225 lines
17 KiB
HTML
225 lines
17 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>mbstowcs, mbstowcs_s</title>
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<link rel="stylesheet" href="ext.css" />
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<link rel="stylesheet" href="site_modules.css" />
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_string_multibyte_mbstowcs skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading">mbstowcs, mbstowcs_s</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-string.html">string</a>‎ | <a href="c-string-multibyte.html">multibyte</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<table class="t-dcl-begin">
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<td>
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<div>定义于头文件 <code><stdlib.h></code></div>
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</td>
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<td></td>
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<td></td>
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</tr>
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</tbody>
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<tbody class="t-dcl-rev t-dcl-rev-num">
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<td></td>
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<td rowspan="142">(1)</td>
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<td></td>
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<tr class="t-dcl t-until-c99">
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<div><span class="mw-geshi c source-c"><a href="c-types-size_t.html"><span class="kw100">size_t</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="c-types-size_t.html"><span class="kw100">size_t</span></a> len<span class="br0">)</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-until-c99">(C99 前)</span></td>
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</tr>
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<tr class="t-dcl t-since-c99">
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<td>
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<div><span class="mw-geshi c source-c"><a href="c-types-size_t.html"><span class="kw100">size_t</span></a> mbstowcs<span class="br0">(</span> <span class="kw4">wchar_t</span> <span class="sy2">*</span><span class="kw4">restrict</span> dst, <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> src, <a href="c-types-size_t.html"><span class="kw100">size_t</span></a> len<span class="br0">)</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-c99">(C99 起)</span></td>
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</tr>
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</tbody>
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<tbody>
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<tr class="t-dcl t-since-c11">
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<td>
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<div><span class="mw-geshi c source-c">errno_t mbstowcs_s<span class="br0">(</span><a href="c-types-size_t.html"><span class="kw100">size_t</span></a> <span class="sy2">*</span><span class="kw4">restrict</span> retval, <span class="kw4">wchar_t</span> <span class="sy2">*</span><span class="kw4">restrict</span> dst,<br />
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rsize_t dstsz, <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> src, rsize_t len<span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td>(2)</td>
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<td><span class="t-mark-rev t-since-c11">(C11 起)</span></td>
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</tr>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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</table>
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<div class="t-li1"><span class="t-li">1)</span> 转换来自从首元素为 <code>src</code> 所指的数组的多字节字符串为其宽字符表示。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> 。</div>
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<div class="t-li1"><span class="t-li"></span> 如同以对 <span class="t-lc"><a href="c-string-multibyte-mbtowc.html">mbtowc</a></span> 的调用转换每个字符，除了 mbtowc 转换状态不受影响。若满足任一条件则转换停止：</div>
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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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<div class="t-li1"><span class="t-li"></span> 若 <code>src</code> 与 <code>dst</code> 重叠，则行为未定义</div>
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<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ，除了</div>
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<div class="t-li1"><span class="t-li"></span> * 转换如同以 <span class="t-lc"><a href="c-string-multibyte-mbrtowc.html">mbrtowc</a></span> ，而非 <span class="t-lc"><a href="c-string-multibyte-mbtowc.html">mbtowc</a></span></div>
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<div class="t-li1"><span class="t-li"></span> * 函数用输出参数 <code>retval</code> 返回结果</div>
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<div class="t-li1"><span class="t-li"></span> * 若在写入 <code>len</code> 个宽字符后未写入空字符到 <code>dst</code> ，则存储 <span class="t-c"><span class="mw-geshi c source-c">L<span class="st0">'<span class="es5">\0</span>'</span></span></span> 于 <code>dst[len]</code> ，这表示总计写入 len+1 个宽字符</div>
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<div class="t-li1"><span class="t-li"></span> * 若 <code>dst</code> 是空指针，则存储本会产生的宽字符数于 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>retval</span></span></div>
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<div class="t-li1"><span class="t-li"></span> * 函数从空终止到 <code>dstsz</code> 为止破坏目标数组</div>
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<div class="t-li1"><span class="t-li"></span> * 若 <code>src</code> 与 <code>dst</code> 重叠，则行为未指定。</div>
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<div class="t-li1"><span class="t-li"></span> * 在运行时检测下列错误，并调用当前安装的<a href="c-error-set_constraint_handler_s.html">制约处理</a>函数：
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<dl>
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<dd>
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<ul>
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<li><code>retval</code> 或 <code>src</code> 是空指针</li>
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<li><code>dstsz</code> 或 <code>len</code> 大于 <span class="t-lc">RSIZE_MAX/sizeof(wchar_t)</span> （除非 <code>dst</code> 为空）</li>
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<li><code>dstsz</code> 非零（除非 <code>dst</code> 为空）</li>
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<li><code>src</code> 数组中的首 <code>dstsz</code> 个多字节中无空字符且 <code>len</code> 大于 <code>dstsz</code> （除非 <code>dst</code> 为空）</li>
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</ul>
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</dd>
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<dd></dd>
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<dd>同所有边界检查函数， <code>mbstowcs_s</code> 仅若实现定义了 <span class="t-c"><span class="mw-geshi c source-c">__STDC_LIB_EXT1__</span></span> ，且用户在包含 <code>stdlib.h</code> 前定义 <span class="t-c"><span class="mw-geshi c source-c">__STDC_WANT_LIB_EXT1__</span></span> 为整数常量 <span class="t-c"><span class="mw-geshi c source-c"><span class="nu0">1</span></span></span> 才保证可用。</dd>
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</dl>
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</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>多数实现中， <code>mbstowcs</code> 更新 <span class="t-lc"><a href="c-string-multibyte-mbstate_t.html">mbstate_t</a></span> 类型的全局静态对象，因为它通过字符串处理，而且不能由二个线程同时调用， <span class="t-lc"><a href="c-string-multibyte-mbsrtowcs.html">mbsrtowcs</a></span> 应当用于这种情况。</p>
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<p>POSIX 指定一个常见扩展：若 <code>dst</code> 是空指针，则此函数返回假若转换则写入 <code>dst</code> 的宽字符数。同样的行为对于 <code>mbstowcs_s</code> 和 <span class="t-lc"><a href="c-string-multibyte-mbsrtowcs.html">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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<table class="t-par-begin">
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<tr class="t-par">
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<td>dst</td>
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<td>-</td>
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<td>指向要存储宽字符串的宽字符数组的指针</td>
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</tr>
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<tr class="t-par">
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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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</tr>
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<tr class="t-par">
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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节数</td>
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</tr>
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<tr class="t-par">
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<td>dstsz</td>
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<td>-</td>
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<td>将写入的最大宽字节数（ <code>dst</code> 数组的大小）</td>
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</tr>
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<tr class="t-par">
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<td>retval</td>
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<td>-</td>
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<td>指向将存储结果的 size_t 对象的指针</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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<div class="t-li1"><span class="t-li">1)</span> 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 c source-c">L<span class="st0">'<span class="es5">\0</span>'</span></span></span> 。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 c source-c"><span class="br0">(</span><a href="c-types-size_t.html"><span class="kw100">size_t</span></a><span class="br0">)</span><span class="sy2">-</span><span class="nu0">1</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 成功时为零（该情况下写入或本该写入到 <code>dst</code> 的不含终止零的宽字符存储于 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>retval</span></span> ），错误时为非零，在运行时制约违规的情况，存储 <span class="t-c"><span class="mw-geshi c source-c"><span class="br0">(</span><a href="c-types-size_t.html"><span class="kw100">size_t</span></a><span class="br0">)</span><span class="sy2">-</span><span class="nu0">1</span></span></span> 于 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>retval</span></span> （除非 <code>retval</code> 为空）并设置 <span class="t-c"><span class="mw-geshi c source-c">dst<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span></span></span> 为 <span class="t-c"><span class="mw-geshi c source-c">L<span class="st0">'<span class="es5">\0</span>'</span></span></span> （除非 <code>dst</code> 为空或 <code>dstmax</code> 为零或大于 <span class="t-lc">RSIZE_MAX</span> ）</div>
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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="c source-c">
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<pre class="de1"><span class="co2">#include <stdio.h></span>
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<span class="co2">#include <locale.h></span>
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<span class="co2">#include <stdlib.h></span>
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<span class="co2">#include <wchar.h></span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span>
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<span class="br0">{</span>
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<a href="c-locale-setlocale.html"><span class="kw900">setlocale</span></a><span class="br0">(</span><a href="c-locale-LC_categories.html"><span class="kw903">LC_ALL</span></a>, <span class="st0">"en_US.utf8"</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">// or u8"zß水🍌"</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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mbstowcs<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="c-io-fwprintf.html"><span class="kw864">wprintf</span></a><span class="br0">(</span>L<span class="st0">"MB string: %s<span class="es1">\n</span>"</span>, mbstr<span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-fwprintf.html"><span class="kw864">wprintf</span></a><span class="br0">(</span>L<span class="st0">"Wide string: %ls<span class="es1">\n</span>"</span>, wstr<span class="br0">)</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">MB string: zß水🍌
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Wide string: zß水🍌</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
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<div class="t-ref-std-11">
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<ul>
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<li>C11 标准（ISO/IEC 9899:2011）：</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>7.22.8.1 The mbstowcs function (p: 359)</li>
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</ul>
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</dd>
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</dl>
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<dl>
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<dd>
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<ul>
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<li>K.3.6.5.1 The mbstowcs_s function (p: 611-612)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c99">
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<ul>
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<li>C99 标准（ISO/IEC 9899:1999）：</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>7.20.8.1 The mbstowcs function (p: 323)</li>
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</ul>
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</dd>
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</dl>
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<div class="t-ref-std-c89">
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<ul>
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<li>C89/C90 标准（ISO/IEC 9899:1990）：</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>4.10.8.1 The mbstowcs function</li>
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</ul>
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</dd>
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</dl>
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</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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<table class="t-dsc-begin">
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-string-multibyte-mbsrtowcs.html"><span class="t-lines"><span>mbsrtowcs</span><span>mbsrtowcs_s</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c95">(C95)</span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>给定状态，将窄多字节字符串转换成宽字符串<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-string-multibyte-wcstombs.html"><span class="t-lines"><span>wcstombs</span><span>wcstombs_s</span></span></a></div>
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<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>将宽字符串转换成窄多字节字符串<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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</table>
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</div>
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</div>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</div>
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</body>
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</html>
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