97 lines
7.1 KiB
HTML
97 lines
7.1 KiB
HTML
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<title>std::basic_stringbuf<CharT,Traits,Allocator>::setbuf</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_basic_stringbuf_setbuf 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>setbuf</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_stringbuf.html">basic stringbuf</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">protected</span><span class="sy4">:</span><br />
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<span class="kw1">virtual</span> <a href="cpp-io-basic_streambuf.html"><span class="kw1666">std::<span class="me2">basic_streambuf</span></span></a><span class="sy1"><</span>CharT, Traits<span class="sy1">></span><span class="sy2">*</span> setbuf<span class="br0">(</span> char_type<span class="sy2">*</span> s, <a href="cpp-io-streamsize.html"><span class="kw1804">std::<span class="me2">streamsize</span></span></a> n <span class="br0">)</span></span></div>
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<p>若 <code>s</code> 为空指针且 <code>n</code> 为零，则此函数无效果。</p>
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<p>否则，效果是实现定义的：一些实现不做任何事，而一些实现清空当前用作缓冲区的 <span class="t-lc"><a href="cpp-string-basic_string.html">std::string</a></span> 成员，并开始以用户提供的大小为 <code>n</code> ，首元素为 <code>s</code> 所指向的字符数组，为输入/输出字符序列的缓冲区。</p>
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<p>此函数为受保护虚，仅可通过 <code>pubsetbuf()</code> 或导出自 <code>std::basic_stringbuf</code> 的用户定义类的成员函数调用它。</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>s</td>
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<td>-</td>
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<td>指向用户提供缓冲区首个 CharT 的指针或空指针</td>
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</tr>
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<tr class="t-par">
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<td>n</td>
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<td>-</td>
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<td>用户提供缓冲区中的 CharT 元素数或零</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><span class="t-c"><span class="mw-geshi cpp source-cpp">this</span></span> 。</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p>弃用的流缓冲 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-io-strstreambuf.html"><span class="kw1752">std::<span class="me2">strstreambuf</span></span></a></span></span> 或 boost.IOStreams 设备 <a rel="nofollow" class="external text" href="http://www.boost.org/doc/libs/release/libs/iostreams/doc/classes/array.html#array"><code>boost::basic_array</code></a> 可用于以可移植方式实现用户提供的字符数组上的 I/O 缓冲。</p>
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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-example">
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<p>测试 stringstream 的 setbuf 功能</p>
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <iostream></span>
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<span class="co2">#include <sstream></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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<a href="cpp-io-basic_ostringstream.html"><span class="kw1736">std::<span class="me2">ostringstream</span></span></a> ss<span class="sy4">;</span>
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<span class="kw4">char</span> c<span class="br0">[</span><span class="nu0">1024</span><span class="br0">]</span> <span class="sy1">=</span> <span class="br0">{</span><span class="br0">}</span><span class="sy4">;</span>
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ss.<span class="me1">rdbuf</span><span class="br0">(</span><span class="br0">)</span><span class="sy2">-</span><span class="sy1">></span>pubsetbuf<span class="br0">(</span>c, <span class="nu0">1024</span><span class="br0">)</span><span class="sy4">;</span>
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ss <span class="sy1"><<</span> <span class="nu16">3.14</span> <span class="sy1"><<</span> <span class="st0">'<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> c <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></pre></div>
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</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">3.14 （ GNU g++/libstdc++ 和 SunPro C++/roguewave 上）
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<无> （在 MS Visual Studio 2010 、 SunPro C++/stlport4 、 CLang++/libc++ 上）</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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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-basic_streambuf-pubsetbuf.html"><span class="t-lines"><span>pubsetbuf</span></span></a></div>
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</div>
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</td>
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<td>调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">setbuf<span class="br0">(</span><span class="br0">)</span></span></span><br />
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<span class="t-mark">(<code>std::basic_streambuf<CharT,Traits></code> 的公开成员函数)</span></td>
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