-/* Copyright (C) 1993, 1994, 1995, 1996, 1997 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.
#ifdef _LIBC
# define HAVE_LIMITS_H 1
-# define HAVE_LOCALTIME_R 1
# define STDC_HEADERS 1
#endif
#endif /* DEBUG */
#ifndef __P
-# if defined (__GNUC__) || (defined (__STDC__) && __STDC__)
+# if defined __GNUC__ || (defined __STDC__ && __STDC__)
# define __P(args) args
# else
# define __P(args) ()
# define CHAR_BIT 8
#endif
+/* The extra casts work around common compiler bugs. */
+#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)))
+
#ifndef INT_MIN
-# define INT_MIN (~0 << (sizeof (int) * CHAR_BIT - 1))
+# define INT_MIN TYPE_MINIMUM (int)
#endif
#ifndef INT_MAX
-# define INT_MAX (~0 - INT_MIN)
+# define INT_MAX TYPE_MAXIMUM (int)
#endif
#ifndef TIME_T_MIN
-/* The outer cast to time_t works around a bug in Cray C 5.0.3.0. */
-# define TIME_T_MIN ((time_t) \
- (0 < (time_t) -1 ? (time_t) 0 \
- : ~ (time_t) 0 << (sizeof (time_t) * CHAR_BIT - 1)))
+# define TIME_T_MIN TYPE_MINIMUM (time_t)
#endif
#ifndef TIME_T_MAX
-# define TIME_T_MAX (~ (time_t) 0 - TIME_T_MIN)
+# define TIME_T_MAX TYPE_MAXIMUM (time_t)
#endif
#define TM_YEAR_BASE 1900
#ifdef _LIBC
-# define localtime_r __localtime_r
+# define my_mktime_localtime_r __localtime_r
#else
-# if ! HAVE_LOCALTIME_R && ! defined localtime_r
-/* Approximate localtime_r as best we can in its absence. */
-# define localtime_r my_mktime_localtime_r
-static struct tm *localtime_r __P ((const time_t *, struct tm *));
+/* 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 *
-localtime_r (t, tp)
- const time_t *t;
- struct tm *tp;
+my_mktime_localtime_r (const time_t *t, struct tm *tp)
{
struct tm *l = localtime (t);
if (! l)
*tp = *l;
return tp;
}
-# 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;
+ time_t t, dt, 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,
- and leap seconds. POSIX.1 prohibits leap seconds, but some hosts
- have them anyway. */
- int remaining_probes = 4;
+ 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. */
tm.tm_yday = tm.tm_hour = tm.tm_min = tm.tm_sec = 0;
t0 = ydhms_tm_diff (year, yday, hour, min, sec, &tm);
- for (t = t0 + *offset;
+ for (t = t1 = t2 = t0 + *offset;
(dt = ydhms_tm_diff (year, yday, hour, min, sec,
ranged_convert (convert, &t, &tm)));
- t += dt)
- if (--remaining_probes == 0)
+ t1 = t2, t2 = t, t += dt)
+ if (t == t1 && t != t2
+ && (isdst < 0 || 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 DT. Follow the common
+ practice in this case, which is to return a time that is DT
+ away from the requested time, preferring a time whose
+ tm_isdst differs from the requested value. In practice,
+ this is more useful than returning -1. */
+ break;
+ else if (--remaining_probes == 0)
return -1;
- /* Check whether tm.tm_isdst has the requested value, if any. */
- if (0 <= isdst && 0 <= tm.tm_isdst)
+ /* If we have a match, check whether tm.tm_isdst has the requested
+ value, if any. */
+ 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;
}
}
}
double dday = 366 * dyear + mday;
double dsec = 60 * (60 * (24 * dday + hour) + min) + sec_requested;
- if (TIME_T_MAX / 3 - TIME_T_MIN / 3 < (dsec < 0 ? - dsec : dsec))
+ /* On Irix4.0.5 cc, dividing TIME_T_MIN by 3 does not produce
+ correct results, ie., it erroneously gives a positive value
+ of 715827882. Setting a variable first then doing math on it
+ seems to work. (ghazi@caip.rutgers.edu) */
+
+ const time_t time_t_max = TIME_T_MAX;
+ const time_t time_t_min = TIME_T_MIN;
+
+ if (time_t_max / 3 - time_t_min / 3 < (dsec < 0 ? - dsec : dsec))
return -1;
}
\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