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