131 lines
10 KiB
HTML
131 lines
10 KiB
HTML
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<title>std::mbstowcs</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_string_multibyte_mbstowcs 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>mbstowcs</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-multibyte.html">multibyte</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-cstdlib.html"><cstdlib></a></code></div>
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<td></td>
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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> mbstowcs<span class="br0">(</span> <span class="kw4">wchar_t</span><span class="sy2">*</span> dst, <span class="kw4">const</span> <span class="kw4">char</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> len<span class="br0">)</span><span class="sy4">;</span></span></div>
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<p>转换来自首元素为 <code>src</code> 所指向的数组的多字节字符串到其宽字符表示。被转换的字符存储于 <code>dst</code> 所指向数组的相继元素。写入目标数组的宽字符数不多于 <code>len</code> 。</p>
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<p>如同以调用 <span class="t-lc"><a href="cpp-string-multibyte-mbtowc.html">std::mbtowc</a></span> 转换每个字符，除了 mbtowc 转换状态不受影响。若满足下列条件则转换停止：</p>
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<div class="t-li1"><span class="t-li"></span> * 转换并存储了多字节空字符。</div>
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<div class="t-li1"><span class="t-li"></span> * 遇到（当前 C 本地环境中的）非法多字节字符。</div>
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<div class="t-li1"><span class="t-li"></span> * 本要存储的下个宽字符会超出 <code>len</code> 。</div>
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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>大多数实现中， 此函数在处理过字符串时更新 <span class="t-lc"><a href="cpp-string-multibyte-mbstate_t.html">std::mbstate_t</a></span> 类型的全局静态对象，而且不能为二个线程所同时调用，这种情况应该用 <span class="t-lc"><a href="cpp-string-multibyte-mbsrtowcs.html">std::mbsrtowcs</a></span> 。</p>
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<p>POSIX 指定一个常见扩展：若 <code>dst</code> 是空指针，则此函数返回假设转换则写入 <code>dst</code> 的宽字符数。类似行为对于 <span class="t-lc"><a href="cpp-string-multibyte-mbsrtowcs.html">std::mbsrtowcs</a></span> 是标准。</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>dst</td>
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<td>-</td>
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<td>指向将存储宽字符串的宽字符数组的指针</td>
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<td>src</td>
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<td>-</td>
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<td>指向要转换的空终止多字节字符串的首元素的指针</td>
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<td>len</td>
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<td>-</td>
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<td>dst 所指向的数组中的可用宽字符数</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>成功时，返回目标数组的宽字符数，不含终止符 <span class="t-c"><span class="mw-geshi cpp source-cpp">L<span class="st0">'<span class="es5">\0</span>'</span></span></span> 。</p>
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<p>转换错误时（若遇到非法多字节字符），返回 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">static_cast</span><span class="sy1"><</span><a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a><span class="sy1">></span><span class="br0">(</span><span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span></span></span> 。</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 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 <clocale></span>
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<span class="co2">#include <cstdlib></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">"en_US.utf8"</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="me1">imbue</span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1893">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="st0">"en_US.utf8"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> mbstr <span class="sy1">=</span> u8<span class="st0">"z<span class="es3">\u00df</span><span class="es3">\u6c34</span><span class="es4">\U0001f34c</span>"</span><span class="sy4">;</span> <span class="co1">// 或 u8"zß水🍌"</span>
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<span class="co1">// 或 "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9f\x8d\x8c";</span>
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<span class="kw4">wchar_t</span> wstr<span class="br0">[</span><span class="nu0">5</span><span class="br0">]</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">mbstowcs</span><span class="br0">(</span>wstr, mbstr, <span class="nu0">5</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">"wide string: "</span> <span class="sy1"><<</span> wstr <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 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">wide string: zß水🍌</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 class="t-dsc-member-div">
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<div><a href="cpp-string-multibyte-mbsrtowcs.html"><span class="t-lines"><span>mbsrtowcs</span></span></a></div>
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</td>
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<td>给定状态，转换窄多字节字符串到宽字符串<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-string-multibyte-wcstombs.html"><span class="t-lines"><span>wcstombs</span></span></a></div>
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</div>
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</td>
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<td>转换宽字符串为窄多字节字符串<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-codecvt-in.html"><span class="t-lines"><span>do_in</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>从 externT 转换字符串为 internT ，如在从文件读取时<br />
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<span class="t-mark">(<code>std::codecvt<InternT,ExternT,State></code> 的虚受保护成员函数)</span></td>
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