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 )
67 if (cur_time_params) {
68 FG_LOG( FG_GENERAL, FG_ALERT,
69 "Error: only one instance of SGTime allowed" );
73 cur_time_params = this;
76 zone.append( "Timezone" );
77 zone.append( "zone.tab" );
79 FG_LOG( FG_EVENT, FG_INFO, "Reading timezone info from: " << zone.str() );
80 tzContainer = new TimezoneContainer( zone.c_str() );
92 void SGTime::updateLocal( double lon, double lat, const string& root )
95 time_t aircraftLocalTime;
96 GeoCoord location( RAD_TO_DEG * lat, RAD_TO_DEG * lon );
97 GeoCoord* nearestTz = tzContainer->getNearest(location);
99 zone.append ("Timezone" );
100 zone.append ( nearestTz->getDescription() );
104 zonename = strdup( zone.c_str() );
105 currGMT = get_gmt( gmtime(&cur_time) );
106 aircraftLocalTime = get_gmt( (fgLocaltime(&cur_time, zone.c_str())) );
107 local_offset = aircraftLocalTime - currGMT;
108 cout << "Using " << local_offset << " as local time offset Timezone is "
112 // Initialize the time dependent variables (maybe I'll put this in the
113 // constructor later)
114 void SGTime::init( double lon, double lat, const string& root )
115 // time_t timeOffset, sgTimingOffsetType offsetType )
117 FG_LOG( FG_EVENT, FG_INFO, "Initializing Time" );
121 time_t systemLocalTime;
122 time_t aircraftLocalTime;
124 // would it be better to put these sanity checks in the options
125 // parsing code? (CLO)
127 cur_time = time(NULL);
129 // printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
130 // printf ("Current local time = %24s", asctime(localtime(&cur_time)));
131 // time_t tmp = cur_time;
132 GeoCoord location( RAD_TO_DEG * lat, RAD_TO_DEG * lon );
134 GeoCoord* nearestTz = tzContainer->getNearest(location);
137 zone.append( "Timezone" );
138 zone.append( nearestTz->getDescription() );
140 cout << "Using " << zone.str() << " for timezone information" << endl;
141 zonename = strdup( zone.c_str() );
142 cout << "zonename = " << zonename << endl;
143 //show( buffer.c_str(), cur_time, 1);
144 //printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
145 //printf ("Current local time = %24s", asctime(localtime(&cur_time)));
146 currGMT = get_gmt( gmtime(&cur_time) );
147 cout << "currGMT = " << currGMT << endl;
149 systemLocalTime = get_gmt( localtime(&cur_time) );
150 cout << "systemLocalTime = " << systemLocalTime << endl;
152 aircraftLocalTime = get_gmt( fgLocaltime(&cur_time, zone.c_str()) );
153 //printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
154 //printf ("Current local time = %24s", asctime(localtime(&cur_time)));
156 //printf("LT = %d\n", computerLocalTime);
157 // Okay, in principle, this trick allows to calculate the
158 // difference between GMT and localtime, in seconds.
159 // printf("Gmt = %d, SLT = %d, (difference = %d)\n", currGMT, systemLocalTime, (currGMT - systemLocalTime));
160 // printf("Gmt = %d, ALT = %d, (difference = %d)\n", currGMT, aircraftLocalTime, (currGMT - aircraftLocalTime));
164 // Okay, we now have six possible scenarios
167 case SG_TIME_SYS_OFFSET:
170 case SG_TIME_GMT_OFFSET:
171 warp = timeOffset - (currGMT - systemLocalTime);
173 case SG_TIME_LAT_OFFSET:
174 // warp = timeOffset - (currGMT - systemLocalTime +
175 // (currGMT - aircraftLocalTime));
176 warp = timeOffset - (aircraftLocalTime - systemLocalTime);
178 case SG_TIME_SYS_ABSOLUTE:
179 warp = timeOffset - cur_time;
180 //printf("warp = %d\n", warp);
182 case SG_TIME_GMT_ABSOLUTE:
183 warp = timeOffset - currGMT;
185 case SG_TIME_LAT_ABSOLUTE:
186 warp = timeOffset - (aircraftLocalTime - systemLocalTime) -
190 printf("Unsupported type\n");
195 // pause = current_options.get_pause();
201 // given a date in months, mn, days, dy, years, yr, return the
202 // modified Julian date (number of days elapsed since 1900 jan 0.5),
203 // mjd. Adapted from Xephem.
205 void SGTime::cal_mjd (int mn, double dy, int yr)
207 //static double last_mjd, last_dy;
209 //static int last_mn, last_yr;
213 if (mn == last_mn && yr == last_yr && dy == last_dy) {
218 y = (yr < 0) ? yr + 1 : yr;
224 if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
233 c = (long)((365.25*y) - 0.75) - 694025L;
235 c = (long)(365.25*y) - 694025L;
238 d = (int)(30.6001*(m+1));
240 mjd = b + c + d + dy - 0.5;
249 // given an mjd, calculate greenwich mean sidereal time, gst
250 void SGTime::utc_gst ()
252 double day = floor(mjd-0.5)+0.5;
253 double hr = (mjd-day)*24.0;
256 T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
257 x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
259 gst = (1.0/SIDRATE)*hr + x;
261 FG_LOG( FG_EVENT, FG_INFO, " gst => " << gst );
265 // given Julian Date and Longitude (decimal degrees West) compute
266 // Local Sidereal Time, in decimal hours.
268 // Provided courtesy of ecdowney@noao.edu (Elwood Downey)
270 double SGTime::sidereal_precise (double lng)
274 /* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
277 // convert to required internal units
280 // compute LST and print
282 lstTmp = gst - RADHR (lng);
283 lstTmp -= 24.0*floor(lstTmp/24.0);
284 // printf ("%7.4f\n", lstTmp);
291 // return a courser but cheaper estimate of sidereal time
292 double SGTime::sidereal_course(double lng)
296 time_t start_gmt, now;
297 double diff, part, days, hours, lstTmp;
303 start_gmt = get_gmt(gmt->tm_year, 2, 21, 12, 0, 0);
305 FG_LOG( FG_EVENT, FG_DEBUG, " COURSE: GMT = " << format_time(gmt, tbuf) );
306 FG_LOG( FG_EVENT, FG_DEBUG, " March 21 noon (GMT) = " << start_gmt );
308 diff = (now - start_gmt) / (3600.0 * 24.0);
310 FG_LOG( FG_EVENT, FG_DEBUG,
311 " Time since 3/21/" << gmt->tm_year << " GMT = " << diff );
313 part = fmod(diff, 1.0);
315 hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
317 lstTmp = (days - lng)/15.0 + hours - 12;
319 while ( lstTmp < 0.0 ) {
323 FG_LOG( FG_EVENT, FG_DEBUG,
324 " days = " << days << " hours = " << hours << " lon = "
325 << lng << " lst = " << lstTmp );
331 // Update time variables such as gmt, julian date, and sidereal time
332 void SGTime::update( double lon, double lat, double alt_m, long int warp ) {
333 double gst_precise, gst_course;
335 FG_LOG( FG_EVENT, FG_INFO, "Updating time" );
337 // get current Unix calendar time (in seconds)
338 // warp += warp_delta;
339 cur_time = time(NULL) + warp;
340 FG_LOG( FG_EVENT, FG_INFO,
341 " Current Unix calendar time = " << cur_time
342 << " warp = " << warp );
344 // get GMT break down for current time
345 gmt = gmtime(&cur_time);
346 FG_LOG( FG_EVENT, FG_INFO,
347 " Current GMT = " << gmt->tm_mon+1 << "/"
348 << gmt->tm_mday << "/" << gmt->tm_year << " "
349 << gmt->tm_hour << ":" << gmt->tm_min << ":"
352 // calculate modified Julian date
353 // t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
354 // (int)(t->gmt->tm_year + 1900));
355 cal_mjd ((int)(gmt->tm_mon+1), (double)gmt->tm_mday,
356 (int)(gmt->tm_year + 1900));
358 // add in partial day
359 mjd += (gmt->tm_hour / 24.0) + (gmt->tm_min / (24.0 * 60.0)) +
360 (gmt->tm_sec / (24.0 * 60.0 * 60.0));
362 // convert "back" to Julian date + partial day (as a fraction of one)
364 FG_LOG( FG_EVENT, FG_INFO, " Current Julian Date = " << jd );
366 // printf(" Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG);
368 // Calculate local side real time
369 if ( gst_diff < -100.0 ) {
370 // first time through do the expensive calculation & cheap
371 // calculation to get the difference.
372 FG_LOG( FG_EVENT, FG_INFO, " First time, doing precise gst" );
373 gst_precise = gst = sidereal_precise(0.00);
374 gst_course = sidereal_course(0.00);
376 gst_diff = gst_precise - gst_course;
378 lst = sidereal_course(-(lon * RAD_TO_DEG)) + gst_diff;
380 // course + difference should drift off very slowly
381 gst = sidereal_course( 0.00 ) + gst_diff;
382 lst = sidereal_course( -(lon * RAD_TO_DEG)) + gst_diff;
385 FG_LOG( FG_EVENT, FG_INFO,
386 " Current lon=0.00 Sidereal Time = " << gst );
387 FG_LOG( FG_EVENT, FG_INFO,
388 " Current LOCAL Sidereal Time = " << lst << " ("
389 << sidereal_precise(-(lon * RAD_TO_DEG))
390 << ") (diff = " << gst_diff << ")" );
394 /******************************************************************
395 * The following are some functions that were included as SGTime
396 * members, although they currently don't make use of any of the
397 * class's variables. Maybe this'll change in the future
398 *****************************************************************/
400 // Return time_t for Sat Mar 21 12:00:00 GMT
402 // On many systems it is ambiguous if mktime() assumes the input is in
403 // GMT, or local timezone. To address this, a new function called
404 // timegm() is appearing. It works exactly like mktime() but
405 // explicitely interprets the input as GMT.
407 // timegm() is available and documented under FreeBSD. It is
408 // available, but completely undocumented on my current Debian 2.1
411 // In the absence of timegm() we have to guess what mktime() might do.
413 // Many older BSD style systems have a mktime() that assumes the input
414 // time in GMT. But FreeBSD explicitly states that mktime() assumes
417 // The mktime() on many SYSV style systems (such as Linux) usually
418 // returns its result assuming you have specified the input time in
419 // your local timezone. Therefore, in the absence if timegm() you
420 // have to go to extra trouble to convert back to GMT.
422 // If you are having problems with incorrectly positioned astronomical
423 // bodies, this is a really good place to start looking.
425 time_t SGTime::get_gmt(int year, int month, int day, int hour, int min, int sec)
435 mt.tm_isdst = -1; // let the system determine the proper time zone
437 // For now we assume that if daylight is not defined in
438 // /usr/include/time.h that we have a machine with a mktime() that
439 // assumes input is in GMT ... this only matters if we are
440 // building on a system that does not have timegm()
441 #if !defined(HAVE_DAYLIGHT)
442 # define MK_TIME_IS_GMT 1
445 #if defined( HAVE_TIMEGM )
446 return ( timegm(&mt) );
447 #elif defined( MK_TIME_IS_GMT )
448 return ( mktime(&mt) );
449 #else // ! defined ( MK_TIME_IS_GMT )
451 // timezone seems to work as a proper offset for Linux & Solaris
452 # if defined( __linux__ ) || defined( __sun__ )
453 # define TIMEZONE_OFFSET_WORKS 1
456 long int start = mktime(&mt);
458 FG_LOG( FG_EVENT, FG_DEBUG, "start1 = " << start );
459 // the ctime() call can screw up time progression on some versions
461 // fgPrintf( FG_EVENT, FG_DEBUG, "start2 = %s", ctime(&start));
462 FG_LOG( FG_EVENT, FG_DEBUG, "(tm_isdst = " << mt.tm_isdst << ")" );
464 timezone = fix_up_timezone( timezone );
466 # if defined( TIMEZONE_OFFSET_WORKS )
467 FG_LOG( FG_EVENT, FG_DEBUG,
468 "start = " << start << ", timezone = " << timezone );
469 return( start - timezone );
470 # else // ! defined( TIMEZONE_OFFSET_WORKS )
472 daylight = mt.tm_isdst;
473 if ( daylight > 0 ) {
475 } else if ( daylight < 0 ) {
476 FG_LOG( FG_EVENT, FG_WARN,
477 "OOOPS, problem in sg_time.cxx, no daylight savings info." );
480 long int offset = -(timezone / 3600 - daylight);
482 FG_LOG( FG_EVENT, FG_DEBUG, " Raw time zone offset = " << timezone );
483 FG_LOG( FG_EVENT, FG_DEBUG, " Daylight Savings = " << daylight );
484 FG_LOG( FG_EVENT, FG_DEBUG, " Local hours from GMT = " << offset );
486 long int start_gmt = start - timezone + (daylight * 3600);
488 FG_LOG( FG_EVENT, FG_DEBUG, " March 21 noon (CST) = " << start );
490 return ( start_gmt );
491 # endif // ! defined( TIMEZONE_OFFSET_WORKS )
492 #endif // ! defined ( MK_TIME_IS_GMT )
495 // Fix up timezone if using ftime()
496 long int SGTime::fix_up_timezone( long int timezone_orig )
498 #if !defined( HAVE_GETTIMEOFDAY ) && defined( HAVE_FTIME )
499 // ftime() needs a little extra help finding the current timezone
500 struct timeb current;
502 return( current.timezone * 60 );
504 return( timezone_orig );
509 char* SGTime::format_time( const struct tm* p, char* buf )
511 sprintf( buf, "%d/%d/%2d %d:%02d:%02d",
512 p->tm_mon, p->tm_mday, p->tm_year,
513 p->tm_hour, p->tm_min, p->tm_sec);
518 SGTime* SGTime::cur_time_params = 0;