~drizzle-trunk/drizzle/development

/* Convert a `struct tm' to a time_t value.

   Copyright (C) 1993-1999, 2002-2005, 2006, 2007 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Paul Eggert <eggert@twinsun.com>.

   This program 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, or (at your option)

   any later version.

   This program 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 this program; if not, write to the Free Software Foundation,

   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */

#ifndef _LIBC

# include <config.h>

#endif

/* Assume that leap seconds are possible, unless told otherwise.

   If the host has a `zic' command with a `-L leapsecondfilename' option,

   then it supports leap seconds; otherwise it probably doesn't.  */

#ifndef LEAP_SECONDS_POSSIBLE

# define LEAP_SECONDS_POSSIBLE 1

#endif

#include <time.h>

#include <limits.h>

#include <string.h>		/* For the real memcpy prototype.  */

/* Shift A right by B bits portably, by dividing A by 2**B and

   truncating towards minus infinity.  A and B should be free of side

   effects, and B should be in the range 0 <= B <= INT_BITS - 2, where

   INT_BITS is the number of useful bits in an int.  GNU code can

   assume that INT_BITS is at least 32.

   ISO C99 says that A >> B is implementation-defined if A < 0.  Some

   implementations (e.g., UNICOS 9.0 on a Cray Y-MP EL) don't shift

   right in the usual way when A < 0, so SHR falls back on division if

   ordinary A >> B doesn't seem to be the usual signed shift.  */

#define SHR(a, b)	\

  (-1 >> 1 == -1	\

   ? (a) >> (b)		\

   : (a) / (1 << (b)) - ((a) % (1 << (b)) < 0))

/* The extra casts in the following macros work around compiler bugs,

   e.g., in Cray C 5.0.3.0.  */

/* True if the arithmetic type T is an integer type.  bool counts as

   an integer.  */

#define TYPE_IS_INTEGER(t) ((t) 1.5 == 1)

/* True if negative values of the signed integer type T use two's

   complement, ones' complement, or signed magnitude representation,

   respectively.  Much GNU code assumes two's complement, but some

   people like to be portable to all possible C hosts.  */

#define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1)

#define TYPE_ONES_COMPLEMENT(t) ((t) ~ (t) 0 == 0)

#define TYPE_SIGNED_MAGNITUDE(t) ((t) ~ (t) 0 < (t) -1)

/* True if the arithmetic type T is signed.  */

#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))

/* The maximum and minimum values for the integer type T.  These

   macros have undefined behavior if T is signed and has padding bits.

   If this is a problem for you, please let us know how to fix it for

   your host.  */

#define TYPE_MINIMUM(t) \

  ((t) (! TYPE_SIGNED (t) \

	? (t) 0 \

	: TYPE_SIGNED_MAGNITUDE (t) \

	? ~ (t) 0 \

	: ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1)))

#define TYPE_MAXIMUM(t) \

  ((t) (! TYPE_SIGNED (t) \

	? (t) -1 \

	: ~ (~ (t) 0 << (sizeof (t) * CHAR_BIT - 1))))

#ifndef TIME_T_MIN

# define TIME_T_MIN TYPE_MINIMUM (time_t)

#endif

#ifndef TIME_T_MAX

# define TIME_T_MAX TYPE_MAXIMUM (time_t)

#endif

#define TIME_T_MIDPOINT (SHR (TIME_T_MIN + TIME_T_MAX, 1) + 1)

/* Verify a requirement at compile-time (unlike assert, which is runtime).  */

#define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; }

verify (time_t_is_integer, TYPE_IS_INTEGER (time_t));

verify (twos_complement_arithmetic, TYPE_TWOS_COMPLEMENT (int));

/* The code also assumes that signed integer overflow silently wraps

   around, but this assumption can't be stated without causing a

   diagnostic on some hosts.  */

#define EPOCH_YEAR 1970

#define TM_YEAR_BASE 1900

verify (base_year_is_a_multiple_of_100, TM_YEAR_BASE % 100 == 0);

/* Return 1 if YEAR + TM_YEAR_BASE is a leap year.  */

static inline int

leapyear (long int year)

{

  /* Don't add YEAR to TM_YEAR_BASE, as that might overflow.

     Also, work even if YEAR is negative.  */

  return

    ((year & 3) == 0

     && (year % 100 != 0

	 || ((year / 100) & 3) == (- (TM_YEAR_BASE / 100) & 3)));

}

/* How many days come before each month (0-12).  */

#ifndef _LIBC

static

#endif

const unsigned short int __mon_yday[2][13] =

  {

    /* Normal years.  */

    { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 },

    /* Leap years.  */

    { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 }

  };

#ifndef _LIBC

/* Portable standalone applications should supply a <time.h> that

   declares a POSIX-compliant localtime_r, for the benefit of older

   implementations that lack localtime_r or have a nonstandard one.

   See the gnulib time_r module for one way to implement this.  */

# undef __localtime_r

# define __localtime_r localtime_r

# define __mktime_internal mktime_internal

#endif

/* Return an integer value measuring (YEAR1-YDAY1 HOUR1:MIN1:SEC1) -

   (YEAR0-YDAY0 HOUR0:MIN0:SEC0) in seconds, assuming that the clocks

   were not adjusted between the time stamps.

   The YEAR values uses the same numbering as TP->tm_year.  Values

   need not be in the usual range.  However, YEAR1 must not be less

   than 2 * INT_MIN or greater than 2 * INT_MAX.

   The result may overflow.  It is the caller's responsibility to

   detect overflow.  */

static inline time_t

ydhms_diff (long int year1, long int yday1, int hour1, int min1, int sec1,

	    int year0, int yday0, int hour0, int min0, int sec0)

{

  verify (C99_integer_division, -1 / 2 == 0);

  verify (long_int_year_and_yday_are_wide_enough,

	  INT_MAX <= LONG_MAX / 2 || TIME_T_MAX <= UINT_MAX);

  /* Compute intervening leap days correctly even if year is negative.

     Take care to avoid integer overflow here.  */

  int a4 = SHR (year1, 2) + SHR (TM_YEAR_BASE, 2) - ! (year1 & 3);

  int b4 = SHR (year0, 2) + SHR (TM_YEAR_BASE, 2) - ! (year0 & 3);

  int a100 = a4 / 25 - (a4 % 25 < 0);

  int b100 = b4 / 25 - (b4 % 25 < 0);

  int a400 = SHR (a100, 2);

  int b400 = SHR (b100, 2);

  int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400);

  /* Compute the desired time in time_t precision.  Overflow might

     occur here.  */

  time_t tyear1 = year1;

  time_t years = tyear1 - year0;

  time_t days = 365 * years + yday1 - yday0 + intervening_leap_days;

  time_t hours = 24 * days + hour1 - hour0;

  time_t minutes = 60 * hours + min1 - min0;

  time_t seconds = 60 * minutes + sec1 - sec0;

  return seconds;

}

/* Return a time_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC),

   assuming that *T corresponds to *TP and that no clock adjustments

   occurred between *TP and the desired time.

   If TP is null, return a value not equal to *T; this avoids false matches.

   If overflow occurs, yield the minimal or maximal value, except do not

   yield a value equal to *T.  */

static time_t

guess_time_tm (long int year, long int yday, int hour, int min, int sec,

	       const time_t *t, const struct tm *tp)

{

  if (tp)

    {

      time_t d = ydhms_diff (year, yday, hour, min, sec,

			     tp->tm_year, tp->tm_yday,

			     tp->tm_hour, tp->tm_min, tp->tm_sec);

      time_t t1 = *t + d;

      if ((t1 < *t) == (TYPE_SIGNED (time_t) ? d < 0 : TIME_T_MAX / 2 < d))

	return t1;

    }

  /* Overflow occurred one way or another.  Return the nearest result

     that is actually in range, except don't report a zero difference

     if the actual difference is nonzero, as that would cause a false

     match; and don't oscillate between two values, as that would

     confuse the spring-forward gap detector.  */

  return (*t < TIME_T_MIDPOINT

	  ? (*t <= TIME_T_MIN + 1 ? *t + 1 : TIME_T_MIN)

	  : (TIME_T_MAX - 1 <= *t ? *t - 1 : TIME_T_MAX));

}

/* Use CONVERT to convert *T to a broken down time in *TP.

   If *T is out of range for conversion, adjust it so that

   it is the nearest in-range value and then convert that.  */

static struct tm *

ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),

		time_t *t, struct tm *tp)

{

  struct tm *r = convert (t, tp);

  if (!r && *t)

    {

      time_t bad = *t;

      time_t ok = 0;

      /* BAD is a known unconvertible time_t, and OK is a known good one.

	 Use binary search to narrow the range between BAD and OK until

	 they differ by 1.  */

      while (bad != ok + (bad < 0 ? -1 : 1))

	{

	  time_t mid = *t = (bad < 0

			     ? bad + ((ok - bad) >> 1)

			     : ok + ((bad - ok) >> 1));

	  r = convert (t, tp);

	  if (r)

	    ok = mid;

	  else

	    bad = mid;

	}

      if (!r && ok)

	{

	  /* The last conversion attempt failed;

	     revert to the most recent successful attempt.  */

	  *t = ok;

	  r = convert (t, tp);

	}

    }

  return r;

}

extern time_t

__mktime_internal (struct tm *tp,

		   struct tm *(*convert) (const time_t *, struct tm *),

		   time_t *offset);

/* Convert *TP to a time_t value, inverting

   the monotonic and mostly-unit-linear conversion function CONVERT.

   Use *OFFSET to keep track of a guess at the offset of the result,

   compared to what the result would be for UTC without leap seconds.

   If *OFFSET's guess is correct, only one CONVERT call is needed.

   This function is external because it is used also by timegm.c.  */

time_t

__mktime_internal (struct tm *tp,

		   struct tm *(*convert) (const time_t *, struct tm *),

		   time_t *offset)

{

  time_t t, gt, t0, t1, t2;

  struct tm tm;

  /* The maximum number of probes (calls to CONVERT) should be enough

     to handle any combinations of time zone rule changes, solar time,

     leap seconds, and oscillations around a spring-forward gap.

     POSIX.1 prohibits leap seconds, but some hosts have them anyway.  */

  int remaining_probes = 6;

  /* Time requested.  Copy it in case CONVERT modifies *TP; this can

     occur if TP is localtime's returned value and CONVERT is localtime.  */

  int sec = tp->tm_sec;

  int min = tp->tm_min;

  int hour = tp->tm_hour;

  int mday = tp->tm_mday;

  int mon = tp->tm_mon;

  int year_requested = tp->tm_year;

  /* Normalize the value.  */

  int isdst = ((tp->tm_isdst >> (8 * sizeof (tp->tm_isdst) - 1))

	       | (tp->tm_isdst != 0));

  /* 1 if the previous probe was DST.  */

  int dst2;

  /* Ensure that mon is in range, and set year accordingly.  */

  int mon_remainder = mon % 12;

  int negative_mon_remainder = mon_remainder < 0;

  int mon_years = mon / 12 - negative_mon_remainder;

  long int lyear_requested = year_requested;

  long int year = lyear_requested + mon_years;

  /* The other values need not be in range:

     the remaining code handles minor overflows correctly,

     assuming int and time_t arithmetic wraps around.

     Major overflows are caught at the end.  */

  /* Calculate day of year from year, month, and day of month.

     The result need not be in range.  */

  int mon_yday = ((__mon_yday[leapyear (year)]

		   [mon_remainder + 12 * negative_mon_remainder])

		  - 1);

  long int lmday = mday;

  long int yday = mon_yday + lmday;

  time_t guessed_offset = *offset;

  int sec_requested = sec;

  if (LEAP_SECONDS_POSSIBLE)

    {

      /* Handle out-of-range seconds specially,

	 since ydhms_tm_diff assumes every minute has 60 seconds.  */

      if (sec < 0)

	sec = 0;

      if (59 < sec)

	sec = 59;

    }

  /* Invert CONVERT by probing.  First assume the same offset as last

     time.  */

  t0 = ydhms_diff (year, yday, hour, min, sec,

		   EPOCH_YEAR - TM_YEAR_BASE, 0, 0, 0, - guessed_offset);

  if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3)

    {

      /* time_t isn't large enough to rule out overflows, so check

	 for major overflows.  A gross check suffices, since if t0

	 has overflowed, it is off by a multiple of TIME_T_MAX -

	 TIME_T_MIN + 1.  So ignore any component of the difference

	 that is bounded by a small value.  */

      /* Approximate log base 2 of the number of time units per

	 biennium.  A biennium is 2 years; use this unit instead of

	 years to avoid integer overflow.  For example, 2 average

	 Gregorian years are 2 * 365.2425 * 24 * 60 * 60 seconds,

	 which is 63113904 seconds, and rint (log2 (63113904)) is

	 26.  */

      int ALOG2_SECONDS_PER_BIENNIUM = 26;

      int ALOG2_MINUTES_PER_BIENNIUM = 20;

      int ALOG2_HOURS_PER_BIENNIUM = 14;

      int ALOG2_DAYS_PER_BIENNIUM = 10;

      int LOG2_YEARS_PER_BIENNIUM = 1;

      int approx_requested_biennia =

	(SHR (year_requested, LOG2_YEARS_PER_BIENNIUM)

	 - SHR (EPOCH_YEAR - TM_YEAR_BASE, LOG2_YEARS_PER_BIENNIUM)

	 + SHR (mday, ALOG2_DAYS_PER_BIENNIUM)

	 + SHR (hour, ALOG2_HOURS_PER_BIENNIUM)

	 + SHR (min, ALOG2_MINUTES_PER_BIENNIUM)

	 + (LEAP_SECONDS_POSSIBLE

	    ? 0

	    : SHR (sec, ALOG2_SECONDS_PER_BIENNIUM)));

      int approx_biennia = SHR (t0, ALOG2_SECONDS_PER_BIENNIUM);

      int diff = approx_biennia - approx_requested_biennia;

      int abs_diff = diff < 0 ? - diff : diff;

      /* IRIX 4.0.5 cc miscaculates TIME_T_MIN / 3: it erroneously

	 gives a positive value of 715827882.  Setting a variable

	 first then doing math on it seems to work.

	 (ghazi@caip.rutgers.edu) */

      time_t time_t_max = TIME_T_MAX;

      time_t time_t_min = TIME_T_MIN;

      time_t overflow_threshold =

	(time_t_max / 3 - time_t_min / 3) >> ALOG2_SECONDS_PER_BIENNIUM;

      if (overflow_threshold < abs_diff)

	{

	  /* Overflow occurred.  Try repairing it; this might work if

	     the time zone offset is enough to undo the overflow.  */

	  time_t repaired_t0 = -1 - t0;

	  approx_biennia = SHR (repaired_t0, ALOG2_SECONDS_PER_BIENNIUM);

	  diff = approx_biennia - approx_requested_biennia;

	  abs_diff = diff < 0 ? - diff : diff;

	  if (overflow_threshold < abs_diff)

	    return -1;

	  guessed_offset += repaired_t0 - t0;

	  t0 = repaired_t0;

	}

    }

  /* Repeatedly use the error to improve the guess.  */

  for (t = t1 = t2 = t0, dst2 = 0;

       (gt = guess_time_tm (year, yday, hour, min, sec, &t,

			    ranged_convert (convert, &t, &tm)),

	t != gt);

       t1 = t2, t2 = t, t = gt, dst2 = tm.tm_isdst != 0)

    if (t == t1 && t != t2

	&& (tm.tm_isdst < 0

	    || (isdst < 0

		? dst2 <= (tm.tm_isdst != 0)

		: (isdst != 0) != (tm.tm_isdst != 0))))

      /* We can't possibly find a match, as we are oscillating

	 between two values.  The requested time probably falls

	 within a spring-forward gap of size GT - T.  Follow the common

	 practice in this case, which is to return a time that is GT - T

	 away from the requested time, preferring a time whose

	 tm_isdst differs from the requested value.  (If no tm_isdst

	 was requested and only one of the two values has a nonzero

	 tm_isdst, prefer that value.)  In practice, this is more

	 useful than returning -1.  */

      goto offset_found;

    else if (--remaining_probes == 0)

      return -1;

  /* We have a match.  Check whether tm.tm_isdst has the requested

     value, if any.  */

  if (isdst != tm.tm_isdst && 0 <= isdst && 0 <= tm.tm_isdst)

    {

      /* tm.tm_isdst has the wrong value.  Look for a neighboring

	 time with the right value, and use its UTC offset.

	 Heuristic: probe the adjacent timestamps in both directions,

	 looking for the desired isdst.  This should work for all real

	 time zone histories in the tz database.  */

      /* Distance between probes when looking for a DST boundary.  In

	 tzdata2003a, the shortest period of DST is 601200 seconds

	 (e.g., America/Recife starting 2000-10-08 01:00), and the

	 shortest period of non-DST surrounded by DST is 694800

	 seconds (Africa/Tunis starting 1943-04-17 01:00).  Use the

	 minimum of these two values, so we don't miss these short

	 periods when probing.  */

      int stride = 601200;

      /* The longest period of DST in tzdata2003a is 536454000 seconds

	 (e.g., America/Jujuy starting 1946-10-01 01:00).  The longest

	 period of non-DST is much longer, but it makes no real sense

	 to search for more than a year of non-DST, so use the DST

	 max.  */

      int duration_max = 536454000;

      /* Search in both directions, so the maximum distance is half

	 the duration; add the stride to avoid off-by-1 problems.  */

      int delta_bound = duration_max / 2 + stride;

      int delta, direction;

      for (delta = stride; delta < delta_bound; delta += stride)

	for (direction = -1; direction <= 1; direction += 2)

	  {

	    time_t ot = t + delta * direction;

	    if ((ot < t) == (direction < 0))

	      {

		struct tm otm;

		ranged_convert (convert, &ot, &otm);

		if (otm.tm_isdst == isdst)

		  {

		    /* We found the desired tm_isdst.

		       Extrapolate back to the desired time.  */

		    t = guess_time_tm (year, yday, hour, min, sec, &ot, &otm);

		    ranged_convert (convert, &t, &tm);

		    goto offset_found;

		  }

	      }

	  }

    }

 offset_found:

  *offset = guessed_offset + t - t0;

  if (LEAP_SECONDS_POSSIBLE && sec_requested != tm.tm_sec)

    {

      /* Adjust time to reflect the tm_sec requested, not the normalized value.

	 Also, repair any damage from a false match due to a leap second.  */

      int sec_adjustment = (sec == 0 && tm.tm_sec == 60) - sec;

      t1 = t + sec_requested;

      t2 = t1 + sec_adjustment;

      if (((t1 < t) != (sec_requested < 0))

	  | ((t2 < t1) != (sec_adjustment < 0))

	  | ! convert (&t2, &tm))

	return -1;

      t = t2;

    }

  *tp = tm;

  return t;

}

/* FIXME: This should use a signed type wide enough to hold any UTC

   offset in seconds.  'int' should be good enough for GNU code.  We

   can't fix this unilaterally though, as other modules invoke

   __mktime_internal.  */

static time_t localtime_offset;

/* Convert *TP to a time_t value.  */

time_t

mktime (struct tm *tp)

{

#ifdef _LIBC

  /* POSIX.1 8.1.1 requires that whenever mktime() is called, the

     time zone names contained in the external variable `tzname' shall

     be set as if the tzset() function had been called.  */

  __tzset ();

#endif

  return __mktime_internal (tp, __localtime_r, &localtime_offset);

}

#ifdef weak_alias

weak_alias (mktime, timelocal)

#endif

#ifdef _LIBC

libc_hidden_def (mktime)

libc_hidden_weak (timelocal)

#endif