72 lines
8.8 KiB
HTML
72 lines
8.8 KiB
HTML
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<title>C++ 具名要求：有格式输入函数 (FormattedInputFunction)</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">C++ 具名要求：</span><span style="font-style:italic">有格式输入函数</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(FormattedInputFunction)</span></h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-named_req.html">named req</a></span></div>
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<h3><span class="mw-headline" id=".E8.A6.81.E6.B1.82">要求</span></h3>
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<p><strong class="selflink"><span style="font-style:italic">有格式输入函数</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(FormattedInputFunction)</span></strong> 是进行下列操作的流输入函数：</p>
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<ul>
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<li>构造一个具有自动存储期的 <a href="cpp-io-basic_istream-sentry.html"><tt>basic_istream::sentry</tt></a> 类型的对象，并将 <code>noskipws</code> 实参设为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span>，这导致进行下列操作</li>
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<li>若输入流上设置了 <a href="cpp-io-ios_base-iostate.html"><tt>eofbit</tt></a> 或 <a href="cpp-io-ios_base-iostate.html"><tt>badbit</tt></a>，则一同设置 <code>failbit</code>，且若此输入流的异常掩码中启用了 failbit 上的异常，则抛出 <a href="cpp-io-ios_base-failure.html"><tt>ios_base::failure</tt></a>。</li>
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<li>冲洗其所 tie() 的输出流，若适用</li>
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<li>若此输入流上设置了 <code>ios_base::skipws</code> 标志，则提取并舍弃来自输入流的字符，直至下列之一为真：</li>
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</ul>
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<li>输入流上的下个可用字符不是空白字符（以此输入流中当前浸染的本地环境的 <span class="t-lc"><a href="cpp-locale-ctype.html">std::ctype</a></span> 刻面进行测试）。不提取非空白字符。</li>
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<li>抵达流尾，该情况下设置 <code>failbit</code> 和 <code>eofbit</code>，而且若该流开启了这些位之一上的异常，则抛出 <a href="cpp-io-ios_base-failure.html"><tt>ios_base::failure</tt></a>。</li>
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</ul>
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</dd>
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</dl>
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</dd>
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</dl>
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<ul>
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<li>通过调用 <code>sentry::operator bool()</code> 检查 sentry 的状态，这等价于 <a href="cpp-io-basic_ios-good.html"><tt>basic_ios::good</tt></a>。</li>
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<li>若 sentry 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 或 sentry 的构造函数抛异常，则不发生输入。</li>
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<li>若 sentry 返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span>，则如同通过调用 <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>sbumpc<span class="br0">(</span><span class="br0">)</span></span></span> 或 <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>sgetc<span class="br0">(</span><span class="br0">)</span></span></span> 一样进行输入。</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>若抵达流尾（对 <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>sbumpc<span class="br0">(</span><span class="br0">)</span></span></span> 或 <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>sgetc<span class="br0">(</span><span class="br0">)</span></span></span> 的调用返回 <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>），则设置 <code>eofbit</code>。若此流的异常掩码中启用了 eofbit 上的异常，则抛出 <a href="cpp-io-ios_base-failure.html"><tt>ios_base::failure</tt></a>。</li>
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<li>若在输入期间抛出了异常，则在输入流中设置 <code>badbit</code>。若此流的异常掩码中启用了 badbit 上的异常，则重抛这个异常。</li>
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<li>若未抛出任何异常，则返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span>。</li>
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</ul>
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</dd>
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<li>任何事件中，无论是因异常终止还是返回，离开此函数前都会调用 sentry 的析构函数。</li>
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</ul>
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<h3><span class="mw-headline" id=".E6.A0.87.E5.87.86.E5.BA.93">标准库</span></h3>
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<p>下列标准库函数是<strong class="selflink"><span style="font-style:italic">有格式输入函数</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(FormattedInputFunction)</span></strong> 。</p>
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<ul>
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<li><a href="cpp-io-basic_istream-operator_gtgt.html"><tt>basic_istream::operator>><span class="t-dsc-small">(int, long, double, void*, bool)</span></tt></a></li>
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<li><a href="cpp-io-basic_istream-operator_gtgt2.html"><tt>operator>><span class="t-dsc-small">(std::basic_istream, char&)</span></tt></a></li>
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<li><a href="cpp-io-basic_istream-operator_gtgt2.html"><tt>operator>><span class="t-dsc-small">(std::basic_istream, char*)</span></tt></a></li>
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<li><a href="cpp-utility-bitset-operator_ltltgtgt2.html"><tt>operator>><span class="t-dsc-small">(std::basic_istream, std::bitset)</span></tt></a></li>
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<li><a href="cpp-string-basic_string-operator_ltltgtgt.html"><tt>operator>><span class="t-dsc-small">(std::basic_istream, std::string)</span></tt></a></li>
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<li><code>operator>></code>，在 <span class="t-lc"><a href="cpp-io-manip-get_money.html">std::get_money</a></span> 的返回值上调用时。</li>
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