timezone/tzfile.h

   1 /* Layout and location of TZif files.  */
   2
   3 #ifndef TZFILE_H
   4
   5 #define TZFILE_H
   6
   7 /*
   8 ** This file is in the public domain, so clarified as of
   9 ** 1996-06-05 by Arthur David Olson.
  10 */
  11
  12 /*
  13 ** This header is for use ONLY with the time conversion code.
  14 ** There is no guarantee that it will remain unchanged,
  15 ** or that it will remain at all.
  16 ** Do NOT copy it to any system include directory.
  17 ** Thank you!
  18 */
  19
  20 /*
  21 ** Information about time zone files.
  22 */
  23
  24 #ifndef TZDIR
  25 #define TZDIR   "/usr/share/zoneinfo" /* Time zone object file directory */
  26 #endif /* !defined TZDIR */
  27
  28 #ifndef TZDEFAULT
  29 #define TZDEFAULT       "/etc/localtime"
  30 #endif /* !defined TZDEFAULT */
  31
  32 #ifndef TZDEFRULES
  33 #define TZDEFRULES      "posixrules"
  34 #endif /* !defined TZDEFRULES */
  35
  36
  37 /* See Internet RFC 8536 for more details about the following format.  */
  38
  39 /*
  40 ** Each file begins with. . .
  41 */
  42
  43 #define TZ_MAGIC        "TZif"
  44
  45 struct tzhead {
  46         char    tzh_magic[4];           /* TZ_MAGIC */
  47         char    tzh_version[1];         /* '\0' or '2' or '3' as of 2013 */
  48         char    tzh_reserved[15];       /* reserved; must be zero */
  49         char    tzh_ttisutcnt[4];       /* coded number of trans. time flags */
  50         char    tzh_ttisstdcnt[4];      /* coded number of trans. time flags */
  51         char    tzh_leapcnt[4];         /* coded number of leap seconds */
  52         char    tzh_timecnt[4];         /* coded number of transition times */
  53         char    tzh_typecnt[4];         /* coded number of local time types */
  54         char    tzh_charcnt[4];         /* coded number of abbr. chars */
  55 };
  56
  57 /*
  58 ** . . .followed by. . .
  59 **
  60 **      tzh_timecnt (char [4])s         coded transition times a la time(2)
  61 **      tzh_timecnt (unsigned char)s    types of local time starting at above
  62 **      tzh_typecnt repetitions of
  63 **              one (char [4])          coded UT offset in seconds
  64 **              one (unsigned char)     used to set tm_isdst
  65 **              one (unsigned char)     that's an abbreviation list index
  66 **      tzh_charcnt (char)s             '\0'-terminated zone abbreviations
  67 **      tzh_leapcnt repetitions of
  68 **              one (char [4])          coded leap second transition times
  69 **              one (char [4])          total correction after above
  70 **      tzh_ttisstdcnt (char)s          indexed by type; if 1, transition
  71 **                                      time is standard time, if 0,
  72 **                                      transition time is local (wall clock)
  73 **                                      time; if absent, transition times are
  74 **                                      assumed to be local time
  75 **      tzh_ttisutcnt (char)s           indexed by type; if 1, transition
  76 **                                      time is UT, if 0, transition time is
  77 **                                      local time; if absent, transition
  78 **                                      times are assumed to be local time.
  79 **                                      When this is 1, the corresponding
  80 **                                      std/wall indicator must also be 1.
  81 */
  82
  83 /*
  84 ** If tzh_version is '2' or greater, the above is followed by a second instance
  85 ** of tzhead and a second instance of the data in which each coded transition
  86 ** time uses 8 rather than 4 chars,
  87 ** then a POSIX-TZ-environment-variable-style string for use in handling
  88 ** instants after the last transition time stored in the file
  89 ** (with nothing between the newlines if there is no POSIX representation for
  90 ** such instants).
  91 **
  92 ** If tz_version is '3' or greater, the above is extended as follows.
  93 ** First, the POSIX TZ string's hour offset may range from -167
  94 ** through 167 as compared to the POSIX-required 0 through 24.
  95 ** Second, its DST start time may be January 1 at 00:00 and its stop
  96 ** time December 31 at 24:00 plus the difference between DST and
  97 ** standard time, indicating DST all year.
  98 */
  99
 100 /*
 101 ** In the current implementation, "tzset()" refuses to deal with files that
 102 ** exceed any of the limits below.
 103 */
 104
 105 #ifndef TZ_MAX_TIMES
 106 #define TZ_MAX_TIMES    2000
 107 #endif /* !defined TZ_MAX_TIMES */
 108
 109 #ifndef TZ_MAX_TYPES
 110 /* This must be at least 17 for Europe/Samara and Europe/Vilnius.  */
 111 #define TZ_MAX_TYPES    256 /* Limited by what (unsigned char)'s can hold */
 112 #endif /* !defined TZ_MAX_TYPES */
 113
 114 #ifndef TZ_MAX_CHARS
 115 #define TZ_MAX_CHARS    50      /* Maximum number of abbreviation characters */
 116                                 /* (limited by what unsigned chars can hold) */
 117 #endif /* !defined TZ_MAX_CHARS */
 118
 119 #ifndef TZ_MAX_LEAPS
 120 #define TZ_MAX_LEAPS    50      /* Maximum number of leap second corrections */
 121 #endif /* !defined TZ_MAX_LEAPS */
 122
 123 #endif /* !defined TZFILE_H */