PostgreSQL Source Code  git master
tzfile.h
Go to the documentation of this file.
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 */
char tzh_timecnt[4]
Definition: tzfile.h:47
char tzh_ttisutcnt[4]
Definition: tzfile.h:44
char tzh_magic[4]
Definition: tzfile.h:41
char tzh_leapcnt[4]
Definition: tzfile.h:46
Definition: tzfile.h:39
char tzh_typecnt[4]
Definition: tzfile.h:48
char tzh_version[1]
Definition: tzfile.h:42
char tzh_charcnt[4]
Definition: tzfile.h:49
char tzh_ttisstdcnt[4]
Definition: tzfile.h:45
char tzh_reserved[15]
Definition: tzfile.h:43