83 lines
7.9 KiB
HTML
83 lines
7.9 KiB
HTML
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<title>std::basic_ios<CharT,Traits>::copyfmt</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_io_basic_ios_copyfmt 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_ios<CharT,Traits>::</span>copyfmt</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_ios.html">basic ios</a></span></div>
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<div><span class="mw-geshi cpp source-cpp">basic_ios<span class="sy3">&</span> copyfmt<span class="br0">(</span><span class="kw4">const</span> basic_ios<span class="sy3">&</span> other<span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>若 <span class="t-c"><span class="mw-geshi cpp source-cpp">other</span></span> 与 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 指代同一对象，则无效果。否则复制流 <code>other</code> 的状态到 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 中。以下列序列进行：</p>
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<div class="t-li1"><span class="t-li">1)</span> 传递 <a href="cpp-io-ios_base-event.html"><tt>erase_event</tt></a> 为参数，调用 <span class="t-lc"><a href="cpp-io-ios_base-register_callback.html">register_callback()</a></span> 所注册的每个回调。</div>
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<div class="t-li1"><span class="t-li">2)</span> 从 <code>other</code> 复制所有成员对象到 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> ，除了 <span class="t-lc"><a href="cpp-io-basic_ios-rdstate.html">rdstate()</a></span> 、异常掩码和 <span class="t-lc"><a href="cpp-io-basic_ios-rdbuf.html">rdbuf()</a></span> 。特别是复制本地环境、格式化标志、数组 <span class="t-lc"><a href="cpp-io-ios_base-iword.html">std::ios_base::iword</a></span> 和 <span class="t-lc"><a href="cpp-io-ios_base-pword.html">std::ios_base::pword</a></span> 的内容（但不是 <code>iword</code> 和 <code>pword</code> 指针本身）、回调和 tie 的流。</div>
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<div class="t-li1"><span class="t-li">3)</span> 传递 <a href="cpp-io-ios_base-event.html"><tt>copyfmt_event</tt></a>为参数，调用 <span class="t-lc"><a href="cpp-io-ios_base-register_callback.html">register_callback()</a></span> 所注册的每个回调。</div>
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<div class="t-li1"><span class="t-li">4)</span> 从 <code>other</code> 复制异常掩码到 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> ，如同通过调用 <span class="t-c"><span class="mw-geshi cpp source-cpp">exceptions<span class="br0">(</span>other.<span class="me1">exceptions</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span></span></span> 。</div>
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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>other</td>
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<td>-</td>
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<td>用作源的另一流</td>
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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"><span class="sy2">*</span>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>通过回调的第二趟可用于深复制 <span class="t-lc"><a href="cpp-io-ios_base-pword.html">std::ios_base::pword</a></span> 中的指针所指向的用户定义对象。</p>
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<p><code>copyfmt()</code> 可用于保存和恢复流状态。 Boost 为相同目的提供更加细粒度的 <a rel="nofollow" class="external text" href="http://www.boost.org/doc/libs/release/libs/io/doc/ios_state.html">IO state savers</a> 库。</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>令 ofstream 对象 "out" 表现准确地类似 std::cout ，包括格式化、 tie() 到 std::cin 等。</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 <fstream></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_ofstream.html"><span class="kw1733">std::<span class="me2">ofstream</span></span></a> out<span class="sy4">;</span>
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out.<span class="me1">copyfmt</span><span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 复制 rdstate 和 rdbuf 外的所有内容</span>
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out.<span class="me1">clear</span><span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>.<span class="me1">rdstate</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 复制 rdstate</span>
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out.<span class="me1">basic_ios</span><span class="sy1"><</span><span class="kw4">char</span><span class="sy1">></span><span class="sy4">::</span><span class="me2">rdbuf</span><span class="br0">(</span><a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>.<span class="me1">rdbuf</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 共享缓冲</span>
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out <span class="sy1"><<</span> <span class="st0">"Hello, world<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">Hello, world</pre></div>
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