sg_time.hxx

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// Written by Curtis Olson, started August 1997.
//
// Copyright (C) 1997  Curtis L. Olson  - http://www.flightgear.org/~curt
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public
// License as published by the Free Software Foundation; either
// version 2 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
// Library General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
//
// $Id: sg__time_8hxx_source.html,v 1.3 2010/02/23 22:10:16 curt Exp $


#ifndef _SG_TIME_HXX
#define _SG_TIME_HXX


#ifndef __cplusplus
# error This library requires C++
#endif


#include <simgear/compiler.h>

#include <ctime>

#include <simgear/timing/timezone.h>


class SGTime {

private:
    // tzContainer stores all the current Timezone control points/
    SGTimeZoneContainer* tzContainer;

    // Points to the current local timezone name;
    std::string zonename;

    // Unix "calendar" time in seconds
    time_t cur_time;

    // Break down of equivalent GMT time
    struct tm m_gmt;    // copy of system gmtime(&time_t) structure

    // offset of local time relative to GMT
    time_t local_offset;

    // Julian date
    double jd;

    // modified Julian date
    double mjd;

    // side real time at prime meridian
    double gst;

    // local sidereal time
    double lst;

    // the difference between the precise / expensive sidereal time
    // algorithm result and the quick course result.  course_gst +
    // gst_diff has pretty good accuracy over the span of a couple hours
    double gst_diff;

    void init( double lon_rad, double lat_rad, const std::string& root,
               time_t init_time );

public:

    SGTime();

    SGTime( double lon_rad, double lat_rad, const std::string& root,
            time_t init_time );

    SGTime( const std::string& root );

    ~SGTime();

    void update( double lon_rad, double lat_rad, time_t ct, long int warp );

    void updateLocal( double lon_rad, double lat_rad, const std::string& root );

    inline time_t get_cur_time() const { return cur_time; };

    inline const char * get_zonename() const { return zonename.c_str(); }

    inline struct tm* getGmt()const { return (struct tm *)&m_gmt; };

    inline double getJD() const { return jd; };

    inline double getMjd() const { return mjd; };

    inline double getLst() const { return lst; };

    inline double getGst() const { return gst; };

    inline time_t get_local_offset() const { return local_offset; };
};


// Some useful utility functions that don't make sense to be part of
// the SGTime class

time_t sgTimeGetGMT(int year, int month, int day, 
                    int hour, int minute, int second);

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_mon,
                        the_time->tm_mday,
                        the_time->tm_hour,
                        the_time->tm_min,
                        the_time->tm_sec);
}

double sgTimeCalcMJD(int mn, double dy, int yr);

double sgTimeCurrentMJD( time_t ct /* = 0 */, long int warp /* = 0 */ );

double sgTimeCalcGST( double mjd );

char* sgTimeFormatTime( const struct tm* p, char* buf );


#endif // _SG_TIME_HXX

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