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| /**************************************************************************** |
| * |
| * Open Watcom Project |
| * |
| * Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved. |
| * |
| * ======================================================================== |
| * |
| * This file contains Original Code and/or Modifications of Original |
| * Code as defined in and that are subject to the Sybase Open Watcom |
| * Public License version 1.0 (the 'License'). You may not use this file |
| * except in compliance with the License. BY USING THIS FILE YOU AGREE TO |
| * ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is |
| * provided with the Original Code and Modifications, and is also |
| * available at www.sybase.com/developer/opensource. |
| * |
| * The Original Code and all software distributed under the License are |
| * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER |
| * EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM |
| * ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF |
| * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR |
| * NON-INFRINGEMENT. Please see the License for the specific language |
| * governing rights and limitations under the License. |
| * |
| * ======================================================================== |
| * |
| * Description: __brktime() is an internal function to convert time to struct tm |
| * |
| ****************************************************************************/ |
| |
| #include "variety.h" |
| #include <time.h> |
| #include "thetime.h" |
| #include "timedata.h" |
| |
| // #define DAYS_IN_4_YRS ( 365 + 365 + 365 + 366 ) |
| // #define DAYS_IN_400_YRS ( ( 100 * DAYS_IN_4_YRS ) - 3 ) |
| |
| // #define SECONDS_PER_DAY ( 24 * 60 * 60 ) |
| // extern short __diyr[], __dilyr[]; |
| |
| /* |
| The number of leap years from year 1 to year 1900 is 460. |
| The number of leap years from year 1 to current year is |
| expressed by "years/4 - years/100 + years/400". To determine |
| the number of leap years from current year to 1900, we subtract |
| 460 from the formula result. We do this since "days" is the |
| number of days since 1900. |
| */ |
| |
| static unsigned long __DaysToJan1( unsigned year ) |
| { |
| unsigned years = 1900 + year - 1; |
| unsigned leap_days = years / 4 - years / 100 + years / 400 - 460; |
| |
| return( year * 365UL + leap_days ); |
| } |
| |
| /* __brktime breaks down a calendar time (clock) into a struct tm t */ |
| |
| struct tm *__brktime( unsigned long days, |
| time_t wallclock, |
| long gmtdelta, // localtime - gmtime |
| struct tm *t ) |
| { |
| unsigned long secs; |
| unsigned year; |
| int day_of_year; |
| int month; |
| short const *month_start; |
| |
| /* |
| If date is Jan 1, 1970 0:00 to 12:00 UTC and we are west of UTC |
| then add a day to wallclock, subtract the gmtdelta value, and |
| decrement the calculated days. This prevents local times |
| such as "Wed Dec 31 19:00:00 1969 (EST)" from being |
| erroneously reported as "Sun Feb 6 01:28:16 2106 (EST)" |
| since (wallclock - gmtdelta) wraps (i.e., wallclock < gmtdelta). |
| */ |
| if( wallclock < 12 * 60 * 60UL && gmtdelta > 0 ) |
| wallclock += SECONDS_PER_DAY, days--; /* days compensated for wallclock one day ahead */ |
| wallclock -= ( time_t ) gmtdelta; |
| days += wallclock / SECONDS_PER_DAY; |
| secs = wallclock % SECONDS_PER_DAY; |
| t->tm_hour = ( int ) ( secs / 3600 ) ; |
| secs = secs % 3600; |
| t->tm_min = ( int ) ( secs / 60 ); |
| t->tm_sec = secs % 60; |
| |
| // The following two lines are not needed in the current implementation |
| // because the range of values for days does not exceed DAYS_IN_400_YRS. |
| // Even if it did, the algorithm still computes the correct values. |
| // |
| // unsigned year400s; |
| // |
| // year400s = (days / DAYS_IN_400_YRS) * 400; |
| // days %= DAYS_IN_400_YRS; |
| // |
| // It is OK to reduce days to a value less than DAYS_IN_400_YRS, because |
| // DAYS_IN_400_YRS is exactly divisible by 7. If it wasn't divisible by 7, |
| // then the following line which appears at the bottom, should be computed |
| // before the value of days is range reduced. |
| // t->tm_wday = (days + 1) % 7; /* 24-sep-92 */ |
| // |
| year = days / 365; |
| day_of_year = ( int ) ( days - __DaysToJan1( year ) ); |
| while( day_of_year < 0 ) { |
| --year; |
| day_of_year += __leapyear( year + 1900 ) + 365; |
| } |
| // year += year400s; |
| |
| t->tm_yday = day_of_year; |
| t->tm_year = ( int ) year; |
| month_start = __diyr; |
| if( __leapyear( year + 1900 ) ) |
| month_start = __dilyr; |
| month = day_of_year / 31; /* approximate month */ |
| if( day_of_year >= month_start[month + 1] ) |
| ++month; |
| t->tm_mon = month; |
| t->tm_mday = day_of_year - month_start[month] + 1; |
| |
| /* Calculate the day of the week */ |
| /* Jan 1,1900 is a Monday */ |
| |
| t->tm_wday = ( days + 1 ) % 7; /* 24-sep-92 */ |
| return( t ); |
| } |
| |
| _WCRTLINK struct tm *_gmtime( const time_t *timer, struct tm *tm ) |
| { |
| tm->tm_isdst = 0; /* assume not */ |
| return __brktime( DAYS_FROM_1900_TO_1970, *timer, 0L, tm ); |
| } |
| |
| _WCRTLINK struct tm *gmtime( const time_t *timer ) |
| { |
| _INITTHETIME; |
| return( _gmtime( timer, &_THE_TIME ) ); |
| } |