-/* mktime: convert a `struct tm' to a time_t value zzzzzz
- Copyright (C) 1993-1997, 1998 Free Software Foundation, Inc.
+/* mktime: convert a `struct tm' to a time_t value
+ Copyright (C) 1993-1998, 1999 Free Software Foundation, Inc.
Contributed by Paul Eggert (eggert@twinsun.com).
NOTE: The canonical source of this file is maintained with the GNU C Library.
# include <config.h>
#endif
-/* Some systems need this in order to declare localtime_r properly. */
-#ifndef __EXTENSIONS__
-# define __EXTENSIONS__ 1
-#endif
-
#ifdef _LIBC
# define HAVE_LIMITS_H 1
-# define HAVE_LOCALTIME_R 1
# define STDC_HEADERS 1
#endif
# define LEAP_SECONDS_POSSIBLE 1
#endif
-/* Some systems require <unistd.h> to be included before <time.h>
- for localtime_r to be declared properly. */
-#if HAVE_UNISTD_H
-# include <unistd.h>
-#endif
-
#include <sys/types.h> /* Some systems define `time_t' here. */
#include <time.h>
#endif /* DEBUG */
#ifndef __P
-# if defined (__GNUC__) || (defined (__STDC__) && __STDC__)
+# if defined __GNUC__ || (defined __STDC__ && __STDC__)
# define __P(args) args
# else
# define __P(args) ()
#ifdef _LIBC
-# define localtime_r __localtime_r
+# define my_mktime_localtime_r __localtime_r
#else
-# if HAVE_LOCALTIME_R == defined localtime_r
-/* Provide our own substitute for a missing or possibly broken localtime_r. */
+/* If we're a mktime substitute in a GNU program, then prefer
+ localtime to localtime_r, since many localtime_r implementations
+ are buggy. */
static struct tm *my_mktime_localtime_r __P ((const time_t *, struct tm *));
static struct tm *
-my_mktime_localtime_r (t, tp)
- const time_t *t;
- struct tm *tp;
+my_mktime_localtime_r (const time_t *t, struct tm *tp)
{
-# ifdef localtime_r
- /* Digital Unix 4.0A and 4.0D have a macro localtime_r with the
- standard meaning, along with an unwanted, nonstandard function
- localtime_r. The placeholder function my_mktime_localtime_r
- invokes the macro; use that instead of the system's bogus
- localtime_r. */
- return localtime_r (t, tp);
-# undef localtime_r
-# else /* ! defined (localtime_r) */
- /* Approximate localtime_r as best we can in its absence. */
struct tm *l = localtime (t);
if (! l)
return 0;
*tp = *l;
return tp;
-# endif /* ! defined localtime_r */
}
-# define localtime_r my_mktime_localtime_r
-# endif /* HAVE_LOCALTIME_R == defined localtime_r */
#endif /* ! _LIBC */
If TP is null, return a nonzero value.
If overflow occurs, yield the low order bits of the correct answer. */
static time_t
-ydhms_tm_diff (year, yday, hour, min, sec, tp)
- int year, yday, hour, min, sec;
- const struct tm *tp;
+ydhms_tm_diff (int year, int yday, int hour, int min, int sec,
+ const struct tm *tp)
{
if (!tp)
return 1;
/* Convert *TP to a time_t value. */
time_t
-mktime (tp)
- struct tm *tp;
+mktime (struct tm *tp)
{
#ifdef _LIBC
/* POSIX.1 8.1.1 requires that whenever mktime() is called, the
__tzset ();
#endif
- return __mktime_internal (tp, localtime_r, &localtime_offset);
+ return __mktime_internal (tp, my_mktime_localtime_r, &localtime_offset);
}
/* 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 (convert, t, tp)
- struct tm *(*convert) __P ((const time_t *, struct tm *));
- time_t *t;
- struct tm *tp;
+ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
+ time_t *t, struct tm *tp)
{
struct tm *r;
compared to what the result would be for UTC without leap seconds.
If *OFFSET's guess is correct, only one CONVERT call is needed. */
time_t
-__mktime_internal (tp, convert, offset)
- struct tm *tp;
- struct tm *(*convert) __P ((const time_t *, struct tm *));
- time_t *offset;
+__mktime_internal (struct tm *tp,
+ struct tm *(*convert) (const time_t *, struct tm *),
+ time_t *offset)
{
time_t t, dt, t0, t1, t2;
struct tm tm;
/* If we have a match, check whether tm.tm_isdst has the requested
value, if any. */
- if (dt == 0 && 0 <= isdst && 0 <= tm.tm_isdst)
+ if (dt == 0 && isdst != tm.tm_isdst && 0 <= isdst && 0 <= tm.tm_isdst)
{
- int dst_diff = (isdst != 0) - (tm.tm_isdst != 0);
- if (dst_diff)
+ /* tm.tm_isdst has the wrong value. Look for a neighboring
+ time with the right value, and use its UTC offset.
+ Heuristic: probe the previous three calendar quarters (approximately),
+ looking for the desired isdst. This isn't perfect,
+ but it's good enough in practice. */
+ int quarter = 7889238; /* seconds per average 1/4 Gregorian year */
+ int i;
+
+ /* If we're too close to the time_t limit, look in future quarters. */
+ if (t < TIME_T_MIN + 3 * quarter)
+ quarter = -quarter;
+
+ for (i = 1; i <= 3; i++)
{
- /* Move two hours in the direction indicated by the disagreement,
- probe some more, and switch to a new time if found.
- The largest known fallback due to daylight savings is two hours:
- once, in Newfoundland, 1988-10-30 02:00 -> 00:00. */
- time_t ot = t - 2 * 60 * 60 * dst_diff;
- while (--remaining_probes != 0)
+ time_t ot = t - i * quarter;
+ struct tm otm;
+ ranged_convert (convert, &ot, &otm);
+ if (otm.tm_isdst == isdst)
{
- struct tm otm;
- if (! (dt = ydhms_tm_diff (year, yday, hour, min, sec,
- ranged_convert (convert, &ot, &otm))))
- {
- t = ot;
- tm = otm;
- break;
- }
- if ((ot += dt) == t)
- break; /* Avoid a redundant probe. */
+ /* We found the desired tm_isdst.
+ Extrapolate back to the desired time. */
+ t = ot + ydhms_tm_diff (year, yday, hour, min, sec, &otm);
+ ranged_convert (convert, &t, &tm);
+ break;
}
}
}
\f
/*
Local Variables:
-compile-command: "gcc -DDEBUG -D__EXTENSIONS__ -DHAVE_LIMITS_H -DHAVE_LOCALTIME_R -DSTDC_HEADERS -Wall -W -O -g mktime.c -o mktime"
+compile-command: "gcc -DDEBUG -DHAVE_LIMITS_H -DSTDC_HEADERS -Wall -W -O -g mktime.c -o mktime"
End:
*/
projects / gnulib.git / blobdiff