From Jason Turner

[time.zone.timezone]

C++17 → C++20 3.8 KB 120 lines
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+ ### Class `time_zone` <a id="time.zone.timezone">[[time.zone.timezone]]</a>
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+
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+ #### Overview <a id="time.zone.overview">[[time.zone.overview]]</a>
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+
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+ ``` cpp
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+ namespace std::chrono {
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+ class time_zone {
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+ public:
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+ time_zone(time_zone&&) = default;
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+ time_zone& operator=(time_zone&&) = default;
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+
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+ // unspecified additional constructors
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+
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+ string_view name() const noexcept;
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+
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+ template<class Duration> sys_info get_info(const sys_time<Duration>& st) const;
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+ template<class Duration> local_info get_info(const local_time<Duration>& tp) const;
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+
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+ template<class Duration>
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+ sys_time<common_type_t<Duration, seconds>>
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+ to_sys(const local_time<Duration>& tp) const;
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+
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+ template<class Duration>
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+ sys_time<common_type_t<Duration, seconds>>
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+ to_sys(const local_time<Duration>& tp, choose z) const;
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+
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+ template<class Duration>
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+ local_time<common_type_t<Duration, seconds>>
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+ to_local(const sys_time<Duration>& tp) const;
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+ };
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+ }
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+ ```
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+
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+ A `time_zone` represents all time zone transitions for a specific
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+ geographic area. `time_zone` construction is unspecified, and performed
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+ as part of database initialization.
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+
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+ [*Note 1*: `const time_zone` objects can be accessed via functions such
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+ as `locate_zone`. — *end note*]
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+
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+ #### Member functions <a id="time.zone.members">[[time.zone.members]]</a>
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+
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+ ``` cpp
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+ string_view name() const noexcept;
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+ ```
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+
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+ *Returns:* The name of the `time_zone`.
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+
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+ [*Example 1*: `"America/New_York"`. — *end example*]
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+
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+ ``` cpp
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+ template<class Duration>
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+ sys_info get_info(const sys_time<Duration>& st) const;
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+ ```
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+
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+ *Returns:* A `sys_info` `i` for which `st` is in the range \[`i.begin`,
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+ `i.end`).
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+
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+ ``` cpp
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+ template<class Duration>
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+ local_info get_info(const local_time<Duration>& tp) const;
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+ ```
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+
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+ *Returns:* A `local_info` for `tp`.
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+
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+ ``` cpp
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+ template<class Duration>
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+ sys_time<common_type_t<Duration, seconds>>
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+ to_sys(const local_time<Duration>& tp) const;
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+ ```
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+
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+ *Returns:* A `sys_time` that is at least as fine as `seconds`, and will
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+ be finer if the argument `tp` has finer precision. This `sys_time` is
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+ the UTC equivalent of `tp` according to the rules of this `time_zone`.
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+
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+ *Throws:* If the conversion from `tp` to a `sys_time` is ambiguous,
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+ throws `ambiguous_local_time`. If the `tp` represents a non-existent
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+ time between two UTC `time_points`, throws `nonexistent_local_time`.
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+
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+ ``` cpp
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+ template<class Duration>
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+ sys_time<common_type_t<Duration, seconds>>
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+ to_sys(const local_time<Duration>& tp, choose z) const;
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+ ```
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+
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+ *Returns:* A `sys_time` that is at least as fine as `seconds`, and will
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+ be finer if the argument `tp` has finer precision. This `sys_time` is
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+ the UTC equivalent of `tp` according to the rules of this `time_zone`.
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+ If the conversion from `tp` to a `sys_time` is ambiguous, returns the
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+ earlier `sys_time` if `z == choose::earliest`, and returns the later
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+ `sys_time` if `z == choose::latest`. If the `tp` represents a
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+ non-existent time between two UTC `time_points`, then the two UTC
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+ `time_points` will be the same, and that UTC `time_point` will be
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+ returned.
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+
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+ ``` cpp
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+ template<class Duration>
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+ local_time<common_type_t<Duration, seconds>>
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+ to_local(const sys_time<Duration>& tp) const;
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+ ```
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+
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+ *Returns:* The `local_time` associated with `tp` and this `time_zone`.
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+
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+ #### Non-member functions <a id="time.zone.nonmembers">[[time.zone.nonmembers]]</a>
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+
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+ ``` cpp
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+ bool operator==(const time_zone& x, const time_zone& y) noexcept;
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+ ```
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+
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+ *Returns:* `x.name() == y.name()`.
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+
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+ ``` cpp
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+ strong_ordering operator<=>(const time_zone& x, const time_zone& y) noexcept;
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+ ```
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+
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+ *Returns:* `x.name() <=> y.name()`.
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+