tests/test-mktime.cxx

   1 // test the systems mktime() function
   2
   3
   4 #ifdef HAVE_CONFIG_H
   5 #  include <config.h>
   6 #endif
   7
   8 #include <math.h>
   9 #include <stdio.h>
  10 #include <time.h>
  11
  12 #ifdef HAVE_SYS_TIMEB_H
  13 #  include <sys/types.h>
  14 #  include <sys/timeb.h> // for ftime() and struct timeb
  15 #endif
  16 #ifdef HAVE_UNISTD_H
  17 #  include <unistd.h>    // for gettimeofday()
  18 #endif
  19 #ifdef HAVE_SYS_TIME_H
  20 #  include <sys/time.h>  // for get/setitimer, gettimeofday, struct timeval
  21 #endif
  22
  23 #define LST_MAGIC_TIME_1998 890481600
  24
  25 // For now we assume that if daylight is not defined in
  26 // /usr/include/time.h that we have a machine with a BSD behaving
  27 // mktime()
  28 #if !defined(HAVE_DAYLIGHT)
  29 #  define MK_TIME_IS_GMT 1
  30 #endif
  31
  32
  33 // Fix up timezone if using ftime()
  34 long int fix_up_timezone( long int timezone_orig ) {
  35 #if !defined( HAVE_GETTIMEOFDAY ) && defined( HAVE_FTIME )
  36     // ftime() needs a little extra help finding the current timezone
  37     struct timeb current;
  38     ftime(&current);
  39     return( current.timezone * 60 );
  40 #else
  41     return( timezone_orig );
  42 #endif
  43 }
  44
  45
  46 // Return time_t for Sat Mar 21 12:00:00 GMT
  47 //
  48 // I believe the mktime() has a SYSV vs. BSD behavior difference.
  49 //
  50 // The BSD style mktime() is nice because it returns its result
  51 // assuming you have specified the input time in GMT
  52 //
  53 // The SYSV style mktime() is a pain because it returns its result
  54 // assuming you have specified the input time in your local timezone.
  55 // Therefore you have to go to extra trouble to convert back to GMT.
  56 //
  57 // If you are having problems with incorrectly positioned astronomical
  58 // bodies, this is a really good place to start looking.
  59
  60 time_t get_start_gmt(int year) {
  61     struct tm mt;
  62
  63     mt.tm_mon = 2;
  64     mt.tm_mday = 21;
  65     mt.tm_year = year;
  66     mt.tm_hour = 12;
  67     mt.tm_min = 0;
  68     mt.tm_sec = 0;
  69     mt.tm_isdst = -1; // let the system determine the proper time zone
  70
  71 #if defined( HAVE_TIMEGM )
  72     return ( timegm(&mt) );
  73 #elif defined( MK_TIME_IS_GMT )
  74     return ( mktime(&mt) );
  75 #else // ! defined ( MK_TIME_IS_GMT )
  76
  77     // timezone seems to work as a proper offset for Linux & Solaris
  78 #  if defined( __linux__ ) || defined(__sun) || defined( __CYGWIN__ )
  79 #   define TIMEZONE_OFFSET_WORKS 1
  80 #  endif
  81
  82 #if defined(__CYGWIN__)
  83 #define TIMEZONE _timezone
  84 #else
  85 #define TIMEZONE timezone
  86 #endif
  87
  88     time_t start = mktime(&mt);
  89
  90     printf("start1 = %ld\n", start);
  91     printf("start2 = %s", ctime(&start));
  92     printf("(tm_isdst = %d)\n", mt.tm_isdst);
  93
  94     TIMEZONE = fix_up_timezone( TIMEZONE );
  95
  96 #  if defined( TIMEZONE_OFFSET_WORKS )
  97     printf("start = %ld, timezone = %ld\n", start, TIMEZONE);
  98     return( start - TIMEZONE );
  99 #  else // ! defined( TIMEZONE_OFFSET_WORKS )
 100
 101     daylight = mt.tm_isdst;
 102     if ( daylight > 0 ) {
 103         daylight = 1;
 104     } else if ( daylight < 0 ) {
 105         printf("OOOPS, problem in fg_time.cxx, no daylight savings info.\n");
 106     }
 107
 108     long int offset = -(TIMEZONE / 3600 - daylight);
 109
 110     printf("  Raw time zone offset = %ld\n", TIMEZONE);
 111     printf("  Daylight Savings = %d\n", daylight);
 112     printf("  Local hours from GMT = %ld\n", offset);
 113
 114     long int start_gmt = start - TIMEZONE + (daylight * 3600);
 115
 116     printf("  March 21 noon (CST) = %ld\n", start);
 117
 118     return ( start_gmt );
 119 #  endif // ! defined( TIMEZONE_OFFSET_WORKS )
 120 #endif // ! defined ( MK_TIME_IS_GMT )
 121 }
 122
 123
 124 int main() {
 125     time_t start_gmt;
 126
 127     start_gmt = get_start_gmt(98);
 128
 129
 130     if ( start_gmt == LST_MAGIC_TIME_1998 ) {
 131         printf("Time test = PASSED\n\n");
 132 #ifdef HAVE_TIMEGM
 133         printf("You have timegm() which is just like mktime() except that\n");
 134         printf("it explicitely expects input in GMT ... lucky you!\n");
 135 #elif MK_TIME_IS_GMT
 136         printf("You don't seem to have timegm(), but mktime() seems to\n");
 137         printf("assume input is GMT on your system ... I guess that works\n");
 138 #else
 139         printf("mktime() assumes local time zone on your system, but we can\n");
 140         printf("compensate just fine.\n");
 141 #endif
 142     } else {
 143         printf("Time test = FAILED\n\n");
 144         printf("There is likely a problem with mktime() on your system.\n");
 145         printf("This will cause the sun/moon/stars/planets to be in the\n");
 146         printf("wrong place in the sky and the rendered time of day will be\n");
 147         printf("incorrect.\n\n");
 148         printf("Please report this to http://www.flightgear.org/~curt so we can work to fix\n");
 149         printf("the problem on your platform.\n");
 150     }
 151 }