-/* Convert a `struct tm' to a time_t value.
- Copyright (C) 1993-1999, 2002, 2003, 2004 Free Software Foundation, Inc.
+/* Convert a 'struct tm' to a time_t value.
+ Copyright (C) 1993-2013 Free Software Foundation, Inc.
This file is part of the GNU C Library.
- Contributed by Paul Eggert (eggert@twinsun.com).
+ 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 General Public License as published by
- the Free Software Foundation; either version 2, or (at your option)
- any later version.
+ 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.
- This program is distributed in the hope that it will be useful,
+ 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 General Public License for more details.
+ 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 General Public License along
- with this program; if not, write to the Free Software Foundation,
- Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
/* Define this to have a standalone program to test this implementation of
mktime. */
/* #define DEBUG 1 */
-#ifdef HAVE_CONFIG_H
+#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,
+ 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 <sys/types.h> /* Some systems define `time_t' here. */
#include <time.h>
#include <limits.h>
+#include <string.h> /* For the real memcpy prototype. */
+
#if DEBUG
# include <stdio.h>
# include <stdlib.h>
-# include <string.h>
/* Make it work even if the system's libc has its own mktime routine. */
+# undef mktime
# define mktime my_mktime
#endif /* DEBUG */
-/* The extra casts work around common compiler bugs. */
+/* Some of the code in this file assumes that signed integer overflow
+ silently wraps around. This assumption can't easily be programmed
+ around, nor can it be checked for portably at compile-time or
+ easily eliminated at run-time.
+
+ Define WRAPV to 1 if the assumption is valid and if
+ #pragma GCC optimize ("wrapv")
+ does not trigger GCC bug 51793
+ <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51793>.
+ Otherwise, define it to 0; this forces the use of slower code that,
+ while not guaranteed by the C Standard, works on all production
+ platforms that we know about. */
+#ifndef WRAPV
+# if (((__GNUC__ == 4 && 4 <= __GNUC_MINOR__) || 4 < __GNUC__) \
+ && defined __GLIBC__)
+# pragma GCC optimize ("wrapv")
+# define WRAPV 1
+# else
+# define WRAPV 0
+# endif
+#endif
+
+/* Verify a requirement at compile-time (unlike assert, which is runtime). */
+#define verify(name, assertion) struct name { char a[(assertion) ? 1 : -1]; }
+
+/* A signed type that is at least one bit wider than int. */
+#if INT_MAX <= LONG_MAX / 2
+typedef long int long_int;
+#else
+typedef long long int long_int;
+#endif
+verify (long_int_is_wide_enough, INT_MAX == INT_MAX * (long_int) 2 / 2);
+
+/* 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 \
+ && (long_int) -1 >> 1 == -1 \
+ && ((time_t) -1 >> 1 == -1 || ! TYPE_SIGNED (time_t))) \
+ ? (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, or if T is an unsigned integer type. */
+#define TYPE_TWOS_COMPLEMENT(t) ((t) ~ (t) 0 == (t) -1)
+
+/* True if the arithmetic type T is signed. */
#define TYPE_SIGNED(t) (! ((t) 0 < (t) -1))
-/* The outer cast is needed to work around a bug in Cray C 5.0.3.0.
- It is necessary at least when t == time_t. */
-#define TYPE_MINIMUM(t) ((t) (TYPE_SIGNED (t) \
- ? ~ (t) 0 << (sizeof (t) * CHAR_BIT - 1) : (t) 0))
-#define TYPE_MAXIMUM(t) ((t) (~ (t) 0 - TYPE_MINIMUM (t)))
+
+/* 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_MAXIMUM (t)))
+#define TYPE_MAXIMUM(t) \
+ ((t) (! TYPE_SIGNED (t) \
+ ? (t) -1 \
+ : ((((t) 1 << (sizeof (t) * CHAR_BIT - 2)) - 1) * 2 + 1)))
#ifndef TIME_T_MIN
# define TIME_T_MIN TYPE_MINIMUM (time_t)
#ifndef TIME_T_MAX
# define TIME_T_MAX TYPE_MAXIMUM (time_t)
#endif
-#define TIME_T_MIDPOINT (((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]; }
+#define TIME_T_MIDPOINT (SHR (TIME_T_MIN + TIME_T_MAX, 1) + 1)
-verify (time_t_is_integer, (time_t) 0.5 == 0);
-verify (twos_complement_arithmetic, -1 == ~1 + 1);
-verify (right_shift_propagates_sign, -1 >> 1 == -1);
-/* 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. */
+verify (time_t_is_integer, TYPE_IS_INTEGER (time_t));
+verify (twos_complement_arithmetic,
+ (TYPE_TWOS_COMPLEMENT (int)
+ && TYPE_TWOS_COMPLEMENT (long_int)
+ && TYPE_TWOS_COMPLEMENT (time_t)));
#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)
+static int
+leapyear (long_int year)
{
/* Don't add YEAR to TM_YEAR_BASE, as that might overflow.
Also, work even if YEAR is negative. */
#ifndef _LIBC
-/* Portable standalone applications should supply a "time_r.h" that
+/* 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. */
-# include "time_r.h"
# undef __localtime_r
# define __localtime_r localtime_r
# define __mktime_internal mktime_internal
+# include "mktime-internal.h"
#endif
+/* Return 1 if the values A and B differ according to the rules for
+ tm_isdst: A and B differ if one is zero and the other positive. */
+static int
+isdst_differ (int a, int b)
+{
+ return (!a != !b) && (0 <= a) && (0 <= b);
+}
+
/* 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 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,
+static 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 = (year1 >> 2) + (TM_YEAR_BASE >> 2) - ! (year1 & 3);
- int b4 = (year0 >> 2) + (TM_YEAR_BASE >> 2) - ! (year0 & 3);
+ 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 = a100 >> 2;
- int b400 = b100 >> 2;
+ 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
return seconds;
}
+/* Return the average of A and B, even if A + B would overflow. */
+static time_t
+time_t_avg (time_t a, time_t b)
+{
+ return SHR (a, 1) + SHR (b, 1) + (a & b & 1);
+}
+
+/* Return 1 if A + B does not overflow. If time_t is unsigned and if
+ B's top bit is set, assume that the sum represents A - -B, and
+ return 1 if the subtraction does not wrap around. */
+static int
+time_t_add_ok (time_t a, time_t b)
+{
+ if (! TYPE_SIGNED (time_t))
+ {
+ time_t sum = a + b;
+ return (sum < a) == (TIME_T_MIDPOINT <= b);
+ }
+ else if (WRAPV)
+ {
+ time_t sum = a + b;
+ return (sum < a) == (b < 0);
+ }
+ else
+ {
+ time_t avg = time_t_avg (a, b);
+ return TIME_T_MIN / 2 <= avg && avg <= TIME_T_MAX / 2;
+ }
+}
+
+/* Return 1 if A + B does not overflow. */
+static int
+time_t_int_add_ok (time_t a, int b)
+{
+ verify (int_no_wider_than_time_t, INT_MAX <= TIME_T_MAX);
+ if (WRAPV)
+ {
+ time_t sum = a + b;
+ return (sum < a) == (b < 0);
+ }
+ else
+ {
+ int a_odd = a & 1;
+ time_t avg = SHR (a, 1) + (SHR (b, 1) + (a_odd & b));
+ return TIME_T_MIN / 2 <= avg && avg <= TIME_T_MAX / 2;
+ }
+}
/* Return a time_t value corresponding to (YEAR-YDAY HOUR:MIN:SEC),
assuming that *T corresponds to *TP and that no clock adjustments
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,
+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;
+ if (time_t_add_ok (*t, d))
+ return *t + d;
}
/* 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. */
+ match; and don't oscillate between two values, as that would
+ confuse the spring-forward gap detector. */
return (*t < TIME_T_MIDPOINT
- ? TIME_T_MIN + (*t == TIME_T_MIN)
- : TIME_T_MAX - (*t == TIME_T_MAX));
+ ? (*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.
ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
time_t *t, struct tm *tp)
{
- struct tm *r;
+ struct tm *r = convert (t, tp);
- if (! (r = (*convert) (t, tp)) && *t)
+ if (!r && *t)
{
time_t bad = *t;
time_t ok = 0;
- struct tm tm;
/* 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));
- if ((r = (*convert) (t, tp)))
- {
- tm = *r;
- ok = mid;
- }
+ time_t mid = *t = time_t_avg (ok, bad);
+ r = convert (t, tp);
+ if (r)
+ ok = mid;
else
bad = mid;
}
/* The last conversion attempt failed;
revert to the most recent successful attempt. */
*t = ok;
- *tp = tm;
- r = tp;
+ r = convert (t, tp);
}
}
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;
+ 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,
int mon_yday = ((__mon_yday[leapyear (year)]
[mon_remainder + 12 * negative_mon_remainder])
- 1);
- long int lmday = mday;
- long int yday = mon_yday + lmday;
+ long_int lmday = mday;
+ long_int yday = mon_yday + lmday;
time_t guessed_offset = *offset;
int LOG2_YEARS_PER_BIENNIUM = 1;
int approx_requested_biennia =
- ((year_requested >> LOG2_YEARS_PER_BIENNIUM)
- - ((EPOCH_YEAR - TM_YEAR_BASE) >> LOG2_YEARS_PER_BIENNIUM)
- + (mday >> ALOG2_DAYS_PER_BIENNIUM)
- + (hour >> ALOG2_HOURS_PER_BIENNIUM)
- + (min >> ALOG2_MINUTES_PER_BIENNIUM)
- + (LEAP_SECONDS_POSSIBLE ? 0 : sec >> ALOG2_SECONDS_PER_BIENNIUM));
-
- int approx_biennia = t0 >> ALOG2_SECONDS_PER_BIENNIUM;
+ (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;
+ int approx_abs_diff = diff < 0 ? -1 - diff : diff;
- /* IRIX 4.0.5 cc miscaculates TIME_T_MIN / 3: it erroneously
+ /* IRIX 4.0.5 cc miscalculates 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 overflow_threshold =
(time_t_max / 3 - time_t_min / 3) >> ALOG2_SECONDS_PER_BIENNIUM;
- if (overflow_threshold < abs_diff)
+ if (overflow_threshold < approx_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 = repaired_t0 >> ALOG2_SECONDS_PER_BIENNIUM;
+ 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)
+ approx_abs_diff = diff < 0 ? -1 - diff : diff;
+ if (overflow_threshold < approx_abs_diff)
return -1;
guessed_offset += repaired_t0 - t0;
t0 = repaired_t0;
/* 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)
+ if (isdst_differ (isdst, tm.tm_isdst))
{
/* tm.tm_isdst has the wrong value. Look for a neighboring
time with the right value, and use its UTC offset.
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;
- }
- }
- }
+ if (time_t_int_add_ok (t, delta * direction))
+ {
+ time_t ot = t + delta * direction;
+ struct tm otm;
+ ranged_convert (convert, &ot, &otm);
+ if (! isdst_differ (isdst, otm.tm_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:
/* 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;
+ if (! time_t_int_add_ok (t, sec_requested))
+ return -1;
t1 = t + sec_requested;
+ if (! time_t_int_add_ok (t1, sec_adjustment))
+ return -1;
t2 = t1 + sec_adjustment;
- if (((t1 < t) != (sec_requested < 0))
- | ((t2 < t1) != (sec_adjustment < 0))
- | ! (*convert) (&t, &tm))
+ if (! convert (&t2, &tm))
return -1;
+ t = t2;
}
*tp = tm;
{
#ifdef _LIBC
/* POSIX.1 8.1.1 requires that whenever mktime() is called, the
- time zone names contained in the external variable `tzname' shall
+ time zone names contained in the external variable 'tzname' shall
be set as if the tzset() function had been called. */
__tzset ();
#endif
| (a->tm_mon ^ b->tm_mon)
| (a->tm_year ^ b->tm_year)
| (a->tm_yday ^ b->tm_yday)
- | (a->tm_isdst ^ b->tm_isdst));
+ | isdst_differ (a->tm_isdst, b->tm_isdst));
}
static void
\f
/*
Local Variables:
-compile-command: "gcc -DDEBUG -Wall -W -O -g mktime.c -o mktime"
+compile-command: "gcc -DDEBUG -I. -Wall -W -O2 -g mktime.c -o mktime"
End:
*/
projects / gnulib.git / blobdiff