145 lines
4.1 KiB
C++
145 lines
4.1 KiB
C++
// test the systems mktime() function
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <math.h>
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#include <stdio.h>
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#include <time.h>
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#ifdef HAVE_SYS_TIMEB_H
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# include <sys/types.h>
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# include <sys/timeb.h> // for ftime() and struct timeb
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#endif
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#ifdef HAVE_UNISTD_H
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# include <unistd.h> // for gettimeofday()
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#endif
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#ifdef HAVE_SYS_TIME_H
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# include <sys/time.h> // for get/setitimer, gettimeofday, struct timeval
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#endif
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#define LST_MAGIC_TIME_1998 890481600
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// For now we assume that if daylight is not defined in
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// /usr/include/time.h that we have a machine with a BSD behaving
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// mktime()
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#if !defined(HAVE_DAYLIGHT)
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# define MK_TIME_IS_GMT 1
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#endif
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// Fix up timezone if using ftime()
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long int fix_up_timezone( long int timezone_orig ) {
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#if !defined( HAVE_GETTIMEOFDAY ) && defined( HAVE_FTIME )
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// ftime() needs a little extra help finding the current timezone
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struct timeb current;
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ftime(¤t);
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return( current.timezone * 60 );
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#else
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return( timezone_orig );
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#endif
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}
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// Return time_t for Sat Mar 21 12:00:00 GMT
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//
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// I believe the mktime() has a SYSV vs. BSD behavior difference.
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//
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// The BSD style mktime() is nice because it returns its result
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// assuming you have specified the input time in GMT
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//
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// The SYSV style mktime() is a pain because it returns its result
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// assuming you have specified the input time in your local timezone.
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// Therefore you have to go to extra trouble to convert back to GMT.
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//
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// If you are having problems with incorrectly positioned astronomical
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// bodies, this is a really good place to start looking.
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time_t get_start_gmt(int year) {
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struct tm mt;
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mt.tm_mon = 2;
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mt.tm_mday = 21;
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mt.tm_year = year;
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mt.tm_hour = 12;
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mt.tm_min = 0;
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mt.tm_sec = 0;
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mt.tm_isdst = -1; // let the system determine the proper time zone
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#if defined( HAVE_TIMEGM )
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return ( timegm(&mt) );
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#elif defined( MK_TIME_IS_GMT )
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return ( mktime(&mt) );
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#else // ! defined ( MK_TIME_IS_GMT )
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// timezone seems to work as a proper offset for Linux & Solaris
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# if defined( __linux__ ) || defined( __sun__ )
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# define TIMEZONE_OFFSET_WORKS 1
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# endif
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time_t start = mktime(&mt);
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printf("start1 = %ld\n", start);
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printf("start2 = %s", ctime(&start));
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printf("(tm_isdst = %d)\n", mt.tm_isdst);
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timezone = fix_up_timezone( timezone );
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# if defined( TIMEZONE_OFFSET_WORKS )
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printf("start = %ld, timezone = %ld\n", start, timezone);
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return( start - timezone );
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# else // ! defined( TIMEZONE_OFFSET_WORKS )
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daylight = mt.tm_isdst;
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if ( daylight > 0 ) {
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daylight = 1;
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} else if ( daylight < 0 ) {
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printf("OOOPS, problem in fg_time.cxx, no daylight savings info.\n");
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}
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long int offset = -(timezone / 3600 - daylight);
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printf(" Raw time zone offset = %ld\n", timezone);
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printf(" Daylight Savings = %d\n", daylight);
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printf(" Local hours from GMT = %ld\n", offset);
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long int start_gmt = start - timezone + (daylight * 3600);
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printf(" March 21 noon (CST) = %ld\n", start);
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return ( start_gmt );
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# endif // ! defined( TIMEZONE_OFFSET_WORKS )
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#endif // ! defined ( MK_TIME_IS_GMT )
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}
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int main() {
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time_t start_gmt;
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start_gmt = get_start_gmt(98);
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if ( start_gmt == LST_MAGIC_TIME_1998 ) {
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printf("Time test = PASSED\n\n");
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#ifdef HAVE_TIMEGM
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printf("You have timegm() which is just like mktime() except that\n");
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printf("it explicitely expects input in GMT ... lucky you!\n");
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#elif MK_TIME_IS_GMT
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printf("You don't seem to have timegm(), but mktime() seems to\n");
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printf("assume input is GMT on your system ... I guess that works\n");
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#else
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printf("mktime() assumes local time zone on your system, but we can\n");
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printf("compensate just fine.\n");
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#endif
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} else {
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printf("Time test = FAILED\n\n");
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printf("There is likely a problem with mktime() on your system.\n");
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printf("This will cause the sun/moon/stars/planets to be in the\n");
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printf("wrong place in the sky and the rendered time of day will be\n");
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printf("incorrect.\n\n");
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printf("Please report this to curt@me.umn.edu so we can work to fix\n");
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printf("the problem on your platform.\n");
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}
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}
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