78 lines
5.6 KiB
HTML
78 lines
5.6 KiB
HTML
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<title>std::basic_streambuf<CharT,Traits>::showmanyc</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_basic_streambuf_showmanyc 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_streambuf<CharT,Traits>::</span>showmanyc</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"><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> showmanyc<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>估计关联字符序列中可用于输入的字符数。保证直至释出那么多字符时， <span class="t-lc"><a href="cpp-io-basic_streambuf-underflow.html">underflow()</a></span> 不返回 <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> 或抛出异常。</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>关联字符序列中确定可用的字符数，或若 <code>showmanyc</code> 能确定不阻塞则无字符可用则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">-</span><span class="nu0">1</span></span></span> 。若 <code>showmanyc</code> 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">-</span><span class="nu0">1</span></span></span> ，则 <span class="t-lc"><a href="cpp-io-basic_streambuf-underflow.html">underflow()</a></span> 和 <span class="t-lc"><a href="cpp-io-basic_streambuf-uflow.html">uflow()</a></span> 肯定会返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">Traits<span class="sy4">::</span><span class="me2">eof</span></span></span> 或抛出。</p>
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<p>基类版本返回 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> ，这表示“不缺地你给关联序列中是否有字符可用”。</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>此函数的名称表示“流：多少字符？”，故它读作“ S how many C ”，而不是“ show many C ”。</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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<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><a href="cpp-io-basic_streambuf-in_avail.html"><span class="t-lines"><span>in_avail</span></span></a></div>
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<td>获得获取区中立即可用的字符数<br />
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<span class="t-mark">(公开成员函数)</span></td>
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<div><a href="cpp-io-basic_filebuf-showmanyc.html"><span class="t-lines"><span>showmanyc</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-cmark">[虚]</span></span></span></div>
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<td>可选地提供可用于从文件输入的字符数<br />
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<span class="t-mark">(<code>std::basic_filebuf<CharT,Traits></code> 的虚受保护成员函数)</span></td>
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