X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fmktime.c;h=1feb4046b07f631108526dc655a9723fde1a6710;hb=e9721c2f5a8ea905fba888055ca0fd0767f8873d;hp=952befe9351e1e6069aa7d83dda484972dd0d199;hpb=fd396561f6e42cfb5c750b19cca61494b92569e4;p=gnulib.git diff --git a/lib/mktime.c b/lib/mktime.c index 952befe93..1feb4046b 100644 --- a/lib/mktime.c +++ b/lib/mktime.c @@ -1,4 +1,5 @@ -/* 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. @@ -27,14 +28,8 @@ # include #endif -/* Some systems need this in order to declare localtime_r properly. */ -#ifndef _REENTRANT -# define _REENTRANT 1 -#endif - #ifdef _LIBC # define HAVE_LIMITS_H 1 -# define HAVE_LOCALTIME_R 1 # define STDC_HEADERS 1 #endif @@ -62,7 +57,7 @@ #endif /* DEBUG */ #ifndef __P -# if defined (__GNUC__) || (defined (__STDC__) && __STDC__) +# if defined __GNUC__ || (defined __STDC__ && __STDC__) # define __P(args) args # else # define __P(args) () @@ -73,21 +68,26 @@ # 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 @@ -119,16 +119,14 @@ time_t __mktime_internal __P ((struct tm *, #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) @@ -136,7 +134,6 @@ localtime_r (t, tp) *tp = *l; return tp; } -# endif /* ! HAVE_LOCALTIME_R && ! defined (localtime_r) */ #endif /* ! _LIBC */ @@ -147,9 +144,8 @@ localtime_r (t, tp) 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; @@ -181,8 +177,7 @@ static time_t localtime_offset; /* 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 @@ -191,17 +186,15 @@ mktime (tp) __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; @@ -248,19 +241,18 @@ ranged_convert (convert, t, tp) 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. */ @@ -306,36 +298,52 @@ __mktime_internal (tp, convert, offset) 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; } } } @@ -365,7 +373,15 @@ __mktime_internal (tp, convert, offset) 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; } @@ -517,6 +533,6 @@ main (argc, argv) /* 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: */