1 // Copyright 2016 Google Inc. All Rights Reserved.
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 //   https://www.apache.org/licenses/LICENSE-2.0
8 //
9 //   Unless required by applicable law or agreed to in writing, software
10 //   distributed under the License is distributed on an "AS IS" BASIS,
11 //   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 //   See the License for the specific language governing permissions and
13 //   limitations under the License.
14 
15 // Parsing of a POSIX zone spec as described in the TZ part of section 8.3 in
16 // http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html.
17 //
18 // The current POSIX spec for America/Los_Angeles is "PST8PDT,M3.2.0,M11.1.0",
19 // which would be broken down as ...
20 //
21 //   PosixTimeZone {
22 //     std_abbr = "PST"
23 //     std_offset = -28800
24 //     dst_abbr = "PDT"
25 //     dst_offset = -25200
26 //     dst_start = PosixTransition {
27 //       date {
28 //         m {
29 //           month = 3
30 //           week = 2
31 //           weekday = 0
32 //         }
33 //       }
34 //       time {
35 //         offset = 7200
36 //       }
37 //     }
38 //     dst_end = PosixTransition {
39 //       date {
40 //         m {
41 //           month = 11
42 //           week = 1
43 //           weekday = 0
44 //         }
45 //       }
46 //       time {
47 //         offset = 7200
48 //       }
49 //     }
50 //   }
51 
52 #ifndef ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_POSIX_H_
53 #define ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_POSIX_H_
54 
55 #include <cstdint>
56 #include <string>
57 
58 #include "absl/base/config.h"
59 
60 namespace absl {
61 ABSL_NAMESPACE_BEGIN
62 namespace time_internal {
63 namespace cctz {
64 
65 // The date/time of the transition. The date is specified as either:
66 // (J) the Nth day of the year (1 <= N <= 365), excluding leap days, or
67 // (N) the Nth day of the year (0 <= N <= 365), including leap days, or
68 // (M) the Nth weekday of a month (e.g., the 2nd Sunday in March).
69 // The time, specified as a day offset, identifies the particular moment
70 // of the transition, and may be negative or >= 24h, and in which case
71 // it would take us to another day, and perhaps week, or even month.
72 struct PosixTransition {
73   enum DateFormat { J, N, M };
74 
75   struct Date {
76     struct NonLeapDay {
77       std::int_fast16_t day;  // day of non-leap year [1:365]
78     };
79     struct Day {
80       std::int_fast16_t day;  // day of year [0:365]
81     };
82     struct MonthWeekWeekday {
83       std::int_fast8_t month;    // month of year [1:12]
84       std::int_fast8_t week;     // week of month [1:5] (5==last)
85       std::int_fast8_t weekday;  // 0==Sun, ..., 6=Sat
86     };
87 
88     DateFormat fmt;
89 
90     union {
91       NonLeapDay j;
92       Day n;
93       MonthWeekWeekday m;
94     };
95   };
96 
97   struct Time {
98     std::int_fast32_t offset;  // seconds before/after 00:00:00
99   };
100 
101   Date date;
102   Time time;
103 };
104 
105 // The entirety of a POSIX-string specified time-zone rule. The standard
106 // abbreviation and offset are always given. If the time zone includes
107 // daylight saving, then the daylight abbrevation is non-empty and the
108 // remaining fields are also valid. Note that the start/end transitions
109 // are not ordered---in the southern hemisphere the transition to end
110 // daylight time occurs first in any particular year.
111 struct PosixTimeZone {
112   std::string std_abbr;
113   std::int_fast32_t std_offset;
114 
115   std::string dst_abbr;
116   std::int_fast32_t dst_offset;
117   PosixTransition dst_start;
118   PosixTransition dst_end;
119 };
120 
121 // Breaks down a POSIX time-zone specification into its constituent pieces,
122 // filling in any missing values (DST offset, or start/end transition times)
123 // with the standard-defined defaults. Returns false if the specification
124 // could not be parsed (although some fields of *res may have been altered).
125 bool ParsePosixSpec(const std::string& spec, PosixTimeZone* res);
126 
127 }  // namespace cctz
128 }  // namespace time_internal
129 ABSL_NAMESPACE_END
130 }  // namespace absl
131 
132 #endif  // ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_POSIX_H_
133