97 lines
8.4 KiB
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97 lines
8.4 KiB
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<title>std::basic_streambuf<CharT,Traits>::sputn, std::basic_streambuf<CharT,Traits>::xsputn</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::basic_streambuf<CharT,Traits>::</span>sputn, <span style="font-size:0.7em; line-height:130%">std::basic_streambuf<CharT,Traits>::</span>xsputn</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_streambuf.html">basic streambuf</a></span></div>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-io-streamsize.html"><span class="kw1804">std::<span class="me2">streamsize</span></span></a> sputn<span class="br0">(</span> <span class="kw4">const</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> count <span class="br0">)</span><span class="sy4">;</span></span></div>
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<td>(1)</td>
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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-streamsize.html"><span class="kw1804">std::<span class="me2">streamsize</span></span></a> xsputn<span class="br0">(</span> <span class="kw4">const</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> count <span class="br0">)</span><span class="sy4">;</span></span></div>
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<div class="t-li1"><span class="t-li">1)</span> 调用最终导出类的 <code>xsputn(s, count)</code> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 从首元素为 <code>s</code> 所指向的数组写 <code>count</code> 个字符到输出序列。如同以重复调用 <span class="t-lc"><a href="cpp-io-basic_streambuf-sputc.html">sputc()</a></span> 写入字符。在写入 <code>count</code> 字符后或调用 <span class="t-lc"><a href="cpp-io-basic_streambuf-sputc.html">sputc()</a></span> 会返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">Traits<span class="sy4">::</span><span class="me2">eof</span><span class="br0">(</span><span class="br0">)</span></span></span> 时写入停止。</div>
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<p>若放置区变满（ <span class="t-c"><span class="mw-geshi cpp source-cpp">pptr<span class="br0">(</span><span class="br0">)</span> <span class="sy1">==</span> epptr<span class="br0">(</span><span class="br0">)</span></span></span> ），则此函数可调用 <span class="t-lc"><a href="cpp-io-basic_streambuf-overflow.html">overflow()</a></span> ，或以其他未指定手段达成调用 <code>overflow()</code> 的效果。</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>成功写入的字符数。</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>“以未指定手段达成 <code>overflow()</code> 的效果”容许无中间缓冲的大量 I/O ：这是一些 iostream 的实现中， <span class="t-lc"><a href="cpp-io-basic_ostream-write.html">std::ofstream::write</a></span> 简单地传递指针给适合的系统调用的缘由。</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 <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> s1<span class="sy4">;</span>
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<a href="cpp-io-streamsize.html"><span class="kw1804">std::<span class="me2">streamsize</span></span></a> sz <span class="sy1">=</span> s1.<span class="me1">rdbuf</span><span class="br0">(</span><span class="br0">)</span><span class="sy2">-</span><span class="sy1">></span>sputn<span class="br0">(</span><span class="st0">"This is a test"</span>, <span class="nu0">14</span><span class="br0">)</span><span class="sy4">;</span>
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s1 <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> <span class="st0">"The call to sputn() returned "</span> <span class="sy1"><<</span> sz <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"The output sequence contains "</span> <span class="sy1"><<</span> s1.<span class="me1">str</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-basic_istringstream.html"><span class="kw1735">std::<span class="me2">istringstream</span></span></a> s2<span class="sy4">;</span>
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sz <span class="sy1">=</span> s2.<span class="me1">rdbuf</span><span class="br0">(</span><span class="br0">)</span><span class="sy2">-</span><span class="sy1">></span>sputn<span class="br0">(</span><span class="st0">"This is a test"</span>, <span class="nu0">14</span><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> <span class="sy1"><<</span> <span class="st0">"The call to sputn() on an input stream returned "</span> <span class="sy1"><<</span> sz <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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<p>输出：</p>
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<div class="text source-text">
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<pre class="de1">The call to sputn() returned 14
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The output sequence contains This is a test
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The call to sputn() on an input stream returned 0</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><a href="cpp-io-basic_streambuf-sgetn.html"><span class="t-lines"><span>sgetn</span></span></a></div>
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<td>调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">xsgetn<span class="br0">(</span><span class="br0">)</span></span></span><br />
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<span class="t-mark">(公开成员函数)</span></td>
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