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  1. /*-------------------------------------------------------------------------
  2.    time.c - stdlib time conversion routines
  3.  
  4.    Copyright (C) 2001, Johan Knol <johan.knol AT iduna.nl>
  5.  
  6.    This library is free software; you can redistribute it and/or modify it
  7.    under the terms of the GNU General Public License as published by the
  8.    Free Software Foundation; either version 2, or (at your option) any
  9.    later version.
  10.  
  11.    This library is distributed in the hope that it will be useful,
  12.    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13.    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14.    GNU General Public License for more details.
  15.  
  16.    You should have received a copy of the GNU General Public License
  17.    along with this library; see the file COPYING. If not, write to the
  18.    Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
  19.    MA 02110-1301, USA.
  20.  
  21.    As a special exception, if you link this library with other files,
  22.    some of which are compiled with SDCC, to produce an executable,
  23.    this library does not by itself cause the resulting executable to
  24.    be covered by the GNU General Public License. This exception does
  25.    not however invalidate any other reasons why the executable file
  26.    might be covered by the GNU General Public License.
  27. -------------------------------------------------------------------------*/
  28.  
  29. #include <stdio.h>
  30. #include <time.h>
  31.  
  32. // please note that the tm structure has the years since 1900,
  33. // but time returns the seconds since 1970
  34.  
  35. /* You need some kind of real time clock for the time() function.
  36.    Either a rtc-chip or some kind of DCF device will do. For TINI, the
  37.    HAVE_RTC is defined in tinibios.h
  38.    If not, the conversion routines still work.
  39. */
  40.  
  41. #ifndef HAVE_RTC
  42. unsigned char RtcRead(struct tm *timeptr) {
  43.   // no real time hardware
  44.   timeptr; // hush the compiler
  45.   return 0;
  46. }
  47. #endif
  48.  
  49. // return the calendar time, seconds since the Epoch (Jan 1 1970 00:00:00)
  50. time_t time(time_t *timeptr) {
  51.   struct tm now;
  52.   time_t t=(time_t) -1;
  53.  
  54.   if (RtcRead(&now)) {
  55.     t=mktime(&now);
  56.   }
  57.   if (timeptr) {
  58.     *timeptr=t;
  59.   }
  60.   return t;
  61. }
  62.  
  63. static const char monthDays[]={31,28,31,30,31,30,31,31,30,31,30,31};
  64.  
  65. const const char *const __month[]={"Jan","Feb","Mar","Apr","May","Jun",
  66.                                     "Jul","Aug","Sep","Oct","Nov","Dec"};
  67.  
  68. const const char *const __day[]={"Sun","Mon","Tue","Wed","Thu","Fri","Sat"};
  69.  
  70. static char ascTimeBuffer[32];
  71.  
  72. // validate the tm structure
  73. static void CheckTime(struct tm *timeptr) {
  74.     // we could do some normalization here, e.g.
  75.     // change 40 october to 9 november
  76.     #if !__TIME_UNSIGNED
  77.     if (timeptr->tm_sec<0) timeptr->tm_sec=0;
  78.     if (timeptr->tm_min<0) timeptr->tm_min=0;
  79.     if (timeptr->tm_hour<0) timeptr->tm_hour=0;
  80.     if (timeptr->tm_wday<0) timeptr->tm_wday=0;
  81.     if (timeptr->tm_mon<0) timeptr->tm_mon=0;
  82.     #endif
  83.    
  84.     if (timeptr->tm_sec>59) timeptr->tm_sec=59;
  85.     if (timeptr->tm_min>59) timeptr->tm_min=59;
  86.     if (timeptr->tm_hour>23) timeptr->tm_hour=23;
  87.     if (timeptr->tm_wday>6) timeptr->tm_wday=6;
  88.     if (timeptr->tm_mday<1) timeptr->tm_mday=1;
  89.     else if (timeptr->tm_mday>31) timeptr->tm_mday=31;
  90.     if (timeptr->tm_mon>11) timeptr->tm_mon=11;
  91.     if (timeptr->tm_year<0) timeptr->tm_year=0;
  92. }
  93.  
  94. // format the time into "Sat Feb 17 17:45:23 2001\n"
  95. char *asctime(struct tm *timeptr) {
  96.   CheckTime(timeptr);
  97.   sprintf (ascTimeBuffer, "%s %s %2d %02d:%02d:%02d %04d\n",
  98.            __day[timeptr->tm_wday], __month[timeptr->tm_mon], timeptr->tm_mday,
  99.            timeptr->tm_hour, timeptr->tm_min, timeptr->tm_sec,
  100.            timeptr->tm_year+1900);
  101.   return ascTimeBuffer;
  102. }
  103.  
  104. char *ctime(time_t *timep) {
  105.   return asctime(localtime(timep));
  106. }
  107.  
  108. static struct tm lastTime;
  109.  
  110. /* convert calendar time (seconds since 1970) to broken-time
  111.    This only works for dates between 01-01-1970 00:00:00 and
  112.    19-01-2038 03:14:07
  113.  
  114.    A leap year is ((((year%4)==0) && ((year%100)!=0)) || ((year%400)==0))
  115.    but since we have no fancy years between 1970 and 2038 we can do:
  116. */
  117.  
  118. #define LEAP_YEAR(year) ((year%4)==0)
  119.  
  120. // forget about timezones for now
  121. struct tm *localtime(time_t *timep) {
  122.     return gmtime(timep);
  123. }
  124.  
  125. struct tm *gmtime(time_t *timep) {
  126.   unsigned long epoch=*timep;
  127.   unsigned int year;
  128.   unsigned char month, monthLength;
  129.   unsigned long days;
  130.  
  131.   lastTime.tm_sec=epoch%60;
  132.   epoch/=60; // now it is minutes
  133.   lastTime.tm_min=epoch%60;
  134.   epoch/=60; // now it is hours
  135.   lastTime.tm_hour=epoch%24;
  136.   epoch/=24; // now it is days
  137.   lastTime.tm_wday=(epoch+4)%7;
  138.  
  139.   year=1970;
  140.   days=0;
  141.   while((days += (LEAP_YEAR(year) ? 366 : 365)) <= epoch) {
  142.     year++;
  143.   }
  144.   lastTime.tm_year=year-1900;
  145.  
  146.   days -= LEAP_YEAR(year) ? 366 : 365;
  147.   epoch -= days; // now it is days in this year, starting at 0
  148.   lastTime.tm_yday=epoch;
  149.  
  150.   days=0;
  151.   month=0;
  152.   monthLength=0;
  153.   for (month=0; month<12; month++) {
  154.     if (month==1) { // februari
  155.       if (LEAP_YEAR(year)) {
  156.         monthLength=29;
  157.       } else {
  158.         monthLength=28;
  159.       }
  160.     } else {
  161.       monthLength = monthDays[month];
  162.     }
  163.    
  164.     if (epoch>=monthLength) {
  165.       epoch-=monthLength;
  166.     } else {
  167.         break;
  168.     }
  169.   }
  170.   lastTime.tm_mon=month;
  171.   lastTime.tm_mday=epoch+1;
  172.  
  173.   lastTime.tm_isdst=0;
  174.  
  175.   return &lastTime;
  176. }
  177.  
  178. // convert broken time to calendar time (seconds since 1970)
  179. time_t mktime(struct tm *timeptr) {
  180.     int year=timeptr->tm_year+1900, month=timeptr->tm_mon, i;
  181.     long seconds;
  182.    
  183.     CheckTime(timeptr);
  184.  
  185.     // seconds from 1970 till 1 jan 00:00:00 this year
  186.     seconds= (year-1970)*(60*60*24L*365);
  187.  
  188.     // add extra days for leap years
  189.     for (i=1970; i<year; i++) {
  190.         if (LEAP_YEAR(i)) {
  191.             seconds+= 60*60*24L;
  192.         }
  193.     }
  194.  
  195.     // add days for this year
  196.     for (i=0; i<month; i++) {
  197.       if (i==1 && LEAP_YEAR(year)) {
  198.         seconds+= 60*60*24L*29;
  199.       } else {
  200.         seconds+= 60*60*24L*monthDays[i];
  201.       }
  202.     }
  203.  
  204.     seconds+= (timeptr->tm_mday-1)*60*60*24L;
  205.     seconds+= timeptr->tm_hour*60*60L;
  206.     seconds+= timeptr->tm_min*60;
  207.     seconds+= timeptr->tm_sec;
  208.     return seconds;
  209. }
  210.