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// http://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 CCTZ_TIME_ZONE_POSIX_H_
53#define CCTZ_TIME_ZONE_POSIX_H_
54
55#include <cstdint>
56#include <string>
57
58namespace cctz {
59
60// The date/time of the transition. The date is specified as either:
61// (J) the Nth day of the year (1 <= N <= 365), excluding leap days, or
62// (N) the Nth day of the year (0 <= N <= 365), including leap days, or
63// (M) the Nth weekday of a month (e.g., the 2nd Sunday in March).
64// The time, specified as a day offset, identifies the particular moment
65// of the transition, and may be negative or >= 24h, and in which case
66// it would take us to another day, and perhaps week, or even month.
67struct PosixTransition {
68 enum DateFormat { J, N, M };
69 struct {
70 DateFormat fmt;
71 union {
72 struct {
73 std::int_fast16_t day; // day of non-leap year [1:365]
74 } j;
75 struct {
76 std::int_fast16_t day; // day of year [0:365]
77 } n;
78 struct {
79 std::int_fast8_t month; // month of year [1:12]
80 std::int_fast8_t week; // week of month [1:5] (5==last)
81 std::int_fast8_t weekday; // 0==Sun, ..., 6=Sat
82 } m;
83 };
84 } date;
85 struct {
86 std::int_fast32_t offset; // seconds before/after 00:00:00
87 } time;
88};
89
90// The entirety of a POSIX-string specified time-zone rule. The standard
91// abbreviation and offset are always given. If the time zone includes
92// daylight saving, then the daylight abbrevation is non-empty and the
93// remaining fields are also valid. Note that the start/end transitions
94// are not ordered---in the southern hemisphere the transition to end
95// daylight time occurs first in any particular year.
96struct PosixTimeZone {
97 std::string std_abbr;
98 std::int_fast32_t std_offset;
99
100 std::string dst_abbr;
101 std::int_fast32_t dst_offset;
102 PosixTransition dst_start;
103 PosixTransition dst_end;
104};
105
106// Breaks down a POSIX time-zone specification into its constituent pieces,
107// filling in any missing values (DST offset, or start/end transition times)
108// with the standard-defined defaults. Returns false if the specification
109// could not be parsed (although some fields of *res may have been altered).
110bool ParsePosixSpec(const std::string& spec, PosixTimeZone* res);
111
112} // namespace cctz
113
114#endif // CCTZ_TIME_ZONE_POSIX_H_
115