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Diffstat (limited to 'third_party/abseil-cpp/absl/time/internal/cctz/include/cctz/time_zone.h')
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diff --git a/third_party/abseil-cpp/absl/time/internal/cctz/include/cctz/time_zone.h b/third_party/abseil-cpp/absl/time/internal/cctz/include/cctz/time_zone.h new file mode 100644 index 0000000000..d05147a17c --- /dev/null +++ b/third_party/abseil-cpp/absl/time/internal/cctz/include/cctz/time_zone.h @@ -0,0 +1,384 @@ +// 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. + +// A library for translating between absolute times (represented by +// std::chrono::time_points of the std::chrono::system_clock) and civil +// times (represented by cctz::civil_second) using the rules defined by +// a time zone (cctz::time_zone). + +#ifndef ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_H_ +#define ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_H_ + +#include <chrono> +#include <cstdint> +#include <string> +#include <utility> + +#include "absl/base/config.h" +#include "absl/time/internal/cctz/include/cctz/civil_time.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace time_internal { +namespace cctz { + +// Convenience aliases. Not intended as public API points. +template <typename D> +using time_point = std::chrono::time_point<std::chrono::system_clock, D>; +using seconds = std::chrono::duration<std::int_fast64_t>; +using sys_seconds = seconds; // Deprecated. Use cctz::seconds instead. + +namespace detail { +template <typename D> +inline std::pair<time_point<seconds>, D> split_seconds( + const time_point<D>& tp) { + auto sec = std::chrono::time_point_cast<seconds>(tp); + auto sub = tp - sec; + if (sub.count() < 0) { + sec -= seconds(1); + sub += seconds(1); + } + return {sec, std::chrono::duration_cast<D>(sub)}; +} +inline std::pair<time_point<seconds>, seconds> split_seconds( + const time_point<seconds>& tp) { + return {tp, seconds::zero()}; +} +} // namespace detail + +// cctz::time_zone is an opaque, small, value-type class representing a +// geo-political region within which particular rules are used for mapping +// between absolute and civil times. Time zones are named using the TZ +// identifiers from the IANA Time Zone Database, such as "America/Los_Angeles" +// or "Australia/Sydney". Time zones are created from factory functions such +// as load_time_zone(). Note: strings like "PST" and "EDT" are not valid TZ +// identifiers. +// +// Example: +// cctz::time_zone utc = cctz::utc_time_zone(); +// cctz::time_zone pst = cctz::fixed_time_zone(std::chrono::hours(-8)); +// cctz::time_zone loc = cctz::local_time_zone(); +// cctz::time_zone lax; +// if (!cctz::load_time_zone("America/Los_Angeles", &lax)) { ... } +// +// See also: +// - http://www.iana.org/time-zones +// - https://en.wikipedia.org/wiki/Zoneinfo +class time_zone { + public: + time_zone() : time_zone(nullptr) {} // Equivalent to UTC + time_zone(const time_zone&) = default; + time_zone& operator=(const time_zone&) = default; + + std::string name() const; + + // An absolute_lookup represents the civil time (cctz::civil_second) within + // this time_zone at the given absolute time (time_point). There are + // additionally a few other fields that may be useful when working with + // older APIs, such as std::tm. + // + // Example: + // const cctz::time_zone tz = ... + // const auto tp = std::chrono::system_clock::now(); + // const cctz::time_zone::absolute_lookup al = tz.lookup(tp); + struct absolute_lookup { + civil_second cs; + // Note: The following fields exist for backward compatibility with older + // APIs. Accessing these fields directly is a sign of imprudent logic in + // the calling code. Modern time-related code should only access this data + // indirectly by way of cctz::format(). + int offset; // civil seconds east of UTC + bool is_dst; // is offset non-standard? + const char* abbr; // time-zone abbreviation (e.g., "PST") + }; + absolute_lookup lookup(const time_point<seconds>& tp) const; + template <typename D> + absolute_lookup lookup(const time_point<D>& tp) const { + return lookup(detail::split_seconds(tp).first); + } + + // A civil_lookup represents the absolute time(s) (time_point) that + // correspond to the given civil time (cctz::civil_second) within this + // time_zone. Usually the given civil time represents a unique instant + // in time, in which case the conversion is unambiguous. However, + // within this time zone, the given civil time may be skipped (e.g., + // during a positive UTC offset shift), or repeated (e.g., during a + // negative UTC offset shift). To account for these possibilities, + // civil_lookup is richer than just a single time_point. + // + // In all cases the civil_lookup::kind enum will indicate the nature + // of the given civil-time argument, and the pre, trans, and post + // members will give the absolute time answers using the pre-transition + // offset, the transition point itself, and the post-transition offset, + // respectively (all three times are equal if kind == UNIQUE). If any + // of these three absolute times is outside the representable range of a + // time_point<seconds> the field is set to its maximum/minimum value. + // + // Example: + // cctz::time_zone lax; + // if (!cctz::load_time_zone("America/Los_Angeles", &lax)) { ... } + // + // // A unique civil time. + // auto jan01 = lax.lookup(cctz::civil_second(2011, 1, 1, 0, 0, 0)); + // // jan01.kind == cctz::time_zone::civil_lookup::UNIQUE + // // jan01.pre is 2011/01/01 00:00:00 -0800 + // // jan01.trans is 2011/01/01 00:00:00 -0800 + // // jan01.post is 2011/01/01 00:00:00 -0800 + // + // // A Spring DST transition, when there is a gap in civil time. + // auto mar13 = lax.lookup(cctz::civil_second(2011, 3, 13, 2, 15, 0)); + // // mar13.kind == cctz::time_zone::civil_lookup::SKIPPED + // // mar13.pre is 2011/03/13 03:15:00 -0700 + // // mar13.trans is 2011/03/13 03:00:00 -0700 + // // mar13.post is 2011/03/13 01:15:00 -0800 + // + // // A Fall DST transition, when civil times are repeated. + // auto nov06 = lax.lookup(cctz::civil_second(2011, 11, 6, 1, 15, 0)); + // // nov06.kind == cctz::time_zone::civil_lookup::REPEATED + // // nov06.pre is 2011/11/06 01:15:00 -0700 + // // nov06.trans is 2011/11/06 01:00:00 -0800 + // // nov06.post is 2011/11/06 01:15:00 -0800 + struct civil_lookup { + enum civil_kind { + UNIQUE, // the civil time was singular (pre == trans == post) + SKIPPED, // the civil time did not exist (pre >= trans > post) + REPEATED, // the civil time was ambiguous (pre < trans <= post) + } kind; + time_point<seconds> pre; // uses the pre-transition offset + time_point<seconds> trans; // instant of civil-offset change + time_point<seconds> post; // uses the post-transition offset + }; + civil_lookup lookup(const civil_second& cs) const; + + // Finds the time of the next/previous offset change in this time zone. + // + // By definition, next_transition(tp, &trans) returns false when tp has + // its maximum value, and prev_transition(tp, &trans) returns false + // when tp has its minimum value. If the zone has no transitions, the + // result will also be false no matter what the argument. + // + // Otherwise, when tp has its minimum value, next_transition(tp, &trans) + // returns true and sets trans to the first recorded transition. Chains + // of calls to next_transition()/prev_transition() will eventually return + // false, but it is unspecified exactly when next_transition(tp, &trans) + // jumps to false, or what time is set by prev_transition(tp, &trans) for + // a very distant tp. + // + // Note: Enumeration of time-zone transitions is for informational purposes + // only. Modern time-related code should not care about when offset changes + // occur. + // + // Example: + // cctz::time_zone nyc; + // if (!cctz::load_time_zone("America/New_York", &nyc)) { ... } + // const auto now = std::chrono::system_clock::now(); + // auto tp = cctz::time_point<cctz::seconds>::min(); + // cctz::time_zone::civil_transition trans; + // while (tp <= now && nyc.next_transition(tp, &trans)) { + // // transition: trans.from -> trans.to + // tp = nyc.lookup(trans.to).trans; + // } + struct civil_transition { + civil_second from; // the civil time we jump from + civil_second to; // the civil time we jump to + }; + bool next_transition(const time_point<seconds>& tp, + civil_transition* trans) const; + template <typename D> + bool next_transition(const time_point<D>& tp, civil_transition* trans) const { + return next_transition(detail::split_seconds(tp).first, trans); + } + bool prev_transition(const time_point<seconds>& tp, + civil_transition* trans) const; + template <typename D> + bool prev_transition(const time_point<D>& tp, civil_transition* trans) const { + return prev_transition(detail::split_seconds(tp).first, trans); + } + + // version() and description() provide additional information about the + // time zone. The content of each of the returned strings is unspecified, + // however, when the IANA Time Zone Database is the underlying data source + // the version() std::string will be in the familar form (e.g, "2018e") or + // empty when unavailable. + // + // Note: These functions are for informational or testing purposes only. + std::string version() const; // empty when unknown + std::string description() const; + + // Relational operators. + friend bool operator==(time_zone lhs, time_zone rhs) { + return &lhs.effective_impl() == &rhs.effective_impl(); + } + friend bool operator!=(time_zone lhs, time_zone rhs) { return !(lhs == rhs); } + + template <typename H> + friend H AbslHashValue(H h, time_zone tz) { + return H::combine(std::move(h), &tz.effective_impl()); + } + + class Impl; + + private: + explicit time_zone(const Impl* impl) : impl_(impl) {} + const Impl& effective_impl() const; // handles implicit UTC + const Impl* impl_; +}; + +// Loads the named time zone. May perform I/O on the initial load. +// If the name is invalid, or some other kind of error occurs, returns +// false and "*tz" is set to the UTC time zone. +bool load_time_zone(const std::string& name, time_zone* tz); + +// Returns a time_zone representing UTC. Cannot fail. +time_zone utc_time_zone(); + +// Returns a time zone that is a fixed offset (seconds east) from UTC. +// Note: If the absolute value of the offset is greater than 24 hours +// you'll get UTC (i.e., zero offset) instead. +time_zone fixed_time_zone(const seconds& offset); + +// Returns a time zone representing the local time zone. Falls back to UTC. +// Note: local_time_zone.name() may only be something like "localtime". +time_zone local_time_zone(); + +// Returns the civil time (cctz::civil_second) within the given time zone at +// the given absolute time (time_point). Since the additional fields provided +// by the time_zone::absolute_lookup struct should rarely be needed in modern +// code, this convert() function is simpler and should be preferred. +template <typename D> +inline civil_second convert(const time_point<D>& tp, const time_zone& tz) { + return tz.lookup(tp).cs; +} + +// Returns the absolute time (time_point) that corresponds to the given civil +// time within the given time zone. If the civil time is not unique (i.e., if +// it was either repeated or non-existent), then the returned time_point is +// the best estimate that preserves relative order. That is, this function +// guarantees that if cs1 < cs2, then convert(cs1, tz) <= convert(cs2, tz). +inline time_point<seconds> convert(const civil_second& cs, + const time_zone& tz) { + const time_zone::civil_lookup cl = tz.lookup(cs); + if (cl.kind == time_zone::civil_lookup::SKIPPED) return cl.trans; + return cl.pre; +} + +namespace detail { +using femtoseconds = std::chrono::duration<std::int_fast64_t, std::femto>; +std::string format(const std::string&, const time_point<seconds>&, + const femtoseconds&, const time_zone&); +bool parse(const std::string&, const std::string&, const time_zone&, + time_point<seconds>*, femtoseconds*, std::string* err = nullptr); +} // namespace detail + +// Formats the given time_point in the given cctz::time_zone according to +// the provided format string. Uses strftime()-like formatting options, +// with the following extensions: +// +// - %Ez - RFC3339-compatible numeric UTC offset (+hh:mm or -hh:mm) +// - %E*z - Full-resolution numeric UTC offset (+hh:mm:ss or -hh:mm:ss) +// - %E#S - Seconds with # digits of fractional precision +// - %E*S - Seconds with full fractional precision (a literal '*') +// - %E#f - Fractional seconds with # digits of precision +// - %E*f - Fractional seconds with full precision (a literal '*') +// - %E4Y - Four-character years (-999 ... -001, 0000, 0001 ... 9999) +// +// Note that %E0S behaves like %S, and %E0f produces no characters. In +// contrast %E*f always produces at least one digit, which may be '0'. +// +// Note that %Y produces as many characters as it takes to fully render the +// year. A year outside of [-999:9999] when formatted with %E4Y will produce +// more than four characters, just like %Y. +// +// Tip: Format strings should include the UTC offset (e.g., %z, %Ez, or %E*z) +// so that the resulting string uniquely identifies an absolute time. +// +// Example: +// cctz::time_zone lax; +// if (!cctz::load_time_zone("America/Los_Angeles", &lax)) { ... } +// auto tp = cctz::convert(cctz::civil_second(2013, 1, 2, 3, 4, 5), lax); +// std::string f = cctz::format("%H:%M:%S", tp, lax); // "03:04:05" +// f = cctz::format("%H:%M:%E3S", tp, lax); // "03:04:05.000" +template <typename D> +inline std::string format(const std::string& fmt, const time_point<D>& tp, + const time_zone& tz) { + const auto p = detail::split_seconds(tp); + const auto n = std::chrono::duration_cast<detail::femtoseconds>(p.second); + return detail::format(fmt, p.first, n, tz); +} + +// Parses an input string according to the provided format string and +// returns the corresponding time_point. Uses strftime()-like formatting +// options, with the same extensions as cctz::format(), but with the +// exceptions that %E#S is interpreted as %E*S, and %E#f as %E*f. %Ez +// and %E*z also accept the same inputs. +// +// %Y consumes as many numeric characters as it can, so the matching data +// should always be terminated with a non-numeric. %E4Y always consumes +// exactly four characters, including any sign. +// +// Unspecified fields are taken from the default date and time of ... +// +// "1970-01-01 00:00:00.0 +0000" +// +// For example, parsing a string of "15:45" (%H:%M) will return a time_point +// that represents "1970-01-01 15:45:00.0 +0000". +// +// Note that parse() returns time instants, so it makes most sense to parse +// fully-specified date/time strings that include a UTC offset (%z, %Ez, or +// %E*z). +// +// Note also that parse() only heeds the fields year, month, day, hour, +// minute, (fractional) second, and UTC offset. Other fields, like weekday (%a +// or %A), while parsed for syntactic validity, are ignored in the conversion. +// +// Date and time fields that are out-of-range will be treated as errors rather +// than normalizing them like cctz::civil_second() would do. For example, it +// is an error to parse the date "Oct 32, 2013" because 32 is out of range. +// +// A second of ":60" is normalized to ":00" of the following minute with +// fractional seconds discarded. The following table shows how the given +// seconds and subseconds will be parsed: +// +// "59.x" -> 59.x // exact +// "60.x" -> 00.0 // normalized +// "00.x" -> 00.x // exact +// +// Errors are indicated by returning false. +// +// Example: +// const cctz::time_zone tz = ... +// std::chrono::system_clock::time_point tp; +// if (cctz::parse("%Y-%m-%d", "2015-10-09", tz, &tp)) { +// ... +// } +template <typename D> +inline bool parse(const std::string& fmt, const std::string& input, + const time_zone& tz, time_point<D>* tpp) { + time_point<seconds> sec; + detail::femtoseconds fs; + const bool b = detail::parse(fmt, input, tz, &sec, &fs); + if (b) { + // TODO: Return false if unrepresentable as a time_point<D>. + *tpp = std::chrono::time_point_cast<D>(sec); + *tpp += std::chrono::duration_cast<D>(fs); + } + return b; +} + +} // namespace cctz +} // namespace time_internal +ABSL_NAMESPACE_END +} // namespace absl + +#endif // ABSL_TIME_INTERNAL_CCTZ_TIME_ZONE_H_ |