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flightgear/Simulator/Time/fg_time.cxx

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// fg_time.cxx -- data structures and routines for managing time related stuff.
//
// Written by Curtis Olson, started August 1997.
//
// Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program 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
// 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., 675 Mass Ave, Cambridge, MA 02139, USA.
//
// $Id$
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <Include/compiler.h>
#ifdef FG_HAVE_STD_INCLUDES
# include <cmath>
# include <cstdio>
# include <cstdlib>
# include <ctime>
#else
# include <math.h>
# include <stdio.h>
# include <stdlib.h>
# include <time.h>
#endif
#ifdef HAVE_SYS_TIMEB_H
# include <sys/timeb.h> // for ftime() and struct timeb
#endif
#ifdef HAVE_UNISTD_H
# include <unistd.h> // for gettimeofday()
#endif
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h> // for get/setitimer, gettimeofday, struct timeval
#endif
#include <Debug/logstream.hxx>
#include <Astro/sky.hxx>
#include <Astro/solarsystem.hxx>
#include <FDM/flight.hxx>
#include <Include/fg_constants.h>
#include <Main/options.hxx>
#include <Time/light.hxx>
#include "fg_time.hxx"
#define DEGHR(x) ((x)/15.)
#define RADHR(x) DEGHR(x*RAD_TO_DEG)
// #define MK_TIME_IS_GMT 0 // default value
// #define TIME_ZONE_OFFSET_WORK 0 // default value
FGTime::FGTime()
{
if (cur_time_params) {
FG_LOG( FG_GENERAL, FG_ALERT,
"Error: only one instance of FGTime allowed" );
exit(-1);
}
cur_time_params = this;
}
FGTime::~FGTime()
{
}
// Initialize the time dependent variables (maybe I'll put this in the
// constructor later)
void FGTime::init()
{
FG_LOG( FG_EVENT, FG_INFO, "Initializing Time" );
gst_diff = -9999.0;
FG_LOG( FG_EVENT, FG_DEBUG,
"time offset = " << current_options.get_time_offset() );
time_t timeOffset = current_options.get_time_offset();
time_t gstStart = current_options.get_start_gst();
time_t lstStart = current_options.get_start_lst();
// would it be better to put these sanity checks in the options
// parsing code? (CLO)
if (timeOffset && gstStart)
{
FG_LOG( FG_EVENT, FG_ALERT, "Error: you specified both a time offset and a gst. Confused now!" );
current_options.usage();
exit(1);
}
if (timeOffset && lstStart)
{
FG_LOG( FG_EVENT, FG_ALERT, "Error: you specified both a time offset and a lst. Confused now!" );
current_options.usage();
exit(1);
}
if (gstStart && lstStart)
{
FG_LOG( FG_EVENT, FG_ALERT, "Error: you specified both a time offset and a lst. Confused now!" );
current_options.usage();
exit(1);
}
cur_time = time(NULL);
if (gstStart)
warp = gstStart - cur_time;
else if (lstStart) // I need to use the time zone info for this one, but I'll do that later.
// Until then, Gst and LST are the same
{
warp = lstStart - cur_time;
}
else if (timeOffset)
{
warp = timeOffset;
}
else
{
warp = 0;
}
warp_delta = 0;
pause = current_options.get_pause();
}
// 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.
void FGTime::cal_mjd (int mn, double dy, int yr)
{
//static double last_mjd, last_dy;
//double mjd;
//static int last_mn, last_yr;
int b, d, m, y;
long c;
if (mn == last_mn && yr == last_yr && dy == last_dy) {
mjd = last_mjd;
//return(mjd);
}
m = mn;
y = (yr < 0) ? yr + 1 : yr;
if (mn < 3) {
m += 12;
y -= 1;
}
if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
b = 0;
} else {
int a;
a = y/100;
b = 2 - a + a/4;
}
if (y < 0) {
c = (long)((365.25*y) - 0.75) - 694025L;
} else {
c = (long)(365.25*y) - 694025L;
}
d = (int)(30.6001*(m+1));
mjd = b + c + d + dy - 0.5;
last_mn = mn;
last_dy = dy;
last_yr = yr;
last_mjd = mjd;
//return(mjd);
}
// given an mjd, calculate greenwich mean sidereal time, gst
void FGTime::utc_gst ()
{
double day = floor(mjd-0.5)+0.5;
double hr = (mjd-day)*24.0;
double T, x;
T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
x /= 3600.0;
gst = (1.0/SIDRATE)*hr + x;
FG_LOG( FG_EVENT, FG_DEBUG, " gst => " << gst );
}
// given Julian Date and Longitude (decimal degrees West) compute
// Local Sidereal Time, in decimal hours.
//
// Provided courtesy of ecdowney@noao.edu (Elwood Downey)
double FGTime::sidereal_precise (double lng)
{
double lstTmp;
/* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
mjd + MJD0, lng); */
// convert to required internal units
lng *= DEG_TO_RAD;
// compute LST and print
utc_gst();
lstTmp = gst - RADHR (lng);
lstTmp -= 24.0*floor(lst/24.0);
// printf ("%7.4f\n", lst);
// that's all
return (lstTmp);
}
// return a courser but cheaper estimate of sidereal time
double FGTime::sidereal_course(double lng)
{
//struct tm *gmt;
//double lstTmp;
time_t start_gmt, now;
double diff, part, days, hours, lstTmp;
char tbuf[64];
//gmt = t->gmt;
//now = t->cur_time;
now = cur_time;
start_gmt = get_gmt(gmt->tm_year, 2, 21, 12, 0, 0);
FG_LOG( FG_EVENT, FG_DEBUG, " COURSE: GMT = " << format_time(gmt, tbuf) );
FG_LOG( FG_EVENT, FG_DEBUG, " March 21 noon (GMT) = " << start_gmt );
diff = (now - start_gmt) / (3600.0 * 24.0);
FG_LOG( FG_EVENT, FG_DEBUG,
" Time since 3/21/" << gmt->tm_year << " GMT = " << diff );
part = fmod(diff, 1.0);
days = diff - part;
hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
lstTmp = (days - lng)/15.0 + hours - 12;
while ( lstTmp < 0.0 ) {
lstTmp += 24.0;
}
FG_LOG( FG_EVENT, FG_DEBUG,
" days = " << days << " hours = " << hours << " lon = "
<< lng << " lst = " << lstTmp );
return(lstTmp);
}
// Update time variables such as gmt, julian date, and sidereal time
void FGTime::update(FGInterface *f)
{
double gst_precise, gst_course;
FG_LOG( FG_EVENT, FG_DEBUG, "Updating time" );
// get current Unix calendar time (in seconds)
warp += warp_delta;
cur_time = time(NULL) + warp;
FG_LOG( FG_EVENT, FG_DEBUG,
" Current Unix calendar time = " << cur_time
<< " warp = " << warp << " delta = " << warp_delta );
if ( warp_delta ) {
// time is changing so force an update
local_update_sky_and_lighting_params();
}
// get GMT break down for current time
gmt = gmtime(&cur_time);
FG_LOG( FG_EVENT, FG_DEBUG,
" Current GMT = " << gmt->tm_mon+1 << "/"
<< gmt->tm_mday << "/" << gmt->tm_year << " "
<< gmt->tm_hour << ":" << gmt->tm_min << ":"
<< gmt->tm_sec );
// calculate modified Julian date
// t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
// (int)(t->gmt->tm_year + 1900));
cal_mjd ((int)(gmt->tm_mon+1), (double)gmt->tm_mday,
(int)(gmt->tm_year + 1900));
// add in partial day
mjd += (gmt->tm_hour / 24.0) + (gmt->tm_min / (24.0 * 60.0)) +
(gmt->tm_sec / (24.0 * 60.0 * 60.0));
// convert "back" to Julian date + partial day (as a fraction of one)
jd = mjd + MJD0;
FG_LOG( FG_EVENT, FG_DEBUG, " Current Julian Date = " << jd );
// printf(" Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG);
// Calculate local side real time
if ( gst_diff < -100.0 ) {
// first time through do the expensive calculation & cheap
// calculation to get the difference.
FG_LOG( FG_EVENT, FG_INFO, " First time, doing precise gst" );
gst_precise = gst = sidereal_precise(0.00);
gst_course = sidereal_course(0.00);
gst_diff = gst_precise - gst_course;
lst = sidereal_course(-(f->get_Longitude() * RAD_TO_DEG)) + gst_diff;
} else {
// course + difference should drift off very slowly
gst = sidereal_course( 0.00 ) + gst_diff;
lst = sidereal_course( -(f->get_Longitude() * RAD_TO_DEG)) + gst_diff;
}
FG_LOG( FG_EVENT, FG_DEBUG,
" Current lon=0.00 Sidereal Time = " << gst );
FG_LOG( FG_EVENT, FG_DEBUG,
" Current LOCAL Sidereal Time = " << lst << " ("
<< sidereal_precise(-(f->get_Longitude() * RAD_TO_DEG))
<< ") (diff = " << gst_diff << ")" );
}
/******************************************************************
* The following are some functions that were included as FGTime
* members, although they currently don't make used of any of the
* class's variables. Maybe this'll change in the future
*****************************************************************/
// Return time_t for Sat Mar 21 12:00:00 GMT
//
// I believe the mktime() has a SYSV vs. BSD behavior difference.
//
// The BSD style mktime() is nice because it returns its result
// assuming you have specified the input time in GMT
//
// The SYSV style mktime() is a pain because it returns its result
// assuming you have specified the input time in your local timezone.
// Therefore you have to go to extra trouble to convert back to GMT.
//
// If you are having problems with incorrectly positioned astronomical
// bodies, this is a really good place to start looking.
time_t FGTime::get_gmt(int year, int month, int day, int hour, int min, int sec)
{
struct tm mt;
// For now we assume that if daylight is not defined in
// /usr/include/time.h that we have a machine with a BSD behaving
// mktime()
# if !defined(HAVE_DAYLIGHT)
# define MK_TIME_IS_GMT 1
# endif
// timezone seems to work as a proper offset for Linux & Solaris
# if defined( __linux__ ) || defined( __sun__ )
# define TIMEZONE_OFFSET_WORKS 1
# endif
mt.tm_mon = month;
mt.tm_mday = day;
mt.tm_year = year;
mt.tm_hour = hour;
mt.tm_min = min;
mt.tm_sec = sec;
mt.tm_isdst = -1; // let the system determine the proper time zone
# if defined( MK_TIME_IS_GMT )
return ( mktime(&mt) );
# else // ! defined ( MK_TIME_IS_GMT )
long int start = mktime(&mt);
FG_LOG( FG_EVENT, FG_DEBUG, "start1 = " << start );
// the ctime() call can screw up time progression on some versions
// of Linux
// fgPrintf( FG_EVENT, FG_DEBUG, "start2 = %s", ctime(&start));
FG_LOG( FG_EVENT, FG_DEBUG, "(tm_isdst = " << mt.tm_isdst << ")" );
timezone = fix_up_timezone( timezone );
# if defined( TIMEZONE_OFFSET_WORKS )
FG_LOG( FG_EVENT, FG_DEBUG,
"start = " << start << ", timezone = " << timezone );
return( start - timezone );
# else // ! defined( TIMEZONE_OFFSET_WORKS )
daylight = mt.tm_isdst;
if ( daylight > 0 ) {
daylight = 1;
} else if ( daylight < 0 ) {
FG_LOG( FG_EVENT, FG_WARN,
"OOOPS, problem in fg_time.cxx, no daylight savings info." );
}
long int offset = -(timezone / 3600 - daylight);
FG_LOG( FG_EVENT, FG_DEBUG, " Raw time zone offset = " << timezone );
FG_LOG( FG_EVENT, FG_DEBUG, " Daylight Savings = " << daylight );
FG_LOG( FG_EVENT, FG_DEBUG, " Local hours from GMT = " << offset );
long int start_gmt = start - timezone + (daylight * 3600);
FG_LOG( FG_EVENT, FG_DEBUG, " March 21 noon (CST) = " << start );
return ( start_gmt );
# endif // ! defined( TIMEZONE_OFFSET_WORKS )
# endif // ! defined ( MK_TIME_IS_GMT )
}
// Fix up timezone if using ftime()
long int FGTime::fix_up_timezone( long int timezone_orig )
{
#if !defined( HAVE_GETTIMEOFDAY ) && defined( HAVE_FTIME )
// ftime() needs a little extra help finding the current timezone
struct timeb current;
ftime(&current);
return( current.timezone * 60 );
#else
return( timezone_orig );
#endif
}
char* FGTime::format_time( const struct tm* p, char* buf )
{
sprintf( buf, "%d/%d/%2d %d:%02d:%02d",
p->tm_mon, p->tm_mday, p->tm_year,
p->tm_hour, p->tm_min, p->tm_sec);
return buf;
}
// Force an update of the sky and lighting parameters
void FGTime::local_update_sky_and_lighting_params( void ) {
// fgSunInit();
SolarSystem::theSolarSystem->rebuild();
cur_light_params.Update();
fgSkyColorsInit();
}
FGTime* FGTime::cur_time_params = 0;
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