144 lines
12 KiB
HTML
144 lines
12 KiB
HTML
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<title>std::wcsxfrm</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_string_wide_wcsxfrm 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::</span>wcsxfrm</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-string.html">string</a>‎ | <a href="cpp-string-wide.html">wide</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-cwchar.html"><cwchar></a></code></div>
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<div><span class="mw-geshi cpp source-cpp"><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> wcsxfrm<span class="br0">(</span> <span class="kw4">wchar_t</span><span class="sy2">*</span> dest, <span class="kw4">const</span> <span class="kw4">wchar_t</span><span class="sy2">*</span> src, <a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> count <span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>变换 <code>src</code> 所指向的空终止宽字符串为实现定义形式，满足在当前 C 本地环境中，用 <span class="t-lc"><a href="cpp-string-wide-wcscmp.html">std::wcscmp</a></span> 比较二个变换后的字符串给出的结果与用 <span class="t-lc"><a href="cpp-string-wide-wcscoll.html">std::wcscoll</a></span> 比较源字符串者相同。</p>
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<p>将变换后字符串的首 <code>count</code> 个字符写入目标，包含空终止符，并返回完整的变换后字符串长度，排除空终止符。</p>
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<p>若 <code>count</code> 为 <span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> ，则允许 <code>dest</code> 为空指针。</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>能接收整个变换后字符串的正确缓冲区长度是 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="nu0">1</span><span class="sy2">+</span>std<span class="sy4">::</span><span class="me2">wcsxfrm</span><span class="br0">(</span><a href="cpp-types-NULL.html"><span class="kw103">NULL</span></a>, src, <span class="nu0">0</span><span class="br0">)</span></span></span> 。</p>
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<p>在以同一宽字符串或宽字符串集进行本地环境依赖比较时使用此函数，因为只用 <code>std::wcsxfrm</code> 变换所有字符串一次，再以 <span class="t-lc"><a href="cpp-string-wide-wcscmp.html">std::wcscmp</a></span> 进行后续比较更为高效。</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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<td>dest</td>
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<td>-</td>
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<td>指向要写入变换后字符串到的空终止宽字符数组首元素的指针</td>
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<td>src</td>
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<td>-</td>
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<td>指向要变换的空终止宽字符串的指针</td>
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<tr class="t-par">
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<td>count</td>
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<td>-</td>
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<td>要输出的最大字符数</td>
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</tr>
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</table>
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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>变换后的空终止宽字符串的长度，不包含空终止字符。</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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<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 <cwchar></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-locale-setlocale.html"><span class="kw1989">std::<span class="me2">setlocale</span></span></a><span class="br0">(</span><a href="cpp-locale-LC_categories.html"><span class="kw1992">LC_ALL</span></a>, <span class="st0">"sv_SE.utf8"</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-string-basic_string.html"><span class="kw1231">std::<span class="me2">wstring</span></span></a> in1 <span class="sy1">=</span> L<span class="st0">"<span class="es3">\u00e5</span>r"</span><span class="sy4">;</span>
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<a href="cpp-string-basic_string.html"><span class="kw1231">std::<span class="me2">wstring</span></span></a> out1<span class="br0">(</span><span class="nu0">1</span><span class="sy2">+</span>std<span class="sy4">::</span><span class="me2">wcsxfrm</span><span class="br0">(</span>nullptr, in1.<span class="me1">c_str</span><span class="br0">(</span><span class="br0">)</span>, <span class="nu0">0</span><span class="br0">)</span>, L<span class="st0">' '</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-string-basic_string.html"><span class="kw1231">std::<span class="me2">wstring</span></span></a> in2 <span class="sy1">=</span> L<span class="st0">"<span class="es3">\u00e4</span>ngel"</span><span class="sy4">;</span>
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<a href="cpp-string-basic_string.html"><span class="kw1231">std::<span class="me2">wstring</span></span></a> out2<span class="br0">(</span><span class="nu0">1</span><span class="sy2">+</span>std<span class="sy4">::</span><span class="me2">wcsxfrm</span><span class="br0">(</span>nullptr, in2.<span class="me1">c_str</span><span class="br0">(</span><span class="br0">)</span>, <span class="nu0">0</span><span class="br0">)</span>, L<span class="st0">' '</span><span class="br0">)</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">wcsxfrm</span><span class="br0">(</span><span class="sy3">&</span>out1<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span>, in1.<span class="me1">c_str</span><span class="br0">(</span><span class="br0">)</span>, out1.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">wcsxfrm</span><span class="br0">(</span><span class="sy3">&</span>out2<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span>, in2.<span class="me1">c_str</span><span class="br0">(</span><span class="br0">)</span>, out2.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</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">wcout</span></span></a> <span class="sy1"><<</span> <span class="st0">"In the Swedish locale: "</span><span class="sy4">;</span>
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<span class="kw1">if</span><span class="br0">(</span>out1 <span class="sy1"><</span> out2<span class="br0">)</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> in1 <span class="sy1"><<</span> <span class="st0">" before "</span> <span class="sy1"><<</span> in2 <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="kw1">else</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> in2 <span class="sy1"><<</span> <span class="st0">" before "</span> <span class="sy1"><<</span> in1 <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">wcout</span></span></a> <span class="sy1"><<</span> <span class="st0">"In lexicographical comparison: "</span><span class="sy4">;</span>
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<span class="kw1">if</span><span class="br0">(</span>in1 <span class="sy1"><</span> in2<span class="br0">)</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> in1 <span class="sy1"><<</span> <span class="st0">" before "</span> <span class="sy1"><<</span> in2 <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
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<span class="kw1">else</span>
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<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> in2 <span class="sy1"><<</span> <span class="st0">" before "</span> <span class="sy1"><<</span> in1 <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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</div>
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<p>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">In the Swedish locale: år before ängel
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In lexicographical comparison: ängel before år</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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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-byte-strxfrm.html"><span class="t-lines"><span>strxfrm</span></span></a></div>
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</div>
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</td>
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<td>变换字符串，使得 strcmp 会返回与 strcoll 相同的结果<br />
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<span class="t-mark">(函数)</span></td>
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<tr class="t-dsc">
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<div class="t-dsc-member-div">
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<div><a href="cpp-locale-collate-transform.html"><span class="t-lines"><span>do_transform</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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</div>
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</td>
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<td>变换字符串，使得能用比较替换对照<br />
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<span class="t-mark">(<code>std::collate<CharT></code> 的虚受保护成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-wide-wcscoll.html"><span class="t-lines"><span>wcscoll</span></span></a></div>
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</div>
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</td>
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<td>按照当前本地环境比较两个宽字符串<br />
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<span class="t-mark">(函数)</span></td>
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<div class="visualClear"></div>
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