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/*
* (C)2012 Michael Duane Rice All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer. Redistributions in binary
* form must reproduce the above copyright notice, this list of conditions
* and the following disclaimer in the documentation and/or other materials
* provided with the distribution. Neither the name of the copyright holders
* nor the names of contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/* $Id: week_of_year.c 2362 2013-04-26 22:22:46Z swfltek $ */
/*
Return the week of year, where 'base' represents the first day of the week.
In the USA, the week is generally considered to start on Sunday (base = 0),
while in Europe it is generally considered to be Monday (base = 1).
Return value ranges from 0 to 52.
*/
#include <time.h>
uint8_t
week_of_year(const struct tm * timestruct, uint8_t base)
{
int first, n;
/* find the first base day of the year (start of week 1) */
first = 7 + timestruct->tm_yday - timestruct->tm_wday + base;
first %= 7;
/* find days since that first base day*/
n = timestruct->tm_yday - first;
/* if negative, we are in week 0 */
if (n < 0)
return 0;
return n / 7 + 1;
}
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