X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=simgear%2Ftiming%2Fsg_time.cxx;h=45fd41c1488ce08e2dca0c37906e53368bcfa255;hb=6a7c2000027cd22eea603e936ddbad1a5bfc8b04;hp=29750535871610eba4ee19be621f6f02c165edcb;hpb=8159b749f49be587e794a8438db7a4373d527b1d;p=simgear.git

diff --git a/simgear/timing/sg_time.cxx b/simgear/timing/sg_time.cxx
index 29750535..45fd41c1 100644
--- a/simgear/timing/sg_time.cxx
+++ b/simgear/timing/sg_time.cxx
@@ -2,272 +2,127 @@
 //
 // Written by Curtis Olson, started August 1997.
 //
-// Copyright (C) 1997  Curtis L. Olson  - curt@infoplane.com
+// Copyright (C) 1997  Curtis L. Olson  - http://www.flightgear.org/~curt
 //
-// This program is free software; you can redistribute it and/or
-// modify it under the terms of the GNU General Public License as
-// published by the Free Software Foundation; either version 2 of the
-// License, or (at your option) any later version.
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Library General Public
+// License as published by the Free Software Foundation; either
+// version 2 of the License, or (at your option) any later version.
 //
-// This program is distributed in the hope that it will be useful, but
-// WITHOUT ANY WARRANTY; without even the implied warranty of
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-// General Public License for more details.
+// Library General Public License for more details.
 //
 // You should have received a copy of the GNU General Public License
 // along with this program; if not, write to the Free Software
-// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 //
 // $Id$
 
 
 #ifdef HAVE_CONFIG_H
-#  include <config.h>
+#  include <simgear_config.h>
 #endif
 
 #include <simgear/compiler.h>
 
-#ifdef FG_HAVE_STD_INCLUDES
-#  include <cmath>
-#  include <cstdio>
-#  include <cstdlib>
-#  include <ctime>
-#else
-#  include <math.h>
-#  include <stdio.h>
-#  include <stdlib.h>
-#  include <time.h>
-#endif
+#include <errno.h>		// for errno
+
+#include <cstdio>
+#include <cstdlib>
+#include <ctime>
+
+#include <string>
 
+#ifdef HAVE_SYS_TIME_H
+#  include <sys/time.h>  // for get/setitimer, gettimeofday, struct timeval
+#endif
 #ifdef HAVE_SYS_TIMEB_H
 #  include <sys/timeb.h> // for ftime() and struct timeb
 #endif
 #ifdef HAVE_UNISTD_H
 #  include <unistd.h>    // for gettimeofday()
 #endif
-#ifdef HAVE_SYS_TIME_H
-#  include <sys/time.h>  // for get/setitimer, gettimeofday, struct timeval
-#endif
+
+#include <math.h>        // for NAN
 
 #include <simgear/constants.h>
 #include <simgear/debug/logstream.hxx>
-// #include <simgear/magvar/magvar.hxx>
-#include <simgear/misc/fgpath.hxx>
-
-// #include <FDM/flight.hxx>
-// #include <Main/options.hxx>
-// #include <Time/light.hxx>
+#include <simgear/misc/sg_path.hxx>
 
 #include "sg_time.hxx"
 #include "timezone.h"
 #include "lowleveltime.h"
-// #include "moonpos.hxx"
-// #include "sunpos.hxx"
-
 
 #define DEGHR(x)        ((x)/15.)
-#define RADHR(x)        DEGHR(x*RAD_TO_DEG)
+#define RADHR(x)        DEGHR(x*SGD_RADIANS_TO_DEGREES)
 
 
-// #define MK_TIME_IS_GMT 0         // default value
-// #define TIME_ZONE_OFFSET_WORK 0  // default value
+static const double MJD0    = 2415020.0;
+static const double J2000   = 2451545.0 - MJD0;
+static const double SIDRATE = 0.9972695677;
 
 
-SGTime::SGTime( const string& root )
+void SGTime::init( double lon_rad, double lat_rad,
+                   const string& root, time_t init_time )
 {
-    if (cur_time_params) {
-	FG_LOG( FG_GENERAL, FG_ALERT, 
-		"Error: only one instance of SGTime allowed" );
-	exit(-1);
-    }
+    SG_LOG( SG_EVENT, SG_INFO, "Initializing Time" );
 
-    cur_time_params = this;
-
-    FGPath zone( root );
-    zone.append( "Timezone" );
-    zone.append( "zone.tab" );
-
-    FG_LOG( FG_EVENT, FG_INFO, "Reading timezone info from: " << zone.str() );
-    tzContainer = new TimezoneContainer( zone.c_str() );
-    warp=0;
-    warp_delta=0;
-}
+    gst_diff = -9999.0;
 
+    if ( init_time ) {
+	cur_time = init_time;
+    } else {
+	cur_time = time(NULL); 
+    }
 
-SGTime::~SGTime()
-{
-    delete tzContainer;
-    delete zonename;
+    SG_LOG( SG_EVENT, SG_INFO,
+                "Current greenwich mean time = " << asctime(gmtime(&cur_time)));
+    SG_LOG( SG_EVENT, SG_INFO,
+             "Current local time          = " << asctime(localtime(&cur_time)));
+
+    if ( !root.empty()) {
+        SGPath zone( root );
+        zone.append( "zone.tab" );
+        SG_LOG( SG_EVENT, SG_INFO, "Reading timezone info from: "
+                << zone.str() );
+        tzContainer = new SGTimeZoneContainer( zone.c_str() );
+
+        SGGeoCoord location( SGD_RADIANS_TO_DEGREES * lat_rad, SGD_RADIANS_TO_DEGREES * lon_rad );
+        SGGeoCoord* nearestTz = tzContainer->getNearest(location);
+
+        SGPath name( root );
+        name.append( nearestTz->getDescription() );
+        zonename = name.str();
+        SG_LOG( SG_EVENT, SG_INFO, "Using zonename = " << zonename );
+    } else {
+        SG_LOG( SG_EVENT, SG_INFO, "*** NO TIME ZONE NAME ***" );
+        tzContainer = NULL;
+        zonename.erase();
+    }
 }
 
-void SGTime::updateLocal( double lon, double lat, const string& root )
+SGTime::SGTime( double lon_rad, double lat_rad, const string& root,
+                time_t init_time )
 {
-  time_t currGMT;
-  time_t aircraftLocalTime;
-  GeoCoord location( RAD_TO_DEG * lat, RAD_TO_DEG * lon );
-  GeoCoord* nearestTz = tzContainer->getNearest(location);
-  FGPath zone( root );
-  zone.append ("Timezone" );
-  zone.append ( nearestTz->getDescription() );
-  if ( zonename ) {
-      delete zonename;
-  }
-  zonename = strdup( zone.c_str() );
-  currGMT = get_gmt( gmtime(&cur_time) );
-  aircraftLocalTime = get_gmt( (fgLocaltime(&cur_time, zone.c_str())) );
-  localOffset = aircraftLocalTime - currGMT;
-  // cerr << "Using " << localOffset << " as local time offset Timezone is " 
-  //      << zonename << endl;
+    init( lon_rad, lat_rad, root, init_time );
 }
 
-// Initialize the time dependent variables (maybe I'll put this in the
-// constructor later)
-void SGTime::init( double lon, double lat, const string& root, 
-		   time_t timeOffset, sgTimingOffsetType offsetType )
-{
-    FG_LOG( FG_EVENT, FG_INFO, "Initializing Time" );
-    gst_diff = -9999.0;
-    FG_LOG( FG_EVENT, FG_DEBUG, 
-	    "time offset = " << timeOffset );
-    // time_t timeOffset = current_options.get_time_offset();
-    // int offsetType = current_options.get_time_offset_type();
-
-    time_t currGMT;
-    time_t systemLocalTime;
-    time_t aircraftLocalTime;
 
-    // would it be better to put these sanity checks in the options
-    // parsing code? (CLO)
-
-    cur_time = time(NULL); 
-
-    // printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
-    // printf ("Current local time          = %24s", asctime(localtime(&cur_time)));
-    // time_t tmp = cur_time;
-    GeoCoord location( RAD_TO_DEG * lat, RAD_TO_DEG * lon );
-
-    GeoCoord* nearestTz = tzContainer->getNearest(location);
-
-    FGPath zone( root );
-    zone.append( "Timezone" );
-    zone.append( nearestTz->getDescription() );
-
-    // printf("Using %s for timezone information\n", buffer);
-    zonename = strdup( zone.c_str() );
-    //show( buffer.c_str(), cur_time, 1); 
-    //printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
-    //printf ("Current local time          = %24s", asctime(localtime(&cur_time)));
-    currGMT = get_gmt( gmtime(&cur_time) );
-    systemLocalTime = get_gmt( localtime(&cur_time) );
-    aircraftLocalTime = get_gmt( fgLocaltime(&cur_time, zone.c_str()) ); 
-    //printf ("Current greenwich mean time = %24s", asctime(gmtime(&cur_time)));
-    //printf ("Current local time          = %24s", asctime(localtime(&cur_time)));
-
-    //printf("LT  = %d\n", computerLocalTime);
-    // Okay, in principle, this trick allows to calculate the
-    // difference between GMT and localtime, in seconds.
-    // printf("Gmt = %d, SLT = %d, (difference = %d)\n", currGMT, systemLocalTime,   (currGMT - systemLocalTime));
-    // printf("Gmt = %d, ALT = %d, (difference = %d)\n", currGMT, aircraftLocalTime, (currGMT - aircraftLocalTime));
-    // exit(1);
-    // Okay, we now have six possible scenarios
-    switch (offsetType)
-	{
-	case SG_TIME_SYS_OFFSET:
-	    warp = timeOffset;
-	    break;
-	case SG_TIME_GMT_OFFSET:
-	    warp = timeOffset - (currGMT - systemLocalTime);
-	    break;
-	case SG_TIME_LAT_OFFSET:
-	    // warp = timeOffset - (currGMT - systemLocalTime + 
-	    //        (currGMT - aircraftLocalTime));
-	    warp = timeOffset - (aircraftLocalTime - systemLocalTime); 
-	    break;
-	case SG_TIME_SYS_ABSOLUTE:
-	    warp = timeOffset - cur_time;
-	    //printf("warp = %d\n", warp); 
-	    break;
-	case SG_TIME_GMT_ABSOLUTE:
-	    warp = timeOffset - currGMT;
-	    break;
-	case SG_TIME_LAT_ABSOLUTE:
-	    warp = timeOffset - (aircraftLocalTime - systemLocalTime) - 
-		cur_time; 
-	    break;
-	default:
-	    printf("Unsupported type\n");
-	    exit(1);
-	}
-
-    warp_delta = 0;
-    // pause = current_options.get_pause();
+SGTime::SGTime( const string& root ) {
+    init( 0.0, 0.0, root, 0 );
 }
 
 
-// given a date in months, mn, days, dy, years, yr, return the
-// modified Julian date (number of days elapsed since 1900 jan 0.5),
-// mjd.  Adapted from Xephem.
-
-void SGTime::cal_mjd (int mn, double dy, int yr) 
-{
-    //static double last_mjd, last_dy;
-    //double mjd;
-    //static int last_mn, last_yr;
-    int b, d, m, y;
-    long c;
-  
-    if (mn == last_mn && yr == last_yr && dy == last_dy) {
-	mjd = last_mjd;
-	//return(mjd);
-    }
-  
-    m = mn;
-    y = (yr < 0) ? yr + 1 : yr;
-    if (mn < 3) {
-	m += 12;
-	y -= 1;
-    }
-  
-    if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
-	b = 0;
-    } else {
-	int a;
-	a = y/100;
-	b = 2 - a + a/4;
-    }
-  
-    if (y < 0) {
-	c = (long)((365.25*y) - 0.75) - 694025L;
-    } else {
-	c = (long)(365.25*y) - 694025L;
-    }
-  
-    d = (int)(30.6001*(m+1));
-  
-    mjd = b + c + d + dy - 0.5;
-  
-    last_mn = mn;
-    last_dy = dy;
-    last_yr = yr;
-    last_mjd = mjd;
-  
-    //return(mjd);
+SGTime::SGTime() {
+    init( 0.0, 0.0, "", 0 );
 }
 
 
-// given an mjd, calculate greenwich mean sidereal time, gst
-void SGTime::utc_gst () 
+SGTime::~SGTime()
 {
-    double day = floor(mjd-0.5)+0.5;
-    double hr = (mjd-day)*24.0;
-    double T, x;
-
-    T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
-    x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
-    x /= 3600.0;
-    gst = (1.0/SIDRATE)*hr + x;
-
-    FG_LOG( FG_EVENT, FG_DEBUG, "  gst => " << gst );
+    delete tzContainer;
 }
 
 
@@ -275,48 +130,41 @@ void SGTime::utc_gst ()
 // Local Sidereal Time, in decimal hours.
 //
 // Provided courtesy of ecdowney@noao.edu (Elwood Downey) 
-
-double SGTime::sidereal_precise (double lng) 
+static double sidereal_precise( double mjd, double lng )
 {
-    double lstTmp;
-
     /* printf ("Current Lst on JD %13.5f at %8.4f degrees West: ", 
        mjd + MJD0, lng); */
 
     // convert to required internal units
-    lng *= DEG_TO_RAD;
+    lng *= SGD_DEGREES_TO_RADIANS;
 
     // compute LST and print
-    utc_gst();
-    lstTmp = gst - RADHR (lng);
-    lstTmp -= 24.0*floor(lstTmp/24.0);
+    double gst = sgTimeCalcGST( mjd );
+    double lst = gst - RADHR( lng );
+    lst -= 24.0 * floor( lst / 24.0 );
     // printf ("%7.4f\n", lstTmp);
 
-    // that's all
-    return (lstTmp);
+    return lst;
 }
 
 
 // return a courser but cheaper estimate of sidereal time
-double SGTime::sidereal_course(double lng) 
+static double sidereal_course( time_t cur_time, const struct tm *gmt, double lng )
 {
-    //struct tm *gmt;
-    //double lstTmp;
     time_t start_gmt, now;
     double diff, part, days, hours, lstTmp;
     char tbuf[64];
   
-    //gmt = t->gmt;
-    //now = t->cur_time;
     now = cur_time;
-    start_gmt = get_gmt(gmt->tm_year, 2, 21, 12, 0, 0);
+    start_gmt = sgTimeGetGMT(gmt->tm_year, 2, 21, 12, 0, 0);
   
-    FG_LOG( FG_EVENT, FG_DEBUG, "  COURSE: GMT = " << format_time(gmt, tbuf) );
-    FG_LOG( FG_EVENT, FG_DEBUG, "  March 21 noon (GMT) = " << start_gmt );
+    SG_LOG( SG_EVENT, SG_DEBUG, "  COURSE: GMT = "
+	    << sgTimeFormatTime(gmt, tbuf) );
+    SG_LOG( SG_EVENT, SG_DEBUG, "  March 21 noon (GMT) = " << start_gmt );
   
     diff = (now - start_gmt) / (3600.0 * 24.0);
   
-    FG_LOG( FG_EVENT, FG_DEBUG, 
+    SG_LOG( SG_EVENT, SG_DEBUG, 
 	    "  Time since 3/21/" << gmt->tm_year << " GMT = " << diff );
   
     part = fmod(diff, 1.0);
@@ -329,47 +177,48 @@ double SGTime::sidereal_course(double lng)
 	lstTmp += 24.0;
     }
   
-    FG_LOG( FG_EVENT, FG_DEBUG,
+    SG_LOG( SG_EVENT, SG_DEBUG,
 	    "  days = " << days << "  hours = " << hours << "  lon = " 
 	    << lng << "  lst = " << lstTmp );
   
-    return(lstTmp);
+    return lstTmp;
 }
 
 
-// Update time variables such as gmt, julian date, and sidereal time
-void SGTime::update( double lon, double lat, double alt_m ) {
+// Update the time related variables
+void SGTime::update( double lon_rad, double lat_rad,
+                     time_t ct, long int warp )
+{
     double gst_precise, gst_course;
 
-    FG_LOG( FG_EVENT, FG_DEBUG, "Updating time" );
 
-    // get current Unix calendar time (in seconds)
-    warp += warp_delta;
-    cur_time = time(NULL) + warp;
-    FG_LOG( FG_EVENT, FG_DEBUG, 
-	    "  Current Unix calendar time = " << cur_time 
-	    << "  warp = " << warp << "  delta = " << warp_delta );
+    tm * gmt = &m_gmt;
+
+
+    SG_LOG( SG_EVENT, SG_DEBUG, "Updating time" );
 
-#if 0
-    if ( warp_delta ) {
-	// time is changing so force an update
-	local_update_sky_and_lighting_params();
+    // get current Unix calendar time (in seconds)
+    // warp += warp_delta;
+    if ( ct ) {
+	cur_time = ct + warp;
+    } else {
+	cur_time = time(NULL) + warp;
     }
-#endif
+    SG_LOG( SG_EVENT, SG_DEBUG, 
+	    "  Current Unix calendar time = " << cur_time 
+	    << "  warp = " << warp );
 
     // get GMT break down for current time
-    gmt = gmtime(&cur_time);
-    FG_LOG( FG_EVENT, FG_DEBUG, 
+
+    memcpy( gmt, gmtime(&cur_time), sizeof(tm) );
+    SG_LOG( SG_EVENT, SG_DEBUG, 
 	    "  Current GMT = " << gmt->tm_mon+1 << "/" 
-	    << gmt->tm_mday << "/" << gmt->tm_year << " "
+	    << gmt->tm_mday << "/" << (1900 + gmt->tm_year) << " "
 	    << gmt->tm_hour << ":" << gmt->tm_min << ":" 
 	    << gmt->tm_sec );
 
-    // calculate modified Julian date
-    // t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday, 
-    //     (int)(t->gmt->tm_year + 1900));
-    cal_mjd ((int)(gmt->tm_mon+1), (double)gmt->tm_mday, 
-	     (int)(gmt->tm_year + 1900));
+    // calculate modified Julian date starting with current
+    mjd = sgTimeCurrentMJD( ct, warp );
 
     // add in partial day
     mjd += (gmt->tm_hour / 24.0) + (gmt->tm_min / (24.0 * 60.0)) +
@@ -377,36 +226,212 @@ void SGTime::update( double lon, double lat, double alt_m ) {
 
     // convert "back" to Julian date + partial day (as a fraction of one)
     jd = mjd + MJD0;
-    FG_LOG( FG_EVENT, FG_DEBUG, "  Current Julian Date = " << jd );
+    SG_LOG( SG_EVENT, SG_DEBUG, "  Current Julian Date = " << jd );
 
-    // printf("  Current Longitude = %.3f\n", FG_Longitude * RAD_TO_DEG);
+    // printf("  Current Longitude = %.3f\n", FG_Longitude * SGD_RADIANS_TO_DEGREES);
 
     // Calculate local side real time
     if ( gst_diff < -100.0 ) {
 	// first time through do the expensive calculation & cheap
         // calculation to get the difference.
-	FG_LOG( FG_EVENT, FG_INFO, "  First time, doing precise gst" );
-	gst_precise = gst = sidereal_precise(0.00);
-	gst_course = sidereal_course(0.00);
+	SG_LOG( SG_EVENT, SG_INFO, "  First time, doing precise gst" );
+	gst_precise = gst = sidereal_precise( mjd, 0.00 );
+	gst_course = sidereal_course( cur_time, gmt, 0.00 );
       
 	gst_diff = gst_precise - gst_course;
 
-	lst = sidereal_course(-(lon * RAD_TO_DEG)) + gst_diff;
+	lst = sidereal_course( cur_time, gmt,
+                               -(lon_rad * SGD_RADIANS_TO_DEGREES) ) + gst_diff;
     } else {
 	// course + difference should drift off very slowly
-	gst = sidereal_course( 0.00 ) + gst_diff;
-	lst = sidereal_course( -(lon * RAD_TO_DEG)) + gst_diff;
+	gst = sidereal_course( cur_time, gmt, 0.00 ) + gst_diff;
+	lst = sidereal_course( cur_time, gmt,
+                               -(lon_rad * SGD_RADIANS_TO_DEGREES) ) + gst_diff;
     }
 
-    FG_LOG( FG_EVENT, FG_DEBUG,
+    SG_LOG( SG_EVENT, SG_DEBUG,
 	    "  Current lon=0.00 Sidereal Time = " << gst );
-    FG_LOG( FG_EVENT, FG_DEBUG,
+    SG_LOG( SG_EVENT, SG_DEBUG,
 	    "  Current LOCAL Sidereal Time = " << lst << " (" 
-	    << sidereal_precise(-(lon * RAD_TO_DEG)) 
+	    << sidereal_precise( mjd, -(lon_rad * SGD_RADIANS_TO_DEGREES) ) 
 	    << ") (diff = " << gst_diff << ")" );
 }
 
 
+// Given lon/lat, update timezone information and local_offset
+void SGTime::updateLocal( double lon_rad, double lat_rad, const string& root ) {
+    // sanity checking
+    if ( lon_rad < -SGD_PI || lon_rad> SGD_PI ) {
+        // not within -180 ... 180
+        lon_rad = 0.0;
+    }
+    if ( lat_rad < -SGD_PI_2 || lat_rad > SGD_PI_2 ) {
+        // not within -90 ... 90
+        lat_rad = 0.0;
+    }
+    if ( lon_rad != lon_rad ) {
+        // only true if lon_rad == nan
+        SG_LOG( SG_EVENT, SG_ALERT,
+                "  Detected lon_rad == nan, resetting to 0.0" );
+        lon_rad = 0.0;
+    }
+    if ( lat_rad != lat_rad ) {
+        // only true if lat_rad == nan
+        SG_LOG( SG_EVENT, SG_ALERT,
+                "  Detected lat_rad == nan, resetting to 0.0" );
+        lat_rad = 0.0;
+    }
+    time_t currGMT;
+    time_t aircraftLocalTime;
+    SGGeoCoord location( SGD_RADIANS_TO_DEGREES * lat_rad,
+                         SGD_RADIANS_TO_DEGREES * lon_rad );
+    SGGeoCoord* nearestTz = tzContainer->getNearest(location);
+    SGPath zone( root );
+    zone.append ( nearestTz->getDescription() );
+    zonename = zone.str();
+
+    //Avoid troubles when zone.tab hasn't got the right line endings
+    if (zonename[zonename.size()-1] == '\r')
+    {
+      zonename[zonename.size()-1]=0;
+      zone.set( zonename );
+    }
+
+    currGMT = sgTimeGetGMT( gmtime(&cur_time) );
+    aircraftLocalTime = sgTimeGetGMT( (fgLocaltime(&cur_time, zone.c_str())) );
+    local_offset = aircraftLocalTime - currGMT;
+    // cout << "Using " << local_offset << " as local time offset Timezone is " 
+    //      << zonename << endl;
+}
+
+
+// given a date in months, mn, days, dy, years, yr, return the
+// modified Julian date (number of days elapsed since 1900 jan 0.5),
+// mjd.  Adapted from Xephem.
+double sgTimeCalcMJD(int mn, double dy, int yr) {
+    double mjd;
+
+    // internal book keeping data
+    static double last_mjd, last_dy;
+    static int last_mn, last_yr;
+
+    int b, d, m, y;
+    long c;
+  
+    if (mn == last_mn && yr == last_yr && dy == last_dy) {
+	mjd = last_mjd;
+    }
+  
+    m = mn;
+    y = (yr < 0) ? yr + 1 : yr;
+    if (mn < 3) {
+	m += 12;
+	y -= 1;
+    }
+  
+    if (yr < 1582 || (yr == 1582 && (mn < 10 || (mn == 10 && dy < 15)))) {
+	b = 0;
+    } else {
+	int a;
+	a = y/100;
+	b = 2 - a + a/4;
+    }
+  
+    if (y < 0) {
+	c = (long)((365.25*y) - 0.75) - 694025L;
+    } else {
+	c = (long)(365.25*y) - 694025L;
+    }
+  
+    d = (int)(30.6001*(m+1));
+  
+    mjd = b + c + d + dy - 0.5;
+  
+    last_mn = mn;
+    last_dy = dy;
+    last_yr = yr;
+    last_mjd = mjd;
+
+    return mjd;
+}
+
+
+// return the current modified Julian date (number of days elapsed
+// since 1900 jan 0.5), mjd.
+double sgTimeCurrentMJD( time_t ct, long int warp ) {
+
+    struct tm m_gmt;    // copy of system gmtime(&time_t) structure
+    struct tm *gmt = &m_gmt;
+
+    // get current Unix calendar time (in seconds)
+    // warp += warp_delta;
+    time_t cur_time;
+    if ( ct ) {
+        cur_time = ct + warp;
+    } else {
+        cur_time = time(NULL) + warp;
+    }
+    SG_LOG( SG_EVENT, SG_DEBUG, 
+	    "  Current Unix calendar time = " << cur_time 
+	    << "  warp = " << warp );
+
+    // get GMT break down for current time
+    memcpy( gmt, gmtime(&cur_time), sizeof(tm) );
+    SG_LOG( SG_EVENT, SG_DEBUG, 
+	    "  Current GMT = " << gmt->tm_mon+1 << "/" 
+	    << gmt->tm_mday << "/" << (1900 + gmt->tm_year) << " "
+	    << gmt->tm_hour << ":" << gmt->tm_min << ":" 
+	    << gmt->tm_sec );
+
+    // calculate modified Julian date
+    // t->mjd = cal_mjd ((int)(t->gmt->tm_mon+1), (double)t->gmt->tm_mday, 
+    //     (int)(t->gmt->tm_year + 1900));
+    double mjd = sgTimeCalcMJD( (int)(gmt->tm_mon+1), (double)gmt->tm_mday, 
+                                (int)(gmt->tm_year + 1900) );
+
+    return mjd;
+}
+
+
+// given an mjd, calculate greenwich mean sidereal time, gst
+double sgTimeCalcGST( double mjd ) {
+    double gst;
+
+    double day = floor(mjd-0.5)+0.5;
+    double hr = (mjd-day)*24.0;
+    double T, x;
+
+    T = ((int)(mjd - 0.5) + 0.5 - J2000)/36525.0;
+    x = 24110.54841 + (8640184.812866 + (0.093104 - 6.2e-6 * T) * T) * T;
+    x /= 3600.0;
+    gst = (1.0/SIDRATE)*hr + x;
+
+    SG_LOG( SG_EVENT, SG_DEBUG, "  gst => " << gst );
+
+    return gst;
+}
+
+
+#if defined( HAVE_TIMEGM ) 
+    // ignore this function
+#elif defined( MK_TIME_IS_GMT )
+    // ignore this function
+#else // ! defined ( MK_TIME_IS_GMT )
+
+    // Fix up timezone if using ftime()
+    static long int fix_up_timezone( long int timezone_orig ) {
+#   if !defined( HAVE_GETTIMEOFDAY ) && defined( HAVE_FTIME )
+	// ftime() needs a little extra help finding the current timezone
+	struct timeb current;
+	ftime(&current);
+	return( current.timezone * 60 );
+#   else
+        return( timezone_orig );
+#   endif
+    }
+#endif
+
+
 /******************************************************************
  * The following are some functions that were included as SGTime
  * members, although they currently don't make use of any of the
@@ -438,7 +463,7 @@ void SGTime::update( double lon, double lat, double alt_m ) {
 // If you are having problems with incorrectly positioned astronomical
 // bodies, this is a really good place to start looking.
 
-time_t SGTime::get_gmt(int year, int month, int day, int hour, int min, int sec)
+time_t sgTimeGetGMT(int year, int month, int day, int hour, int min, int sec)
 {
     struct tm mt;
 
@@ -458,77 +483,86 @@ time_t SGTime::get_gmt(int year, int month, int day, int hour, int min, int sec)
 #  define MK_TIME_IS_GMT 1
 #endif
 
-#if defined( HAVE_TIMEGM ) 
+#if defined( HAVE_TIMEGM )
     return ( timegm(&mt) );
 #elif defined( MK_TIME_IS_GMT )
-    return ( mktime(&mt) );
+    time_t ret = mktime(&mt);
+
+#ifdef __CYGWIN__
+	ret -= _timezone;
+#endif
+
+    // This is necessary as some mktime() calls may
+    // try to access the system timezone files
+    // if this open fails errno is set to 2
+    // CYGWIN for one does this
+    // if ( errno ) {
+    //     perror( "sgTimeGetGMT()" );
+    //     errno = 0;
+    // }
+
+    // reset errno in any event.
+    errno = 0;
+
+    return ret;
 #else // ! defined ( MK_TIME_IS_GMT )
 
     // timezone seems to work as a proper offset for Linux & Solaris
-#   if defined( __linux__ ) || defined( __sun__ ) 
+#   if defined( __linux__ ) || defined(__sun) ||defined(__CYGWIN__)
 #       define TIMEZONE_OFFSET_WORKS 1
 #   endif
 
-    long int start = mktime(&mt);
+#if defined(__CYGWIN__)
+#define TIMEZONE _timezone
+#else
+#define TIMEZONE timezone
+#endif
+	
+    time_t start = mktime(&mt);
 
-    FG_LOG( FG_EVENT, FG_DEBUG, "start1 = " << start );
+    SG_LOG( SG_EVENT, SG_DEBUG, "start1 = " << start );
     // the ctime() call can screw up time progression on some versions
     // of Linux
-    // fgPrintf( FG_EVENT, FG_DEBUG, "start2 = %s", ctime(&start));
-    FG_LOG( FG_EVENT, FG_DEBUG, "(tm_isdst = " << mt.tm_isdst << ")" );
+    // fgPrintf( SG_EVENT, SG_DEBUG, "start2 = %s", ctime(&start));
+    SG_LOG( SG_EVENT, SG_DEBUG, "(tm_isdst = " << mt.tm_isdst << ")" );
 
-    timezone = fix_up_timezone( timezone );
+    TIMEZONE = fix_up_timezone( TIMEZONE );
 
 #  if defined( TIMEZONE_OFFSET_WORKS )
-    FG_LOG( FG_EVENT, FG_DEBUG, 
-	    "start = " << start << ", timezone = " << timezone );
-    return( start - timezone );
+    SG_LOG( SG_EVENT, SG_DEBUG,
+	    "start = " << start << ", timezone = " << TIMEZONE );
+    return( start - TIMEZONE );
 #  else // ! defined( TIMEZONE_OFFSET_WORKS )
 
     daylight = mt.tm_isdst;
     if ( daylight > 0 ) {
 	daylight = 1;
     } else if ( daylight < 0 ) {
-	FG_LOG( FG_EVENT, FG_WARN, 
+	SG_LOG( SG_EVENT, FG_WARN, 
 		"OOOPS, problem in sg_time.cxx, no daylight savings info." );
     }
 
-    long int offset = -(timezone / 3600 - daylight);
+    long int offset = -(TIMEZONE / 3600 - daylight);
 
-    FG_LOG( FG_EVENT, FG_DEBUG, "  Raw time zone offset = " << timezone );
-    FG_LOG( FG_EVENT, FG_DEBUG, "  Daylight Savings = " << daylight );
-    FG_LOG( FG_EVENT, FG_DEBUG, "  Local hours from GMT = " << offset );
+    SG_LOG( SG_EVENT, SG_DEBUG, "  Raw time zone offset = " << TIMEZONE );
+    SG_LOG( SG_EVENT, SG_DEBUG, "  Daylight Savings = " << daylight );
+    SG_LOG( SG_EVENT, SG_DEBUG, "  Local hours from GMT = " << offset );
     
-    long int start_gmt = start - timezone + (daylight * 3600);
+    long int start_gmt = start - TIMEZONE + (daylight * 3600);
     
-    FG_LOG( FG_EVENT, FG_DEBUG, "  March 21 noon (CST) = " << start );
+    SG_LOG( SG_EVENT, SG_DEBUG, "  March 21 noon (CST) = " << start );
 
     return ( start_gmt );
 #  endif // ! defined( TIMEZONE_OFFSET_WORKS )
 #endif // ! defined ( MK_TIME_IS_GMT )
 }
 
-// Fix up timezone if using ftime()
-long int SGTime::fix_up_timezone( long int timezone_orig ) 
-{
-#if !defined( HAVE_GETTIMEOFDAY ) && defined( HAVE_FTIME )
-    // ftime() needs a little extra help finding the current timezone
-    struct timeb current;
-    ftime(&current);
-    return( current.timezone * 60 );
-#else
-    return( timezone_orig );
-#endif
-}
 
-
-char* SGTime::format_time( const struct tm* p, char* buf )
+// format time
+char* sgTimeFormatTime( const struct tm* p, char* buf )
 {
     sprintf( buf, "%d/%d/%2d %d:%02d:%02d", 
 	     p->tm_mon, p->tm_mday, p->tm_year,
 	     p->tm_hour, p->tm_min, p->tm_sec);
     return buf;
 }
-
-
-SGTime* SGTime::cur_time_params = 0;