251 lines
8.8 KiB
C
251 lines
8.8 KiB
C
/****************************************************************************
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*
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* Open Watcom Project
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*
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* Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
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*
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* ========================================================================
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*
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* This file contains Original Code and/or Modifications of Original
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* Code as defined in and that are subject to the Sybase Open Watcom
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* Public License version 1.0 (the 'License'). You may not use this file
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* except in compliance with the License. BY USING THIS FILE YOU AGREE TO
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* ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
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* provided with the Original Code and Modifications, and is also
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* available at www.sybase.com/developer/opensource.
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*
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* The Original Code and all software distributed under the License are
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* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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* EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
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* ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
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* NON-INFRINGEMENT. Please see the License for the specific language
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* governing rights and limitations under the License.
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*
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* ========================================================================
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*
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* Description: time utility functions
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*
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****************************************************************************/
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#include "variety.h"
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#include <time.h>
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#include "rtdata.h"
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#include "timedata.h"
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static int time_less( const struct tm *t1, const struct tm *t2 );
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static int calc_yday( const struct tm *timetm, int year )
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{
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struct tm tmptm;
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int month_days;
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int first_wday;
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int nth_week;
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short const *diyr;
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if( timetm->tm_isdst == 0 ) { // M.m.n.d form
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diyr = ( __leapyear( ( unsigned ) year + 1900 ) ) ? __dilyr : __diyr;
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month_days = diyr[timetm->tm_mon + 1] - diyr[timetm->tm_mon];
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tmptm.tm_sec = 0;
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tmptm.tm_min = 0;
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tmptm.tm_hour = 0;
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tmptm.tm_mday = 1;
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tmptm.tm_mon = timetm->tm_mon;
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tmptm.tm_year = year;
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tmptm.tm_isdst = 0;
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( void ) mktime( &tmptm );
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first_wday = ( timetm->tm_wday - tmptm.tm_wday + 7 ) % 7;
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if( timetm->tm_mday == 5 ) {
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if( ( 1 + first_wday + ( timetm->tm_mday - 1 ) * 7 ) > month_days )
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nth_week = timetm->tm_mday - 2; // fifth req. weekday does not exist
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else
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nth_week = timetm->tm_mday - 1;
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} else
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nth_week = timetm->tm_mday - 1;
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return( tmptm.tm_yday + first_wday + nth_week * 7 );
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}
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if( timetm->tm_isdst == 1 ) /* if Jn form */
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return( timetm->tm_yday - 1 );
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return( timetm->tm_yday );
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}
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/* determine if in souther hemisphere -> start is after end */
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static int check_order( const struct tm *start, const struct tm *end, int year )
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{
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int start_day;
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int end_day;
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/* these quick checks should always be enough */
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if( ( start->tm_isdst == 0 ) && ( end->tm_isdst == 0 ) ) { // M.m.n.d form
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if( start->tm_mon > end->tm_mon )
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return( 1 );
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if( start->tm_mon < end->tm_mon )
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return( 0 );
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}
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/* start/end of daylight savings time is in the same month (rare case) */
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/* these are *expensive* calculations under NT since 2 TZ checks must be done */
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start_day = calc_yday( start, year );
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end_day = calc_yday( end, year );
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if( start_day > end_day )
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return( 1 );
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return( 0 );
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}
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/* determine if daylight savings time */
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int __isindst( struct tm *t )
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{
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int month;
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int dst;
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int n1;
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int n2;
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int month_days;
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int time_check;
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int south;
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struct tm const *start;
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struct tm const *end;
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short const *diyr;
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// already determined -- if we are sure
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if( t->tm_isdst >= 0 )
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return( t->tm_isdst );
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dst = 0;
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// if zone doesn't have a daylight savings period
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if( _RWD_daylight == 0 )
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return( t->tm_isdst = dst );
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// // check for no daylight savings time rule
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// if( tzname[1][0] == '\0' ) { // doesn't work since Win32 says
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// return( t->tm_isdst = dst );// daylight zone name = standard zone name
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// }
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south = check_order( &_RWD_start_dst, &_RWD_end_dst, t->tm_year );
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if( south ) {
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// if southern hemisphere
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// invert start and end dates and then invert return value
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start = &_RWD_end_dst;
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end = &_RWD_start_dst;
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} else {
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start = &_RWD_start_dst;
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end = &_RWD_end_dst;
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}
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month = t->tm_mon;
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diyr = ( __leapyear( ( unsigned ) t->tm_year + 1900 ) ) ? __dilyr : __diyr;
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month_days = diyr[month + 1] - diyr[month];
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time_check = 0;
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/*
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* M.m.n.d form
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* m = start->tm_mon (month 0-11)
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* n = start->tm_mday (n'th week day 1-5)
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* d = start->tm_wday (week day 0-6)
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*/
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if( start->tm_isdst == 0 ) { /* if Mm.n.d form */
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if( month > start->tm_mon )
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dst = 1; /* assume dst for now */
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else if( month == start->tm_mon ) {
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/* calculate for current day */
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n1 = t->tm_mday - ( t->tm_wday + 7 - start->tm_wday ) % 7;
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/* calculate for previous day */
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n2 = t->tm_mday - 1 - ( t->tm_wday - 1 + 7 - start->tm_wday ) % 7;
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// n_ stands for the day of the month that is past &&
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// is closest to today && is the required weekday
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if( start->tm_mday == 5 ) {
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if( n1 > month_days - 7 ) {
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dst = 1; /* assume dst for now */
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if( n2 <= month_days - 7 )
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time_check = 1;
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}
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} else {
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if( n1 >= 7 * ( start->tm_mday - 1 ) + 1 ) {
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dst = 1; /* assume dst for now */
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if( n2 < 7 * ( start->tm_mday - 1 ) + 1 )
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time_check = 1;
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}
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}
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}
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} else {
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n1 = start->tm_yday;
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if( start->tm_isdst == 1 ) { /* if Jn form */
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if( __leapyear( ( unsigned ) t->tm_year + 1900 ) ) {
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if( n1 > __diyr[2] )
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n1++; /* past Feb 28 */
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}
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n1--;
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}
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if( t->tm_yday >= n1 ) {
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dst = 1; /* assume dst for now */
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if( t->tm_yday == n1 )
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time_check = 1;
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}
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}
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/* if it is the day for a switch-over then check the time too */
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if( time_check )
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dst = !time_less( t, start );
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/* if we are certain that it is before daylight saving then return */
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if( dst == 0 ) {
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if( south )
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dst = south - dst; /* invert value of dst */
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return( t->tm_isdst = dst );
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}
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/* now see if it is after daylight saving */
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time_check = 0;
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if( end->tm_isdst == 0 ) { /* if Mm.n.d form */
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if( month > end->tm_mon )
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dst = 0; /* not dst */
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else if( month == end->tm_mon ) {
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dst = 0;
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/* calculate for current day */
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n1 = t->tm_mday - ( t->tm_wday + 7 - end->tm_wday ) % 7;
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/* calculate for previous day */
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n2 = t->tm_mday - 1 -
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( t->tm_wday - 1 + 7 - end->tm_wday ) % 7;
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if( end->tm_mday == 5 ) {
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if( n1 <= month_days - 7 )
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dst = 1;
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else if( n2 <= month_days - 7 )
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time_check = 1;
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} else {
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if( n1 < 7 * ( end->tm_mday - 1 ) + 1 )
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dst = 1;
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else if( n2 < 7 * ( end->tm_mday - 1 ) + 1 )
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time_check = 1;
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}
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}
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} else {
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n1 = end->tm_yday;
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if( end->tm_isdst == 1 ) { /* if Jn form */
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if( __leapyear( ( unsigned ) t->tm_year + 1900 ) ) {
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if( n1 > __diyr[2] )
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n1++; /* past Feb 28 */
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}
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n1--;
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}
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if( t->tm_yday >= n1 ) {
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dst = 0;
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if( t->tm_yday == n1 )
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time_check = 1;
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}
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}
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/* if it is the day for a switch-over then check the time too */
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if( time_check )
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dst = time_less( t, end );
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if( south )
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dst = south - dst; /* invert value of dst */
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return( t->tm_isdst = dst );
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}
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static int time_less( const struct tm *t1, const struct tm *t2 )
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{
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int before;
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before = 0;
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if( t1->tm_hour < t2->tm_hour )
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before = 1;
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else if( t1->tm_hour == t2->tm_hour ) {
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if( t1->tm_min < t2->tm_min
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|| t1->tm_min == t2->tm_min && t1->tm_sec < t2->tm_sec )
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before = 1;
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}
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return( before );
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}
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