/**
* A class to calculate and manage a variety of time parameters.
+ * The SGTime class provides many real-world time values. It
+ * calculates current time in seconds, GMT time, local time zone,
+ * local offset in seconds from GMT, Julian date, and sidereal
+ * time. All of these operate with seconds as their granularity so
+ * this class is not intended for timing sub-second events. These
+ * values are intended as input to things like real world lighting
+ * calculations and real astronomical object placement.
+
+ * To properly use the SGTime class there are a couple of things to be
+ * aware of. After creating an instance of the class, you will need to
+ * periodically (i.e. before every frame) call the update()
+ * method. Optionally, if you care about updating time zone
+ * information based on your latitude and longitude, you can call the
+ * updateLocal() method periodically as your position changes by
+ * significant amounts.
+
*/
class SGTime {
/**
* Create an instance based on a specified position and data file path.
+ * This creates an instance of the SGTime object. When calling the
+ * constructor you need to provide a root path pointing to your
+ * time zone definition tree. Optionally, you can call a form of
+ * the constructor that accepts your current longitude and
+ * latitude in radians.
+ *
+ * If you don't know your position when you call the SGTime
+ * constructor, you can just use the first form (which assumes 0,
+ * 0).
* @param lon current longitude
* @param lat current latitude
- * @param root root path point to data file location (timezone, etc.)
- */
+ * @param root root path point to data file location (timezone, etc.) */
SGTime( double lon, double lat, const string& root );
/**
- * Create an instance given a data file path
+ * Create an instance given a data file path.
* @param root root path point to data file location (timezone, etc.)
*/
SGTime( const string& root );
/**
* Update the time related variables.
+ * The update() method requires you to pass in your position and
+ * an optional time offset in seconds. The offset (or warp) allows
+ * you to offset "sim" time relative to "real" time. The update()
+ * method is designed to be called by the host application before
+ * every frame.
* @param lon current longitude
* @param lat current latitude
* @param warp an optional time offset specified in seconds. This
- * allows us to advance or rewind "time" if we choose to.
- */
+ * allows us to advance or rewind "time" if we choose to. */
void update( double lon, double lat, long int warp = 0 );
- // Given lon/lat, update timezone information and local_offset
+ /**
+ * Given lon/lat, update timezone information and local_offset
+ * The updateLocal() method is intended to be called less
+ * frequently - only when your position is likely to be changed
+ * enough that your timezone may have changed as well. In the
+ * FlightGear project we call updateLocal() every few minutes from
+ * our periodic event manager.
+ * @param lon current longitude
+ * @param lat current latitude
+ * @param root base path containing time zone directory */
void updateLocal( double lon, double lat, const string& root );
+ /** @return current system/unix time in seconds */
inline time_t get_cur_time() const { return cur_time; };
+
+ /** @return time zone name for your current position*/
inline char* get_zonename() const { return zonename; }
+
+ /** @return GMT in a "brokent down" tm structure */
inline struct tm* getGmt()const { return gmt; };
+
+ /** @return julian date */
inline double getJD() const { return jd; };
+
+ /** @return modified julian date */
inline double getMjd() const { return mjd; };
+
+ /** @return local side real time */
inline double getLst() const { return lst; };
+
+ /** @return grenich side real time (lst when longitude == 0) */
inline double getGst() const { return gst; };
};
// Some useful utility functions that don't make sense to be part of
// the SGTime class
-// Return unix time in seconds for the given data (relative to GMT)
+/**
+ * \relates SGTime
+ * Return unix time in seconds for the given data (relative to GMT)
+ * @param year current GMT year
+ * @param month current GMT month
+ * @param day current GMT day
+ * @param hour current GMT hour
+ * @param minute current minute
+ * @param second current second
+ * @return unix/system time in seconds
+ */
time_t sgTimeGetGMT(int year, int month, int day,
int hour, int minute, int second);
-// this is just a wrapper
+/**
+ * \relates SGTime
+ * this is just a wrapper for sgTimeGetGMT that allows an alternate
+ * form of input parameters.
+ * @param the_time the current GMT time in the tm structure
+ * @return unix/system time in seconds
+ */
inline time_t sgTimeGetGMT(struct tm* the_time) {
// printf("Using: %24s as input\n", asctime(the_time));
return sgTimeGetGMT(the_time->tm_year,
the_time->tm_sec);
}
-// given a date in months, mn, days, dy, years, yr, return the
-// modified Julian date (number of days elapsed since 1900 jan 0.5),
-// mjd. Adapted from Xephem.
+/**
+ * \relates SGTime
+ * Given a date in our form, return the equivalent modified Julian
+ * date (number of days elapsed since 1900 jan 0.5), mjd. Adapted
+ * from Xephem.
+ * @param mn month
+ * @param dy day
+ * @param yr year
+ * @return modified julian date */
double sgTimeCalcMJD(int mn, double dy, int yr);
-// given an mjd, calculate greenwich mean sidereal time, gst
+/**
+ * \relates SGTime
+ * Given an mjd, calculate greenwich mean sidereal time, gst
+ * @param mjd modified julian date
+ * @return greenwich mean sidereal time (gst)
+ */
double sgTimeCalcGST( double mjd );
-// format time
+/**
+ * \relates SGTime
+ * Format time in a pretty form
+ * @param p time specified in a tm struct
+ * @param buf buffer space to contain the result
+ * @return pointer to character array containt the result
+ */
char* sgTimeFormatTime( const struct tm* p, char* buf );
-// timestamp.hxx -- class for managing a timestamp (seconds & milliseconds.)
-//
+/**
+ * \file timestamp.hxx
+ * Provides a class for managing a timestamp (seconds & milliseconds.)
+ */
+
// Written by Curtis Olson, started December 1998.
//
// Copyright (C) 1998 Curtis L. Olson - curt@flightgear.org
SGTimeStamp operator + (const SGTimeStamp& t, const long& m);
long operator - (const SGTimeStamp& a, const SGTimeStamp& b);
+/**
+ * The SGTimeStamp class allows you to mark and compare time stamps
+ * with microsecond accuracy (if your system has support for this
+ * level of accuracy.)
+ *
+ * The SGTimeStamp is useful for tracking the elapsed time of various
+ * events in your program. You can also use it to keep constistant
+ * motion across varying frame rates.
+ */
+
class SGTimeStamp {
private:
public:
+ /** Default constructor */
SGTimeStamp();
+
+ /**
+ * This creates an instance of the SGTimeStamp object. When
+ * calling the constructor you may provide initial seconds an
+ * microseconds values.
+ * @param s initial seconds value
+ * @param m initial microseconds value
+ */
SGTimeStamp( const long s, const long m );
~SGTimeStamp();
- // Set time to current time
+ /** Update stored time to current time (seconds and microseconds) */
void stamp();
+ /** Compare two time stamps for equality */
SGTimeStamp& operator = ( const SGTimeStamp& t );
+ /**
+ * Increment the saved time by the specified number of microseconds
+ * @param t time stamp
+ * @param m microseconds increment
+ * @return new time stamp
+ */
friend SGTimeStamp operator + (const SGTimeStamp& t, const long& m);
+
+ /**
+ * Subtract two time stamps returning the difference in microseconds.
+ * @param a timestamp 1
+ * @param b timestame 2
+ * @return difference in microseconds
+ */
friend long operator - (const SGTimeStamp& a, const SGTimeStamp& b);
+ /** @return the saved seconds of this time stamp */
inline long get_seconds() const { return seconds; }
- // inline long get_usec() const { return usec; }
+
+ /** @return the saved microseconds of this time stamp */
+ inline long get_usec() const { return usec; }
};
inline SGTimeStamp::SGTimeStamp() {
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