/* Convert a `struct tm' to a time_t value.
- Copyright (C) 1993-1999, 2002, 2003, 2004 Free Software Foundation, Inc.
+ 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).
+ 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
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. */
+ Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
/* 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
# 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. */
# define mktime my_mktime
#endif /* DEBUG */
-/* The extra casts work around common compiler bugs. */
+/* 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 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_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)
#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)
+#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, (time_t) 0.5 == 0);
-verify (twos_complement_arithmetic, -1 == ~1 + 1);
-verify (right_shift_propagates_sign, -1 >> 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. */
#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
/* 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
/* 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
time_t mid = *t = (bad < 0
? bad + ((ok - bad) >> 1)
: ok + ((bad - ok) >> 1));
- if ((r = (*convert) (t, tp)))
- {
- tm = *r;
- ok = mid;
- }
+ 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 mday = tp->tm_mday;
int mon = tp->tm_mon;
int year_requested = tp->tm_year;
- int isdst = tp->tm_isdst;
+ /* 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;
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;
/* 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)
t2 = t1 + sec_adjustment;
if (((t1 < t) != (sec_requested < 0))
| ((t2 < t1) != (sec_adjustment < 0))
- | ! (*convert) (&t, &tm))
+ | ! convert (&t2, &tm))
return -1;
+ t = t2;
}
*tp = tm;
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