149 lines
13 KiB
HTML
149 lines
13 KiB
HTML
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<title>std::mbsrtowcs</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_string_multibyte_mbsrtowcs 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>mbsrtowcs</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-cwchar.html"><cwchar></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> mbsrtowcs<span class="br0">(</span> <span class="kw4">wchar_t</span><span class="sy2">*</span> dst,<br /></span>
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<p> <span class="kw4">const</span> <span class="kw4">char</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>转换始于 <code>*ps</code> 所描述的转换状态，来自首元素为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>src</span></span> 所指向的数组的空终止多字节字符序列，到其宽字符表示。若 <code>dst</code> 非空，则存储转换后的字符于 <code>dst</code> 所指向的 wchar_t 数组的相继元素。不写入多于 <code>len</code> 个宽字符到目标数组。</p>
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<p>如同以调用 <span class="t-lc"><a href="cpp-string-multibyte-mbrtowc.html">std::mbrtowc</a></span> 转换每个多字节字符。若满足下列条件则转换终止：</p>
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<ul>
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<li>转换并存储了多字节空字符。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 <code>*ps</code> 表示初始迁移状态。</li>
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<li>遇到任何非法多字节字符（按照当前 C 本地环境）。设置 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>src</span></span> 指向首个未转换的多字节字符的起始。</li>
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<li>将存储的下个宽字符将超出 <code>len</code> 。设置 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>src</span></span> 指向首个未转换的多字节字符的起始。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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<td>dst</td>
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<td>-</td>
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<td>指向将存储结果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>指向空终止多字节字符串首元素的指针</td>
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<td>len</td>
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<td>-</td>
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<td>dst 所指向的字符数组中可用的宽字符数</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>成功时返回写入字符数组的宽字符数，排除终止的 <span class="t-c"><span class="mw-geshi cpp source-cpp">L<span class="st0">'<span class="es5">\0</span>'</span></span></span> 。若 <code>dst</code> 为空指针，则返回给定无限定长度则本会写入的宽字符数。</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> ，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=".E6.B3.A8.E8.A7.A3">注解</span></h3>
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<p>此函数移动 <code>src</code> 指针指向被转换的多字节字符串结尾。若 <code>dst</code> 为空指针则这不发生。</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="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 <cwchar></span>
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<span class="kw4">void</span> print_as_wide<span class="br0">(</span><span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> mbstr<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">mbsrtowcs</span><span class="br0">(</span><a href="cpp-types-NULL.html"><span class="kw103">NULL</span></a>, <span class="sy3">&</span>mbstr, <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">wchar_t</span><span class="sy1">></span> wstr<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">mbsrtowcs</span><span class="br0">(</span><span class="sy3">&</span>wstr<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span>, <span class="sy3">&</span>mbstr, wstr.<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="kw1758">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Wide string: "</span> <span class="sy1"><<</span> <span class="sy3">&</span>wstr<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">"The length, including '<span class="es1">\\</span>0': "</span> <span class="sy1"><<</span> wstr.<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="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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print_as_wide<span class="br0">(</span>mbstr<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 string: zß水🍌
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The length, including '\0': 5</pre></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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<td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-string-multibyte-mbrtowc.html"><span class="t-lines"><span>mbrtowc</span></span></a></div>
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</div>
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</td>
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<td>给定状态，转换下个多字节字符为宽字符<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-wcsrtombs.html"><span class="t-lines"><span>wcsrtombs</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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<td>
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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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