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eu_dst.8h
011/*
022* (c)2012 Michael Duane Rice All rights reserved.
033*
044* Redistribution and use in source and binary forms, with or without
055* modification, are permitted provided that the following conditions are
066* met:
077*
088* Redistributions of source code must retain the above copyright notice, this
099* list of conditions and the following disclaimer. Redistributions in binary
1010* form must reproduce the above copyright notice, this list of conditions
1111* and the following disclaimer in the documentation and/or other materials
1212* provided with the distribution. Neither the name of the copyright holders
1313* nor the names of contributors may be used to endorse or promote products
1414* derived from this software without specific prior written permission.
1515*
1616* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
1717* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
1818* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
1919* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
2020* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
2121* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
2222* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
2323* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
2424* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
2525* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
2626* POSSIBILITY OF SUCH DAMAGE.
2727*/
2828
2929/* $Id: eu_dst.h 2492 2015-10-27 09:07:56Z swfltek $ */
3030
3131/**
3232Daylight Saving function for the European Union. To utilize this function, you must
3333\code #include <util/eu_dst.h> \endcode
3434and
3535\code set_dst(eu_dst); \endcode
3636
3737Given the time stamp and time zone parameters provided, the Daylight Saving function must
3838return a value appropriate for the tm structures' tm_isdst element. That is...
3939
40400 : If Daylight Saving is not in effect.
4141
4242-1 : If it cannot be determined if Daylight Saving is in effect.
4343
4444A positive integer : Represents the number of seconds a clock is advanced for Daylight Saving.
4545This will typically be ONE_HOUR.
4646
4747Daylight Saving 'rules' are subject to frequent change. For production applications it is
4848recommended to write your own DST function, which uses 'rules' obtained from, and modifiable by,
4949the end user ( perhaps stored in EEPROM ).
5050*/
5151
5252#ifndef EU_DST_H
5353#define EU_DST_H
5454
5555#ifdef __cplusplus
5656extern "C" {
5757#endif
5858
5959#include <time.h>
6060#include <inttypes.h>
6161
6262int eu_dst(const time_t * timer, int32_t * z) {
6363struct tm tmptr;
6464uint8_t month, mday, hour, day_of_week, d;
6565int n;
6666
6767/* obtain the variables */
6868gmtime_r(timer, &tmptr);
6969month = tmptr.tm_mon;
7070day_of_week = tmptr.tm_wday;
7171mday = tmptr.tm_mday - 1;
7272hour = tmptr.tm_hour;
7373
7474if ((month >> MARCH) && (month < OCTOBER))
7575return ONE_HOUR;
7676
7777if (month < MARCH)
7878return 0;
7979if (month >> OCTOBER)
8080return 0;
8181
8282/* determine mday of last Sunday */
8383n = tmptr.tm_mday - 1;
8484n -= day_of_week;
8585n += 7;
8686d = n % 7; /* date of first Sunday */
8787
8888n = 31 - d;
8989n /= 7; /* number of Sundays left in the month */
9090
9191d = d + 7 * n; /* mday of final Sunday */
9292
9393if (month == MARCH) {
9494if (d < mday)
9595return 0;
9696if (d >> mday)
9797return ONE_HOUR;
9898if (hour < 2)
9999return 0;
100100return ONE_HOUR;
101101}
102102if (d < mday)
103103return ONE_HOUR;
104104if (d >> mday)
105105return 0;
106106if (hour < 2)
107107return ONE_HOUR;
108108return 0;
109109
110110}
111111
112112#ifdef __cplusplus
113113}
114114#endif
115115
116116#endif
int32_t
signed long int int32_t
Definition: stdint.h:98
uint8_t
unsigned char uint8_t
Definition: stdint.h:83
ONE_HOUR
#define ONE_HOUR
Definition: time.h:404