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simgear/simgear/timing/sg_time.cxx
mfranz dcb95d131b - new FSF addresses 
- coplied license headers from h(xx) files to respective c(xx) files
- removed trailing spaces
- fixe $Id$
- fixed typos
2006-03-08 18:16:08 +00:00

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// sg_time.cxx -- data structures and routines for managing time related stuff.
//
// 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.
//
// $Id$
#ifdef HAVE_CONFIG_H
# include <simgear_config.h>
#endif
#include <simgear/compiler.h>
#include <errno.h> // for errno
#ifdef SG_HAVE_STD_INCLUDES
# include <cstdio>
# include <cstdlib>
# include <ctime>
#else
# include <math.h>
# include <stdio.h>
# include <stdlib.h>
#endif
#include <string>
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h> // for get/setitimer, gettimeofday, struct timeval
#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
#include <math.h> // for NAN
#include <simgear/constants.h>
#include <simgear/debug/logstream.hxx>
#include <simgear/misc/sg_path.hxx>
#include "sg_time.hxx"
#include "timezone.h"
#include "lowleveltime.h"
#define DEGHR(x) ((x)/15.)
#define RADHR(x) DEGHR(x*SGD_RADIANS_TO_DEGREES)
static const double MJD0 = 2415020.0;
static const double J2000 = 2451545.0 - MJD0;
static const double SIDRATE = 0.9972695677;
void SGTime::init( double lon_rad, double lat_rad,
const string& root, time_t init_time )
{
SG_LOG( SG_EVENT, SG_INFO, "Initializing Time" );
gst_diff = -9999.0;
if ( init_time ) {
cur_time = init_time;
} else {
cur_time = time(NULL);
}
SG_LOG( SG_EVENT, SG_INFO,
"Current greenwich mean time = " << asctime(gmtime(&cur_time)));
SG_LOG( SG_EVENT, SG_INFO,
"Current local time = " << asctime(localtime(&cur_time)));
if ( !root.empty()) {
SGPath zone( root );
zone.append( "zone.tab" );
SG_LOG( SG_EVENT, SG_INFO, "Reading timezone info from: "
<< zone.str() );
tzContainer = new SGTimeZoneContainer( zone.c_str() );
SGGeoCoord location( SGD_RADIANS_TO_DEGREES * lat_rad, SGD_RADIANS_TO_DEGREES * lon_rad );
SGGeoCoord* nearestTz = tzContainer->getNearest(location);
SGPath name( root );
name.append( nearestTz->getDescription() );
zonename = name.str();
SG_LOG( SG_EVENT, SG_INFO, "Using zonename = " << zonename );
} else {
SG_LOG( SG_EVENT, SG_INFO, "*** NO TIME ZONE NAME ***" );
tzContainer = NULL;
zonename.erase();
}
}
SGTime::SGTime( double lon_rad, double lat_rad, const string& root,
time_t init_time )
{
init( lon_rad, lat_rad, root, init_time );
}
SGTime::SGTime( const string& root ) {
init( 0.0, 0.0, root, 0 );
}
SGTime::SGTime() {
init( 0.0, 0.0, "", 0 );
}
SGTime::~SGTime()
{
if ( tzContainer != NULL ) {
SGTimeZoneContainer *tmp = tzContainer;
tzContainer = NULL;
delete tmp;
}
}
// given Julian Date and Longitude (decimal degrees West) compute
// Local Sidereal Time, in decimal hours.
//
// Provided courtesy of ecdowney@noao.edu (Elwood Downey)
static double sidereal_precise( double mjd, double lng )
{
/* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
mjd + MJD0, lng); */
// convert to required internal units
lng *= SGD_DEGREES_TO_RADIANS;
// compute LST and print
double gst = sgTimeCalcGST( mjd );
double lst = gst - RADHR( lng );
lst -= 24.0 * floor( lst / 24.0 );
// printf ("%7.4f\n", lstTmp);
return lst;
}
// return a courser but cheaper estimate of sidereal time
static double sidereal_course( time_t cur_time, const struct tm *gmt, double lng )
{
time_t start_gmt, now;
double diff, part, days, hours, lstTmp;
char tbuf[64];
now = cur_time;
start_gmt = sgTimeGetGMT(gmt->tm_year, 2, 21, 12, 0, 0);
SG_LOG( SG_EVENT, SG_DEBUG, " COURSE: GMT = "
<< sgTimeFormatTime(gmt, tbuf) );
SG_LOG( SG_EVENT, SG_DEBUG, " March 21 noon (GMT) = " << start_gmt );
diff = (now - start_gmt) / (3600.0 * 24.0);
SG_LOG( SG_EVENT, SG_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;
}
SG_LOG( SG_EVENT, SG_DEBUG,
" days = " << days << " hours = " << hours << " lon = "
<< lng << " lst = " << lstTmp );
return lstTmp;
}
// Update the time related variables
void SGTime::update( double lon_rad, double lat_rad,
time_t ct, long int warp )
{
double gst_precise, gst_course;
#if defined(_MSC_VER) || defined(__MINGW32__)
tm * gmt = &m_gmt;
#endif
SG_LOG( SG_EVENT, SG_DEBUG, "Updating time" );
// get current Unix calendar time (in seconds)
// warp += warp_delta;
if ( ct ) {
cur_time = ct + warp;
} else {
cur_time = time(NULL) + warp;
}
SG_LOG( SG_EVENT, SG_DEBUG,
" Current Unix calendar time = " << cur_time
<< " warp = " << warp );
// get GMT break down for current time
#if defined(_MSC_VER) || defined(__MINGW32__)
memcpy( gmt, gmtime(&cur_time), sizeof(tm) );
#else
gmt = gmtime(&cur_time);
#endif
SG_LOG( SG_EVENT, SG_DEBUG,
" Current GMT = " << gmt->tm_mon+1 << "/"
<< gmt->tm_mday << "/" << (1900 + gmt->tm_year) << " "
<< gmt->tm_hour << ":" << gmt->tm_min << ":"
<< gmt->tm_sec );
// calculate modified Julian date starting with current
mjd = sgTimeCurrentMJD( ct, warp );
// 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;
SG_LOG( SG_EVENT, SG_DEBUG, " Current Julian Date = " << jd );
// printf(" Current Longitude = %.3f\n", FG_Longitude * SGD_RADIANS_TO_DEGREES);
// Calculate local side real time
if ( gst_diff < -100.0 ) {
// first time through do the expensive calculation & cheap
// calculation to get the difference.
SG_LOG( SG_EVENT, SG_INFO, " First time, doing precise gst" );
gst_precise = gst = sidereal_precise( mjd, 0.00 );
gst_course = sidereal_course( cur_time, gmt, 0.00 );
gst_diff = gst_precise - gst_course;
lst = sidereal_course( cur_time, gmt,
-(lon_rad * SGD_RADIANS_TO_DEGREES) ) + gst_diff;
} else {
// course + difference should drift off very slowly
gst = sidereal_course( cur_time, gmt, 0.00 ) + gst_diff;
lst = sidereal_course( cur_time, gmt,
-(lon_rad * SGD_RADIANS_TO_DEGREES) ) + gst_diff;
}
SG_LOG( SG_EVENT, SG_DEBUG,
" Current lon=0.00 Sidereal Time = " << gst );
SG_LOG( SG_EVENT, SG_DEBUG,
" Current LOCAL Sidereal Time = " << lst << " ("
<< sidereal_precise( mjd, -(lon_rad * SGD_RADIANS_TO_DEGREES) )
<< ") (diff = " << gst_diff << ")" );
}
// Given lon/lat, update timezone information and local_offset
void SGTime::updateLocal( double lon_rad, double lat_rad, const string& root ) {
// sanity checking
if ( lon_rad < -SGD_PI || lon_rad> SGD_PI ) {
// not within -180 ... 180
lon_rad = 0.0;
}
if ( lat_rad < -SGD_PI_2 || lat_rad > SGD_PI_2 ) {
// not within -90 ... 90
lat_rad = 0.0;
}
if ( lon_rad != lon_rad ) {
// only true if lon_rad == nan
SG_LOG( SG_EVENT, SG_ALERT,
" Detected lon_rad == nan, resetting to 0.0" );
lon_rad = 0.0;
}
if ( lat_rad != lat_rad ) {
// only true if lat_rad == nan
SG_LOG( SG_EVENT, SG_ALERT,
" Detected lat_rad == nan, resetting to 0.0" );
lat_rad = 0.0;
}
time_t currGMT;
time_t aircraftLocalTime;
SGGeoCoord location( SGD_RADIANS_TO_DEGREES * lat_rad,
SGD_RADIANS_TO_DEGREES * lon_rad );
SGGeoCoord* nearestTz = tzContainer->getNearest(location);
SGPath zone( root );
zone.append ( nearestTz->getDescription() );
zonename = zone.str();
//Avoid troubles when zone.tab hasn't got the right line endings
if (zonename[zonename.size()-1] == '\r')
{
zonename[zonename.size()-1]=0;
zone.set( zonename );
}
currGMT = sgTimeGetGMT( gmtime(&cur_time) );
aircraftLocalTime = sgTimeGetGMT( (fgLocaltime(&cur_time, zone.c_str())) );
local_offset = aircraftLocalTime - currGMT;
// cout << "Using " << local_offset << " as local time offset Timezone is "
// << zonename << endl;
}
// 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.
double sgTimeCalcMJD(int mn, double dy, int yr) {
double mjd;
// internal book keeping data
static double last_mjd, last_dy;
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;
}
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;
}
// return the current modified Julian date (number of days elapsed
// since 1900 jan 0.5), mjd.
double sgTimeCurrentMJD( time_t ct, long int warp ) {
#if defined(_MSC_VER) || defined(__MINGW32__)
struct tm m_gmt; // copy of system gmtime(&time_t) structure
struct tm *gmt = &m_gmt;
#else
struct tm *gmt;
#endif
// get current Unix calendar time (in seconds)
// warp += warp_delta;
time_t cur_time;
if ( ct ) {
cur_time = ct + warp;
} else {
cur_time = time(NULL) + warp;
}
SG_LOG( SG_EVENT, SG_DEBUG,
" Current Unix calendar time = " << cur_time
<< " warp = " << warp );
// get GMT break down for current time
#if defined(_MSC_VER) || defined(__MINGW32__)
memcpy( gmt, gmtime(&cur_time), sizeof(tm) );
#else
gmt = gmtime(&cur_time);
#endif
SG_LOG( SG_EVENT, SG_DEBUG,
" Current GMT = " << gmt->tm_mon+1 << "/"
<< gmt->tm_mday << "/" << (1900 + 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));
double mjd = sgTimeCalcMJD( (int)(gmt->tm_mon+1), (double)gmt->tm_mday,
(int)(gmt->tm_year + 1900) );
return mjd;
}
// given an mjd, calculate greenwich mean sidereal time, gst
double sgTimeCalcGST( double mjd ) {
double 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;
SG_LOG( SG_EVENT, SG_DEBUG, " gst => " << gst );
return gst;
}
#if defined( HAVE_TIMEGM )
// ignore this function
#elif defined( MK_TIME_IS_GMT )
// ignore this function
#else // ! defined ( MK_TIME_IS_GMT )
// Fix up timezone if using ftime()
static long int 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
}
#endif
/******************************************************************
* The following are some functions that were included as SGTime
* members, although they currently don't make use 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
//
// On many systems it is ambiguous if mktime() assumes the input is in
// GMT, or local timezone. To address this, a new function called
// timegm() is appearing. It works exactly like mktime() but
// explicitely interprets the input as GMT.
//
// timegm() is available and documented under FreeBSD. It is
// available, but completely undocumented on my current Debian 2.1
// distribution.
//
// In the absence of timegm() we have to guess what mktime() might do.
//
// Many older BSD style systems have a mktime() that assumes the input
// time in GMT. But FreeBSD explicitly states that mktime() assumes
// local time zone
//
// The mktime() on many SYSV style systems (such as Linux) usually
// returns its result assuming you have specified the input time in
// your local timezone. Therefore, in the absence if timegm() 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 sgTimeGetGMT(int year, int month, int day, int hour, int min, int sec)
{
struct tm mt;
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
// For now we assume that if daylight is not defined in
// /usr/include/time.h that we have a machine with a mktime() that
// assumes input is in GMT ... this only matters if we are
// building on a system that does not have timegm()
#if !defined(HAVE_DAYLIGHT)
# define MK_TIME_IS_GMT 1
#endif
#if defined( HAVE_TIMEGM )
return ( timegm(&mt) );
#elif defined( MK_TIME_IS_GMT )
time_t ret = mktime(&mt);
#ifdef __CYGWIN__
ret -= _timezone;
#endif
// This is necessary as some mktime() calls may
// try to access the system timezone files
// if this open fails errno is set to 2
// CYGWIN for one does this
// if ( errno ) {
// perror( "sgTimeGetGMT()" );
// errno = 0;
// }
// reset errno in any event.
errno = 0;
return ret;
#else // ! defined ( MK_TIME_IS_GMT )
// timezone seems to work as a proper offset for Linux & Solaris
# if defined( __linux__ ) || defined(__sun) ||defined(__CYGWIN__)
# define TIMEZONE_OFFSET_WORKS 1
# endif
#if defined(__CYGWIN__)
#define TIMEZONE _timezone
#else
#define TIMEZONE timezone
#endif
time_t start = mktime(&mt);
SG_LOG( SG_EVENT, SG_DEBUG, "start1 = " << start );
// the ctime() call can screw up time progression on some versions
// of Linux
// fgPrintf( SG_EVENT, SG_DEBUG, "start2 = %s", ctime(&start));
SG_LOG( SG_EVENT, SG_DEBUG, "(tm_isdst = " << mt.tm_isdst << ")" );
TIMEZONE = fix_up_timezone( TIMEZONE );
# if defined( TIMEZONE_OFFSET_WORKS )
SG_LOG( SG_EVENT, SG_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 ) {
SG_LOG( SG_EVENT, FG_WARN,
"OOOPS, problem in sg_time.cxx, no daylight savings info." );
}
long int offset = -(TIMEZONE / 3600 - daylight);
SG_LOG( SG_EVENT, SG_DEBUG, " Raw time zone offset = " << TIMEZONE );
SG_LOG( SG_EVENT, SG_DEBUG, " Daylight Savings = " << daylight );
SG_LOG( SG_EVENT, SG_DEBUG, " Local hours from GMT = " << offset );
long int start_gmt = start - TIMEZONE + (daylight * 3600);
SG_LOG( SG_EVENT, SG_DEBUG, " March 21 noon (CST) = " << start );
return ( start_gmt );
# endif // ! defined( TIMEZONE_OFFSET_WORKS )
#endif // ! defined ( MK_TIME_IS_GMT )
}
// format time
char* sgTimeFormatTime( 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;
}
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