100 lines
7.9 KiB
HTML
100 lines
7.9 KiB
HTML
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<title>std::basic_ispanstream<CharT,Traits>::span</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_basic_ispanstream_span skin-cppreference2 action-view cpp-page-template cpp-navbar">
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::basic_ispanstream<CharT,Traits>::</span>span</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-io.html">io</a>‎ | <a href="cpp-io-basic_ispanstream.html">basic ispanstream</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<div class="t-page-template" style="">
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<p></p>
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<table class="t-dcl-begin">
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<div><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">span</span><span class="sy1"><</span><span class="kw4">const</span> CharT<span class="sy1">></span> span<span class="br0">(</span><span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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</td>
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<td>(1)</td>
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<td><span class="t-mark-rev t-since-cxx23">(C++23 起)</span></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> span<span class="br0">(</span> std<span class="sy4">::</span><span class="me2">span</span><span class="sy1"><</span>CharT<span class="sy1">></span> s <span class="br0">)</span> <span class="kw1">noexcept</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-cxx23">(C++23 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> ROS <span class="sy1">></span><br />
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<span class="kw4">void</span> span<span class="br0">(</span> ROS<span class="sy3">&&</span> r <span class="br0">)</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
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</td>
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<td>(3)</td>
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<td><span class="t-mark-rev t-since-cxx23">(C++23 起)</span></td>
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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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<div class="t-li1"><span class="t-li">1)</span> 若包装的 <span class="t-lc">std::basic_spanbuf</span> 的打开模式中设置了 <span class="t-lc"><a href="cpp-io-ios_base-openmode.html">std::ios_base::out</a></span> ，则获取引用被写入区域的 <code>span</code> ，否则获取引用底层缓冲区的 <code>span</code> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 使包装的 <span class="t-lc">std::basic_spanbuf</span> 进行 <code>s</code> 所引用的缓冲区上的 I/O 。</div>
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<div class="t-li1"><span class="t-li">3)</span> 同 <span class="t-v">(2)</span> ，除了如同通过<br />
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<span class="t-cc"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">span</span><span class="sy1"><</span><span class="kw4">const</span> CharT<span class="sy1">></span> cs<span class="br0">{</span><a href="cpp-utility-forward.html"><span class="kw1117">std::<span class="me2">forward</span></span></a><span class="sy1"><</span>ROS<span class="sy1">></span><span class="br0">(</span>r<span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span><br />
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std<span class="sy4">::</span><span class="me2">span</span><span class="sy1"><</span>CharT<span class="sy1">></span> s<span class="br0">{</span><span class="kw1">const_cast</span><span class="sy1"><</span>CharT<span class="sy2">*</span><span class="sy1">></span><span class="br0">(</span>cs.<span class="me1">data</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span>, cs.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">}</span><span class="sy4">;</span></span></span><br />
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获得 <code>s</code> 。此重载仅若 <code>ROS</code> 实现 <a href="cpp-ranges-borrowed_range.html"><code>borrowed_range</code></a> ， <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">convertible_to</span><span class="sy1"><</span>ROS, std<span class="sy4">::</span><span class="me2">span</span><span class="sy1"><</span>CharT<span class="sy1">>></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 而 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">convertible_to</span><span class="sy1"><</span>ROS, std<span class="sy4">::</span><span class="me2">span</span><span class="sy1"><</span><span class="kw4">const</span> CharT<span class="sy1">>></span></span></span> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 才参与重载决议。</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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<td>s</td>
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<td>-</td>
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<td>引用要用作流的新底层缓冲区的 <span class="t-lc">std::span</span></td>
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</tr>
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<tr class="t-par">
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<td>r</td>
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<td>-</td>
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<td>要用做流的新底层缓冲区的 <a href="cpp-ranges-borrowed_range.html"><code>borrowed_range</code></a></td>
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</tr>
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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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<div class="t-li1"><span class="t-li">1)</span> 引用底层缓冲区或已写入区域的 <span class="t-lc">std::span</span> ，取决于包装的 <span class="t-lc">std::basic_spanbuf</span> 的打开模式。</div>
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<div class="t-li1"><span class="t-li">2-3)</span> （无）</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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<table class="metadata plainlinks ambox mbox-small-left ambox-notice" style="">
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<td class="mbox-empty-cell"></td>
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<td class="mbox-text" style="">本节未完成<br />
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原因：暂无示例</td>
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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-io-basic_spanbuf-span.html"><span class="t-lines"><span>span</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx23">(C++23)</span></span></span></div>
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</div>
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</td>
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<td>根据模式获得或初始化底层缓冲区<br />
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<span class="t-mark">(<code>std::basic_spanbuf<CharT,Traits></code> 的公开成员函数)</span></td>
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</div>
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</body>
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