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 TZDEFRULES 25 # define TZDEFRULES "posixrules" 26 #endif /* !defined TZDEFRULES */ 27 28 29 /* See Internet RFC 8536 for more details about the following format. */ 30 31 /* 32 ** Each file begins with. . . 33 */ 34 35 #define TZ_MAGIC "TZif" 36 37 struct tzhead { 38 char tzh_magic[4]; /* TZ_MAGIC */ 39 char tzh_version[1]; /* '\0' or '2'-'4' as of 2021 */ 40 char tzh_reserved[15]; /* reserved; must be zero */ 41 char tzh_ttisutcnt[4]; /* coded number of trans. time flags */ 42 char tzh_ttisstdcnt[4]; /* coded number of trans. time flags */ 43 char tzh_leapcnt[4]; /* coded number of leap seconds */ 44 char tzh_timecnt[4]; /* coded number of transition times */ 45 char tzh_typecnt[4]; /* coded number of local time types */ 46 char tzh_charcnt[4]; /* coded number of abbr. chars */ 47 }; 48 49 /* 50 ** . . .followed by. . . 51 ** 52 ** tzh_timecnt (char [4])s coded transition times a la time(2) 53 ** tzh_timecnt (unsigned char)s types of local time starting at above 54 ** tzh_typecnt repetitions of 55 ** one (char [4]) coded UT offset in seconds 56 ** one (unsigned char) used to set tm_isdst 57 ** one (unsigned char) that's an abbreviation list index 58 ** tzh_charcnt (char)s '\0'-terminated zone abbreviations 59 ** tzh_leapcnt repetitions of 60 ** one (char [4]) coded leap second transition times 61 ** one (char [4]) total correction after above 62 ** tzh_ttisstdcnt (char)s indexed by type; if 1, transition 63 ** time is standard time, if 0, 64 ** transition time is local (wall clock) 65 ** time; if absent, transition times are 66 ** assumed to be local time 67 ** tzh_ttisutcnt (char)s indexed by type; if 1, transition 68 ** time is UT, if 0, transition time is 69 ** local time; if absent, transition 70 ** times are assumed to be local time. 71 ** When this is 1, the corresponding 72 ** std/wall indicator must also be 1. 73 */ 74 75 /* 76 ** If tzh_version is '2' or greater, the above is followed by a second instance 77 ** of tzhead and a second instance of the data in which each coded transition 78 ** time uses 8 rather than 4 chars, 79 ** then a POSIX-TZ-environment-variable-style string for use in handling 80 ** instants after the last transition time stored in the file 81 ** (with nothing between the newlines if there is no POSIX.1-2017 82 ** representation for such instants). 83 ** 84 ** If tz_version is '3' or greater, the above is extended as follows. 85 ** First, the TZ string's hour offset may range from -167 86 ** through 167 as compared to the POSIX-required 0 through 24. 87 ** Second, its DST start time may be January 1 at 00:00 and its stop 88 ** time December 31 at 24:00 plus the difference between DST and 89 ** standard time, indicating DST all year. 90 */ 91 92 /* 93 ** In the current implementation, "tzset()" refuses to deal with files that 94 ** exceed any of the limits below. 95 */ 96 97 #ifndef TZ_MAX_TIMES 98 /* This must be at least 242 for Europe/London with 'zic -b fat'. */ 99 # define TZ_MAX_TIMES 2000 100 #endif /* !defined TZ_MAX_TIMES */ 101 102 #ifndef TZ_MAX_TYPES 103 /* This must be at least 18 for Europe/Vilnius with 'zic -b fat'. */ 104 # define TZ_MAX_TYPES 256 /* Limited by what (unsigned char)'s can hold */ 105 #endif /* !defined TZ_MAX_TYPES */ 106 107 #ifndef TZ_MAX_CHARS 108 /* This must be at least 40 for America/Anchorage. */ 109 # define TZ_MAX_CHARS 50 /* Maximum number of abbreviation characters */ 110 /* (limited by what unsigned chars can hold) */ 111 #endif /* !defined TZ_MAX_CHARS */ 112 113 #ifndef TZ_MAX_LEAPS 114 /* This must be at least 27 for leap seconds from 1972 through mid-2023. 115 There's a plan to discontinue leap seconds by 2035. */ 116 # define TZ_MAX_LEAPS 50 /* Maximum number of leap second corrections */ 117 #endif /* !defined TZ_MAX_LEAPS */ 118 119 #endif /* !defined TZFILE_H */ 120