forked from HowardHinnant/date
Add tai_clock and gps_clock.
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Howard Hinnant
291
tz.html
291
tz.html
@@ -26,7 +26,7 @@
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<br/>
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<br/>
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<a href="mailto:howard.hinnant@gmail.com">Howard E. Hinnant</a><br/>
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2016-06-06<br/>
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2016-06-07<br/>
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<a rel="license" href="http://creativecommons.org/licenses/by/4.0/"> <img alt="Creative
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Commons License" style="border-width:0"
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src="http://i.creativecommons.org/l/by/4.0/80x15.png" /></a><br /> This work is licensed
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@@ -65,6 +65,8 @@ Commons Attribution 4.0 International License</a>.
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<li><a href="#format"><code>format</code></a></li>
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<li><a href="#parse"><code>parse</code></a></li>
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<li><a href="#utc_clock"><code>utc_clock</code></a></li>
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<li><a href="#tai_clock"><code>tai_clock</code></a></li>
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<li><a href="#gps_clock"><code>gps_clock</code></a></li>
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<li><a href="#leap"><code>leap</code></a></li>
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<li><a href="#link"><code>link</code></a></li>
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</ul>
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@@ -2472,6 +2474,293 @@ seconds specifier when the value represents an inserted leap second.
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</blockquote>
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<a name="tai_clock"></a><h3><code>tai_clock</code></h3>
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<blockquote>
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<pre>
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class tai_clock
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{
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public:
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using duration = std::chrono::system_clock::duration;
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using rep = duration::rep;
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using period = duration::period;
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using time_point = std::chrono::time_point<tai_clock>;
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static constexpr bool is_steady = true;
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static time_point now() noexcept;
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template <class Duration>
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static
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tai_time<std::common_type_t<Duration, std::chrono::seconds>>
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utc_to_tai(utc_time<Duration> t);
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template <class Duration>
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static
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utc_time<std::common_type_t<Duration, std::chrono::seconds>>
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tai_to_utc(tai_time<Duration> u);
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};
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template <class Duration>
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using tai_time = std::chrono::time_point<tai_clock, Duration>;
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using tai_seconds = tai_time<std::chrono::seconds>;
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</pre>
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<p>
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<code>tai_time</code> counts physical seconds continuously like <code>utc_itme</code>,
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but when printed out, <i>always</i> has 60 seconds per minute. It's epoch
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is 1958-01-01 and is offset ahead of <code>utc_time</code> by 10s in 1970-01-01.
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With each leap second, the offset from <code>utc_time</code> grows by another
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second.
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</p>
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<pre>
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static tai_clock::time_point tai_clock::now() noexcept;
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</pre>
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<blockquote>
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<p>
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<i>Returns:</i> <code>to_tai_time(utc_clock::now())</code>.
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</p>
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</blockquote>
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<pre>
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template <class Duration>
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static
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tai_time<std::common_type_t<Duration, std::chrono::seconds>>
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tai_clock::utc_to_tai(utc_time<Duration> t);
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</pre>
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<blockquote>
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<p>
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<i>Returns:</i> A <code>tai_time</code> which represents time as measured by
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TAI at the same instant as the time <code>t</code> in UTC.
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</p>
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</blockquote>
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<pre>
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template <class Duration>
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static
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utc_time<std::common_type_t<Duration, std::chrono::seconds>>
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tai_clock::tai_to_utc(tai_time<Duration> t);
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</pre>
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<blockquote>
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<p>
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<i>Returns:</i> A <code>utc_time</code> <code>u</code>, such that
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<code>tai_clock::utc_to_tai(u) == t</code>.
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</p>
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</blockquote>
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<pre>
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template <class Duration>
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utc_time<std::common_type_t<Duration, std::chrono::seconds>>
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to_utc_time(tai_time<Duration> t)
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</pre>
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<blockquote>
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<p>
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<i>Returns:</i> <code>tai_clock::tai_to_utc(t)</code>.
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</p>
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</blockquote>
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<pre>
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template <class Duration>
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tai_time<std::common_type_t<Duration, std::chrono::seconds>>
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to_tai_time(utc_time<Duration> u)
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</pre>
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<blockquote>
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<p>
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<i>Returns:</i> <code>tai_clock::utc_to_tai(u)</code>.
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</p>
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</blockquote>
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<pre>
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template <class CharT, class Traits, class Duration>
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std::basic_ostream<class CharT, class Traits>&
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operator<<(std::basic_ostream<class CharT, class Traits>& os, const tai_time<Duration>& t)
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</pre>
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<blockquote>
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<p>
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<i>Effects:</i> Streams <code>t</code> to <code>os</code> using the format "%F %T".
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</p>
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<p>
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<i>Returns:</i> <code>os</code>.
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</p>
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</blockquote>
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</blockquote>
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<a name="gps_clock"></a><h3><code>gps_clock</code></h3>
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<blockquote>
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<pre>
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class gps_clock
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{
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public:
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using duration = std::chrono::system_clock::duration;
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using rep = duration::rep;
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using period = duration::period;
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using time_point = std::chrono::time_point<gps_clock>;
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static constexpr bool is_steady = true;
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static time_point now() noexcept;
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template <class Duration>
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static
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gps_time<std::common_type_t<Duration, std::chrono::seconds>>
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utc_to_gps(utc_time<Duration> t);
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template <class Duration>
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static
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utc_time<std::common_type_t<Duration, std::chrono::seconds>>
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gps_to_utc(gps_time<Duration> u);
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};
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template <class Duration>
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using gps_time = std::chrono::time_point<gps_clock, Duration>;
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using gps_seconds = gps_time<std::chrono::seconds>;
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</pre>
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<p>
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<code>gps_time</code> counts physical seconds continuously like <code>utc_itme</code>,
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but when printed out, <i>always</i> has 60 seconds per minute. It's epoch
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is 1980-01-06 and was equivalent to UTC at that time. If falls ahead of UTC
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with each inserted leap second. It is always exactly 19s behind TAI.
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</p>
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<pre>
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static gps_clock::time_point gps_clock::now() noexcept;
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</pre>
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<blockquote>
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<p>
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<i>Returns:</i> <code>to_gps_time(utc_clock::now())</code>.
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</p>
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</blockquote>
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<pre>
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template <class Duration>
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static
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gps_time<std::common_type_t<Duration, std::chrono::seconds>>
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gps_clock::utc_to_gps(utc_time<Duration> t);
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</pre>
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<blockquote>
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<p>
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<i>Returns:</i> A <code>gps_time</code> which represents time as measured by
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GPS at the same instant as the time <code>t</code> in UTC.
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</p>
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</blockquote>
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<pre>
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template <class Duration>
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static
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utc_time<std::common_type_t<Duration, std::chrono::seconds>>
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gps_clock::gps_to_utc(gps_time<Duration> t);
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</pre>
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<blockquote>
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<p>
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<i>Returns:</i> A <code>utc_time</code> <code>u</code>, such that
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<code>gps_clock::utc_to_gps(u) == t</code>.
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</p>
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</blockquote>
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<pre>
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template <class Duration>
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utc_time<std::common_type_t<Duration, std::chrono::seconds>>
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to_utc_time(gps_time<Duration> t)
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</pre>
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<blockquote>
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<p>
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<i>Returns:</i> <code>gps_clock::gps_to_utc(t)</code>.
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</p>
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</blockquote>
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<pre>
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template <class Duration>
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gps_time<std::common_type_t<Duration, std::chrono::seconds>>
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to_gps_time(utc_time<Duration> u)
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</pre>
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<blockquote>
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<p>
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<i>Returns:</i> <code>gps_clock::utc_to_gps(u)</code>.
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</p>
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</blockquote>
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<pre>
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template <class CharT, class Traits, class Duration>
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std::basic_ostream<class CharT, class Traits>&
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operator<<(std::basic_ostream<class CharT, class Traits>& os, const gps_time<Duration>& t)
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</pre>
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<blockquote>
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<p>
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<i>Effects:</i> Streams <code>t</code> to <code>os</code> using the format "%F %T".
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</p>
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<p>
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<i>Returns:</i> <code>os</code>.
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</p>
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</blockquote>
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<p>
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[<i>Example:</i>
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</p>
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<p>
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The following code prints out equivalent time stamps to millisecond precision for
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times near the 2015-06-30 leap second insertion. Note that the mapping to
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<code>sys_time</code> during the leap second collapses down to the last instant
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prior to the leap second. But the maping between UTC, TAI and GPS is all one-to-one.
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</p>
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<blockquote><pre>
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#include "tz.h"
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#include <iostream>
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int
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main()
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{
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using namespace date;
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using namespace std::chrono;
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auto start = to_utc_time(sys_days{2015_y/jul/1} - 500ms);
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auto end = start + 2s;
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for (auto utc = start; utc < end; utc += 100ms)
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{
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auto sys = to_sys_time(utc);
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auto tai = to_tai_time(utc);
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auto gps = to_gps_time(utc);
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std::cout << sys << " SYS == "
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<< utc << " UTC == "
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<< tai << " TAI == "
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<< gps << " GPS\n";
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}
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}
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</pre>
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<p>
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Output:
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</p>
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<pre>
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2015-06-30 23:59:59.500 SYS == 2015-06-30 23:59:59.500 UTC == 2015-07-01 00:00:34.500 TAI == 2015-07-01 00:00:15.500 GPS
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2015-06-30 23:59:59.600 SYS == 2015-06-30 23:59:59.600 UTC == 2015-07-01 00:00:34.600 TAI == 2015-07-01 00:00:15.600 GPS
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2015-06-30 23:59:59.700 SYS == 2015-06-30 23:59:59.700 UTC == 2015-07-01 00:00:34.700 TAI == 2015-07-01 00:00:15.700 GPS
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2015-06-30 23:59:59.800 SYS == 2015-06-30 23:59:59.800 UTC == 2015-07-01 00:00:34.800 TAI == 2015-07-01 00:00:15.800 GPS
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2015-06-30 23:59:59.900 SYS == 2015-06-30 23:59:59.900 UTC == 2015-07-01 00:00:34.900 TAI == 2015-07-01 00:00:15.900 GPS
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2015-06-30 23:59:<b>59.999</b> SYS == 2015-06-30 23:59:<b>60.000</b> UTC == 2015-07-01 00:00:35.000 TAI == 2015-07-01 00:00:16.000 GPS
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2015-06-30 23:59:<b>59.999</b> SYS == 2015-06-30 23:59:<b>60.100</b> UTC == 2015-07-01 00:00:35.100 TAI == 2015-07-01 00:00:16.100 GPS
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2015-06-30 23:59:<b>59.999</b> SYS == 2015-06-30 23:59:<b>60.200</b> UTC == 2015-07-01 00:00:35.200 TAI == 2015-07-01 00:00:16.200 GPS
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2015-06-30 23:59:<b>59.999</b> SYS == 2015-06-30 23:59:<b>60.300</b> UTC == 2015-07-01 00:00:35.300 TAI == 2015-07-01 00:00:16.300 GPS
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2015-06-30 23:59:<b>59.999</b> SYS == 2015-06-30 23:59:<b>60.400</b> UTC == 2015-07-01 00:00:35.400 TAI == 2015-07-01 00:00:16.400 GPS
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2015-06-30 23:59:<b>59.999</b> SYS == 2015-06-30 23:59:<b>60.500</b> UTC == 2015-07-01 00:00:35.500 TAI == 2015-07-01 00:00:16.500 GPS
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2015-06-30 23:59:<b>59.999</b> SYS == 2015-06-30 23:59:<b>60.600</b> UTC == 2015-07-01 00:00:35.600 TAI == 2015-07-01 00:00:16.600 GPS
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2015-06-30 23:59:<b>59.999</b> SYS == 2015-06-30 23:59:<b>60.700</b> UTC == 2015-07-01 00:00:35.700 TAI == 2015-07-01 00:00:16.700 GPS
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2015-06-30 23:59:<b>59.999</b> SYS == 2015-06-30 23:59:<b>60.800</b> UTC == 2015-07-01 00:00:35.800 TAI == 2015-07-01 00:00:16.800 GPS
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2015-06-30 23:59:<b>59.999</b> SYS == 2015-06-30 23:59:<b>60.900</b> UTC == 2015-07-01 00:00:35.900 TAI == 2015-07-01 00:00:16.900 GPS
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2015-07-01 00:00:00.000 SYS == 2015-07-01 00:00:00.000 UTC == 2015-07-01 00:00:36.000 TAI == 2015-07-01 00:00:17.000 GPS
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2015-07-01 00:00:00.100 SYS == 2015-07-01 00:00:00.100 UTC == 2015-07-01 00:00:36.100 TAI == 2015-07-01 00:00:17.100 GPS
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2015-07-01 00:00:00.200 SYS == 2015-07-01 00:00:00.200 UTC == 2015-07-01 00:00:36.200 TAI == 2015-07-01 00:00:17.200 GPS
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2015-07-01 00:00:00.300 SYS == 2015-07-01 00:00:00.300 UTC == 2015-07-01 00:00:36.300 TAI == 2015-07-01 00:00:17.300 GPS
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2015-07-01 00:00:00.400 SYS == 2015-07-01 00:00:00.400 UTC == 2015-07-01 00:00:36.400 TAI == 2015-07-01 00:00:17.400 GPS
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</pre>
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</blockquote>
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<p>
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<i>— end example</i>]
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</p>
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</blockquote>
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<a name="leap"></a><h3><code>leap</code></h3>
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<blockquote>
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<pre>
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