute_tzname_max __P ((size_t));

static size_t num_transitions;
static time_t *transitions = NULL;
static unsigned char *type_idxs = NULL;
static size_t num_types;
static struct ttinfo *types = NULL;
static char *zone_names = NULL;
static size_t num_leaps;
static struct leap *leaps = NULL;

#define	uc2ul(x)	_uc2ul((unsigned char *) (x))
#define	_uc2ul(x)							      \
  ((x)[3] + ((x)[2] << CHAR_BIT) + ((x)[1] << (2 * CHAR_BIT)) +		      \
   ((x)[0] << (3 * CHAR_BIT)))

void
DEFUN(__tzfile_read, (file), CONST char *file)
{
  size_t num_isstd;
  register FILE *f;
  struct tzhead tzhead;
  size_t chars;
  register size_t i;

  __use_tzfile = 0;

  if (transitions != NULL)
    free((PTR) transitions);
  transitions = NULL;
  if (type_idxs != NULL)
    free((PTR) type_idxs);
  type_idxs = NULL;
  if (types != NULL)
    free((PTR) types);
  types = NULL;
  if (zone_names != NULL)
    free((PTR) zone_names);
  zone_names = NULL;
  if (leaps != NULL)
    free((PTR) leaps);
  leaps = NULL;

  if (file == NULL || *file == '\0')
    file = TZDEFAULT;

  if (*file != '/')
    {
      static CONST char tzdir[] = TZDIR;
      register CONST unsigned int len = strlen(file) + 1;
      char *new = (char *) __alloca(sizeof(tzdir) + len);
      memcpy(new, tzdir, sizeof(tzdir) - 1);
      new[sizeof(tzdir) - 1] = '/';
      memcpy(&new[sizeof(tzdir)], file, len);
      file = new;
    }

  f = fopen(file, "r");
  if (f == NULL)
    return;

  if (fread((PTR) &tzhead, sizeof(tzhead), 1, f) != 1)
    goto lose;

  num_transitions = (size_t) uc2ul(tzhead.tzh_timecnt);
  num_types = (size_t) uc2ul(tzhead.tzh_typecnt);
  chars = (size_t) uc2ul(tzhead.tzh_charcnt);
  num_leaps = (size_t) uc2ul(tzhead.tzh_leapcnt);
  num_isstd = (size_t) uc2ul(tzhead.tzh_ttisstdcnt);

  if (num_transitions > 0)
    {
      transitions = (time_t *) malloc (num_transitions * sizeof(time_t));
      if (transitions == NULL)
	goto lose;
      type_idxs = (unsigned char *) malloc (num_transitions);
      if (type_idxs == NULL)
	goto lose;
    }
  if (num_types > 0)
    {
      types = (struct ttinfo *) malloc (num_types * sizeof (struct ttinfo));
      if (types == NULL)
	goto lose;
    }
  if (chars > 0)
    {
      zone_names = (char *) malloc (chars);
      if (zone_names == NULL)
	goto lose;
    }
  if (num_leaps > 0)
    {
      leaps = (struct leap *) malloc (num_leaps * sizeof (struct leap));
      if (leaps == NULL)
	goto lose;
    }

  if (fread((PTR) transitions, sizeof(time_t),
	    num_transitions, f) != num_transitions ||
      fread((PTR) type_idxs, 1, num_transitions, f) != num_transitions)
    goto lose;

  for (i = 0; i < num_transitions; ++i)
    transitions[i] = uc2ul (&transitions[i]);

  for (i = 0; i < num_types; ++i)
    {
      unsigned char x[4];
      if (fread((PTR) x, 1, 4, f) != 4 ||
	  fread((PTR) &types[i].isdst, 1, 1, f) != 1 ||
	  fread((PTR) &types[i].idx, 1, 1, f) != 1)
	goto lose;
      types[i].offset = (long int) uc2ul(x);
    }

  if (fread((PTR) zone_names, 1, chars, f) != chars)
    goto lose;

  for (i = 0; i < num_leaps; ++i)
    {
      unsigned char x[4];
      if (fread((PTR) x, 1, sizeof(x), f) != sizeof(x))
	goto lose;
      leaps[i].transition = (time_t) uc2ul(x);
      if (fread((PTR) x, 1, sizeof(x), f) != sizeof(x))
	goto lose;
      leaps[i].change = (long int) uc2ul(x);
    }

  for (i = 0; i < num_isstd; ++i)
    {
      char c = getc(f);
      if (c == EOF)
	goto lose;
      types[i].isstd = c != 0;
    }
  while (i < num_types)
    types[i++].isstd = 0;

  (void) fclose(f);

  compute_tzname_max (chars);
  
  __use_tzfile = 1;
  return;

 lose:;
  (void) fclose(f);
}

void
DEFUN(__tzfile_default, (std, dst, stdoff, dstoff),
      char *std AND char *dst AND
      long int stdoff AND long int dstoff)
{
  size_t stdlen, dstlen, i;

  __tzfile_read (TZDEFRULES);
  if (!__use_tzfile)
    return;

  if (num_types < 2)
    {
      __use_tzfile = 0;
      return;
    }

  free (zone_names);

  stdlen = strlen (std) + 1;
  dstlen = strlen (dst) + 1;
  zone_names = malloc (stdlen + dstlen);
  if (zone_names == NULL)
    {
      __use_tzfile = 0;
      return;
    }
  memcpy (zone_names, std, stdlen);
  memcpy (&zone_names[stdlen], dst, dstlen);

  for (i = 0; i < num_types; ++i)
    if (types[i].isdst)
      {
	types[i].idx = stdlen;
	if (dst[0] != '\0')
	  types[i].offset = dstoff;
      }
    else
      {
	types[i].idx = 0;
	if (dst[0] != '\0')
	  types[i].offset = stdoff;
      }

  compute_tzname_max (stdlen + dstlen);
}

int
DEFUN(__tzfile_compute, (timer, leap_correct, leap_hit),
      time_t timer AND long int *leap_correct AND int *leap_hit)
{
  struct ttinfo *info;
  register size_t i;

  if (num_transitions == 0 || timer < transitions[0])
    {
      /* TIMER is before any transition (or there are no transitions).
	 Choose the first non-DST type
	 (or the first if they're all DST types).  */
      i = 0;
      while (i < num_types && types[i].isdst)
	++i;
      if (i == num_types)
	i = 0;
    }
  else
    {
      /* Find the first transition after TIMER, and
	 then pick the type of the transition before it.  */
      for (i = 1; i < num_transitions; ++i)
	if (timer < transitions[i])
	  break;
      i = type_idxs[i - 1];
    }

  info = &types[i];
  __daylight = info->isdst;
  __timezone = info->offset;
  for (i = 0; i < num_types && i < sizeof (__tzname) / sizeof (__tzname[0]);
       ++i)
    __tzname[types[i].isdst] = &zone_names[types[i].idx];
  if (info->isdst < sizeof (__tzname) / sizeof (__tzname[0]))
    __tzname[info->isdst] = &zone_names[info->idx];

  *leap_correct = 0L;
  *leap_hit = 0;

  /* Find the last leap second correction transition time before TIMER.  */
  i = num_leaps;
  do
    if (i-- == 0)
      return 1;
  while (timer < leaps[i].transition);

  /* Apply its correction.  */
  *leap_correct = leaps[i].change;

  if (timer == leaps[i].transition && /* Exactly at the transition time.  */
      ((i == 0 && leaps[i].change > 0) ||
       leaps[i].change > leaps[i - 1].change))
    {
      *leap_hit = 1;
      while (i > 0 &&
	     leaps[i].transition == leaps[i - 1].transition + 1 &&
	     leaps[i].change == leaps[i - 1].change + 1)
	{
	  ++*leap_hit;
	  --i;
	}
    }

  return 1;
}

void
DEFUN(compute_tzname_max, (chars), size_t chars)
{
  extern long int __tzname_cur_max; /* Defined in __tzset.c. */

  const char *p;

  p = zone_names;
  do
    {
      const char *start = p;
      while (*p != '\0')
	++p;
      if (p - start > __tzname_cur_max)
	__tzname_cur_max = p - start;
    } while (++p < &zone_names[chars]);
}