libjava/java/util/natVMTimeZone.cc

   1 // natVMTimeZone.cc -- Native side of VMTimeZone class.
   2
   3 /* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
   4    Free Software Foundation
   5
   6    This file is part of libgcj.
   7
   8 This software is copyrighted work licensed under the terms of the
   9 Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
  10 details.  */
  11
  12 #include <config.h>
  13 #include <platform.h>
  14
  15 #include <gcj/cni.h>
  16 #include <jvm.h>
  17
  18 #include <java/util/VMTimeZone.h>
  19 #include <java/lang/Character.h>
  20 #include <java/lang/Integer.h>
  21
  22 #include <stdio.h>
  23
  24 #if TIME_WITH_SYS_TIME
  25 # include <sys/time.h>
  26 # include <time.h>
  27 #else
  28 # if HAVE_SYS_TIME_H
  29 #  include <sys/time.h>
  30 # else
  31 #  include <time.h>
  32 # endif
  33 #endif
  34
  35 #include <string.h>
  36
  37 /**
  38  * This method returns a time zone id string which is in the form
  39  * (standard zone name) or (standard zone name)(GMT offset) or
  40  * (standard zone name)(GMT offset)(daylight time zone name).  The
  41  * GMT offset can be in seconds, or where it is evenly divisible by
  42  * 3600, then it can be in hours.  The offset must be the time to
  43  * add to the local time to get GMT.  If a offset is given and the
  44  * time zone observes daylight saving then the (daylight time zone
  45  * name) must also be given (otherwise it is assumed the time zone
  46  * does not observe any daylight savings).
  47  * <p>
  48  * The result of this method is given to getDefaultTimeZone(String)
  49  * which tries to map the time zone id to a known TimeZone.  See
  50  * that method on how the returned String is mapped to a real
  51  * TimeZone object.
  52  */
  53 jstring
  54 java::util::VMTimeZone::getSystemTimeZoneId()
  55 {
  56   struct tm tim;
  57 #if !defined(HAVE_LOCALTIME_R) || !defined(_POSIX_PTHREAD_SEMANTICS)
  58   struct tm *lt_tim;
  59 #endif
  60 #ifdef HAVE_TM_ZONE
  61   int month;
  62 #endif
  63   time_t current_time;
  64   long tzoffset;
  65   const char *tz1, *tz2;
  66   char *tzid;
  67
  68   time(&current_time);
  69 #if defined(HAVE_LOCALTIME_R) && defined(_POSIX_PTHREAD_SEMANTICS)
  70   localtime_r(&current_time, &tim);
  71 #else
  72   /* Fall back on non-thread safe localtime. */
  73   lt_tim = localtime(&current_time);
  74   memcpy(&tim, lt_tim, sizeof (struct tm));
  75 #endif
  76   mktime(&tim);
  77
  78 #ifdef HAVE_TM_ZONE
  79   /* We will cycle through the months to make sure we hit dst. */
  80   month = tim.tm_mon;
  81   tz1 = tz2 = NULL;
  82   while (tz1 == NULL || tz2 == NULL)
  83     {
  84       if (tim.tm_isdst > 0)
  85         tz2 = tim.tm_zone;
  86       else if (tz1 == NULL)
  87         {
  88           tz1 = tim.tm_zone;
  89           month = tim.tm_mon;
  90         }
  91
  92       if (tz1 == NULL || tz2 == NULL)
  93         {
  94           tim.tm_mon++;
  95           tim.tm_mon %= 12;
  96         }
  97
  98       if (tim.tm_mon == month && tz2 == NULL)
  99         tz2 = "";
 100       else
 101         mktime(&tim);
 102     }
 103   /* We want to make sure the tm struct we use later on is not dst. */
 104   tim.tm_mon = month;
 105   mktime(&tim);
 106 #elif defined (HAVE_TZNAME)
 107   /* If dst is never used, tzname[1] is the empty string. */
 108   tzset();
 109   tz1 = tzname[0];
 110   tz2 = tzname[1];
 111 #else
 112   /* Some targets have no concept of timezones. Assume GMT without dst. */
 113   tz1 = "GMT";
 114   tz2 = "";
 115 #endif
 116
 117 #ifdef STRUCT_TM_HAS_GMTOFF
 118   /* tm_gmtoff is the number of seconds that you must add to GMT to get
 119      local time, we need the number of seconds to add to the local time
 120      to get GMT. */
 121   tzoffset = -1L * tim.tm_gmtoff;
 122 #elif HAVE_UNDERSCORE_TIMEZONE
 123   tzoffset = _timezone;
 124 #elif HAVE_TIMEZONE
 125   /* timezone is secs WEST of UTC. */
 126   tzoffset = timezone;
 127 #else
 128   /* FIXME: there must be another global if neither tm_gmtoff nor timezone
 129      is available, esp. if tzname is valid.
 130      Richard Earnshaw <rearnsha@arm.com> has suggested using difftime to
 131      calculate between gmtime and localtime (and accounting for possible
 132      daylight savings time) as an alternative. */
 133   tzoffset = 0L;
 134 #endif
 135
 136   if ((tzoffset % 3600) == 0)
 137     tzoffset = tzoffset / 3600;
 138
 139   tzid = (char*) _Jv_Malloc (strlen(tz1) + strlen(tz2) + 6);
 140   sprintf(tzid, "%s%ld%s", tz1, tzoffset, tz2);
 141   jstring retval = JvNewStringUTF (tzid);
 142   _Jv_Free (tzid);
 143
 144   return retval;
 145 }