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/magvar/magvar.hxx>
55 #include <simgear/misc/fgpath.hxx>
57 // #include <FDM/flight.hxx>
58 // #include <Main/options.hxx>
59 // #include <Time/light.hxx>
61 #include "sg_time.hxx"
63 #include "lowleveltime.h"
64 // #include "moonpos.hxx"
65 // #include "sunpos.hxx"
68 #define DEGHR(x) ((x)/15.)
69 #define RADHR(x) DEGHR(x*RAD_TO_DEG)
72 // #define MK_TIME_IS_GMT 0 // default value
73 // #define TIME_ZONE_OFFSET_WORK 0 // default value
76 SGTime::SGTime( const string& root )
78 if (cur_time_params) {
79 FG_LOG( FG_GENERAL, FG_ALERT,
80 "Error: only one instance of SGTime allowed" );
84 cur_time_params = this;
87 zone.append( "Timezone" );
88 zone.append( "zone.tab" );
90 FG_LOG( FG_EVENT, FG_INFO, "Reading timezone info from: " << zone.str() );
91 tzContainer = new TimezoneContainer( zone.c_str() );
103 void SGTime::updateLocal( double lon, double lat, const string& root )
106 time_t aircraftLocalTime;
107 GeoCoord location( RAD_TO_DEG * lat, RAD_TO_DEG * lon );
108 GeoCoord* nearestTz = tzContainer->getNearest(location);
110 zone.append ("Timezone" );
111 zone.append ( nearestTz->getDescription() );
115 zonename = strdup( zone.c_str() );
116 currGMT = get_gmt( gmtime(&cur_time) );
117 aircraftLocalTime = get_gmt( (fgLocaltime(&cur_time, zone.c_str())) );
118 localOffset = aircraftLocalTime - currGMT;
119 // cerr << "Using " << localOffset << " as local time offset Timezone is "
120 // << zonename << endl;
123 // Initialize the time dependent variables (maybe I'll put this in the
124 // constructor later)
125 void SGTime::init( double lon, double lat, const string& root,
126 time_t timeOffset, sgTimingOffsetType offsetType )
128 FG_LOG( FG_EVENT, FG_INFO, "Initializing Time" );
130 FG_LOG( FG_EVENT, FG_DEBUG,
131 "time offset = " << timeOffset );
132 // time_t timeOffset = current_options.get_time_offset();
133 // int offsetType = current_options.get_time_offset_type();
136 time_t systemLocalTime;
137 time_t aircraftLocalTime;
139 // would it be better to put these sanity checks in the options
140 // parsing code? (CLO)
142 cur_time = time(NULL);
144 // printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
145 // printf ("Current local time = %24s", asctime(localtime(&cur_time)));
146 // time_t tmp = cur_time;
147 GeoCoord location( RAD_TO_DEG * lat, RAD_TO_DEG * lon );
149 GeoCoord* nearestTz = tzContainer->getNearest(location);
152 zone.append( "Timezone" );
153 zone.append( nearestTz->getDescription() );
155 // printf("Using %s for timezone information\n", buffer);
156 zonename = strdup( zone.c_str() );
157 //show( buffer.c_str(), cur_time, 1);
158 //printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
159 //printf ("Current local time = %24s", asctime(localtime(&cur_time)));
160 currGMT = get_gmt( gmtime(&cur_time) );
161 systemLocalTime = get_gmt( localtime(&cur_time) );
162 aircraftLocalTime = get_gmt( fgLocaltime(&cur_time, zone.c_str()) );
163 //printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
164 //printf ("Current local time = %24s", asctime(localtime(&cur_time)));
166 //printf("LT = %d\n", computerLocalTime);
167 // Okay, in principle, this trick allows to calculate the
168 // difference between GMT and localtime, in seconds.
169 // printf("Gmt = %d, SLT = %d, (difference = %d)\n", currGMT, systemLocalTime, (currGMT - systemLocalTime));
170 // printf("Gmt = %d, ALT = %d, (difference = %d)\n", currGMT, aircraftLocalTime, (currGMT - aircraftLocalTime));
172 // Okay, we now have six possible scenarios
175 case SG_TIME_SYS_OFFSET:
178 case SG_TIME_GMT_OFFSET:
179 warp = timeOffset - (currGMT - systemLocalTime);
181 case SG_TIME_LAT_OFFSET:
182 // warp = timeOffset - (currGMT - systemLocalTime +
183 // (currGMT - aircraftLocalTime));
184 warp = timeOffset - (aircraftLocalTime - systemLocalTime);
186 case SG_TIME_SYS_ABSOLUTE:
187 warp = timeOffset - cur_time;
188 //printf("warp = %d\n", warp);
190 case SG_TIME_GMT_ABSOLUTE:
191 warp = timeOffset - currGMT;
193 case SG_TIME_LAT_ABSOLUTE:
194 warp = timeOffset - (aircraftLocalTime - systemLocalTime) -
198 printf("Unsupported type\n");
203 // pause = current_options.get_pause();
207 // given a date in months, mn, days, dy, years, yr, return the
208 // modified Julian date (number of days elapsed since 1900 jan 0.5),
209 // mjd. Adapted from Xephem.
211 void SGTime::cal_mjd (int mn, double dy, int yr)
213 //static double last_mjd, last_dy;
215 //static int last_mn, last_yr;
219 if (mn == last_mn && yr == last_yr && dy == last_dy) {
225 y = (yr < 0) ? yr + 1 : yr;
231 if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
240 c = (long)((365.25*y) - 0.75) - 694025L;
242 c = (long)(365.25*y) - 694025L;
245 d = (int)(30.6001*(m+1));
247 mjd = b + c + d + dy - 0.5;
258 // given an mjd, calculate greenwich mean sidereal time, gst
259 void SGTime::utc_gst ()
261 double day = floor(mjd-0.5)+0.5;
262 double hr = (mjd-day)*24.0;
265 T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
266 x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
268 gst = (1.0/SIDRATE)*hr + x;
270 FG_LOG( FG_EVENT, FG_DEBUG, " gst => " << gst );
274 // given Julian Date and Longitude (decimal degrees West) compute
275 // Local Sidereal Time, in decimal hours.
277 // Provided courtesy of ecdowney@noao.edu (Elwood Downey)
279 double SGTime::sidereal_precise (double lng)
283 /* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
286 // convert to required internal units
289 // compute LST and print
291 lstTmp = gst - RADHR (lng);
292 lstTmp -= 24.0*floor(lstTmp/24.0);
293 // printf ("%7.4f\n", lstTmp);
300 // return a courser but cheaper estimate of sidereal time
301 double SGTime::sidereal_course(double lng)
305 time_t start_gmt, now;
306 double diff, part, days, hours, lstTmp;
312 start_gmt = get_gmt(gmt->tm_year, 2, 21, 12, 0, 0);
314 FG_LOG( FG_EVENT, FG_DEBUG, " COURSE: GMT = " << format_time(gmt, tbuf) );
315 FG_LOG( FG_EVENT, FG_DEBUG, " March 21 noon (GMT) = " << start_gmt );
317 diff = (now - start_gmt) / (3600.0 * 24.0);
319 FG_LOG( FG_EVENT, FG_DEBUG,
320 " Time since 3/21/" << gmt->tm_year << " GMT = " << diff );
322 part = fmod(diff, 1.0);
324 hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
326 lstTmp = (days - lng)/15.0 + hours - 12;
328 while ( lstTmp < 0.0 ) {
332 FG_LOG( FG_EVENT, FG_DEBUG,
333 " days = " << days << " hours = " << hours << " lon = "
334 << lng << " lst = " << lstTmp );
340 // Update time variables such as gmt, julian date, and sidereal time
341 void SGTime::update( double lon, double lat, double alt_m ) {
342 double gst_precise, gst_course;
344 FG_LOG( FG_EVENT, FG_DEBUG, "Updating time" );
346 // get current Unix calendar time (in seconds)
348 cur_time = time(NULL) + warp;
349 FG_LOG( FG_EVENT, FG_DEBUG,
350 " Current Unix calendar time = " << cur_time
351 << " warp = " << warp << " delta = " << warp_delta );
355 // time is changing so force an update
356 local_update_sky_and_lighting_params();
360 // get GMT break down for current time
361 gmt = gmtime(&cur_time);
362 FG_LOG( FG_EVENT, FG_DEBUG,
363 " Current GMT = " << gmt->tm_mon+1 << "/"
364 << gmt->tm_mday << "/" << gmt->tm_year << " "
365 << gmt->tm_hour << ":" << gmt->tm_min << ":"
368 // calculate modified Julian date
369 // t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
370 // (int)(t->gmt->tm_year + 1900));
371 cal_mjd ((int)(gmt->tm_mon+1), (double)gmt->tm_mday,
372 (int)(gmt->tm_year + 1900));
374 // add in partial day
375 mjd += (gmt->tm_hour / 24.0) + (gmt->tm_min / (24.0 * 60.0)) +
376 (gmt->tm_sec / (24.0 * 60.0 * 60.0));
378 // convert "back" to Julian date + partial day (as a fraction of one)
380 FG_LOG( FG_EVENT, FG_DEBUG, " Current Julian Date = " << jd );
382 // printf(" Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG);
384 // Calculate local side real time
385 if ( gst_diff < -100.0 ) {
386 // first time through do the expensive calculation & cheap
387 // calculation to get the difference.
388 FG_LOG( FG_EVENT, FG_INFO, " First time, doing precise gst" );
389 gst_precise = gst = sidereal_precise(0.00);
390 gst_course = sidereal_course(0.00);
392 gst_diff = gst_precise - gst_course;
394 lst = sidereal_course(-(lon * RAD_TO_DEG)) + gst_diff;
396 // course + difference should drift off very slowly
397 gst = sidereal_course( 0.00 ) + gst_diff;
398 lst = sidereal_course( -(lon * RAD_TO_DEG)) + gst_diff;
401 FG_LOG( FG_EVENT, FG_DEBUG,
402 " Current lon=0.00 Sidereal Time = " << gst );
403 FG_LOG( FG_EVENT, FG_DEBUG,
404 " Current LOCAL Sidereal Time = " << lst << " ("
405 << sidereal_precise(-(lon * RAD_TO_DEG))
406 << ") (diff = " << gst_diff << ")" );
410 /******************************************************************
411 * The following are some functions that were included as SGTime
412 * members, although they currently don't make use of any of the
413 * class's variables. Maybe this'll change in the future
414 *****************************************************************/
416 // Return time_t for Sat Mar 21 12:00:00 GMT
418 // On many systems it is ambiguous if mktime() assumes the input is in
419 // GMT, or local timezone. To address this, a new function called
420 // timegm() is appearing. It works exactly like mktime() but
421 // explicitely interprets the input as GMT.
423 // timegm() is available and documented under FreeBSD. It is
424 // available, but completely undocumented on my current Debian 2.1
427 // In the absence of timegm() we have to guess what mktime() might do.
429 // Many older BSD style systems have a mktime() that assumes the input
430 // time in GMT. But FreeBSD explicitly states that mktime() assumes
433 // The mktime() on many SYSV style systems (such as Linux) usually
434 // returns its result assuming you have specified the input time in
435 // your local timezone. Therefore, in the absence if timegm() you
436 // have to go to extra trouble to convert back to GMT.
438 // If you are having problems with incorrectly positioned astronomical
439 // bodies, this is a really good place to start looking.
441 time_t SGTime::get_gmt(int year, int month, int day, int hour, int min, int sec)
451 mt.tm_isdst = -1; // let the system determine the proper time zone
453 // For now we assume that if daylight is not defined in
454 // /usr/include/time.h that we have a machine with a mktime() that
455 // assumes input is in GMT ... this only matters if we are
456 // building on a system that does not have timegm()
457 #if !defined(HAVE_DAYLIGHT)
458 # define MK_TIME_IS_GMT 1
461 #if defined( HAVE_TIMEGM )
462 return ( timegm(&mt) );
463 #elif defined( MK_TIME_IS_GMT )
464 return ( mktime(&mt) );
465 #else // ! defined ( MK_TIME_IS_GMT )
467 // timezone seems to work as a proper offset for Linux & Solaris
468 # if defined( __linux__ ) || defined( __sun__ )
469 # define TIMEZONE_OFFSET_WORKS 1
472 long int start = mktime(&mt);
474 FG_LOG( FG_EVENT, FG_DEBUG, "start1 = " << start );
475 // the ctime() call can screw up time progression on some versions
477 // fgPrintf( FG_EVENT, FG_DEBUG, "start2 = %s", ctime(&start));
478 FG_LOG( FG_EVENT, FG_DEBUG, "(tm_isdst = " << mt.tm_isdst << ")" );
480 timezone = fix_up_timezone( timezone );
482 # if defined( TIMEZONE_OFFSET_WORKS )
483 FG_LOG( FG_EVENT, FG_DEBUG,
484 "start = " << start << ", timezone = " << timezone );
485 return( start - timezone );
486 # else // ! defined( TIMEZONE_OFFSET_WORKS )
488 daylight = mt.tm_isdst;
489 if ( daylight > 0 ) {
491 } else if ( daylight < 0 ) {
492 FG_LOG( FG_EVENT, FG_WARN,
493 "OOOPS, problem in sg_time.cxx, no daylight savings info." );
496 long int offset = -(timezone / 3600 - daylight);
498 FG_LOG( FG_EVENT, FG_DEBUG, " Raw time zone offset = " << timezone );
499 FG_LOG( FG_EVENT, FG_DEBUG, " Daylight Savings = " << daylight );
500 FG_LOG( FG_EVENT, FG_DEBUG, " Local hours from GMT = " << offset );
502 long int start_gmt = start - timezone + (daylight * 3600);
504 FG_LOG( FG_EVENT, FG_DEBUG, " March 21 noon (CST) = " << start );
506 return ( start_gmt );
507 # endif // ! defined( TIMEZONE_OFFSET_WORKS )
508 #endif // ! defined ( MK_TIME_IS_GMT )
511 // Fix up timezone if using ftime()
512 long int SGTime::fix_up_timezone( long int timezone_orig )
514 #if !defined( HAVE_GETTIMEOFDAY ) && defined( HAVE_FTIME )
515 // ftime() needs a little extra help finding the current timezone
516 struct timeb current;
518 return( current.timezone * 60 );
520 return( timezone_orig );
525 char* SGTime::format_time( const struct tm* p, char* buf )
527 sprintf( buf, "%d/%d/%2d %d:%02d:%02d",
528 p->tm_mon, p->tm_mday, p->tm_year,
529 p->tm_hour, p->tm_min, p->tm_sec);
534 SGTime* SGTime::cur_time_params = 0;