curt
e2b4c0787a
flightgear, especially when this occurs in a simgear .hxx file. This is now expressly forbidden, and will cause problems anyways because we now changed the name to <simgear_config.h> which isn't installed, so you can't include it in an installed header file.
492 lines
14 KiB
C++
492 lines
14 KiB
C++
// sg_time.cxx -- data structures and routines for managing time related stuff.
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//
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// Written by Curtis Olson, started August 1997.
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//
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// Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Library General Public
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// License as published by the Free Software Foundation; either
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// version 2 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Library General Public License for more details.
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//
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// You should have received a copy of the GNU Library General Public
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// License along with this library; if not, write to the
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// Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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// Boston, MA 02111-1307, USA.
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//
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// $Id$
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#include <simgear/compiler.h>
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#include <errno.h> // for errno
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#ifdef SG_HAVE_STD_INCLUDES
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# include <cmath>
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# include <cstdio>
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# include <cstdlib>
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# include <ctime>
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#else
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# include <math.h>
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# include <stdio.h>
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# include <stdlib.h>
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# include <time.h>
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#endif
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#ifdef HAVE_SYS_TIMEB_H
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# include <sys/timeb.h> // for ftime() and struct timeb
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#endif
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#ifdef HAVE_UNISTD_H
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# include <unistd.h> // for gettimeofday()
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#endif
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#ifdef HAVE_SYS_TIME_H
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# include <sys/time.h> // for get/setitimer, gettimeofday, struct timeval
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#endif
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#include <simgear/constants.h>
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#include <simgear/debug/logstream.hxx>
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#include <simgear/misc/sg_path.hxx>
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#include "sg_time.hxx"
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#include "timezone.h"
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#include "lowleveltime.h"
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#define DEGHR(x) ((x)/15.)
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#define RADHR(x) DEGHR(x*SGD_RADIANS_TO_DEGREES)
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static const double MJD0 = 2415020.0;
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static const double J2000 = 2451545.0 - MJD0;
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static const double SIDRATE = 0.9972695677;
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SGTime::SGTime( double lon, double lat, const string& root )
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{
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SG_LOG( SG_EVENT, SG_INFO, "Initializing Time" );
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gst_diff = -9999.0;
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cur_time = time(NULL);
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cout << "Current greenwich mean time = " << asctime(gmtime(&cur_time))
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<< endl;
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cout << "Current local time = "
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<< asctime(localtime(&cur_time)) << endl;
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if ( root != (string)"" ) {
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SGPath zone( root );
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zone.append( "zone.tab" );
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SG_LOG( SG_EVENT, SG_INFO, "Reading timezone info from: "
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<< zone.str() );
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tzContainer = new TimezoneContainer( zone.c_str() );
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GeoCoord location( SGD_RADIANS_TO_DEGREES * lat, SGD_RADIANS_TO_DEGREES * lon );
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GeoCoord* nearestTz = tzContainer->getNearest(location);
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SGPath name( root );
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name.append( nearestTz->getDescription() );
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zonename = strdup( name.c_str() );
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SG_LOG( SG_EVENT, SG_INFO, "Using zonename = " << zonename );
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} else {
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SG_LOG( SG_EVENT, SG_INFO, "*** NO TIME ZONE NAME ***" );
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tzContainer = NULL;
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zonename = NULL;
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}
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}
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SGTime::SGTime( const string& root ) {
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SGTime( 0.0, 0.0, root );
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}
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SGTime::SGTime() {
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SGTime( 0.0, 0.0, "" );
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}
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SGTime::~SGTime()
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{
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if ( tzContainer != NULL ) {
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delete tzContainer;
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}
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if ( zonename != NULL ) {
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delete zonename;
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}
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}
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// given Julian Date and Longitude (decimal degrees West) compute
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// Local Sidereal Time, in decimal hours.
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//
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// Provided courtesy of ecdowney@noao.edu (Elwood Downey)
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static double sidereal_precise( double mjd, double lng )
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{
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/* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
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mjd + MJD0, lng); */
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// convert to required internal units
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lng *= SGD_DEGREES_TO_RADIANS;
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// compute LST and print
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double gst = sgTimeCalcGST( mjd );
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double lst = gst - RADHR( lng );
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lst -= 24.0 * floor( lst / 24.0 );
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// printf ("%7.4f\n", lstTmp);
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return lst;
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}
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// return a courser but cheaper estimate of sidereal time
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static double sidereal_course( time_t cur_time, struct tm *gmt, double lng )
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{
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time_t start_gmt, now;
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double diff, part, days, hours, lstTmp;
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char tbuf[64];
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now = cur_time;
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start_gmt = sgTimeGetGMT(gmt->tm_year, 2, 21, 12, 0, 0);
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SG_LOG( SG_EVENT, SG_DEBUG, " COURSE: GMT = "
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<< sgTimeFormatTime(gmt, tbuf) );
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SG_LOG( SG_EVENT, SG_DEBUG, " March 21 noon (GMT) = " << start_gmt );
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diff = (now - start_gmt) / (3600.0 * 24.0);
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SG_LOG( SG_EVENT, SG_DEBUG,
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" Time since 3/21/" << gmt->tm_year << " GMT = " << diff );
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part = fmod(diff, 1.0);
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days = diff - part;
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hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
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lstTmp = (days - lng)/15.0 + hours - 12;
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while ( lstTmp < 0.0 ) {
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lstTmp += 24.0;
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}
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SG_LOG( SG_EVENT, SG_DEBUG,
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" days = " << days << " hours = " << hours << " lon = "
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<< lng << " lst = " << lstTmp );
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return lstTmp;
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}
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// Update the time related variables
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void SGTime::update( double lon, double lat, long int warp ) {
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double gst_precise, gst_course;
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SG_LOG( SG_EVENT, SG_DEBUG, "Updating time" );
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// get current Unix calendar time (in seconds)
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// warp += warp_delta;
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cur_time = time(NULL) + warp;
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SG_LOG( SG_EVENT, SG_DEBUG,
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" Current Unix calendar time = " << cur_time
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<< " warp = " << warp );
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// get GMT break down for current time
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gmt = gmtime(&cur_time);
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SG_LOG( SG_EVENT, SG_DEBUG,
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" Current GMT = " << gmt->tm_mon+1 << "/"
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<< gmt->tm_mday << "/" << gmt->tm_year << " "
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<< gmt->tm_hour << ":" << gmt->tm_min << ":"
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<< gmt->tm_sec );
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// calculate modified Julian date
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// t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
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// (int)(t->gmt->tm_year + 1900));
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mjd = sgTimeCalcMJD( (int)(gmt->tm_mon+1), (double)gmt->tm_mday,
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(int)(gmt->tm_year + 1900) );
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// add in partial day
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mjd += (gmt->tm_hour / 24.0) + (gmt->tm_min / (24.0 * 60.0)) +
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(gmt->tm_sec / (24.0 * 60.0 * 60.0));
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// convert "back" to Julian date + partial day (as a fraction of one)
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jd = mjd + MJD0;
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SG_LOG( SG_EVENT, SG_DEBUG, " Current Julian Date = " << jd );
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// printf(" Current Longitude = %.3f\n", FG_Longitude * SGD_RADIANS_TO_DEGREES);
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// Calculate local side real time
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if ( gst_diff < -100.0 ) {
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// first time through do the expensive calculation & cheap
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// calculation to get the difference.
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SG_LOG( SG_EVENT, SG_INFO, " First time, doing precise gst" );
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gst_precise = gst = sidereal_precise( mjd, 0.00 );
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gst_course = sidereal_course( cur_time, gmt, 0.00 );
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gst_diff = gst_precise - gst_course;
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lst = sidereal_course( cur_time, gmt, -(lon * SGD_RADIANS_TO_DEGREES) ) + gst_diff;
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} else {
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// course + difference should drift off very slowly
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gst = sidereal_course( cur_time, gmt, 0.00 ) + gst_diff;
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lst = sidereal_course( cur_time, gmt, -(lon * SGD_RADIANS_TO_DEGREES) ) + gst_diff;
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}
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SG_LOG( SG_EVENT, SG_DEBUG,
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" Current lon=0.00 Sidereal Time = " << gst );
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SG_LOG( SG_EVENT, SG_DEBUG,
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" Current LOCAL Sidereal Time = " << lst << " ("
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<< sidereal_precise( mjd, -(lon * SGD_RADIANS_TO_DEGREES) )
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<< ") (diff = " << gst_diff << ")" );
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}
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// Given lon/lat, update timezone information and local_offset
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void SGTime::updateLocal( double lon, double lat, const string& root )
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{
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time_t currGMT;
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time_t aircraftLocalTime;
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GeoCoord location( SGD_RADIANS_TO_DEGREES * lat, SGD_RADIANS_TO_DEGREES * lon );
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GeoCoord* nearestTz = tzContainer->getNearest(location);
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SGPath zone( root );
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zone.append ( nearestTz->getDescription() );
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if ( zonename ) {
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delete zonename;
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}
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zonename = strdup( zone.c_str() );
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currGMT = sgTimeGetGMT( gmtime(&cur_time) );
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aircraftLocalTime = sgTimeGetGMT( (fgLocaltime(&cur_time, zone.c_str())) );
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local_offset = aircraftLocalTime - currGMT;
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// cout << "Using " << local_offset << " as local time offset Timezone is "
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// << zonename << endl;
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}
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// given a date in months, mn, days, dy, years, yr, return the
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// modified Julian date (number of days elapsed since 1900 jan 0.5),
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// mjd. Adapted from Xephem.
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double sgTimeCalcMJD(int mn, double dy, int yr) {
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double mjd;
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// internal book keeping data
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static double last_mjd, last_dy;
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static int last_mn, last_yr;
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int b, d, m, y;
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long c;
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if (mn == last_mn && yr == last_yr && dy == last_dy) {
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mjd = last_mjd;
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}
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m = mn;
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y = (yr < 0) ? yr + 1 : yr;
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if (mn < 3) {
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m += 12;
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y -= 1;
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}
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if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
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b = 0;
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} else {
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int a;
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a = y/100;
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b = 2 - a + a/4;
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}
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if (y < 0) {
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c = (long)((365.25*y) - 0.75) - 694025L;
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} else {
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c = (long)(365.25*y) - 694025L;
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}
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d = (int)(30.6001*(m+1));
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mjd = b + c + d + dy - 0.5;
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last_mn = mn;
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last_dy = dy;
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last_yr = yr;
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last_mjd = mjd;
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return mjd;
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}
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// given an mjd, calculate greenwich mean sidereal time, gst
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double sgTimeCalcGST( double mjd ) {
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double gst;
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double day = floor(mjd-0.5)+0.5;
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double hr = (mjd-day)*24.0;
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double T, x;
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T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
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x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
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x /= 3600.0;
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gst = (1.0/SIDRATE)*hr + x;
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SG_LOG( SG_EVENT, SG_DEBUG, " gst => " << gst );
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return gst;
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}
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#if defined( HAVE_TIMEGM )
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// ignore this function
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#elif defined( MK_TIME_IS_GMT )
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// ignore this function
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#else // ! defined ( MK_TIME_IS_GMT )
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// Fix up timezone if using ftime()
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static long int fix_up_timezone( long int timezone_orig ) {
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# if !defined( HAVE_GETTIMEOFDAY ) && defined( HAVE_FTIME )
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// ftime() needs a little extra help finding the current timezone
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struct timeb current;
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ftime(¤t);
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return( current.timezone * 60 );
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# else
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return( timezone_orig );
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# endif
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}
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#endif
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/******************************************************************
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* The following are some functions that were included as SGTime
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* members, although they currently don't make use of any of the
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* class's variables. Maybe this'll change in the future
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*****************************************************************/
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// Return time_t for Sat Mar 21 12:00:00 GMT
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//
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// On many systems it is ambiguous if mktime() assumes the input is in
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// GMT, or local timezone. To address this, a new function called
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// timegm() is appearing. It works exactly like mktime() but
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// explicitely interprets the input as GMT.
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//
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// timegm() is available and documented under FreeBSD. It is
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// available, but completely undocumented on my current Debian 2.1
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// distribution.
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//
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// In the absence of timegm() we have to guess what mktime() might do.
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//
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// Many older BSD style systems have a mktime() that assumes the input
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// time in GMT. But FreeBSD explicitly states that mktime() assumes
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// local time zone
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//
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// The mktime() on many SYSV style systems (such as Linux) usually
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// returns its result assuming you have specified the input time in
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// your local timezone. Therefore, in the absence if timegm() you
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// have to go to extra trouble to convert back to GMT.
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//
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// If you are having problems with incorrectly positioned astronomical
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// bodies, this is a really good place to start looking.
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time_t sgTimeGetGMT(int year, int month, int day, int hour, int min, int sec)
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{
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struct tm mt;
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mt.tm_mon = month;
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mt.tm_mday = day;
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mt.tm_year = year;
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mt.tm_hour = hour;
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mt.tm_min = min;
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mt.tm_sec = sec;
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mt.tm_isdst = -1; // let the system determine the proper time zone
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// For now we assume that if daylight is not defined in
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// /usr/include/time.h that we have a machine with a mktime() that
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// assumes input is in GMT ... this only matters if we are
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// building on a system that does not have timegm()
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#if !defined(HAVE_DAYLIGHT)
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# define MK_TIME_IS_GMT 1
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#endif
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#if defined( HAVE_TIMEGM )
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return ( timegm(&mt) );
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#elif defined( MK_TIME_IS_GMT )
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time_t ret = mktime(&mt);
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#ifdef __CYGWIN__
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ret -= _timezone;
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#endif
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// This is necessary as some mktime() calls may
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// try to access the system timezone files
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// if this open fails errno is set to 2
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// CYGWIN for one does this
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// if ( errno ) {
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// perror( "sgTimeGetGMT()" );
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// errno = 0;
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// }
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// reset errno in any event.
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errno = 0;
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return ret;
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#else // ! defined ( MK_TIME_IS_GMT )
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// timezone seems to work as a proper offset for Linux & Solaris
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# if defined( __linux__ ) || defined( __sun__ ) ||defined(__CYGWIN__)
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# define TIMEZONE_OFFSET_WORKS 1
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# endif
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#if defined(__CYGWIN__)
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#define TIMEZONE _timezone
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#else
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#define TIMEZONE timezone
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#endif
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time_t start = mktime(&mt);
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SG_LOG( SG_EVENT, SG_DEBUG, "start1 = " << start );
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// the ctime() call can screw up time progression on some versions
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// of Linux
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// fgPrintf( SG_EVENT, SG_DEBUG, "start2 = %s", ctime(&start));
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SG_LOG( SG_EVENT, SG_DEBUG, "(tm_isdst = " << mt.tm_isdst << ")" );
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TIMEZONE = fix_up_timezone( TIMEZONE );
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# if defined( TIMEZONE_OFFSET_WORKS )
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SG_LOG( SG_EVENT, SG_DEBUG,
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"start = " << start << ", timezone = " << TIMEZONE );
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return( start - TIMEZONE );
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# else // ! defined( TIMEZONE_OFFSET_WORKS )
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daylight = mt.tm_isdst;
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if ( daylight > 0 ) {
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daylight = 1;
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} else if ( daylight < 0 ) {
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SG_LOG( SG_EVENT, FG_WARN,
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"OOOPS, problem in sg_time.cxx, no daylight savings info." );
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}
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long int offset = -(TIMEZONE / 3600 - daylight);
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SG_LOG( SG_EVENT, SG_DEBUG, " Raw time zone offset = " << TIMEZONE );
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SG_LOG( SG_EVENT, SG_DEBUG, " Daylight Savings = " << daylight );
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SG_LOG( SG_EVENT, SG_DEBUG, " Local hours from GMT = " << offset );
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long int start_gmt = start - TIMEZONE + (daylight * 3600);
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SG_LOG( SG_EVENT, SG_DEBUG, " March 21 noon (CST) = " << start );
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return ( start_gmt );
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# endif // ! defined( TIMEZONE_OFFSET_WORKS )
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#endif // ! defined ( MK_TIME_IS_GMT )
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}
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// format time
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char* sgTimeFormatTime( const struct tm* p, char* buf )
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{
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sprintf( buf, "%d/%d/%2d %d:%02d:%02d",
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p->tm_mon, p->tm_mday, p->tm_year,
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p->tm_hour, p->tm_min, p->tm_sec);
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return buf;
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}
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