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diff --git a/third_party/abseil-cpp/absl/time/internal/cctz/include/cctz/civil_time.h b/third_party/abseil-cpp/absl/time/internal/cctz/include/cctz/civil_time.h new file mode 100644 index 0000000000..d47ff86fe4 --- /dev/null +++ b/third_party/abseil-cpp/absl/time/internal/cctz/include/cctz/civil_time.h @@ -0,0 +1,332 @@ +// 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. + +#ifndef ABSL_TIME_INTERNAL_CCTZ_CIVIL_TIME_H_ +#define ABSL_TIME_INTERNAL_CCTZ_CIVIL_TIME_H_ + +#include "absl/base/config.h" +#include "absl/time/internal/cctz/include/cctz/civil_time_detail.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace time_internal { +namespace cctz { + +// The term "civil time" refers to the legally recognized human-scale time +// that is represented by the six fields YYYY-MM-DD hh:mm:ss. Modern-day civil +// time follows the Gregorian Calendar and is a time-zone-independent concept. +// A "date" is perhaps the most common example of a civil time (represented in +// this library as cctz::civil_day). This library provides six classes and a +// handful of functions that help with rounding, iterating, and arithmetic on +// civil times while avoiding complications like daylight-saving time (DST). +// +// The following six classes form the core of this civil-time library: +// +// * civil_second +// * civil_minute +// * civil_hour +// * civil_day +// * civil_month +// * civil_year +// +// Each class is a simple value type with the same interface for construction +// and the same six accessors for each of the civil fields (year, month, day, +// hour, minute, and second, aka YMDHMS). These classes differ only in their +// alignment, which is indicated by the type name and specifies the field on +// which arithmetic operates. +// +// Each class can be constructed by passing up to six optional integer +// arguments representing the YMDHMS fields (in that order) to the +// constructor. Omitted fields are assigned their minimum valid value. Hours, +// minutes, and seconds will be set to 0, month and day will be set to 1, and +// since there is no minimum valid year, it will be set to 1970. So, a +// default-constructed civil-time object will have YMDHMS fields representing +// "1970-01-01 00:00:00". Fields that are out-of-range are normalized (e.g., +// October 32 -> November 1) so that all civil-time objects represent valid +// values. +// +// Each civil-time class is aligned to the civil-time field indicated in the +// class's name after normalization. Alignment is performed by setting all the +// inferior fields to their minimum valid value (as described above). The +// following are examples of how each of the six types would align the fields +// representing November 22, 2015 at 12:34:56 in the afternoon. (Note: the +// string format used here is not important; it's just a shorthand way of +// showing the six YMDHMS fields.) +// +// civil_second 2015-11-22 12:34:56 +// civil_minute 2015-11-22 12:34:00 +// civil_hour 2015-11-22 12:00:00 +// civil_day 2015-11-22 00:00:00 +// civil_month 2015-11-01 00:00:00 +// civil_year 2015-01-01 00:00:00 +// +// Each civil-time type performs arithmetic on the field to which it is +// aligned. This means that adding 1 to a civil_day increments the day field +// (normalizing as necessary), and subtracting 7 from a civil_month operates +// on the month field (normalizing as necessary). All arithmetic produces a +// valid civil time. Difference requires two similarly aligned civil-time +// objects and returns the scalar answer in units of the objects' alignment. +// For example, the difference between two civil_hour objects will give an +// answer in units of civil hours. +// +// In addition to the six civil-time types just described, there are +// a handful of helper functions and algorithms for performing common +// calculations. These are described below. +// +// Note: In C++14 and later, this library is usable in a constexpr context. +// +// CONSTRUCTION: +// +// Each of the civil-time types can be constructed in two ways: by directly +// passing to the constructor up to six (optional) integers representing the +// YMDHMS fields, or by copying the YMDHMS fields from a differently aligned +// civil-time type. +// +// civil_day default_value; // 1970-01-01 00:00:00 +// +// civil_day a(2015, 2, 3); // 2015-02-03 00:00:00 +// civil_day b(2015, 2, 3, 4, 5, 6); // 2015-02-03 00:00:00 +// civil_day c(2015); // 2015-01-01 00:00:00 +// +// civil_second ss(2015, 2, 3, 4, 5, 6); // 2015-02-03 04:05:06 +// civil_minute mm(ss); // 2015-02-03 04:05:00 +// civil_hour hh(mm); // 2015-02-03 04:00:00 +// civil_day d(hh); // 2015-02-03 00:00:00 +// civil_month m(d); // 2015-02-01 00:00:00 +// civil_year y(m); // 2015-01-01 00:00:00 +// +// m = civil_month(y); // 2015-01-01 00:00:00 +// d = civil_day(m); // 2015-01-01 00:00:00 +// hh = civil_hour(d); // 2015-01-01 00:00:00 +// mm = civil_minute(hh); // 2015-01-01 00:00:00 +// ss = civil_second(mm); // 2015-01-01 00:00:00 +// +// ALIGNMENT CONVERSION: +// +// The alignment of a civil-time object cannot change, but the object may be +// used to construct a new object with a different alignment. This is referred +// to as "realigning". When realigning to a type with the same or more +// precision (e.g., civil_day -> civil_second), the conversion may be +// performed implicitly since no information is lost. However, if information +// could be discarded (e.g., civil_second -> civil_day), the conversion must +// be explicit at the call site. +// +// void fun(const civil_day& day); +// +// civil_second cs; +// fun(cs); // Won't compile because data may be discarded +// fun(civil_day(cs)); // OK: explicit conversion +// +// civil_day cd; +// fun(cd); // OK: no conversion needed +// +// civil_month cm; +// fun(cm); // OK: implicit conversion to civil_day +// +// NORMALIZATION: +// +// Integer arguments passed to the constructor may be out-of-range, in which +// case they are normalized to produce a valid civil-time object. This enables +// natural arithmetic on constructor arguments without worrying about the +// field's range. Normalization guarantees that there are no invalid +// civil-time objects. +// +// civil_day d(2016, 10, 32); // Out-of-range day; normalized to 2016-11-01 +// +// Note: If normalization is undesired, you can signal an error by comparing +// the constructor arguments to the normalized values returned by the YMDHMS +// properties. +// +// PROPERTIES: +// +// All civil-time types have accessors for all six of the civil-time fields: +// year, month, day, hour, minute, and second. Recall that fields inferior to +// the type's alignment will be set to their minimum valid value. +// +// civil_day d(2015, 6, 28); +// // d.year() == 2015 +// // d.month() == 6 +// // d.day() == 28 +// // d.hour() == 0 +// // d.minute() == 0 +// // d.second() == 0 +// +// COMPARISON: +// +// Comparison always considers all six YMDHMS fields, regardless of the type's +// alignment. Comparison between differently aligned civil-time types is +// allowed. +// +// civil_day feb_3(2015, 2, 3); // 2015-02-03 00:00:00 +// civil_day mar_4(2015, 3, 4); // 2015-03-04 00:00:00 +// // feb_3 < mar_4 +// // civil_year(feb_3) == civil_year(mar_4) +// +// civil_second feb_3_noon(2015, 2, 3, 12, 0, 0); // 2015-02-03 12:00:00 +// // feb_3 < feb_3_noon +// // feb_3 == civil_day(feb_3_noon) +// +// // Iterates all the days of February 2015. +// for (civil_day d(2015, 2, 1); d < civil_month(2015, 3); ++d) { +// // ... +// } +// +// STREAMING: +// +// Each civil-time type may be sent to an output stream using operator<<(). +// The output format follows the pattern "YYYY-MM-DDThh:mm:ss" where fields +// inferior to the type's alignment are omitted. +// +// civil_second cs(2015, 2, 3, 4, 5, 6); +// std::cout << cs << "\n"; // Outputs: 2015-02-03T04:05:06 +// +// civil_day cd(cs); +// std::cout << cd << "\n"; // Outputs: 2015-02-03 +// +// civil_year cy(cs); +// std::cout << cy << "\n"; // Outputs: 2015 +// +// ARITHMETIC: +// +// Civil-time types support natural arithmetic operators such as addition, +// subtraction, and difference. Arithmetic operates on the civil-time field +// indicated in the type's name. Difference requires arguments with the same +// alignment and returns the answer in units of the alignment. +// +// civil_day a(2015, 2, 3); +// ++a; // 2015-02-04 00:00:00 +// --a; // 2015-02-03 00:00:00 +// civil_day b = a + 1; // 2015-02-04 00:00:00 +// civil_day c = 1 + b; // 2015-02-05 00:00:00 +// int n = c - a; // n = 2 (civil days) +// int m = c - civil_month(c); // Won't compile: different types. +// +// EXAMPLE: Adding a month to January 31. +// +// One of the classic questions that arises when considering a civil-time +// library (or a date library or a date/time library) is this: "What happens +// when you add a month to January 31?" This is an interesting question +// because there could be a number of possible answers: +// +// 1. March 3 (or 2 if a leap year). This may make sense if the operation +// wants the equivalent of February 31. +// 2. February 28 (or 29 if a leap year). This may make sense if the operation +// wants the last day of January to go to the last day of February. +// 3. Error. The caller may get some error, an exception, an invalid date +// object, or maybe false is returned. This may make sense because there is +// no single unambiguously correct answer to the question. +// +// Practically speaking, any answer that is not what the programmer intended +// is the wrong answer. +// +// This civil-time library avoids the problem by making it impossible to ask +// ambiguous questions. All civil-time objects are aligned to a particular +// civil-field boundary (such as aligned to a year, month, day, hour, minute, +// or second), and arithmetic operates on the field to which the object is +// aligned. This means that in order to "add a month" the object must first be +// aligned to a month boundary, which is equivalent to the first day of that +// month. +// +// Of course, there are ways to compute an answer the question at hand using +// this civil-time library, but they require the programmer to be explicit +// about the answer they expect. To illustrate, let's see how to compute all +// three of the above possible answers to the question of "Jan 31 plus 1 +// month": +// +// const civil_day d(2015, 1, 31); +// +// // Answer 1: +// // Add 1 to the month field in the constructor, and rely on normalization. +// const auto ans_normalized = civil_day(d.year(), d.month() + 1, d.day()); +// // ans_normalized == 2015-03-03 (aka Feb 31) +// +// // Answer 2: +// // Add 1 to month field, capping to the end of next month. +// const auto next_month = civil_month(d) + 1; +// const auto last_day_of_next_month = civil_day(next_month + 1) - 1; +// const auto ans_capped = std::min(ans_normalized, last_day_of_next_month); +// // ans_capped == 2015-02-28 +// +// // Answer 3: +// // Signal an error if the normalized answer is not in next month. +// if (civil_month(ans_normalized) != next_month) { +// // error, month overflow +// } +// +using civil_year = detail::civil_year; +using civil_month = detail::civil_month; +using civil_day = detail::civil_day; +using civil_hour = detail::civil_hour; +using civil_minute = detail::civil_minute; +using civil_second = detail::civil_second; + +// An enum class with members monday, tuesday, wednesday, thursday, friday, +// saturday, and sunday. These enum values may be sent to an output stream +// using operator<<(). The result is the full weekday name in English with a +// leading capital letter. +// +// weekday wd = weekday::thursday; +// std::cout << wd << "\n"; // Outputs: Thursday +// +using detail::weekday; + +// Returns the weekday for the given civil-time value. +// +// civil_day a(2015, 8, 13); +// weekday wd = get_weekday(a); // wd == weekday::thursday +// +using detail::get_weekday; + +// Returns the civil_day that strictly follows or precedes the given +// civil_day, and that falls on the given weekday. +// +// For example, given: +// +// August 2015 +// Su Mo Tu We Th Fr Sa +// 1 +// 2 3 4 5 6 7 8 +// 9 10 11 12 13 14 15 +// 16 17 18 19 20 21 22 +// 23 24 25 26 27 28 29 +// 30 31 +// +// civil_day a(2015, 8, 13); // get_weekday(a) == weekday::thursday +// civil_day b = next_weekday(a, weekday::thursday); // b = 2015-08-20 +// civil_day c = prev_weekday(a, weekday::thursday); // c = 2015-08-06 +// +// civil_day d = ... +// // Gets the following Thursday if d is not already Thursday +// civil_day thurs1 = next_weekday(d - 1, weekday::thursday); +// // Gets the previous Thursday if d is not already Thursday +// civil_day thurs2 = prev_weekday(d + 1, weekday::thursday); +// +using detail::next_weekday; +using detail::prev_weekday; + +// Returns the day-of-year for the given civil-time value. +// +// civil_day a(2015, 1, 1); +// int yd_jan_1 = get_yearday(a); // yd_jan_1 = 1 +// civil_day b(2015, 12, 31); +// int yd_dec_31 = get_yearday(b); // yd_dec_31 = 365 +// +using detail::get_yearday; + +} // namespace cctz +} // namespace time_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_TIME_INTERNAL_CCTZ_CIVIL_TIME_H_ |