1 /* 2 * (c)2012 Michael Duane Rice All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions are 6 * met: 7 * 8 * Redistributions of source code must retain the above copyright notice, this 9 * list of conditions and the following disclaimer. Redistributions in binary 10 * form must reproduce the above copyright notice, this list of conditions 11 * and the following disclaimer in the documentation and/or other materials 12 * provided with the distribution. Neither the name of the copyright holders 13 * nor the names of contributors may be used to endorse or promote products 14 * derived from this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 20 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 26 * POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 /* $Id: eu_dst.h 2492 2015-10-27 09:07:56Z swfltek $ */ 30 31 /** 32 Daylight Saving function for the European Union. To utilize this function, you must 33 \code #include <util/eu_dst.h> \endcode 34 and 35 \code set_dst(eu_dst); \endcode 36 37 Given the time stamp and time zone parameters provided, the Daylight Saving function must 38 return a value appropriate for the tm structures' tm_isdst element. That is... 39 40 0 : If Daylight Saving is not in effect. 41 42 -1 : If it cannot be determined if Daylight Saving is in effect. 43 44 A positive integer : Represents the number of seconds a clock is advanced for Daylight Saving. 45 This will typically be ONE_HOUR. 46 47 Daylight Saving 'rules' are subject to frequent change. For production applications it is 48 recommended to write your own DST function, which uses 'rules' obtained from, and modifiable by, 49 the end user ( perhaps stored in EEPROM ). 50 */ 51 52 #ifndef EU_DST_H 53 #define EU_DST_H 54 55 #ifdef __cplusplus 56 extern "C" { 57 #endif 58 59 #include <time.h> 60 #include <inttypes.h> 61 eu_dst(const time_t * timer,int32_t * z)62 int eu_dst(const time_t * timer, int32_t * z) { 63 struct tm tmptr; 64 uint8_t month, mday, hour, day_of_week, d; 65 int n; 66 67 /* obtain the variables */ 68 gmtime_r(timer, &tmptr); 69 month = tmptr.tm_mon; 70 day_of_week = tmptr.tm_wday; 71 mday = tmptr.tm_mday - 1; 72 hour = tmptr.tm_hour; 73 74 if ((month > MARCH) && (month < OCTOBER)) 75 return ONE_HOUR; 76 77 if (month < MARCH) 78 return 0; 79 if (month > OCTOBER) 80 return 0; 81 82 /* determine mday of last Sunday */ 83 n = tmptr.tm_mday - 1; 84 n -= day_of_week; 85 n += 7; 86 d = n % 7; /* date of first Sunday */ 87 88 n = 31 - d; 89 n /= 7; /* number of Sundays left in the month */ 90 91 d = d + 7 * n; /* mday of final Sunday */ 92 93 if (month == MARCH) { 94 if (d < mday) 95 return 0; 96 if (d > mday) 97 return ONE_HOUR; 98 if (hour < 2) 99 return 0; 100 return ONE_HOUR; 101 } 102 if (d < mday) 103 return ONE_HOUR; 104 if (d > mday) 105 return 0; 106 if (hour < 2) 107 return ONE_HOUR; 108 return 0; 109 110 } 111 112 #ifdef __cplusplus 113 } 114 #endif 115 116 #endif 117