mbed_mktime.c

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2017-2017 ARM Limited
00003  * SPDX-License-Identifier: Apache-2.0
00004  *
00005  * Licensed under the Apache License, Version 2.0 (the "License");
00006  * you may not use this file except in compliance with the License.
00007  * You may obtain a copy of the License at
00008  *
00009  *     http://www.apache.org/licenses/LICENSE-2.0
00010  *
00011  * Unless required by applicable law or agreed to in writing, software
00012  * distributed under the License is distributed on an "AS IS" BASIS,
00013  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00014  * See the License for the specific language governing permissions and
00015  * limitations under the License.
00016  */
00017 
00018 #include "mbed_mktime.h"
00019 
00020 /* Time constants. */
00021 #define SECONDS_BY_MINUTES 60
00022 #define MINUTES_BY_HOUR 60
00023 #define SECONDS_BY_HOUR (SECONDS_BY_MINUTES * MINUTES_BY_HOUR)
00024 #define HOURS_BY_DAY 24
00025 #define SECONDS_BY_DAY (SECONDS_BY_HOUR * HOURS_BY_DAY)
00026 #define LAST_VALID_YEAR 206
00027 
00028 /* Macros which will be used to determine if we are within valid range. */
00029 #define EDGE_TIMESTAMP_FULL_LEAP_YEAR_SUPPORT 3220095     // 7th of February 1970 at 06:28:15
00030 #define EDGE_TIMESTAMP_4_YEAR_LEAP_YEAR_SUPPORT 3133695  // 6th of February 1970 at 06:28:15
00031 
00032 /*
00033  * 2 dimensional array containing the number of seconds elapsed before a given
00034  * month.
00035  * The second index map to the month while the first map to the type of year:
00036  *   - 0: non leap year
00037  *   - 1: leap year
00038  */
00039 static const uint32_t seconds_before_month[2][12] = {
00040     {
00041         0,
00042         31 * SECONDS_BY_DAY,
00043         (31 + 28) *SECONDS_BY_DAY,
00044         (31 + 28 + 31) *SECONDS_BY_DAY,
00045         (31 + 28 + 31 + 30) *SECONDS_BY_DAY,
00046         (31 + 28 + 31 + 30 + 31) *SECONDS_BY_DAY,
00047         (31 + 28 + 31 + 30 + 31 + 30) *SECONDS_BY_DAY,
00048         (31 + 28 + 31 + 30 + 31 + 30 + 31) *SECONDS_BY_DAY,
00049         (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31) *SECONDS_BY_DAY,
00050         (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30) *SECONDS_BY_DAY,
00051         (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31) *SECONDS_BY_DAY,
00052         (31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30) *SECONDS_BY_DAY,
00053     },
00054     {
00055         0,
00056         31 * SECONDS_BY_DAY,
00057         (31 + 29) *SECONDS_BY_DAY,
00058         (31 + 29 + 31) *SECONDS_BY_DAY,
00059         (31 + 29 + 31 + 30) *SECONDS_BY_DAY,
00060         (31 + 29 + 31 + 30 + 31) *SECONDS_BY_DAY,
00061         (31 + 29 + 31 + 30 + 31 + 30) *SECONDS_BY_DAY,
00062         (31 + 29 + 31 + 30 + 31 + 30 + 31) *SECONDS_BY_DAY,
00063         (31 + 29 + 31 + 30 + 31 + 30 + 31 + 31) *SECONDS_BY_DAY,
00064         (31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30) *SECONDS_BY_DAY,
00065         (31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31) *SECONDS_BY_DAY,
00066         (31 + 29 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30) *SECONDS_BY_DAY,
00067     }
00068 };
00069 
00070 bool _rtc_is_leap_year(int year, rtc_leap_year_support_t leap_year_support)
00071 {
00072     /*
00073      * since in practice, the value manipulated by this algorithm lie in the
00074      * range: [70 : 206] the algorithm can be reduced to: year % 4 with exception for 200 (year 2100 is not leap year).
00075      * The algorithm valid over the full range of value is:
00076 
00077         year = 1900 + year;
00078         if (year % 4) {
00079             return false;
00080         } else if (year % 100) {
00081             return true;
00082         } else if (year % 400) {
00083             return false;
00084         }
00085         return true;
00086 
00087      */
00088     if (leap_year_support == RTC_FULL_LEAP_YEAR_SUPPORT && year == 200) {
00089         return false; // 2100 is not a leap year
00090     }
00091 
00092     return (year) % 4 ? false : true;
00093 }
00094 
00095 bool _rtc_maketime(const struct tm *time, time_t *seconds, rtc_leap_year_support_t leap_year_support)
00096 {
00097     if (seconds == NULL || time == NULL) {
00098         return false;
00099     }
00100 
00101     /* Partial check for the upper bound of the range - check years only. Full check will be performed after the
00102      * elapsed time since the beginning of the year is calculated.
00103      */
00104     if ((time->tm_year < 70) || (time->tm_year > LAST_VALID_YEAR)) {
00105         return false;
00106     }
00107 
00108     uint32_t result = time->tm_sec;
00109     result += time->tm_min * SECONDS_BY_MINUTES;
00110     result += time->tm_hour * SECONDS_BY_HOUR;
00111     result += (time->tm_mday - 1) * SECONDS_BY_DAY;
00112     result += seconds_before_month[_rtc_is_leap_year(time->tm_year, leap_year_support)][time->tm_mon];
00113 
00114     /* Check if we are within valid range. */
00115     if (time->tm_year == LAST_VALID_YEAR) {
00116         if ((leap_year_support == RTC_FULL_LEAP_YEAR_SUPPORT && result > EDGE_TIMESTAMP_FULL_LEAP_YEAR_SUPPORT) ||
00117                 (leap_year_support == RTC_4_YEAR_LEAP_YEAR_SUPPORT && result > EDGE_TIMESTAMP_4_YEAR_LEAP_YEAR_SUPPORT)) {
00118             return false;
00119         }
00120     }
00121 
00122     if (time->tm_year > 70) {
00123         /* Valid in the range [70:206]. */
00124         uint32_t count_of_leap_days = ((time->tm_year - 1) / 4) - (70 / 4);
00125         if (leap_year_support == RTC_FULL_LEAP_YEAR_SUPPORT) {
00126             if (time->tm_year > 200) {
00127                 count_of_leap_days--; // 2100 is not a leap year
00128             }
00129         }
00130 
00131         result += (((time->tm_year - 70) * 365) + count_of_leap_days) * SECONDS_BY_DAY;
00132     }
00133 
00134     *seconds = result;
00135 
00136     return true;
00137 }
00138 
00139 bool _rtc_localtime(time_t timestamp, struct tm *time_info, rtc_leap_year_support_t leap_year_support)
00140 {
00141     if (time_info == NULL) {
00142         return false;
00143     }
00144 
00145     uint32_t seconds = (uint32_t)timestamp;
00146 
00147     time_info->tm_sec = seconds % 60;
00148     seconds = seconds / 60;   // timestamp in minutes
00149     time_info->tm_min = seconds % 60;
00150     seconds = seconds / 60;  // timestamp in hours
00151     time_info->tm_hour = seconds % 24;
00152     seconds = seconds / 24;  // timestamp in days;
00153 
00154     /* Compute the weekday.
00155      * The 1st of January 1970 was a Thursday which is equal to 4 in the weekday representation ranging from [0:6].
00156      */
00157     time_info->tm_wday = (seconds + 4) % 7;
00158 
00159     /* Years start at 70. */
00160     time_info->tm_year = 70;
00161     while (true) {
00162         if (_rtc_is_leap_year(time_info->tm_year, leap_year_support) && seconds >= 366) {
00163             ++time_info->tm_year;
00164             seconds -= 366;
00165         } else if (!_rtc_is_leap_year(time_info->tm_year, leap_year_support) && seconds >= 365) {
00166             ++time_info->tm_year;
00167             seconds -= 365;
00168         } else {
00169             /* The remaining days are less than a years. */
00170             break;
00171         }
00172     }
00173 
00174     time_info->tm_yday = seconds;
00175 
00176     /* Convert days into seconds and find the current month. */
00177     seconds *= SECONDS_BY_DAY;
00178     time_info->tm_mon = 11;
00179     bool leap = _rtc_is_leap_year(time_info->tm_year, leap_year_support);
00180     for (uint32_t i = 0; i < 12; ++i) {
00181         if ((uint32_t) seconds < seconds_before_month[leap][i]) {
00182             time_info->tm_mon = i - 1;
00183             break;
00184         }
00185     }
00186 
00187     /* Remove month from timestamp and compute the number of days.
00188      * Note: unlike other fields, days are not 0 indexed.
00189      */
00190     seconds -= seconds_before_month[leap][time_info->tm_mon];
00191     time_info->tm_mday = (seconds / SECONDS_BY_DAY) + 1;
00192 
00193     return true;
00194 }