250 lines
21 KiB
HTML
250 lines
21 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>wcstombs, wcstombs_s</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_string_multibyte_wcstombs 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">wcstombs, wcstombs_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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<tr class="t-dsc-header">
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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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<tr class="t-dcl-rev-aux">
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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>
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<tr class="t-dcl t-until-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> wcstombs<span class="br0">(</span> <span class="kw4">char</span> <span class="sy2">*</span>dst, <span class="kw4">const</span> <span class="kw4">wchar_t</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 class="sy4">;</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> wcstombs<span class="br0">(</span> <span class="kw4">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> dst, <span class="kw4">const</span> <span class="kw4">wchar_t</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 class="sy4">;</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 wcstombs_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">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> dst, rsize_t dstsz,<br />
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<span class="kw4">const</span> <span class="kw4">wchar_t</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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</tr>
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</tbody>
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</table>
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<div class="t-li1"><span class="t-li">1)</span> 转换来自首元素为 <code>src</code> 所指向的数组到其始于初始迁移状态的多字节表示。转换出的字符被存储于 <code>dst</code> 所指向的数组的相继元素。写入目标数组的字节数不多于 <code>len</code> 。</div>
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<div class="t-li1"><span class="t-li"></span> 如同以调用 <span class="t-lc"><a href="c-string-multibyte-wctomb.html">wctomb</a></span> 每个字符，除了 wctomb 的转换状态不受影响。若满足下列条件则转换停止：</div>
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<div class="t-li1"><span class="t-li"></span> * 转换并存储空字符 <span class="t-c"><span class="mw-geshi c source-c">L<span class="st0">'<span class="es5">\0</span>'</span></span></span> 。此情况下存储的字节为无迁移序列（若需要）后随 <span class="t-c"><span class="mw-geshi c source-c"><span class="st0">'<span class="es5">\0</span>'</span></span></span> ，</div>
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<div class="t-li1"><span class="t-li"></span> * 找到当前 C 本地环境中不对应合法字符的 <span class="t-c"><span class="mw-geshi c source-c"><span class="kw4">wchar_t</span></span></span> 。</div>
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<div class="t-li1"><span class="t-li"></span> * 下个要存储的多字节字符会超出 <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，则行为未指定。</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-wcrtomb.html">wcrtomb</a></span> ，而非 <span class="t-lc"><a href="c-string-multibyte-wctomb.html">wctomb</a></span></div>
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<div class="t-li1"><span class="t-li"></span> * 函数将其结果作为输出参数 <code>retval</code> 返回</div>
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<div class="t-li1"><span class="t-li"></span> * 若转换停止而不写入控制符，则函数将在 <code>dst</code> 中的下个字符，可以是 <code>dst[len]</code> 或 <code>dst[dstsz]</code> 的先到来者，存储 <span class="t-c"><span class="mw-geshi c source-c"><span class="st0">'<span class="es5">\0</span>'</span></span></span> （表示可能写入总计至多 len+1/dsz+1 个字符）。该情况下，空终止前不写入无迁移序列。</div>
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<div class="t-li1"><span class="t-li"></span> * 若 <code>dst</code> 是空指针，则将本会产生的字节数存储于 <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> * 函数从空终止起到 <code>dstsz</code> 前为止破坏目标数组</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</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>len</code> 大于 <code>dstsz</code> 且直到抵达 <code>dstsz</code> 时，转换未于 <code>src</code> 数组遇到空字符或编码错误（除非 <code>dst</code> 为空）</li>
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</ul>
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</dd>
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<dd>同所有边界检查函数， <code>wcstombs_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>大多数实现中， <code>wcstombs</code> 在处理过字符串时更新 <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，而且不能为二个线程同时调用，这种情况下应使用 <span class="t-lc"><a href="c-string-multibyte-wcsrtombs.html">wcsrtombs</a></span> 或 <code>wcstombs_s</code> 。</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会写入 <code>dst</code> 的字节数。类似行为对于 <span class="t-lc"><a href="c-string-multibyte-wcsrtombs.html">wcsrtombs</a></span> 和 <code>wcstombs_s</code> 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>指向窄字符数组的指针，其中将存储多字节字符</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宽字符串首字符的指针</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 所指向数组中的可用字节数</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 size_t 对象的指针，其中将存储结果</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，返回写入首元素为 <code>dst</code> 所指向的字符数组的字节数（包含任何迁移序列，但不含终止的 <span class="t-c"><span class="mw-geshi c source-c"><span class="st0">'<span class="es5">\0</span>'</span></span></span> ）。转换错误时（若遇到非法宽字符），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> 成功时返回零（该情况下，将被或本应写入 <code>dst</code> 的字节数，排除终止零，存储于 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>retval</span></span> ），错误时返回非零。运行时制约违规的情况下，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"><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 <stdlib.h></span>
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<span class="co2">#include <locale.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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<span class="co1">// 4 wide characters</span>
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<span class="kw4">const</span> <span class="kw4">wchar_t</span> src<span class="br0">[</span><span class="br0">]</span> <span class="sy1">=</span> L<span class="st0">"z<span class="es3">\u00df</span><span class="es3">\u6c34</span><span class="es4">\U0001f34c</span>"</span><span class="sy4">;</span>
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<span class="co1">// 它们于 UTF-8 占用 10 个字节</span>
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<span class="kw4">char</span> dst<span class="br0">[</span><span class="nu0">11</span><span class="br0">]</span><span class="sy4">;</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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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"wide-character string: '%ls'<span class="es1">\n</span>"</span>,src<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span><a href="c-types-size_t.html"><span class="kw100">size_t</span></a> ndx<span class="sy1">=</span><span class="nu0">0</span><span class="sy4">;</span> ndx <span class="sy1"><</span> <span class="kw4">sizeof</span> src<span class="sy2">/</span><span class="kw4">sizeof</span> src<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span><span class="sy4">;</span> <span class="sy2">++</span>ndx<span class="br0">)</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">" src[%2zu] = %#8x<span class="es1">\n</span>"</span>, ndx, src<span class="br0">[</span>ndx<span class="br0">]</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">int</span> rtn_val <span class="sy1">=</span> wcstombs<span class="br0">(</span>dst, src, <span class="kw4">sizeof</span> dst<span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"rtn_val = %d<span class="es1">\n</span>"</span>, rtn_val<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span> <span class="br0">(</span>rtn_val <span class="sy1">></span> <span class="nu0">0</span><span class="br0">)</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"multibyte string: '%s'<span class="es1">\n</span>"</span>,dst<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">for</span> <span class="br0">(</span><a href="c-types-size_t.html"><span class="kw100">size_t</span></a> ndx<span class="sy1">=</span><span class="nu0">0</span><span class="sy4">;</span> ndx<span class="sy1"><</span><span class="kw4">sizeof</span> dst<span class="sy4">;</span> <span class="sy2">++</span>ndx<span class="br0">)</span>
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<a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">" dst[%2zu] = %#2x<span class="es1">\n</span>"</span>, ndx, <span class="br0">(</span><span class="kw4">unsigned</span> <span class="kw4">char</span><span class="br0">)</span>dst<span class="br0">[</span>ndx<span class="br0">]</span><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">wide-character string: 'zß水🍌'
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src[ 0] = 0x7a
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src[ 1] = 0xdf
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src[ 2] = 0x6c34
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src[ 3] = 0x1f34c
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src[ 4] = 0
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rtn_val = 10
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multibyte string: 'zß水🍌'
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dst[ 0] = 0x7a
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dst[ 1] = 0xc3
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dst[ 2] = 0x9f
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dst[ 3] = 0xe6
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dst[ 4] = 0xb0
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dst[ 5] = 0xb4
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dst[ 6] = 0xf0
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dst[ 7] = 0x9f
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dst[ 8] = 0x8d
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dst[ 9] = 0x8c
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dst[10] = 0</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>7.22.8.2 The wcstombs function (p: 360)</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.3.6.5.2 The wcstombs_s function (p: 612-614)</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>7.20.8.2 The wcstombs function (p: 324)</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>4.10.8.2 The wcstombs 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-wcsrtombs.html"><span class="t-lines"><span>wcsrtombs</span><span>wcsrtombs_s</span></span></a></div>
|
|
<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>
|
|
</div>
|
|
</td>
|
|
<td>给定状态，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>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="c-string-multibyte-mbstowcs.html"><span class="t-lines"><span>mbstowcs</span><span>mbstowcs_s</span></span></a></div>
|
|
<div><span class="t-lines"><span></span><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
|
|
</div>
|
|
</td>
|
|
<td>将窄多字节字符串转换成宽字符串<br />
|
|
<span class="t-mark">(函数)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
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</html>
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