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+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Parsing of a POSIX zone spec as described in the TZ part of section 8.3 in
+// http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap08.html.
+//
+// The current POSIX spec for America/Los_Angeles is "PST8PDT,M3.2.0,M11.1.0",
+// which would be broken down as ...
+//
+// PosixTimeZone {
+// std_abbr = "PST"
+// std_offset = -28800
+// dst_abbr = "PDT"
+// dst_offset = -25200
+// dst_start = PosixTransition {
+// date {
+// m {
+// month = 3
+// week = 2
+// weekday = 0
+// }
+// }
+// time {
+// offset = 7200
+// }
+// }
+// dst_end = PosixTransition {
+// date {
+// m {
+// month = 11
+// week = 1
+// weekday = 0
+// }
+// }
+// time {
+// offset = 7200
+// }
+// }
+// }
+
+#ifndef ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_POSIX_H_
+#define ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_POSIX_H_
+
+#include <cstdint>
+#include <string>
+
+#include "absl/base/config.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+namespace time_internal {
+namespace cctz {
+
+// The date/time of the transition. The date is specified as either:
+// (J) the Nth day of the year (1 <= N <= 365), excluding leap days, or
+// (N) the Nth day of the year (0 <= N <= 365), including leap days, or
+// (M) the Nth weekday of a month (e.g., the 2nd Sunday in March).
+// The time, specified as a day offset, identifies the particular moment
+// of the transition, and may be negative or >= 24h, and in which case
+// it would take us to another day, and perhaps week, or even month.
+struct PosixTransition {
+ enum DateFormat { J, N, M };
+
+ struct Date {
+ struct NonLeapDay {
+ std::int_fast16_t day; // day of non-leap year [1:365]
+ };
+ struct Day {
+ std::int_fast16_t day; // day of year [0:365]
+ };
+ struct MonthWeekWeekday {
+ std::int_fast8_t month; // month of year [1:12]
+ std::int_fast8_t week; // week of month [1:5] (5==last)
+ std::int_fast8_t weekday; // 0==Sun, ..., 6=Sat
+ };
+
+ DateFormat fmt;
+
+ union {
+ NonLeapDay j;
+ Day n;
+ MonthWeekWeekday m;
+ };
+ };
+
+ struct Time {
+ std::int_fast32_t offset; // seconds before/after 00:00:00
+ };
+
+ Date date;
+ Time time;
+};
+
+// The entirety of a POSIX-string specified time-zone rule. The standard
+// abbreviation and offset are always given. If the time zone includes
+// daylight saving, then the daylight abbrevation is non-empty and the
+// remaining fields are also valid. Note that the start/end transitions
+// are not ordered---in the southern hemisphere the transition to end
+// daylight time occurs first in any particular year.
+struct PosixTimeZone {
+ std::string std_abbr;
+ std::int_fast32_t std_offset;
+
+ std::string dst_abbr;
+ std::int_fast32_t dst_offset;
+ PosixTransition dst_start;
+ PosixTransition dst_end;
+};
+
+// Breaks down a POSIX time-zone specification into its constituent pieces,
+// filling in any missing values (DST offset, or start/end transition times)
+// with the standard-defined defaults. Returns false if the specification
+// could not be parsed (although some fields of *res may have been altered).
+bool ParsePosixSpec(const std::string& spec, PosixTimeZone* res);
+
+} // namespace cctz
+} // namespace time_internal
+ABSL_NAMESPACE_END
+} // namespace absl
+
+#endif // ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_POSIX_H_