diff options
Diffstat (limited to 'libc/misc/time/mktime.c')
| -rw-r--r-- | libc/misc/time/mktime.c | 314 |
1 files changed, 155 insertions, 159 deletions
diff --git a/libc/misc/time/mktime.c b/libc/misc/time/mktime.c index 7f7aabcd7..d6ee2ed42 100644 --- a/libc/misc/time/mktime.c +++ b/libc/misc/time/mktime.c @@ -10,7 +10,7 @@ #define LEAP_SECONDS_POSSIBLE 1 #endif -#include <sys/types.h> /* Some systems define `time_t' here. */ +#include <sys/types.h> /* Some systems define `time_t' here. */ #include <time.h> #if __STDC__ || __GNU_LIBRARY__ || STDC_HEADERS @@ -24,15 +24,15 @@ #endif /* Make it work even if the system's libc has its own mktime routine. */ #define mktime my_mktime -#endif /* DEBUG */ +#endif /* DEBUG */ #ifndef __P #if defined (__GNUC__) || (defined (__STDC__) && __STDC__) #define __P(args) args #else #define __P(args) () -#endif /* GCC. */ -#endif /* Not __P. */ +#endif /* GCC. */ +#endif /* Not __P. */ #ifndef CHAR_BIT #define CHAR_BIT 8 @@ -64,47 +64,47 @@ #endif /* How many days come before each month (0-12). */ -const unsigned short int __mon_yday[2][13] = - { - /* Normal years. */ - { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 }, - /* Leap years. */ - { 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366 } - }; - -static time_t ydhms_tm_diff __P ((int, int, int, int, int, const struct tm *)); -time_t __mktime_internal __P ((struct tm *, - struct tm *(*) (const time_t *, struct tm *), - time_t *)); +const unsigned short int __mon_yday[2][13] = { + /* Normal years. */ + {0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365}, + /* Leap years. */ + {0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366} +}; + +static time_t ydhms_tm_diff + +__P((int, int, int, int, int, const struct tm *)); +time_t __mktime_internal +__P((struct tm *, struct tm * (*)(const time_t *, struct tm *), time_t *)); /* Yield the difference between (YEAR-YDAY HOUR:MIN:SEC) and (*TP), measured in seconds, ignoring leap seconds. YEAR uses the same numbering as TM->tm_year. All values are in range, except possibly YEAR. 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; +static time_t ydhms_tm_diff(year, yday, hour, min, sec, tp) +int year, yday, hour, min, sec; +const struct tm *tp; { - /* Compute intervening leap days correctly even if year is negative. - Take care to avoid int overflow. time_t overflow is OK, since - only the low order bits of the correct time_t answer are needed. - Don't convert to time_t until after all divisions are done, since - time_t might be unsigned. */ - int a4 = (year >> 2) + (TM_YEAR_BASE >> 2) - ! (year & 3); - int b4 = (tp->tm_year >> 2) + (TM_YEAR_BASE >> 2) - ! (tp->tm_year & 3); - int a100 = a4 / 25 - (a4 % 25 < 0); - int b100 = b4 / 25 - (b4 % 25 < 0); - int a400 = a100 >> 2; - int b400 = b100 >> 2; - int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400); - time_t years = year - (time_t) tp->tm_year; - time_t days = (365 * years + intervening_leap_days - + (yday - tp->tm_yday)); - return (60 * (60 * (24 * days + (hour - tp->tm_hour)) - + (min - tp->tm_min)) - + (sec - tp->tm_sec)); + /* Compute intervening leap days correctly even if year is negative. + Take care to avoid int overflow. time_t overflow is OK, since + only the low order bits of the correct time_t answer are needed. + Don't convert to time_t until after all divisions are done, since + time_t might be unsigned. */ + int a4 = (year >> 2) + (TM_YEAR_BASE >> 2) - !(year & 3); + int b4 = (tp->tm_year >> 2) + (TM_YEAR_BASE >> 2) - !(tp->tm_year & 3); + int a100 = a4 / 25 - (a4 % 25 < 0); + int b100 = b4 / 25 - (b4 % 25 < 0); + int a400 = a100 >> 2; + int b400 = b100 >> 2; + int intervening_leap_days = (a4 - b4) - (a100 - b100) + (a400 - b400); + time_t years = year - (time_t) tp->tm_year; + time_t days = (365 * years + intervening_leap_days + + + (yday - tp->tm_yday)); + return (60 * (60 * (24 * days + (hour - tp->tm_hour)) + + (min - tp->tm_min)) + + (sec - tp->tm_sec)); } @@ -112,18 +112,17 @@ static time_t localtime_offset; /* Convert *TP to a time_t value. */ -time_t -mktime (tp) - struct tm *tp; +time_t mktime(tp) +struct tm *tp; { #ifdef _LIBC - /* POSIX.1 8.1.1 requires that whenever mktime() is called, the - time zone names contained in the external variable `tzname' shall - be set as if the tzset() function had been called. */ - __tzset (); + /* POSIX.1 8.1.1 requires that whenever mktime() is called, the + time zone names contained in the external variable `tzname' shall + be set as if the tzset() function had been called. */ + __tzset(); #endif - return __mktime_internal (tp, localtime_r, &localtime_offset); + return __mktime_internal(tp, localtime_r, &localtime_offset); } /* Convert *TP to a time_t value, inverting @@ -131,129 +130,126 @@ mktime (tp) Use *OFFSET to keep track of a guess at the offset of the result, 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; +time_t __mktime_internal(tp, convert, offset) +struct tm *tp; +struct tm *(*convert) __P((const time_t *, struct tm *)); +time_t *offset; { - time_t t, dt, t0; - 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; - - /* Time requested. Copy it in case CONVERT modifies *TP; this can - occur if TP is localtime's returned value and CONVERT is localtime. */ - int sec = tp->tm_sec; - int min = tp->tm_min; - int hour = tp->tm_hour; - int mday = tp->tm_mday; - int mon = tp->tm_mon; - int year_requested = tp->tm_year; - int isdst = tp->tm_isdst; - - /* Ensure that mon is in range, and set year accordingly. */ - int mon_remainder = mon % 12; - int negative_mon_remainder = mon_remainder < 0; - int mon_years = mon / 12 - negative_mon_remainder; - int year = year_requested + mon_years; - - /* The other values need not be in range: - the remaining code handles minor overflows correctly, - assuming int and time_t arithmetic wraps around. - Major overflows are caught at the end. */ - - /* Calculate day of year from year, month, and day of month. - The result need not be in range. */ - int yday = ((__mon_yday[__isleap (year + TM_YEAR_BASE)] - [mon_remainder + 12 * negative_mon_remainder]) - + mday - 1); + time_t t, dt, t0; + 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; + + /* Time requested. Copy it in case CONVERT modifies *TP; this can + occur if TP is localtime's returned value and CONVERT is localtime. */ + int sec = tp->tm_sec; + int min = tp->tm_min; + int hour = tp->tm_hour; + int mday = tp->tm_mday; + int mon = tp->tm_mon; + int year_requested = tp->tm_year; + int isdst = tp->tm_isdst; + + /* Ensure that mon is in range, and set year accordingly. */ + int mon_remainder = mon % 12; + int negative_mon_remainder = mon_remainder < 0; + int mon_years = mon / 12 - negative_mon_remainder; + int year = year_requested + mon_years; + + /* The other values need not be in range: + the remaining code handles minor overflows correctly, + assuming int and time_t arithmetic wraps around. + Major overflows are caught at the end. */ + + /* Calculate day of year from year, month, and day of month. + The result need not be in range. */ + int yday = ((__mon_yday[__isleap(year + TM_YEAR_BASE)] + [mon_remainder + 12 * negative_mon_remainder]) + + mday - 1); #if LEAP_SECONDS_POSSIBLE - /* Handle out-of-range seconds specially, - since ydhms_tm_diff assumes every minute has 60 seconds. */ - int sec_requested = sec; - if (sec < 0) - sec = 0; - if (59 < sec) - sec = 59; + /* Handle out-of-range seconds specially, + since ydhms_tm_diff assumes every minute has 60 seconds. */ + int sec_requested = sec; + + if (sec < 0) + sec = 0; + if (59 < sec) + sec = 59; #endif - /* Invert CONVERT by probing. First assume the same offset as last time. - Then repeatedly use the error to improve the guess. */ - - tm.tm_year = EPOCH_YEAR - TM_YEAR_BASE; - 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; - (dt = ydhms_tm_diff (year, yday, hour, min, sec, (*convert) (&t, &tm))); - t += dt) - if (--remaining_probes == 0) - return -1; - - /* Check whether tm.tm_isdst has the requested value, if any. */ - if (0 <= isdst && 0 <= tm.tm_isdst) - { - int dst_diff = (isdst != 0) - (tm.tm_isdst != 0); - if (dst_diff) - { - /* 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) - { - struct tm otm; - if (! (dt = ydhms_tm_diff (year, yday, hour, min, sec, - (*convert) (&ot, &otm)))) - { - t = ot; - tm = otm; - break; - } - if ((ot += dt) == t) - break; /* Avoid a redundant probe. */ - } - } - } - - *offset = t - t0; + /* Invert CONVERT by probing. First assume the same offset as last time. + Then repeatedly use the error to improve the guess. */ + + tm.tm_year = EPOCH_YEAR - TM_YEAR_BASE; + 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; + (dt = + ydhms_tm_diff(year, yday, hour, min, sec, (*convert) (&t, &tm))); + t += dt) + if (--remaining_probes == 0) + return -1; + + /* Check whether tm.tm_isdst has the requested value, if any. */ + if (0 <= isdst && 0 <= tm.tm_isdst) { + int dst_diff = (isdst != 0) - (tm.tm_isdst != 0); + + if (dst_diff) { + /* 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) { + struct tm otm; + + if (!(dt = ydhms_tm_diff(year, yday, hour, min, sec, + (*convert) (&ot, &otm)))) { + t = ot; + tm = otm; + break; + } + if ((ot += dt) == t) + break; /* Avoid a redundant probe. */ + } + } + } + + *offset = t - t0; #if LEAP_SECONDS_POSSIBLE - if (sec_requested != tm.tm_sec) - { - /* 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. */ - t += sec_requested - sec + (sec == 0 && tm.tm_sec == 60); - (*convert) (&t, &tm); - } + if (sec_requested != tm.tm_sec) { + /* 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. */ + t += sec_requested - sec + (sec == 0 && tm.tm_sec == 60); + (*convert) (&t, &tm); + } #endif #if 0 - if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3) - { - /* time_t isn't large enough to rule out overflows in ydhms_tm_diff, - so check for major overflows. A gross check suffices, - since if t has overflowed, it is off by a multiple of - TIME_T_MAX - TIME_T_MIN + 1. So ignore any component of - the difference that is bounded by a small value. */ - - double dyear = (double) year_requested + mon_years - tm.tm_year; - 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)) - return -1; - } + if (TIME_T_MAX / INT_MAX / 366 / 24 / 60 / 60 < 3) { + /* time_t isn't large enough to rule out overflows in ydhms_tm_diff, + so check for major overflows. A gross check suffices, + since if t has overflowed, it is off by a multiple of + TIME_T_MAX - TIME_T_MIN + 1. So ignore any component of + the difference that is bounded by a small value. */ + + double dyear = (double) year_requested + mon_years - tm.tm_year; + 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)) + return -1; + } #endif - *tp = tm; - return t; + *tp = tm; + return t; } - |