258 lines
30 KiB
HTML
258 lines
30 KiB
HTML
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<title>std::chrono::clock_time_conversion</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_chrono_clock_time_conversion skin-cppreference2 action-view cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::</span>clock_time_conversion</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-chrono.html">chrono</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-chrono.html"><chrono></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> Dest, <span class="kw1">class</span> Source<span class="sy1">></span> <span class="kw1">struct</span> clock_time_conversion <span class="br0">{</span> <span class="br0">}</span><span class="sy4">;</span></span></div>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<p><code>std::chrono::clock_time_conversion</code> 是特性类，指定如何转换 <code>Source</code> 时钟的 <span class="t-lc"><a href="cpp-chrono-time_point.html">std::chrono::time_point</a></span> 到 <code>Dest</code> 时钟的时间点。它通过提供 const 可调用的，接受 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1"><</span>Source, Duration<span class="sy1">></span></span></span> 类型参数并返回表示等价时间点的 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1"><</span>Dest, OtherDuration<span class="sy1">></span></span></span> 的 <code>operator()</code> 进行转换。以对每个特化有所变化的方式，计算返回时间点的时长。通常只通过 <span class="t-lc">std::chrono::clock_cast</span> 间接使用 <code>clock_time_conversion</code> 。</p>
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<p>程序可以特化 <code>clock_time_conversion</code> ，若至少一个模板形参是用户定义类型。</p>
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<p>初等模板是空 struct 。标准定义下列特化：</p>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> Clock<span class="sy1">></span> <span class="kw1">struct</span> clock_time_conversion<span class="sy1"><</span>Clock, Clock<span class="sy1">></span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><></span> <span class="kw1">struct</span> clock_time_conversion<span class="sy1"><</span><a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a>, <a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a><span class="sy1">></span><span class="sy4">;</span></span></div>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><></span> <span class="kw1">struct</span> clock_time_conversion<span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span>, std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span><span class="sy1">></span><span class="sy4">;</span></span></div>
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<td>(3)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><></span> <span class="kw1">struct</span> clock_time_conversion<span class="sy1"><</span><a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a>, std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span><span class="sy1">></span><span class="sy4">;</span></span></div>
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<td>(4)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><></span> <span class="kw1">struct</span> clock_time_conversion<span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span>, <a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a><span class="sy1">></span><span class="sy4">;</span></span></div>
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<td>(5)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> Clock<span class="sy1">></span> <span class="kw1">struct</span> clock_time_conversion<span class="sy1"><</span>Clock, <a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a><span class="sy1">></span><span class="sy4">;</span></span></div>
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<td>(6)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> Clock<span class="sy1">></span> <span class="kw1">struct</span> clock_time_conversion<span class="sy1"><</span><a href="cpp-chrono-system_clock.html"><span class="kw1004">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">system_clock</span></span></a>, Clock<span class="sy1">></span><span class="sy4">;</span></span></div>
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<td>(7)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> Clock<span class="sy1">></span> <span class="kw1">struct</span> clock_time_conversion<span class="sy1"><</span>Clock, std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span><span class="sy1">></span><span class="sy4">;</span></span></div>
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<td>(8)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> Clock<span class="sy1">></span> <span class="kw1">struct</span> clock_time_conversion<span class="sy1"><</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span>, Clock<span class="sy1">></span><span class="sy4">;</span></span></div>
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<td>(9)</td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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<div class="t-li1"><span class="t-li">1-3)</span> 恒等转换： <code>operator()</code> 返回参数的副本。</div>
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<div class="t-li1"><span class="t-li">4-5)</span> <span class="t-lc">std::chrono::sys_time</span> 与 <span class="t-lc">std::chrono::utc_time</span> 间的转换： <code>operator()</code> 分别调用 <span class="t-lc">std::chrono::utc_clock::to_sys</span> 和 <span class="t-lc">std::chrono::utc_clock::from_sys</span> 。</div>
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<div class="t-li1"><span class="t-li">6-7)</span> <code>Clock</code> 支持 <code>from_sys</code> 和 <code>to_sys</code> 时，来自和到 <span class="t-lc">std::chrono::sys_time</span> 的转换： <code>operator()</code> 分别调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">to_sys</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">from_sys</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">8-9)</span> <code>Clock</code> 支持 <code>from_utc</code> 和 <code>to_utc</code> 时，来自和到 <span class="t-lc">std::chrono::utc_time</span> 的转换： <code>operator()</code> 分别调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">to_utc</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">from_utc</span></span></span> 。</div>
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<h3><span class="mw-headline" id=".E6.88.90.E5.91.98.E5.87.BD.E6.95.B0">成员函数</span></h3>
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<p>每个特化都有隐式声明的默认构造函数、复制构造函数、移动构造函数、复制赋值运算符、移动赋值运算符和析构函数。</p>
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<div class="t-member">
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<h2><span class="mw-headline" id="std::chrono::clock_time_conversion::operator.28.29"><span style="font-size:0.7em; line-height:130%">std::chrono::clock_time_conversion::</span>operator()</span></h2>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> Duration<span class="sy1">></span><br /></span>
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<p><a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1"><</span>Clock, Duration<span class="sy1">></span><br /></p>
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operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> <a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1"><</span>Clock, Duration<span class="sy1">></span><span class="sy3">&</span> t<span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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<td>(1)</td>
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<td><span class="t-mark">(特化 <span class="t-v">(1)</span> 的成员)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> Duration<span class="sy1">></span><br /></span>
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<p>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">sys_time</span><span class="sy1"><</span>Duration<span class="sy1">></span><br /></p>
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operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">sys_time</span><span class="sy1"><</span>Duration<span class="sy1">></span> <span class="sy3">&</span> t<span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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<td>(2)</td>
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<td><span class="t-mark">(特化 <span class="t-v">(2)</span> 的成员)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> Duration<span class="sy1">></span><br /></span>
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<p>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_time</span><span class="sy1"><</span>Duration<span class="sy1">></span><br /></p>
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operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_time</span><span class="sy1"><</span>Duration<span class="sy1">></span><span class="sy3">&</span> t<span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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<td>(3)</td>
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<td><span class="t-mark">(特化 <span class="t-v">(3)</span> 的成员)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> Duration<span class="sy1">></span><br /></span>
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<p>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">sys_time</span><span class="sy1"><</span>Duration<span class="sy1">></span><br /></p>
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operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_time</span><span class="sy1"><</span>Duration<span class="sy1">></span><span class="sy3">&</span> t<span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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<td>(4)</td>
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<td><span class="t-mark">(特化 <span class="t-v">(4)</span> 的成员)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> Duration<span class="sy1">></span><br /></span>
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<p>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_time</span><span class="sy1"><</span>Duration<span class="sy1">></span><br /></p>
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operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">sys_time</span><span class="sy1"><</span>Duration<span class="sy1">></span><span class="sy3">&</span> t<span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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<td>(5)</td>
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<td><span class="t-mark">(特化 <span class="t-v">(5)</span> 的成员)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> Duration<span class="sy1">></span><br /></span>
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<p><span class="kw4">auto</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">sys_time</span><span class="sy1"><</span>Duration<span class="sy1">></span><span class="sy3">&</span> t<span class="br0">)</span> <span class="kw4">const</span><br /></p>
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<span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span>Clock<span class="sy4">::</span><span class="me2">from_sys</span><span class="br0">(</span>t<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></div>
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<td>(6)</td>
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<td><span class="t-mark">(特化 <span class="t-v">(6)</span> 的成员)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> Duration<span class="sy1">></span><br /></span>
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<p><span class="kw4">auto</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> <a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1"><</span>SourceClock, Duration<span class="sy1">></span><span class="sy3">&</span> t<span class="br0">)</span> <span class="kw4">const</span><br /></p>
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<span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span>Clock<span class="sy4">::</span><span class="me2">to_sys</span><span class="br0">(</span>t<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td>(7)</td>
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<td><span class="t-mark">(特化 <span class="t-v">(7)</span> 的成员)</span></td>
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> Duration<span class="sy1">></span><br /></span>
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<p><span class="kw4">auto</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_time</span><span class="sy1"><</span>Duration<span class="sy1">></span><span class="sy3">&</span> t<span class="br0">)</span> <span class="kw4">const</span><br /></p>
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<span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span>Clock<span class="sy4">::</span><span class="me2">from_utc</span><span class="br0">(</span>t<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td>(8)</td>
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<td><span class="t-mark">(特化 <span class="t-v">(8)</span> 的成员)</span></td>
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</tr>
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<tr class="t-dcl">
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<td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> Duration<span class="sy1">></span><br /></span>
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<p><span class="kw4">auto</span> operator<span class="br0">(</span><span class="br0">)</span><span class="br0">(</span><span class="kw4">const</span> <a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1"><</span>Clock, Duration<span class="sy1">></span><span class="sy3">&</span> t<span class="br0">)</span> <span class="kw4">const</span><br /></p>
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<span class="sy2">-</span><span class="sy1">></span> decltype<span class="br0">(</span>Clock<span class="sy4">::</span><span class="me2">to_utc</span><span class="br0">(</span>t<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></div>
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</td>
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<td>(9)</td>
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<td><span class="t-mark">(特化 <span class="t-v">(9)</span> 的成员)</span></td>
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</tr>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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</tr>
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</tbody>
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</table>
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<p>转换参数 <span class="t-lc"><a href="cpp-chrono-time_point.html">std::chrono::time_point</a></span> 为目标时钟。</p>
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<div class="t-li1"><span class="t-li">1-3)</span> 恒等转换。返回不更改的 <code>t</code> 。</div>
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<div class="t-li1"><span class="t-li">4)</span> 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span><span class="sy4">::</span><span class="me2">to_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">5)</span> 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span><span class="sy4">::</span><span class="me2">from_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">6)</span> 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">from_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。此重载仅若表达式 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">from_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 为良式才参与重载决议。若 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">from_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 不返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1"><</span>Clock, Duration<span class="sy1">></span></span></span> ，其中 <code>Duration</code> 是 <span class="t-lc"><a href="cpp-chrono-duration.html">std::chrono::duration</a></span> 的某个合法特化，则程序为病式。</div>
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<div class="t-li1"><span class="t-li">7)</span> 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">to_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。此重载仅若表达式 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">to_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 为良式才参与重载决议。若 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">to_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 不返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">sys_time</span><span class="sy1"><</span>Duration<span class="sy1">></span></span></span> ，其中 <code>Duration</code> 是 <span class="t-lc"><a href="cpp-chrono-duration.html">std::chrono::duration</a></span> 的某个合法特化，则程序为病式。</div>
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<div class="t-li1"><span class="t-li">8)</span> Returns <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">from_utc</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。此重载仅若表达式 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">from_utc</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 为良式才参与重载决议。若 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">from_utc</span><span class="br0">(</span>t<span class="br0">)</span></span></span>不返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-chrono-time_point.html"><span class="kw991">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point</span></span></a><span class="sy1"><</span>Clock, Duration<span class="sy1">></span></span></span> ，其中 <code>Duration</code> 是 <span class="t-lc"><a href="cpp-chrono-duration.html">std::chrono::duration</a></span> 的某个合法特化，则程序为病式。</div>
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<div class="t-li1"><span class="t-li">9)</span> 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">to_utc</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。此重载仅若表达式 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">to_utc</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 为良式才参与重载决议。若 <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">to_utc</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 不返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_time</span><span class="sy1"><</span>Duration<span class="sy1">></span></span></span> ，其中 <code>Duration</code> 是 <span class="t-lc"><a href="cpp-chrono-duration.html">std::chrono::duration</a></span> 的某个合法特化，则程序为病式。</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<table class="t-par-begin">
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<tr class="t-par">
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<td>t</td>
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<td>-</td>
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<td>要转化的时间点</td>
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</tr>
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</table>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>上述的转换结果：</p>
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<div class="t-li1"><span class="t-li">1-3)</span> <code>t</code> 。</div>
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<div class="t-li1"><span class="t-li">4)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span><span class="sy4">::</span><span class="me2">to_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">5)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">utc_clock</span><span class="sy4">::</span><span class="me2">from_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">6)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">from_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">7)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">to_sys</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">8)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">from_utc</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">9)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">Clock<span class="sy4">::</span><span class="me2">to_utc</span><span class="br0">(</span>t<span class="br0">)</span></span></span> 。</div>
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</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-clock_cast.html"><span class="t-lines"><span>clock_cast</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>转换一个时钟的时间点为另一个<br />
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<span class="t-mark">(函数模板)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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