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 library is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU Library General Public
9 // License as published by the Free Software Foundation; either
10 // version 2 of the License, or (at your option) any later version.
12 // This library is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // Library General Public License for more details.
17 // You should have received a copy of the GNU Library General Public
18 // License along with this library; if not, write to the
19 // Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 // Boston, MA 02111-1307, USA.
26 # include <simgear_config.h>
29 #include <simgear/compiler.h>
31 #include <errno.h> // for errno
33 #ifdef SG_HAVE_STD_INCLUDES
43 #ifdef HAVE_SYS_TIME_H
44 # include <sys/time.h> // for get/setitimer, gettimeofday, struct timeval
46 #ifdef HAVE_SYS_TIMEB_H
47 # include <sys/timeb.h> // for ftime() and struct timeb
50 # include <unistd.h> // for gettimeofday()
53 #include <math.h> // for NAN
55 #include <simgear/constants.h>
56 #include <simgear/debug/logstream.hxx>
57 #include <simgear/misc/sg_path.hxx>
59 #include "sg_time.hxx"
61 #include "lowleveltime.h"
64 #define DEGHR(x) ((x)/15.)
65 #define RADHR(x) DEGHR(x*SGD_RADIANS_TO_DEGREES)
68 static const double MJD0 = 2415020.0;
69 static const double J2000 = 2451545.0 - MJD0;
70 static const double SIDRATE = 0.9972695677;
73 SGTime::SGTime( double lon, double lat, const string& root, time_t init_time )
75 SG_LOG( SG_EVENT, SG_INFO, "Initializing Time" );
82 cur_time = time(NULL);
85 cout << "Current greenwich mean time = " << asctime(gmtime(&cur_time))
87 cout << "Current local time = "
88 << asctime(localtime(&cur_time)) << endl;
90 if ( root != (string)"" ) {
92 zone.append( "zone.tab" );
93 SG_LOG( SG_EVENT, SG_INFO, "Reading timezone info from: "
95 tzContainer = new TimezoneContainer( zone.c_str() );
97 GeoCoord location( SGD_RADIANS_TO_DEGREES * lat, SGD_RADIANS_TO_DEGREES * lon );
98 GeoCoord* nearestTz = tzContainer->getNearest(location);
101 name.append( nearestTz->getDescription() );
102 zonename = strdup( name.c_str() );
103 SG_LOG( SG_EVENT, SG_INFO, "Using zonename = " << zonename );
105 SG_LOG( SG_EVENT, SG_INFO, "*** NO TIME ZONE NAME ***" );
112 SGTime::SGTime( const string& root ) {
113 SGTime( 0.0, 0.0, root );
118 SGTime( 0.0, 0.0, "" );
124 if ( tzContainer != NULL ) {
125 TimezoneContainer *tmp = tzContainer;
130 if ( zonename != NULL ) {
131 char *tmp = zonename;
138 // given Julian Date and Longitude (decimal degrees West) compute
139 // Local Sidereal Time, in decimal hours.
141 // Provided courtesy of ecdowney@noao.edu (Elwood Downey)
142 static double sidereal_precise( double mjd, double lng )
144 /* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ",
147 // convert to required internal units
148 lng *= SGD_DEGREES_TO_RADIANS;
150 // compute LST and print
151 double gst = sgTimeCalcGST( mjd );
152 double lst = gst - RADHR( lng );
153 lst -= 24.0 * floor( lst / 24.0 );
154 // printf ("%7.4f\n", lstTmp);
160 // return a courser but cheaper estimate of sidereal time
161 static double sidereal_course( time_t cur_time, struct tm *gmt, double lng )
163 time_t start_gmt, now;
164 double diff, part, days, hours, lstTmp;
168 start_gmt = sgTimeGetGMT(gmt->tm_year, 2, 21, 12, 0, 0);
170 SG_LOG( SG_EVENT, SG_DEBUG, " COURSE: GMT = "
171 << sgTimeFormatTime(gmt, tbuf) );
172 SG_LOG( SG_EVENT, SG_DEBUG, " March 21 noon (GMT) = " << start_gmt );
174 diff = (now - start_gmt) / (3600.0 * 24.0);
176 SG_LOG( SG_EVENT, SG_DEBUG,
177 " Time since 3/21/" << gmt->tm_year << " GMT = " << diff );
179 part = fmod(diff, 1.0);
181 hours = gmt->tm_hour + gmt->tm_min/60.0 + gmt->tm_sec/3600.0;
183 lstTmp = (days - lng)/15.0 + hours - 12;
185 while ( lstTmp < 0.0 ) {
189 SG_LOG( SG_EVENT, SG_DEBUG,
190 " days = " << days << " hours = " << hours << " lon = "
191 << lng << " lst = " << lstTmp );
197 // Update the time related variables
198 void SGTime::update( double lon, double lat, time_t ct, long int warp ) {
199 double gst_precise, gst_course;
201 #if defined(_MSC_VER) || defined(__MINGW32__)
205 SG_LOG( SG_EVENT, SG_DEBUG, "Updating time" );
207 // get current Unix calendar time (in seconds)
208 // warp += warp_delta;
210 cur_time = ct + warp;
212 cur_time = time(NULL) + warp;
214 SG_LOG( SG_EVENT, SG_DEBUG,
215 " Current Unix calendar time = " << cur_time
216 << " warp = " << warp );
218 // get GMT break down for current time
219 #if defined(_MSC_VER) || defined(__MINGW32__)
220 memcpy( gmt, gmtime(&cur_time), sizeof(tm) );
222 gmt = gmtime(&cur_time);
224 SG_LOG( SG_EVENT, SG_DEBUG,
225 " Current GMT = " << gmt->tm_mon+1 << "/"
226 << gmt->tm_mday << "/" << (1900 + gmt->tm_year) << " "
227 << gmt->tm_hour << ":" << gmt->tm_min << ":"
230 // calculate modified Julian date starting with current
231 mjd = sgTimeCurrentMJD( warp );
233 // add in partial day
234 mjd += (gmt->tm_hour / 24.0) + (gmt->tm_min / (24.0 * 60.0)) +
235 (gmt->tm_sec / (24.0 * 60.0 * 60.0));
237 // convert "back" to Julian date + partial day (as a fraction of one)
239 SG_LOG( SG_EVENT, SG_DEBUG, " Current Julian Date = " << jd );
241 // printf(" Current Longitude = %.3f\n", FG_Longitude * SGD_RADIANS_TO_DEGREES);
243 // Calculate local side real time
244 if ( gst_diff < -100.0 ) {
245 // first time through do the expensive calculation & cheap
246 // calculation to get the difference.
247 SG_LOG( SG_EVENT, SG_INFO, " First time, doing precise gst" );
248 gst_precise = gst = sidereal_precise( mjd, 0.00 );
249 gst_course = sidereal_course( cur_time, gmt, 0.00 );
251 gst_diff = gst_precise - gst_course;
253 lst = sidereal_course( cur_time, gmt, -(lon * SGD_RADIANS_TO_DEGREES) ) + gst_diff;
255 // course + difference should drift off very slowly
256 gst = sidereal_course( cur_time, gmt, 0.00 ) + gst_diff;
257 lst = sidereal_course( cur_time, gmt, -(lon * SGD_RADIANS_TO_DEGREES) ) + gst_diff;
260 SG_LOG( SG_EVENT, SG_DEBUG,
261 " Current lon=0.00 Sidereal Time = " << gst );
262 SG_LOG( SG_EVENT, SG_DEBUG,
263 " Current LOCAL Sidereal Time = " << lst << " ("
264 << sidereal_precise( mjd, -(lon * SGD_RADIANS_TO_DEGREES) )
265 << ") (diff = " << gst_diff << ")" );
269 // Given lon/lat, update timezone information and local_offset
270 void SGTime::updateLocal( double lon, double lat, const string& root ) {
272 if ( lon < -SGD_PI || lon > SGD_PI ) {
273 // not within -180 ... 180
276 if ( lat < -SGD_PI * 0.5 || lat > SGD_PI * 0.5 ) {
277 // not within -90 ... 90
281 // only true if lon == nan
282 SG_LOG( SG_EVENT, SG_ALERT, " Detected lon == nan, resetting to 0.0" );
286 // only true if lat == nan
287 SG_LOG( SG_EVENT, SG_ALERT, " Detected lat == nan, resetting to 0.0" );
291 time_t aircraftLocalTime;
292 GeoCoord location( SGD_RADIANS_TO_DEGREES * lat, SGD_RADIANS_TO_DEGREES * lon );
293 GeoCoord* nearestTz = tzContainer->getNearest(location);
295 zone.append ( nearestTz->getDescription() );
297 char *ptr = zonename;
301 zonename = strdup( zone.c_str() );
303 //Avoid troubles when zone.tab hasn't got the right line endings
304 if (zonename[strlen(zonename)-1] == '\r')
306 zonename[strlen(zonename)-1]=0;
307 zone.set( zonename );
310 currGMT = sgTimeGetGMT( gmtime(&cur_time) );
311 aircraftLocalTime = sgTimeGetGMT( (fgLocaltime(&cur_time, zone.c_str())) );
312 local_offset = aircraftLocalTime - currGMT;
313 // cout << "Using " << local_offset << " as local time offset Timezone is "
314 // << zonename << endl;
318 // given a date in months, mn, days, dy, years, yr, return the
319 // modified Julian date (number of days elapsed since 1900 jan 0.5),
320 // mjd. Adapted from Xephem.
321 double sgTimeCalcMJD(int mn, double dy, int yr) {
324 // internal book keeping data
325 static double last_mjd, last_dy;
326 static int last_mn, last_yr;
331 if (mn == last_mn && yr == last_yr && dy == last_dy) {
336 y = (yr < 0) ? yr + 1 : yr;
342 if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
351 c = (long)((365.25*y) - 0.75) - 694025L;
353 c = (long)(365.25*y) - 694025L;
356 d = (int)(30.6001*(m+1));
358 mjd = b + c + d + dy - 0.5;
369 // return the current modified Julian date (number of days elapsed
370 // since 1900 jan 0.5), mjd.
371 double sgTimeCurrentMJD( time_t ct, long int warp ) {
373 #if defined(_MSC_VER) || defined(__MINGW32__)
374 struct tm m_gmt; // copy of system gmtime(&time_t) structure
375 struct tm *gmt = &m_gmt;
380 // get current Unix calendar time (in seconds)
381 // warp += warp_delta;
382 time_t cur_time = time(NULL) + warp;
383 SG_LOG( SG_EVENT, SG_DEBUG,
384 " Current Unix calendar time = " << cur_time
385 << " warp = " << warp );
387 // get GMT break down for current time
388 #if defined(_MSC_VER) || defined(__MINGW32__)
389 memcpy( gmt, gmtime(&cur_time), sizeof(tm) );
391 gmt = gmtime(&cur_time);
393 SG_LOG( SG_EVENT, SG_DEBUG,
394 " Current GMT = " << gmt->tm_mon+1 << "/"
395 << gmt->tm_mday << "/" << (1900 + gmt->tm_year) << " "
396 << gmt->tm_hour << ":" << gmt->tm_min << ":"
399 // calculate modified Julian date
400 // t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday,
401 // (int)(t->gmt->tm_year + 1900));
402 double mjd = sgTimeCalcMJD( (int)(gmt->tm_mon+1), (double)gmt->tm_mday,
403 (int)(gmt->tm_year + 1900) );
409 // given an mjd, calculate greenwich mean sidereal time, gst
410 double sgTimeCalcGST( double mjd ) {
413 double day = floor(mjd-0.5)+0.5;
414 double hr = (mjd-day)*24.0;
417 T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
418 x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
420 gst = (1.0/SIDRATE)*hr + x;
422 SG_LOG( SG_EVENT, SG_DEBUG, " gst => " << gst );
428 #if defined( HAVE_TIMEGM )
429 // ignore this function
430 #elif defined( MK_TIME_IS_GMT )
431 // ignore this function
432 #else // ! defined ( MK_TIME_IS_GMT )
434 // Fix up timezone if using ftime()
435 static long int fix_up_timezone( long int timezone_orig ) {
436 # if !defined( HAVE_GETTIMEOFDAY ) && defined( HAVE_FTIME )
437 // ftime() needs a little extra help finding the current timezone
438 struct timeb current;
440 return( current.timezone * 60 );
442 return( timezone_orig );
448 /******************************************************************
449 * The following are some functions that were included as SGTime
450 * members, although they currently don't make use of any of the
451 * class's variables. Maybe this'll change in the future
452 *****************************************************************/
454 // Return time_t for Sat Mar 21 12:00:00 GMT
456 // On many systems it is ambiguous if mktime() assumes the input is in
457 // GMT, or local timezone. To address this, a new function called
458 // timegm() is appearing. It works exactly like mktime() but
459 // explicitely interprets the input as GMT.
461 // timegm() is available and documented under FreeBSD. It is
462 // available, but completely undocumented on my current Debian 2.1
465 // In the absence of timegm() we have to guess what mktime() might do.
467 // Many older BSD style systems have a mktime() that assumes the input
468 // time in GMT. But FreeBSD explicitly states that mktime() assumes
471 // The mktime() on many SYSV style systems (such as Linux) usually
472 // returns its result assuming you have specified the input time in
473 // your local timezone. Therefore, in the absence if timegm() you
474 // have to go to extra trouble to convert back to GMT.
476 // If you are having problems with incorrectly positioned astronomical
477 // bodies, this is a really good place to start looking.
479 time_t sgTimeGetGMT(int year, int month, int day, int hour, int min, int sec)
489 mt.tm_isdst = -1; // let the system determine the proper time zone
491 // For now we assume that if daylight is not defined in
492 // /usr/include/time.h that we have a machine with a mktime() that
493 // assumes input is in GMT ... this only matters if we are
494 // building on a system that does not have timegm()
495 #if !defined(HAVE_DAYLIGHT)
496 # define MK_TIME_IS_GMT 1
499 #if defined( HAVE_TIMEGM )
500 return ( timegm(&mt) );
501 #elif defined( MK_TIME_IS_GMT )
502 time_t ret = mktime(&mt);
508 // This is necessary as some mktime() calls may
509 // try to access the system timezone files
510 // if this open fails errno is set to 2
511 // CYGWIN for one does this
513 // perror( "sgTimeGetGMT()" );
517 // reset errno in any event.
521 #else // ! defined ( MK_TIME_IS_GMT )
523 // timezone seems to work as a proper offset for Linux & Solaris
524 # if defined( __linux__ ) || defined( __sun__ ) ||defined(__CYGWIN__)
525 # define TIMEZONE_OFFSET_WORKS 1
528 #if defined(__CYGWIN__)
529 #define TIMEZONE _timezone
531 #define TIMEZONE timezone
534 time_t start = mktime(&mt);
536 SG_LOG( SG_EVENT, SG_DEBUG, "start1 = " << start );
537 // the ctime() call can screw up time progression on some versions
539 // fgPrintf( SG_EVENT, SG_DEBUG, "start2 = %s", ctime(&start));
540 SG_LOG( SG_EVENT, SG_DEBUG, "(tm_isdst = " << mt.tm_isdst << ")" );
542 TIMEZONE = fix_up_timezone( TIMEZONE );
544 # if defined( TIMEZONE_OFFSET_WORKS )
545 SG_LOG( SG_EVENT, SG_DEBUG,
546 "start = " << start << ", timezone = " << TIMEZONE );
547 return( start - TIMEZONE );
548 # else // ! defined( TIMEZONE_OFFSET_WORKS )
550 daylight = mt.tm_isdst;
551 if ( daylight > 0 ) {
553 } else if ( daylight < 0 ) {
554 SG_LOG( SG_EVENT, FG_WARN,
555 "OOOPS, problem in sg_time.cxx, no daylight savings info." );
558 long int offset = -(TIMEZONE / 3600 - daylight);
560 SG_LOG( SG_EVENT, SG_DEBUG, " Raw time zone offset = " << TIMEZONE );
561 SG_LOG( SG_EVENT, SG_DEBUG, " Daylight Savings = " << daylight );
562 SG_LOG( SG_EVENT, SG_DEBUG, " Local hours from GMT = " << offset );
564 long int start_gmt = start - TIMEZONE + (daylight * 3600);
566 SG_LOG( SG_EVENT, SG_DEBUG, " March 21 noon (CST) = " << start );
568 return ( start_gmt );
569 # endif // ! defined( TIMEZONE_OFFSET_WORKS )
570 #endif // ! defined ( MK_TIME_IS_GMT )
575 char* sgTimeFormatTime( const struct tm* p, char* buf )
577 sprintf( buf, "%d/%d/%2d %d:%02d:%02d",
578 p->tm_mon, p->tm_mday, p->tm_year,
579 p->tm_hour, p->tm_min, p->tm_sec);