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tzfile.h
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1 #ifndef TZFILE_H
2 #define TZFILE_H
3 
4 /*
5  * This file is in the public domain, so clarified as of
6  * 1996-06-05 by Arthur David Olson.
7  *
8  * IDENTIFICATION
9  * src/timezone/tzfile.h
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 #define TZDEFAULT "localtime"
25 #define TZDEFRULES "posixrules"
26 
27 /*
28  * Each file begins with. . .
29  */
30 
31 #define TZ_MAGIC "TZif"
32 
33 struct tzhead
34 {
35  char tzh_magic[4]; /* TZ_MAGIC */
36  char tzh_version[1]; /* '\0' or '2' or '3' as of 2013 */
37  char tzh_reserved[15]; /* reserved; must be zero */
38  char tzh_ttisgmtcnt[4]; /* coded number of trans. time flags */
39  char tzh_ttisstdcnt[4]; /* coded number of trans. time flags */
40  char tzh_leapcnt[4]; /* coded number of leap seconds */
41  char tzh_timecnt[4]; /* coded number of transition times */
42  char tzh_typecnt[4]; /* coded number of local time types */
43  char tzh_charcnt[4]; /* coded number of abbr. chars */
44 };
45 
46 /*
47  * . . .followed by. . .
48  *
49  * tzh_timecnt (char [4])s coded transition times a la time(2)
50  * tzh_timecnt (unsigned char)s types of local time starting at above
51  * tzh_typecnt repetitions of
52  * one (char [4]) coded UT offset in seconds
53  * one (unsigned char) used to set tm_isdst
54  * one (unsigned char) that's an abbreviation list index
55  * tzh_charcnt (char)s '\0'-terminated zone abbreviations
56  * tzh_leapcnt repetitions of
57  * one (char [4]) coded leap second transition times
58  * one (char [4]) total correction after above
59  * tzh_ttisstdcnt (char)s indexed by type; if 1, transition
60  * time is standard time, if 0,
61  * transition time is wall clock time
62  * if absent, transition times are
63  * assumed to be wall clock time
64  * tzh_ttisgmtcnt (char)s indexed by type; if 1, transition
65  * time is UT, if 0,
66  * transition time is local time
67  * if absent, transition times are
68  * assumed to be local time
69  */
70 
71 /*
72  * If tzh_version is '2' or greater, the above is followed by a second instance
73  * of tzhead and a second instance of the data in which each coded transition
74  * time uses 8 rather than 4 chars,
75  * then a POSIX-TZ-environment-variable-style string for use in handling
76  * instants after the last transition time stored in the file
77  * (with nothing between the newlines if there is no POSIX representation for
78  * such instants).
79  *
80  * If tz_version is '3' or greater, the above is extended as follows.
81  * First, the POSIX TZ string's hour offset may range from -167
82  * through 167 as compared to the POSIX-required 0 through 24.
83  * Second, its DST start time may be January 1 at 00:00 and its stop
84  * time December 31 at 24:00 plus the difference between DST and
85  * standard time, indicating DST all year.
86  */
87 
88 /*
89  * In the current implementation, "tzset()" refuses to deal with files that
90  * exceed any of the limits below.
91  */
92 
93 #define TZ_MAX_TIMES 2000
94 
95 /* This must be at least 17 for Europe/Samara and Europe/Vilnius. */
96 #define TZ_MAX_TYPES 256 /* Limited by what (unsigned char)'s can hold */
97 
98 #define TZ_MAX_CHARS 50 /* Maximum number of abbreviation characters */
99  /* (limited by what unsigned chars can hold) */
100 
101 #define TZ_MAX_LEAPS 50 /* Maximum number of leap second corrections */
102 
103 #endif /* !defined TZFILE_H */
char tzh_timecnt[4]
Definition: tzfile.h:41
char tzh_magic[4]
Definition: tzfile.h:35
char tzh_leapcnt[4]
Definition: tzfile.h:40
Definition: tzfile.h:33
char tzh_typecnt[4]
Definition: tzfile.h:42
char tzh_version[1]
Definition: tzfile.h:36
char tzh_charcnt[4]
Definition: tzfile.h:43
char tzh_ttisstdcnt[4]
Definition: tzfile.h:39
char tzh_reserved[15]
Definition: tzfile.h:37
char tzh_ttisgmtcnt[4]
Definition: tzfile.h:38