90 lines
8.2 KiB
HTML
90 lines
8.2 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::ostrstream::str</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_ostrstream_str 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::ostrstream::</span>str</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-ostrstream.html">ostrstream</a></span></div>
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<div class="t-page-template" style="">
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<p></p>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw4">char</span><span class="sy2">*</span> str<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>冻结缓冲区后，返回指向其起始的指针。等效地调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">rdbuf<span class="br0">(</span><span class="br0">)</span><span class="sy2">-</span><span class="sy1">></span>str<span class="br0">(</span><span class="br0">)</span></span></span> 。</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>指向关联 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">strsteambuf</span></span></span> 中缓冲区起始的指针，或若无可用缓冲区则为空指针。</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>若要将结果用作 C 字符串，则调用 <span class="t-lc"><strong class="selflink">str()</strong></span> 前流缓冲区必须为空终止。常规输出，例如 <span class="t-c"><span class="mw-geshi cpp source-cpp">stream <span class="sy1"><<</span> <span class="nu16">1.2</span></span></span> 不存储空终止符，必须显式后附它，典型地用操纵符 <span class="t-lc"><a href="cpp-io-manip-ends.html">std::ends</a></span> 。</p>
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<p>调用 <span class="t-lc"><strong class="selflink">str()</strong></span> 后，动态流变为冻结。要求在退出创建此 <span class="t-c"><span class="mw-geshi cpp source-cpp">ostrstream</span></span> 对象于其中的作用域前调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">freeze<span class="br0">(</span><span class="kw2">false</span><span class="br0">)</span></span></span> 。否则析构函数将泄露内存。还有，一旦到被冻结流的附加输出抵达分配的缓冲区结尾，则它可能被截断，这可能令缓冲区为非空终止。</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="cpp source-cpp">
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<pre class="de1"><span class="co2">#include <strstream></span>
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<span class="co2">#include <iostream></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-ostrstream.html"><span class="kw1754">std::<span class="me2">ostrstream</span></span></a> dyn<span class="sy4">;</span> <span class="co1">// 动态分配的输出缓冲区</span>
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dyn <span class="sy1"><<</span> <span class="st0">"Test: "</span> <span class="sy1"><<</span> <span class="nu16">1.23</span><span class="sy4">;</span> <span class="co1">// 不添加 std::ends 以演示后附行为</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">"The output stream holds <span class="es1">\"</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="me1">write</span><span class="br0">(</span>dyn.<span class="me1">str</span><span class="br0">(</span><span class="br0">)</span>, dyn.<span class="me1">pcount</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\"</span><span class="es1">\n</span>"</span><span class="sy4">;</span>
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<span class="co1">// the stream is now frozen due to str()</span>
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dyn <span class="sy1"><<</span> <span class="st0">" More text"</span> <span class="sy1"><<</span> <a href="cpp-io-manip-ends.html"><span class="kw1789">std::<span class="me2">ends</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">"The output stream holds <span class="es1">\"</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="me1">write</span><span class="br0">(</span>dyn.<span class="me1">str</span><span class="br0">(</span><span class="br0">)</span>, dyn.<span class="me1">pcount</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">"<span class="es1">\"</span><span class="es1">\n</span>"</span><span class="sy4">;</span>
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dyn.<span class="me1">freeze</span><span class="br0">(</span><span class="kw2">false</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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<p>可能的输出：</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">The stream holds "Test: 1.23"
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The stream holds "Test: 1.23 More "</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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<table class="t-dsc-begin">
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<div class="t-dsc-member-div">
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<div><a href="cpp-io-strstreambuf-str.html"><span class="t-lines"><span>str</span></span></a></div>
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</td>
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<td>标记缓冲为冻结并返回输入序列的起始指针<br />
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<span class="t-mark">(<code>std::strstreambuf</code> 的公开成员函数)</span></td>
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<div class="visualClear"></div>
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