1/* $NetBSD: tzfile.h,v 1.14 2025/01/31 18:23:52 christos Exp $ */
2
3#ifndef _TZFILE_H_
4#define _TZFILE_H_
5
6/*
7** This file is in the public domain, so clarified as of
8** 1996-06-05 by Arthur David Olson.
9*/
10
11/*
12** This header is for use ONLY with the time conversion code.
13** There is no guarantee that it will remain unchanged,
14** or that it will remain at all.
15** Do NOT copy it to any system include directory.
16** Thank you!
17*/
18
19/*
20** Information about time zone files.
21*/
22
23#ifndef TZDIR /* Time zone object file directory */
24# define TZDIR "/usr/share/zoneinfo"
25#endif /* !defined TZDIR */
26
27#ifndef TZDEFAULT
28# define TZDEFAULT "/etc/localtime"
29#endif /* !defined TZDEFAULT */
30
31#ifndef TZDEFRULES
32# define TZDEFRULES "posixrules"
33#endif /* !defined TZDEFRULES */
34
35
36/* See Internet RFC 9636 for more details about the following format. */
37
38/*
39** Each file begins with. . .
40*/
41
42#define TZ_MAGIC "TZif"
43
44struct tzhead {
45 char tzh_magic[4]; /* TZ_MAGIC */
46 char tzh_version[1]; /* '\0' or '2' or '3' as of 2013 */
47 char tzh_reserved[15]; /* reserved; must be zero */
48 char tzh_ttisutcnt[4]; /* coded number of trans. time flags */
49 char tzh_ttisstdcnt[4]; /* coded number of trans. time flags */
50 char tzh_leapcnt[4]; /* coded number of leap seconds */
51 char tzh_timecnt[4]; /* coded number of transition times */
52 char tzh_typecnt[4]; /* coded number of local time types */
53 char tzh_charcnt[4]; /* coded number of abbr. chars */
54};
55
56/*
57** . . .followed by. . .
58**
59** tzh_timecnt (char [4])s coded transition times a la time(2)
60** tzh_timecnt (unsigned char)s types of local time starting at above
61** tzh_typecnt repetitions of
62** one (char [4]) coded UT offset in seconds
63** one (unsigned char) used to set tm_isdst
64** one (unsigned char) that's an abbreviation list index
65** tzh_charcnt (char)s '\0'-terminated zone abbreviations
66** tzh_leapcnt repetitions of
67** one (char [4]) coded leap second transition times
68** one (char [4]) total correction after above
69** tzh_ttisstdcnt (char)s indexed by type; if 1, transition
70** time is standard time, if 0,
71** transition time is local (wall clock)
72** time; if absent, transition times are
73** assumed to be local time
74** tzh_ttisutcnt (char)s indexed by type; if 1, transition
75** time is UT, if 0, transition time is
76** local time; if absent, transition
77** times are assumed to be local time.
78** When this is 1, the corresponding
79** std/wall indicator must also be 1.
80*/
81
82/*
83** If tzh_version is '2' or greater, the above is followed by a second instance
84** of tzhead and a second instance of the data in which each coded transition
85** time uses 8 rather than 4 chars,
86** then a POSIX-TZ-environment-variable-style string for use in handling
87** instants after the last transition time stored in the file
88** (with nothing between the newlines if there is no POSIX.1-2017
89** representation for such instants).
90**
91** If tz_version is '3' or greater, the above is extended as follows.
92** First, the TZ string's hour offset may range from -167
93** through 167 as compared to the POSIX-required 0 through 24.
94** Second, its DST start time may be January 1 at 00:00 and its stop
95** time December 31 at 24:00 plus the difference between DST and
96** standard time, indicating DST all year.
97*/
98
99/*
100** In the current implementation, "tzset()" refuses to deal with files that
101** exceed any of the limits below.
102*/
103
104#ifndef TZ_MAX_TIMES
105/* This must be at least 242 for Europe/London with 'zic -b fat'. */
106# define TZ_MAX_TIMES 2000
107#endif /* !defined TZ_MAX_TIMES */
108
109#ifndef TZ_MAX_TYPES
110/* This must be at least 18 for Europe/Vilnius with 'zic -b fat'. */
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/* This must be at least 40 for America/Anchorage. */
116# define TZ_MAX_CHARS 50 /* Maximum number of abbreviation characters */
117 /* (limited by what unsigned chars can hold) */
118#endif /* !defined TZ_MAX_CHARS */
119
120#ifndef TZ_MAX_LEAPS
121/* This must be at least 27 for leap seconds from 1972 through mid-2023.
122 There's a plan to discontinue leap seconds by 2035. */
123# define TZ_MAX_LEAPS 50 /* Maximum number of leap second corrections */
124#endif /* !defined TZ_MAX_LEAPS */
125
126#define SECSPERMIN 60
127#define MINSPERHOUR 60
128#define HOURSPERDAY 24
129#define DAYSPERWEEK 7
130#define DAYSPERNYEAR 365
131#define DAYSPERLYEAR 366
132#define SECSPERHOUR (SECSPERMIN * MINSPERHOUR)
133#define SECSPERDAY ((int_fast32_t) SECSPERHOUR * HOURSPERDAY)
134#define MONSPERYEAR 12
135#define YEARSPERREPEAT 400
136
137#define TM_SUNDAY 0
138#define TM_MONDAY 1
139#define TM_TUESDAY 2
140#define TM_WEDNESDAY 3
141#define TM_THURSDAY 4
142#define TM_FRIDAY 5
143#define TM_SATURDAY 6
144
145#define TM_JANUARY 0
146#define TM_FEBRUARY 1
147#define TM_MARCH 2
148#define TM_APRIL 3
149#define TM_MAY 4
150#define TM_JUNE 5
151#define TM_JULY 6
152#define TM_AUGUST 7
153#define TM_SEPTEMBER 8
154#define TM_OCTOBER 9
155#define TM_NOVEMBER 10
156#define TM_DECEMBER 11
157
158#define TM_YEAR_BASE 1900
159
160#define EPOCH_YEAR 1970
161#define EPOCH_WDAY TM_THURSDAY
162
163#define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
164
165/*
166** Since everything in isleap is modulo 400 (or a factor of 400), we know that
167** isleap(y) == isleap(y % 400)
168** and so
169** isleap(a + b) == isleap((a + b) % 400)
170** or
171** isleap(a + b) == isleap(a % 400 + b % 400)
172** This is true even if % means modulo rather than Fortran remainder
173** (which is allowed by C89 but not C99).
174** We use this to avoid addition overflow problems.
175*/
176
177#define isleap_sum(a, b) isleap((a) % 400 + (b) % 400)
178
179#endif /* !defined _TZFILE_H_ */