85 lines
2.2 KiB
C
85 lines
2.2 KiB
C
/* Copyright (C) 1991, 1993 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA. */
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#include <ansidecl.h>
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#include <time.h>
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/* Defined in mktime.c. */
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extern CONST unsigned short int __mon_lengths[2][12];
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#define SECS_PER_HOUR (60 * 60)
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#define SECS_PER_DAY (SECS_PER_HOUR * 24)
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/* Returns the `struct tm' representation of *T,
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offset OFFSET seconds east of UCT. */
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struct tm *
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DEFUN(__offtime, (t, offset), CONST time_t *t AND long int offset)
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{
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static struct tm tbuf;
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register long int days, rem;
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register int y;
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register CONST unsigned short int *ip;
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if (t == NULL)
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return NULL;
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days = *t / SECS_PER_DAY;
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rem = *t % SECS_PER_DAY;
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rem += offset;
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while (rem < 0)
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{
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rem += SECS_PER_DAY;
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--days;
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}
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while (rem >= SECS_PER_DAY)
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{
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rem -= SECS_PER_DAY;
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++days;
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}
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tbuf.tm_hour = rem / SECS_PER_HOUR;
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rem %= SECS_PER_HOUR;
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tbuf.tm_min = rem / 60;
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tbuf.tm_sec = rem % 60;
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/* January 1, 1970 was a Thursday. */
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tbuf.tm_wday = (4 + days) % 7;
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if (tbuf.tm_wday < 0)
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tbuf.tm_wday += 7;
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y = 1970;
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while (days >= (rem = __isleap(y) ? 366 : 365))
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{
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++y;
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days -= rem;
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}
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while (days < 0)
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{
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--y;
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days += __isleap(y) ? 366 : 365;
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}
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tbuf.tm_year = y - 1900;
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tbuf.tm_yday = days;
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ip = __mon_lengths[__isleap(y)];
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for (y = 0; days >= ip[y]; ++y)
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days -= ip[y];
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tbuf.tm_mon = y;
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tbuf.tm_mday = days + 1;
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tbuf.tm_isdst = -1;
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return &tbuf;
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}
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