Time.cpp

/*
  time.c - low level time and date functions
  Copyright (c) Michael Margolis 2009

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  
  6  Jan 2010 - initial release 
  12 Feb 2010 - fixed leap year calculation error
  1  Nov 2010 - fixed setTime bug (thanks to Korman for this)
*/

#if ARDUINO >= 100
#include <Arduino.h> 
#else
#include <WProgram.h> 
#endif

#include "./Time.h"

static tmElements_t tm;          // a cache of time elements
static time_t       cacheTime;   // the time the cache was updated
static time_t       syncInterval = 300;  // time sync will be attempted after this many seconds

void refreshCache( time_t t){
  if( t != cacheTime)
  {
    breakTime(t, tm); 
    cacheTime = t; 
  }
}

int hour() { // the hour now 
  return hour(now()); 
}

int hour(time_t t) { // the hour for the given time
  refreshCache(t);
  return tm.Hour;  
}

int hourFormat12() { // the hour now in 12 hour format
  return hourFormat12(now()); 
}

int hourFormat12(time_t t) { // the hour for the given time in 12 hour format
  refreshCache(t);
  if( tm.Hour == 0 )
    return 12; // 12 midnight
  else if( tm.Hour  > 12)
    return tm.Hour - 12 ;
  else
    return tm.Hour ;
}

uint8_t isAM() { // returns true if time now is AM
  return !isPM(now()); 
}

uint8_t isAM(time_t t) { // returns true if given time is AM
  return !isPM(t);  
}

uint8_t isPM() { // returns true if PM
  return isPM(now()); 
}

uint8_t isPM(time_t t) { // returns true if PM
  return (hour(t) >= 12); 
}

int minute() {
  return minute(now()); 
}

int minute(time_t t) { // the minute for the given time
  refreshCache(t);
  return tm.Minute;  
}

int second() {
  return second(now()); 
}

int second(time_t t) {  // the second for the given time
  refreshCache(t);
  return tm.Second;
}

int day(){
  return(day(now())); 
}

int day(time_t t) { // the day for the given time (0-6)
  refreshCache(t);
  return tm.Day;
}

int weekday() {   // Sunday is day 1
  return  weekday(now()); 
}

int weekday(time_t t) {
  refreshCache(t);
  return tm.Wday;
}
   
int month(){
  return month(now()); 
}

int month(time_t t) {  // the month for the given time
  refreshCache(t);
  return tm.Month;
}

int year() {  // as in Processing, the full four digit year: (2009, 2010 etc) 
  return year(now()); 
}

int year(time_t t) { // the year for the given time
  refreshCache(t);
  return tmYearToCalendar(tm.Year);
}

/*============================================================================*/	
/* functions to convert to and from system time */
/* These are for interfacing with time serivces and are not normally needed in a sketch */

// leap year calulator expects year argument as years offset from 1970
#define LEAP_YEAR(Y)     ( ((1970+Y)>0) && !((1970+Y)%4) && ( ((1970+Y)%100) || !((1970+Y)%400) ) )

static  const uint8_t monthDays[]={31,28,31,30,31,30,31,31,30,31,30,31}; // API starts months from 1, this array starts from 0
 
void breakTime(time_t time, tmElements_t &tm){
// break the given time_t into time components
// this is a more compact version of the C library localtime function
// note that year is offset from 1970 !!!

  uint8_t year;
  uint8_t month, monthLength;
  unsigned long days;
  
  tm.Second = time % 60;
  time /= 60; // now it is minutes
  tm.Minute = time % 60;
  time /= 60; // now it is hours
  tm.Hour = time % 24;
  time /= 24; // now it is days
  tm.Wday = ((time + 4) % 7) + 1;  // Sunday is day 1 
  
  year = 0;  
  days = 0;
  while((unsigned)(days += (LEAP_YEAR(year) ? 366 : 365)) <= time) {
    year++;
  }
  tm.Year = year; // year is offset from 1970 
  
  days -= LEAP_YEAR(year) ? 366 : 365;
  time  -= days; // now it is days in this year, starting at 0
  
  days=0;
  month=0;
  monthLength=0;
  for (month=0; month<12; month++) {
    if (month==1) { // february
      if (LEAP_YEAR(year)) {
        monthLength=29;
      } else {
        monthLength=28;
      }
    } else {
      monthLength = monthDays[month];
    }
    
    if (time >= monthLength) {
      time -= monthLength;
    } else {
        break;
    }
  }
  tm.Month = month + 1;  // jan is month 1  
  tm.Day = time + 1;     // day of month
}

time_t makeTime(tmElements_t &tm){   
// assemble time elements into time_t 
// note year argument is offset from 1970 (see macros in time.h to convert to other formats)
// previous version used full four digit year (or digits since 2000),i.e. 2009 was 2009 or 9
  
  int i;
  time_t seconds;

  // seconds from 1970 till 1 jan 00:00:00 of the given year
  seconds= tm.Year*(SECS_PER_DAY * 365);
  for (i = 0; i < tm.Year; i++) {
    if (LEAP_YEAR(i)) {
      seconds +=  SECS_PER_DAY;   // add extra days for leap years
    }
  }
  
  // add days for this year, months start from 1
  for (i = 1; i < tm.Month; i++) {
    if ( (i == 2) && LEAP_YEAR(tm.Year)) { 
      seconds += SECS_PER_DAY * 29;
    } else {
      seconds += SECS_PER_DAY * monthDays[i-1];  //monthDay array starts from 0
    }
  }
  seconds+= (tm.Day-1) * SECS_PER_DAY;
  seconds+= tm.Hour * SECS_PER_HOUR;
  seconds+= tm.Minute * SECS_PER_MIN;
  seconds+= tm.Second;
  return seconds; 
}
/*=====================================================*/	
/* Low level system time functions  */

static time_t sysTime = 0;
static time_t prevMillis = 0;
static time_t nextSyncTime = 0;
static timeStatus_t Status = timeNotSet;

getExternalTime getTimePtr;  // pointer to external sync function
//setExternalTime setTimePtr; // not used in this version

#ifdef TIME_DRIFT_INFO   // define this to get drift data
time_t sysUnsyncedTime = 0; // the time sysTime unadjusted by sync  
#endif


time_t now(){
  while( millis() - prevMillis >= 1000){      
    sysTime++;
    prevMillis += 1000;	
#ifdef TIME_DRIFT_INFO
    sysUnsyncedTime++; // this can be compared to the synced time to measure long term drift     
#endif	
  }
  if(nextSyncTime <= sysTime){
	if(getTimePtr != 0){
	  time_t t = getTimePtr();
      if( t != 0)
        setTime(t);
      else
        Status = (Status == timeNotSet) ?  timeNotSet : timeNeedsSync;        
    }
  }  
  return sysTime;
}

void setTime(time_t t){ 
#ifdef TIME_DRIFT_INFO
 if(sysUnsyncedTime == 0) 
   sysUnsyncedTime = t;   // store the time of the first call to set a valid Time   
#endif

  sysTime = t;  
  nextSyncTime = t + syncInterval;
  Status = timeSet; 
  prevMillis = millis();  // restart counting from now (thanks to Korman for this fix)
} 

void  setTime(int hr,int min,int sec,int dy, int mnth, int yr){
 // year can be given as full four digit year or two digts (2010 or 10 for 2010);  
 //it is converted to years since 1970
  if( yr > 99)
      yr = yr - 1970;
  else
      yr += 30;  
  tm.Year = yr;
  tm.Month = mnth;
  tm.Day = dy;
  tm.Hour = hr;
  tm.Minute = min;
  tm.Second = sec;
  setTime(makeTime(tm));
}

void adjustTime(long adjustment){
  sysTime += adjustment;
}

timeStatus_t timeStatus(){ // indicates if time has been set and recently synchronized
  return Status;
}

void setSyncProvider( getExternalTime getTimeFunction){
  getTimePtr = getTimeFunction;  
  nextSyncTime = sysTime;
  now(); // this will sync the clock
}

void setSyncInterval(time_t interval){ // set the number of seconds between re-sync
  syncInterval = interval;
}