97 lines
2.5 KiB
C
97 lines
2.5 KiB
C
/*
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* Copyright (c) 2009 Oliver Lehmann <oliver@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $Id: gmtime.c,v 1.2 2009/08/07 20:02:59 olivleh1 Exp $
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*/
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#define dysize(A) (((A)%4)? 365: 366)
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#include <time.h>
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struct tm *gmtime();
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static char cbuf[26];
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static int dmsize[12]={31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
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struct tm *
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gmtime(tim)
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long *tim;
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{
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register int d0, d1;
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long hms, day;
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static struct tm xtime;
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/*
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* break initial number into days
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*/
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hms = *tim % 86400L;
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day = *tim / 86400L;
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if(hms < 0) {
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hms += 86400L;
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day -= 1;
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}
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/*
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* generate hours:minutes:seconds
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*/
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xtime.tm_sec = hms % 60;
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d1 = hms / 60;
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xtime.tm_min = d1 % 60;
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d1 /= 60;
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xtime.tm_hour = d1;
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/*
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* day is the day number.
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* generate day of the week.
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* The addend is 4 mod 7 (1/1/1970 was Thursday)
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*/
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xtime.tm_wday = (day + 7340036L) % 7;
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/*
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* year number
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*/
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if(day >= 0)
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for(d1=70; day >= dysize(d1); d1++)
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day -= dysize(d1);
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else
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for(d1=70; day < 0; d1--)
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day += dysize(d1-1);
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xtime.tm_year = d1;
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xtime.tm_yday = d0 = day;
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/*
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* generate month
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*/
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if(dysize(d1) == 366)
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dmsize[1] = 29;
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for(d1=0; d0 >= dmsize[d1]; d1++)
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d0 -= dmsize[d1];
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dmsize[1] = 28;
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xtime.tm_mday = d0+1;
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xtime.tm_mon = d1;
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xtime.tm_isdst = 0;
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return(&xtime);
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}
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