182 lines
16 KiB
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182 lines
16 KiB
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<title>std::chrono::ceil(std::chrono::time_point)</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::chrono::</span>ceil<small>(std::chrono::time_point)</small></h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-chrono.html">chrono</a>‎ | <a href="cpp-chrono-time_point.html">time point</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> ToDuration, <span class="kw1">class</span> Clock, <span class="kw1">class</span> Duration<span class="sy1">></span><br /></span>
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<p><span class="kw4">constexpr</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, ToDuration<span class="sy1">></span><br /></p>
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ceil<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> tp<span class="br0">)</span><span class="sy4">;</span></div>
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<td><span class="t-mark-rev t-since-cxx17">(C++17 起)</span></td>
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<p>返回能以 <code>ToDuration</code> 表示的大于或等于 <code>tp</code> 的最小时间点 <code>t</code> 。</p>
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<p>函数不参与重载决议，除非 <code>ToDuration</code> 是 <span class="t-lc"><a href="cpp-chrono-duration.html">std::chrono::duration</a></span> 的特化。</p>
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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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<td>tp</td>
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<td>-</td>
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<td>要向上取整的时间点</td>
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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>向上取整到使用 <code>ToDuration</code> 类型时长的下个时间点的 <code>tp</code> 。</p>
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<h3><span class="mw-headline" id=".E5.8F.AF.E8.83.BD.E7.9A.84.E5.AE.9E.E7.8E.B0">可能的实现</span></h3>
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<pre class="de1"><span class="kw1">namespace</span> detail <span class="br0">{</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span><span class="sy1">></span> <span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> is_duration_v <span class="sy1">=</span> <span class="kw2">false</span><span class="sy4">;</span>
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<span class="kw1">template</span><span class="sy1"><</span><span class="kw1">class</span> Rep, <span class="kw1">class</span> Period<span class="sy1">></span> <span class="kw1">inline</span> <span class="kw4">constexpr</span> <span class="kw4">bool</span> is_duration_v<span class="sy1"><</span>
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<a href="cpp-chrono-duration.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1"><</span>Rep, Period<span class="sy1">>></span> <span class="sy1">=</span> <span class="kw2">true</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">class</span> To, <span class="kw1">class</span> Clock, <span class="kw1">class</span> FromDuration,
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<span class="kw1">class</span> <span class="sy1">=</span> <a href="cpp-types-enable_if.html"><span class="kw631">std::<span class="me2">enable_if_t</span></span></a><span class="sy1"><</span>detail<span class="sy4">::</span><span class="me2">is_duration_v</span><span class="sy1"><</span>To<span class="sy1">>>></span>
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<span class="kw4">constexpr</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, To<span class="sy1">></span>
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ceil<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, FromDuration<span class="sy1">></span><span class="sy3">&</span> tp<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</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, To<span class="sy1">></span><span class="br0">{</span>
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std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">ceil</span><span class="sy1"><</span>To<span class="sy1">></span><span class="br0">(</span>tp.<span class="me1">time_since_epoch</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-template-editlink" style=""></div>
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="co2">#include <chrono></span>
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<span class="co2">#include <string></span>
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<span class="kw1">template</span> <span class="sy1"><</span><span class="kw1">typename</span> TimePoint<span class="sy1">></span>
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<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> to_string<span class="br0">(</span><span class="kw4">const</span> TimePoint<span class="sy3">&</span> time_point<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">return</span> <a href="cpp-string-basic_string-to_string.html"><span class="kw1265">std::<span class="me2">to_string</span></span></a><span class="br0">(</span>time_point.<span class="me1">time_since_epoch</span><span class="br0">(</span><span class="br0">)</span>.<span class="me1">count</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">literals</span><span class="sy4">::</span><span class="me2">chrono_literals</span><span class="sy4">;</span>
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<span class="kw1">using</span> Sec <span class="sy1">=</span> <a href="cpp-chrono-duration.html"><span class="kw997">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">seconds</span></span></a><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Time point<span class="es1">\t</span>"</span> <span class="st0">"Cast<span class="es1">\t</span>"</span> <span class="st0">"Floor<span class="es1">\t</span>"</span> <span class="st0">"Round<span class="es1">\t</span>"</span> <span class="st0">"Ceil<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"(ms)<span class="es1">\t</span><span class="es1">\t</span>"</span> <span class="st0">"(s)<span class="es1">\t</span>"</span> <span class="st0">"(s)<span class="es1">\t</span>"</span> <span class="st0">"(s)<span class="es1">\t</span>"</span> <span class="st0">"(s)<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">const</span> <span class="kw4">auto</span> value_ms<span class="sy4">:</span> <span class="br0">{</span>5432ms, 5678ms<span class="br0">}</span><span class="br0">)</span> <span class="br0">{</span>
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<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><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-duration.html"><span class="kw996">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">milliseconds</span></span></a><span class="sy1">></span>
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time_point_ms<span class="br0">(</span>value_ms<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>
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<span class="sy1"><<</span> to_string<span class="br0">(</span>time_point_ms<span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\t</span><span class="es1">\t</span>"</span>
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<span class="sy1"><<</span> to_string<span class="br0">(</span><a href="cpp-chrono-time_point-time_point_cast.html"><span class="kw992">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">time_point_cast</span></span></a><span class="sy1"><</span>Sec<span class="sy1">></span><span class="br0">(</span>time_point_ms<span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\t</span>"</span>
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<span class="sy1"><<</span> to_string<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">floor</span> <span class="sy1"><</span>Sec<span class="sy1">></span><span class="br0">(</span>time_point_ms<span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\t</span>"</span>
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<span class="sy1"><<</span> to_string<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">round</span> <span class="sy1"><</span>Sec<span class="sy1">></span><span class="br0">(</span>time_point_ms<span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\t</span>"</span>
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<span class="sy1"><<</span> to_string<span class="br0">(</span>std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">ceil</span> <span class="sy1"><</span>Sec<span class="sy1">></span><span class="br0">(</span>time_point_ms<span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="br0">}</span></pre></div>
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<p>输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">Time point Cast Floor Round Ceil
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(ms) (s) (s) (s) (s)
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5432 5 5 5 6
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5678 5 5 6 6</pre></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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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-time_point-time_point_cast.html"><span class="t-lines"><span>time_point_cast</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>转换时间点为同一时钟上拥有不同时长的另一时间点<br />
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<span class="t-mark">(函数模板)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-time_point-floor.html"><span class="t-lines"><span>floor<span class="t-dsc-small">(std::chrono::time_point)</span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>转换 time_point 到另一个，向下取整<br />
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<span class="t-mark">(函数模板)</span></td>
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<tr class="t-dsc">
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<div><a href="cpp-chrono-time_point-round.html"><span class="t-lines"><span>round<span class="t-dsc-small">(std::chrono::time_point)</span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>转换 time_point 到另一个，就近取整，偶数优先<br />
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<span class="t-mark">(函数模板)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-chrono-duration-ceil.html"><span class="t-lines"><span>ceil<span class="t-dsc-small">(std::chrono::duration)</span></span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx17">(C++17)</span></span></span></div>
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</div>
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</td>
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<td>以向上取整的方式，将一个时长转换为另一个时长<br />
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<span class="t-mark">(函数模板)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-numeric-math-ceil.html"><span class="t-lines"><span>ceil</span><span>ceilf</span><span>ceill</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div>
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</div>
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</td>
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<td>不小于给定值的最接近整数值<br />
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<span class="t-mark">(函数)</span></td>
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