1 // sg_time.cxx -- data structures and routines for managing time related stuff.
3 // Written by Curtis Olson, started August 1997.
5 // Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
28 #include <simgear/compiler.h>
30 #ifdef FG_HAVE_STD_INCLUDES
42 #ifdef HAVE_SYS_TIMEB_H
43 # include <sys/timeb.h> // for ftime() and struct timeb
46 # include <unistd.h> // for gettimeofday()
48 #ifdef HAVE_SYS_TIME_H
49 # include <sys/time.h> // for get/setitimer, gettimeofday, struct timeval
52 #include <simgear/constants.h>
53 #include <simgear/debug/logstream.hxx>
54 #include <simgear/misc/fgpath.hxx>
56 #include "sg_time.hxx"
58 #include "lowleveltime.h"
61 #define DEGHR(x) ((x)/15.)
62 #define RADHR(x) DEGHR(x*RAD_TO_DEG)
65 SGTime::SGTime( const string& root )
68 zone.append( "Timezone" );
69 zone.append( "zone.tab" );
71 FG_LOG( FG_EVENT, FG_DEBUG, "Reading timezone info from: " << zone.str() );
72 tzContainer = new TimezoneContainer( zone.c_str() );
82 if ( zonename != NULL ) {
88 // Initialize the time related variables
89 void SGTime::init( double lon, double lat, const string& root )
91 FG_LOG( FG_EVENT, FG_INFO, "Initializing Time" );
95 // time_t systemLocalTime;
96 // time_t aircraftLocalTime;
98 // would it be better to put these sanity checks in the options
99 // parsing code? (CLO)
101 cur_time = time(NULL);
103 // printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
104 // printf ("Current local time = %24s", asctime(localtime(&cur_time)));
105 // time_t tmp = cur_time;
106 GeoCoord location( RAD_TO_DEG * lat, RAD_TO_DEG * lon );
108 GeoCoord* nearestTz = tzContainer->getNearest(location);
111 zone.append( "Timezone" );
112 zone.append( nearestTz->getDescription() );
114 // cout << "Using " << zone.str() << " for timezone information" << endl;
115 zonename = strdup( zone.c_str() );
116 // cout << "zonename = " << zonename << endl;
117 //show( buffer.c_str(), cur_time, 1);
118 //printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
119 //printf ("Current local time = %24s", asctime(localtime(&cur_time)));
120 // currGMT = get_gmt( gmtime(&cur_time) );
121 // cout << "currGMT = " << currGMT << endl;
123 // systemLocalTime = get_gmt( localtime(&cur_time) );
124 // cout << "systemLocalTime = " << systemLocalTime << endl;
126 // aircraftLocalTime = get_gmt( fgLocaltime(&cur_time, zone.c_str()) );
127 //printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
128 //printf ("Current local time = %24s", asctime(localtime(&cur_time)));
132 // Update the time related variables
133 void SGTime::update( double lon, double lat, double alt_m, long int warp ) {
134 double gst_precise, gst_course;
136 FG_LOG( FG_EVENT, FG_DEBUG, "Updating time" );
138 // get current Unix calendar time (in seconds)
139 // warp += warp_delta;
140 cur_time = time(NULL) + warp;
141 FG_LOG( FG_EVENT, FG_DEBUG,
142 " Current Unix calendar time = " << cur_time
143 << " warp = " << warp );
145 // get GMT break down for current time
146 gmt = gmtime(&cur_time);
147 FG_LOG( FG_EVENT, FG_DEBUG,
148 " Current GMT = " << gmt->tm_mon+1 << "/"
149 << gmt->tm_mday << "/" << gmt->tm_year << " "
150 << gmt->tm_hour << ":" << gmt->tm_min << ":"
153 // calculate modified Julian date
154 // t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
155 // (int)(t->gmt->tm_year + 1900));
156 mjd = sgTimeCalcMJD( (int)(gmt->tm_mon+1), (double)gmt->tm_mday,
157 (int)(gmt->tm_year + 1900) );
159 // add in partial day
160 mjd += (gmt->tm_hour / 24.0) + (gmt->tm_min / (24.0 * 60.0)) +
161 (gmt->tm_sec / (24.0 * 60.0 * 60.0));
163 // convert "back" to Julian date + partial day (as a fraction of one)
165 FG_LOG( FG_EVENT, FG_DEBUG, " Current Julian Date = " << jd );
167 // printf(" Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG);
169 // Calculate local side real time
170 if ( gst_diff < -100.0 ) {
171 // first time through do the expensive calculation & cheap
172 // calculation to get the difference.
173 FG_LOG( FG_EVENT, FG_INFO, " First time, doing precise gst" );
174 gst_precise = gst = sidereal_precise(0.00);
175 gst_course = sidereal_course(0.00);
177 gst_diff = gst_precise - gst_course;
179 lst = sidereal_course(-(lon * RAD_TO_DEG)) + gst_diff;
181 // course + difference should drift off very slowly
182 gst = sidereal_course( 0.00 ) + gst_diff;
183 lst = sidereal_course( -(lon * RAD_TO_DEG)) + gst_diff;
186 FG_LOG( FG_EVENT, FG_DEBUG,
187 " Current lon=0.00 Sidereal Time = " << gst );
188 FG_LOG( FG_EVENT, FG_DEBUG,
189 " Current LOCAL Sidereal Time = " << lst << " ("
190 << sidereal_precise(-(lon * RAD_TO_DEG))
191 << ") (diff = " << gst_diff << ")" );
195 // Given lon/lat, update timezone information and local_offset
196 void SGTime::updateLocal( double lon, double lat, const string& root )
199 time_t aircraftLocalTime;
200 GeoCoord location( RAD_TO_DEG * lat, RAD_TO_DEG * lon );
201 GeoCoord* nearestTz = tzContainer->getNearest(location);
203 zone.append ("Timezone" );
204 zone.append ( nearestTz->getDescription() );
208 zonename = strdup( zone.c_str() );
209 currGMT = get_gmt( gmtime(&cur_time) );
210 aircraftLocalTime = get_gmt( (fgLocaltime(&cur_time, zone.c_str())) );
211 local_offset = aircraftLocalTime - currGMT;
212 // cout << "Using " << local_offset << " as local time offset Timezone is "
213 // << zonename << endl;
217 // given Julian Date and Longitude (decimal degrees West) compute
218 // Local Sidereal Time, in decimal hours.
220 // Provided courtesy of ecdowney@noao.edu (Elwood Downey)
221 double SGTime::sidereal_precise( double lng )
225 /* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
228 // convert to required internal units
231 // compute LST and print
232 gst = sgTimeCalcGST( mjd );
233 lstTmp = gst - RADHR (lng);
234 lstTmp -= 24.0*floor(lstTmp/24.0);
235 // printf ("%7.4f\n", lstTmp);
242 // return a courser but cheaper estimate of sidereal time
243 double SGTime::sidereal_course( double lng )
245 time_t start_gmt, now;
246 double diff, part, days, hours, lstTmp;
250 start_gmt = get_gmt(gmt->tm_year, 2, 21, 12, 0, 0);
252 FG_LOG( FG_EVENT, FG_DEBUG, " COURSE: GMT = "
253 << sgTimeFormatTime(gmt, tbuf) );
254 FG_LOG( FG_EVENT, FG_DEBUG, " March 21 noon (GMT) = " << start_gmt );
256 diff = (now - start_gmt) / (3600.0 * 24.0);
258 FG_LOG( FG_EVENT, FG_DEBUG,
259 " Time since 3/21/" << gmt->tm_year << " GMT = " << diff );
261 part = fmod(diff, 1.0);
263 hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
265 lstTmp = (days - lng)/15.0 + hours - 12;
267 while ( lstTmp < 0.0 ) {
271 FG_LOG( FG_EVENT, FG_DEBUG,
272 " days = " << days << " hours = " << hours << " lon = "
273 << lng << " lst = " << lstTmp );
279 // given a date in months, mn, days, dy, years, yr, return the
280 // modified Julian date (number of days elapsed since 1900 jan 0.5),
281 // mjd. Adapted from Xephem.
282 double sgTimeCalcMJD(int mn, double dy, int yr) {
285 // internal book keeping data
286 static double last_mjd, last_dy;
287 static int last_mn, last_yr;
292 if (mn == last_mn && yr == last_yr && dy == last_dy) {
297 y = (yr < 0) ? yr + 1 : yr;
303 if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
312 c = (long)((365.25*y) - 0.75) - 694025L;
314 c = (long)(365.25*y) - 694025L;
317 d = (int)(30.6001*(m+1));
319 mjd = b + c + d + dy - 0.5;
330 // given an mjd, calculate greenwich mean sidereal time, gst
331 double sgTimeCalcGST( double mjd ) {
334 double day = floor(mjd-0.5)+0.5;
335 double hr = (mjd-day)*24.0;
338 T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
339 x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
341 gst = (1.0/SIDRATE)*hr + x;
343 FG_LOG( FG_EVENT, FG_DEBUG, " gst => " << gst );
349 #if defined( HAVE_TIMEGM )
350 // ignore this function
351 #elif defined( MK_TIME_IS_GMT )
352 // ignore this function
353 #else // ! defined ( MK_TIME_IS_GMT )
355 // Fix up timezone if using ftime()
356 static long int fix_up_timezone( long int timezone_orig ) {
357 # if !defined( HAVE_GETTIMEOFDAY ) && defined( HAVE_FTIME )
358 // ftime() needs a little extra help finding the current timezone
359 struct timeb current;
361 return( current.timezone * 60 );
363 return( timezone_orig );
369 /******************************************************************
370 * The following are some functions that were included as SGTime
371 * members, although they currently don't make use of any of the
372 * class's variables. Maybe this'll change in the future
373 *****************************************************************/
375 // Return time_t for Sat Mar 21 12:00:00 GMT
377 // On many systems it is ambiguous if mktime() assumes the input is in
378 // GMT, or local timezone. To address this, a new function called
379 // timegm() is appearing. It works exactly like mktime() but
380 // explicitely interprets the input as GMT.
382 // timegm() is available and documented under FreeBSD. It is
383 // available, but completely undocumented on my current Debian 2.1
386 // In the absence of timegm() we have to guess what mktime() might do.
388 // Many older BSD style systems have a mktime() that assumes the input
389 // time in GMT. But FreeBSD explicitly states that mktime() assumes
392 // The mktime() on many SYSV style systems (such as Linux) usually
393 // returns its result assuming you have specified the input time in
394 // your local timezone. Therefore, in the absence if timegm() you
395 // have to go to extra trouble to convert back to GMT.
397 // If you are having problems with incorrectly positioned astronomical
398 // bodies, this is a really good place to start looking.
400 time_t SGTime::get_gmt(int year, int month, int day, int hour, int min, int sec)
410 mt.tm_isdst = -1; // let the system determine the proper time zone
412 // For now we assume that if daylight is not defined in
413 // /usr/include/time.h that we have a machine with a mktime() that
414 // assumes input is in GMT ... this only matters if we are
415 // building on a system that does not have timegm()
416 #if !defined(HAVE_DAYLIGHT)
417 # define MK_TIME_IS_GMT 1
420 #if defined( HAVE_TIMEGM )
421 return ( timegm(&mt) );
422 #elif defined( MK_TIME_IS_GMT )
423 return ( mktime(&mt) );
424 #else // ! defined ( MK_TIME_IS_GMT )
426 // timezone seems to work as a proper offset for Linux & Solaris
427 # if defined( __linux__ ) || defined( __sun__ )
428 # define TIMEZONE_OFFSET_WORKS 1
431 long int start = mktime(&mt);
433 FG_LOG( FG_EVENT, FG_DEBUG, "start1 = " << start );
434 // the ctime() call can screw up time progression on some versions
436 // fgPrintf( FG_EVENT, FG_DEBUG, "start2 = %s", ctime(&start));
437 FG_LOG( FG_EVENT, FG_DEBUG, "(tm_isdst = " << mt.tm_isdst << ")" );
439 timezone = fix_up_timezone( timezone );
441 # if defined( TIMEZONE_OFFSET_WORKS )
442 FG_LOG( FG_EVENT, FG_DEBUG,
443 "start = " << start << ", timezone = " << timezone );
444 return( start - timezone );
445 # else // ! defined( TIMEZONE_OFFSET_WORKS )
447 daylight = mt.tm_isdst;
448 if ( daylight > 0 ) {
450 } else if ( daylight < 0 ) {
451 FG_LOG( FG_EVENT, FG_WARN,
452 "OOOPS, problem in sg_time.cxx, no daylight savings info." );
455 long int offset = -(timezone / 3600 - daylight);
457 FG_LOG( FG_EVENT, FG_DEBUG, " Raw time zone offset = " << timezone );
458 FG_LOG( FG_EVENT, FG_DEBUG, " Daylight Savings = " << daylight );
459 FG_LOG( FG_EVENT, FG_DEBUG, " Local hours from GMT = " << offset );
461 long int start_gmt = start - timezone + (daylight * 3600);
463 FG_LOG( FG_EVENT, FG_DEBUG, " March 21 noon (CST) = " << start );
465 return ( start_gmt );
466 # endif // ! defined( TIMEZONE_OFFSET_WORKS )
467 #endif // ! defined ( MK_TIME_IS_GMT )
472 char* sgTimeFormatTime( const struct tm* p, char* buf )
474 sprintf( buf, "%d/%d/%2d %d:%02d:%02d",
475 p->tm_mon, p->tm_mday, p->tm_year,
476 p->tm_hour, p->tm_min, p->tm_sec);