75 lines
6.7 KiB
HTML
75 lines
6.7 KiB
HTML
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<title>std::basic_stringbuf<CharT,Traits,Allocator>::view</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_basic_stringbuf_view 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::basic_stringbuf<CharT,Traits,Allocator>::</span>view</h1>
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<div id="bodyContent">
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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_stringbuf.html">basic stringbuf</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><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span> view<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 class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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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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</table>
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<p>创建并返回底层字符序列上的 <span class="t-lc"><a href="cpp-string-basic_string_view.html">std::basic_string_view</a></span> 。</p>
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<ul>
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<li>对于仅输入流，返回视图表示范围 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">[</span>eback<span class="br0">(</span><span class="br0">)</span>, egptr<span class="br0">(</span><span class="br0">)</span><span class="br0">)</span></span></span> 。</li>
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<li>对于输入/输出或仅输出流，引用从 <span class="t-c"><span class="mw-geshi cpp source-cpp">pbase<span class="br0">(</span><span class="br0">)</span></span></span> 到序列中末字符的字符，不考虑 <span class="t-c"><span class="mw-geshi cpp source-cpp">egptr<span class="br0">(</span><span class="br0">)</span></span></span> 和 <span class="t-c"><span class="mw-geshi cpp source-cpp">epptr<span class="br0">(</span><span class="br0">)</span></span></span> 。</li>
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<li>若流既非输入亦非输出，则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span><span class="br0">{</span><span class="br0">}</span></span></span> 。</li>
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</ul>
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<p>为写入打开的缓冲区中的成员字符序列能为效率目的过分配。该情况下，仅引用<i>初始化的字符</i>：从构造函数 string 参数获得的字符、最近对 <code>str()</code> 的设置器重载的 string 参数的字符或来自写入操作的字符。典型的使用过分配的实现维护一个高水位指针，以跟踪缓冲区已初始化部分的结尾，而返回的视图引用从 <span class="t-c"><span class="mw-geshi cpp source-cpp">pbase<span class="br0">(</span><span class="br0">)</span></span></span> 到高水位指针的字符。</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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<p>（无）</p>
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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>底层字符序列上的视图。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p>若底层字符序列被销毁或被非法化，则使用返回值是未定义行为，除非返回值为空。</p>
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<p>常通过 <span class="t-lc">std::basic_istringstream::view()</span> 、 <span class="t-lc">std::basic_ostringstream::view()</span> 或 <span class="t-lc">std::basic_stringstream::view()</span> 访问此函数。</p>
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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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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-basic_stringbuf-str.html"><span class="t-lines"><span>str</span></span></a></div>
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</td>
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<td>替换或获得关联字符串的副本<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-basic_string-operator_basic_string_view.html"><span class="t-lines"><span>operator basic_string_view</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>返回到整个字符串的不可修改的 <code>basic_string_view</code><br />
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<span class="t-mark">(<code>std::basic_string<CharT,Traits,Allocator></code> 的公开成员函数)</span></td>
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</table>
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