tzfile.h (4239B)
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 /* See Internet RFC 9636 for more details about the following format. */ 29 30 /* 31 ** Each file begins with. . . 32 */ 33 34 #define TZ_MAGIC "TZif" 35 36 struct tzhead { 37 char tzh_magic[4]; /* TZ_MAGIC */ 38 char tzh_version[1]; /* '\0' or '2'-'4' as of 2021 */ 39 char tzh_reserved[15]; /* reserved; must be zero */ 40 char tzh_ttisutcnt[4]; /* coded number of trans. time flags */ 41 char tzh_ttisstdcnt[4]; /* coded number of trans. time flags */ 42 char tzh_leapcnt[4]; /* coded number of leap seconds */ 43 char tzh_timecnt[4]; /* coded number of transition times */ 44 char tzh_typecnt[4]; /* coded number of local time types */ 45 char tzh_charcnt[4]; /* coded number of abbr. chars */ 46 }; 47 48 /* 49 ** . . .followed by. . . 50 ** 51 ** tzh_timecnt (char [4])s coded transition times a la time(2) 52 ** tzh_timecnt (unsigned char)s types of local time starting at above 53 ** tzh_typecnt repetitions of 54 ** one (char [4]) coded UT offset in seconds 55 ** one (unsigned char) used to set tm_isdst 56 ** one (unsigned char) that's an abbreviation list index 57 ** tzh_charcnt (char)s '\0'-terminated zone abbreviations 58 ** tzh_leapcnt repetitions of 59 ** one (char [4]) coded leap second transition times 60 ** one (char [4]) total correction after above 61 ** tzh_ttisstdcnt (char)s indexed by type; if 1, transition 62 ** time is standard time, if 0, 63 ** transition time is local (wall clock) 64 ** time; if absent, transition times are 65 ** assumed to be local time 66 ** tzh_ttisutcnt (char)s indexed by type; if 1, transition 67 ** time is UT, if 0, transition time is 68 ** local time; if absent, transition 69 ** times are assumed to be local time. 70 ** When this is 1, the corresponding 71 ** std/wall indicator must also be 1. 72 */ 73 74 /* 75 ** If tzh_version is '2' or greater, the above is followed by a second instance 76 ** of tzhead and a second instance of the data in which each coded transition 77 ** time uses 8 rather than 4 chars, 78 ** then a POSIX.1-2017 proleptic TZ string for use in handling 79 ** instants after the last transition time stored in the file 80 ** (with nothing between the newlines if there is no POSIX.1-2017 81 ** representation for such instants). 82 ** 83 ** If tz_version is '3' or greater, the TZ string can be any POSIX.1-2024 84 ** proleptic TZ string, which means 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 range 0 through 24 required 87 ** by POSIX.1-2017 and earlier. 88 ** Second, its DST start time may be January 1 at 00:00 and its stop 89 ** time December 31 at 24:00 plus the difference between DST and 90 ** standard time, indicating DST all year. 91 */ 92 93 /* 94 ** In the current implementation, "tzset()" refuses to deal with files that 95 ** exceed any of the limits below. 96 */ 97 98 #ifndef TZ_MAX_TIMES 99 /* This must be at least 242 for Europe/London with 'zic -b fat'. */ 100 #define TZ_MAX_TIMES 2000 101 #endif /* !defined TZ_MAX_TIMES */ 102 103 #ifndef TZ_MAX_TYPES 104 /* This must be at least 18 for Europe/Vilnius with 'zic -b fat'. */ 105 #define TZ_MAX_TYPES 256 /* Limited by what (unsigned char)'s can hold */ 106 #endif /* !defined TZ_MAX_TYPES */ 107 108 #ifndef TZ_MAX_CHARS 109 /* This must be at least 40 for America/Anchorage. */ 110 #define TZ_MAX_CHARS 50 /* Maximum number of abbreviation characters */ 111 /* (limited by what unsigned chars can hold) */ 112 #endif /* !defined TZ_MAX_CHARS */ 113 114 #ifndef TZ_MAX_LEAPS 115 /* This must be at least 27 for leap seconds from 1972 through mid-2023. 116 There's a plan to discontinue leap seconds by 2035. */ 117 #define TZ_MAX_LEAPS 50 /* Maximum number of leap second corrections */ 118 #endif /* !defined TZ_MAX_LEAPS */ 119 120 #endif /* !defined TZFILE_H */