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web/cppreference-zh/chmhelp/cpp-string-multibyte-wcsrtombs.html
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web/cppreference-zh/chmhelp/cpp-string-multibyte-wcsrtombs.html
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<!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>std::wcsrtombs</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-cpp_string_multibyte_wcsrtombs 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"><span style="font-size:0.7em; line-height:130%">std::</span>wcsrtombs</h1>
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<div id="bodyContent">
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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 id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<td>
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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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<td></td>
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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> wcsrtombs<span class="br0">(</span> <span class="kw4">char</span><span class="sy2">*</span> dst,<br /></span>
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<p> <span class="kw4">const</span> <span class="kw4">wchar_t</span><span class="sy2">**</span> src,<br />
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<a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> len,<br /></p>
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<a href="cpp-string-multibyte-mbstate_t.html"><span class="kw1178">std::<span class="me2">mbstate_t</span></span></a><span class="sy2">*</span> ps <span class="br0">)</span><span class="sy4">;</span></div>
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<p>转换来自元素为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>src</span></span> 所指向的宽字符序列为其窄多字节表示，始于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>ps</span></span> 所描述的转换状态。若 <code>dst</code> 非空，则存储转换后的字符于 <code>dst</code> 所指向的字符数组的相接元素。不写入多于 <code>len</code> 个字节到目标数组。</p>
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<p>如同以调用 <span class="t-lc"><a href="cpp-string-multibyte-wcrtomb.html">std::wcrtomb</a></span> 转换每个字符。若遇到下列条件则停止转换：</p>
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<ul>
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<li>转换并存储了空字符 <span class="t-c"><span class="mw-geshi cpp source-cpp">L<span class="st0">'<span class="es5">\0</span>'</span></span></span> 。此情况下存储的字节是反迁移序列（若需要）后随 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">'<span class="es5">\0</span>'</span></span></span> ，设置 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>src</span></span> 为空指针并令 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>ps</span></span> 表示初始迁移状态。</li>
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<li>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 cpp source-cpp"><span class="kw4">wchar_t</span></span></span> 。设置 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>src</span></span> 指向首个未转换的宽字符。</li>
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<li>下个多字节字符将超出 <code>len</code> 。设置 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>src</span></span> 指向首个未转换的宽字符。若 <code>dst</code> 为空指针则不检查此条件。</li>
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</ul>
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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>指向指向空终止宽字符串首元素的指针的指针</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 所指向的数组中可用的字节数</td>
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</tr>
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<tr class="t-par">
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<td>ps</td>
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<td>-</td>
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<td>指向转换状态对象的指针</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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<p>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，但不包含终止 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="st0">'<span class="es5">\0</span>'</span></span></span> ）。若 <code>dst</code> 为空指针，则返回本会写入的字节数。</p>
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<p>转换错误时（若遇到非法宽字符），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> ，存储 <span class="t-lc"><a href="cpp-error-errno_macros.html">EILSEQ</a></span> 于 <span class="t-lc"><a href="cpp-error-errno.html">errno</a></span> ，并令 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>ps</span></span> 留在未指定状态。</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 <vector></span>
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<span class="co2">#include <clocale></span>
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<span class="co2">#include <string></span>
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<span class="co2">#include <cwchar></span>
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<span class="kw4">void</span> print_wide<span class="br0">(</span><span class="kw4">const</span> <span class="kw4">wchar_t</span><span class="sy2">*</span> wstr<span class="br0">)</span>
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<span class="br0">{</span>
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<a href="cpp-string-multibyte-mbstate_t.html"><span class="kw1178">std::<span class="me2">mbstate_t</span></span></a> state <span class="sy1">=</span> <a href="cpp-string-multibyte-mbstate_t.html"><span class="kw1178">std::<span class="me2">mbstate_t</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> len <span class="sy1">=</span> <span class="nu0">1</span> <span class="sy2">+</span> std<span class="sy4">::</span><span class="me2">wcsrtombs</span><span class="br0">(</span>nullptr, <span class="sy3">&</span>wstr, <span class="nu0">0</span>, <span class="sy3">&</span>state<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-container-vector.html"><span class="kw1268">std::<span class="me2">vector</span></span></a><span class="sy1"><</span><span class="kw4">char</span><span class="sy1">></span> mbstr<span class="br0">(</span>len<span class="br0">)</span><span class="sy4">;</span>
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std<span class="sy4">::</span><span class="me2">wcsrtombs</span><span class="br0">(</span><span class="sy3">&</span>mbstr<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span>, <span class="sy3">&</span>wstr, mbstr.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span>, <span class="sy3">&</span>state<span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1757">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"multibyte string: "</span> <span class="sy1"><<</span> <span class="sy3">&</span>mbstr<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span>
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<span class="sy1"><<</span> <span class="st0">"Length, including '<span class="es1">\\</span>0': "</span> <span class="sy1"><<</span> mbstr.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span> <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>
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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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<span class="co1">// UTF-8 窄多字节编码</span>
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<span class="kw4">const</span> <span class="kw4">wchar_t</span><span class="sy2">*</span> wstr <span class="sy1">=</span> L<span class="st0">"z<span class="es3">\u00df</span><span class="es3">\u6c34</span><span class="es4">\U0001d10b</span>"</span><span class="sy4">;</span> <span class="co1">// 或 L"zß水𝄋"</span>
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print_wide<span class="br0">(</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">multibyte string: zß水𝄋
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Length, including '\0': 11</pre></div>
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</div>
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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="cpp-string-multibyte-wcrtomb.html"><span class="t-lines"><span>wcrtomb</span></span></a></div>
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</div>
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</td>
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<td>给定状态，转换宽字符到其多字节表示<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="cpp-string-multibyte-mbsrtowcs.html"><span class="t-lines"><span>mbsrtowcs</span></span></a></div>
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</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>
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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="cpp-locale-codecvt-out.html"><span class="t-lines"><span>do_out</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 internT 转换字符串为 externT 转换字符串，如在写入文件时<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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</tr>
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</table>
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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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