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- /****************************************************************************
- * sched/clock/clock_dow.c
- *
- * Copyright (C) 2012 Gregory Nutt. All rights reserved.
- * Author: Gregory Nutt <gnutt@nuttx.org>
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. 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.
- * 3. Neither the name NuttX nor the names of its 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.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <nuttx/config.h>
- #include <stdint.h>
- #include <nuttx/clock.h>
- #include "clock/clock.h"
- /****************************************************************************
- * Private Data
- ****************************************************************************/
- /* 23 * (month + 1) / 9, month = 0..11 */
- static const uint8_t g_lookup[12] =
- {
- 2, 5, 7, 10, 12, 15, 17, 20, 23, 25, 28, 30
- };
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: clock_dow
- *
- * Description:
- * Calculate the day of week (DOW) from they year month and day. Based on
- * an algorithm pubished in 1990 by Michael Keith and Tom Craver with some
- * tweaks to handle months in the range 0-11.
- *
- * Input Parameters:
- * year - year (e.g., 1988)
- * month - 0 through 11
- * day - 1 through 31
- *
- * Returned Value:
- * The day of the week as days since Sunday: 0 = Sunday, 1 = Monday, etc.
- *
- * Assumptions:
- *
- ****************************************************************************/
- int clock_dow(int year, int month, int day)
- {
- day += month < 2 ? year-- : year - 2;
- return ((int)g_lookup[month] + day + 4 + year / 4 - year / 100 + year / 400) % 7;
- }
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