firmware/libc/gmtime.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2012 by Bertrik Sikken
  11  *
  12  * Based on code from: rtc_as3514.c
  13  * Copyright (C) 2007 by Barry Wardell
  14  *
  15  * This program is free software; you can redistribute it and/or
  16  * modify it under the terms of the GNU General Public License
  17  * as published by the Free Software Foundation; either version 2
  18  * of the License, or (at your option) any later version.
  19  *
  20  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  21  * KIND, either express or implied.
  22  *
  23  ****************************************************************************/
  24 #include <stdbool.h>
  25 #include <stdint.h>
  26 #include "time.h"
  27
  28 #define MINUTE_SECONDS      60
  29 #define HOUR_SECONDS        3600
  30 #define DAY_SECONDS         86400
  31 #define WEEK_SECONDS        604800
  32 #define YEAR_SECONDS        31536000
  33 #define LEAP_YEAR_SECONDS   31622400
  34
  35 /* Days in each month */
  36 static uint8_t days_in_month[] =
  37     {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  38
  39 static inline bool is_leapyear(int year)
  40 {
  41     return (((year%4)==0) && (((year%100)!=0) || ((year%400)==0)));
  42 }
  43
  44 struct tm *gmtime(const time_t *timep)
  45 {
  46     static struct tm time;
  47     return gmtime_r(timep, &time);
  48 }
  49
  50 struct tm *gmtime_r(const time_t *timep, struct tm *tm)
  51 {
  52     time_t seconds = *timep;
  53     int year, i, mday, hour, min;
  54
  55     /* weekday */
  56     tm->tm_wday = (seconds / DAY_SECONDS + 4) % 7;
  57
  58     /* Year */
  59     year = 1970;
  60     while (seconds >= LEAP_YEAR_SECONDS)
  61     {
  62         if (is_leapyear(year)){
  63             seconds -= LEAP_YEAR_SECONDS;
  64         } else {
  65             seconds -= YEAR_SECONDS;
  66         }
  67
  68         year++;
  69     }
  70
  71     if (is_leapyear(year)) {
  72         days_in_month[1] = 29;
  73     } else {
  74         days_in_month[1] = 28;
  75         if(seconds>YEAR_SECONDS){
  76             year++;
  77             seconds -= YEAR_SECONDS;
  78         }
  79     }
  80     tm->tm_year = year - 1900;
  81
  82     /* Month */
  83     for (i = 0; i < 12; i++)
  84     {
  85         if (seconds < days_in_month[i]*DAY_SECONDS){
  86             tm->tm_mon = i;
  87             break;
  88         }
  89
  90         seconds -= days_in_month[i]*DAY_SECONDS;
  91     }
  92
  93     /* Month Day */
  94     mday = seconds/DAY_SECONDS;
  95     seconds -= mday*DAY_SECONDS;
  96     tm->tm_mday = mday + 1; /* 1 ... 31 */
  97
  98     /* Hour */
  99     hour = seconds/HOUR_SECONDS;
 100     seconds -= hour*HOUR_SECONDS;
 101     tm->tm_hour = hour;
 102
 103     /* Minute */
 104     min = seconds/MINUTE_SECONDS;
 105     seconds -= min*MINUTE_SECONDS;
 106     tm->tm_min = min;
 107
 108     /* Second */
 109     tm->tm_sec = seconds;
 110
 111     return tm;
 112 }
 113