108 lines
9.7 KiB
HTML
108 lines
9.7 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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<title>std::mbrtoc8</title>
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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_mbrtoc8 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>mbrtoc8</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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<table class="t-dcl-begin">
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<tbody>
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<div>定义于头文件 <code><a href="cpp-header-cuchar.html"><cuchar></a></code></div>
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</td>
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<td></td>
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<td></td>
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<tr class="t-dcl t-since-cxx20">
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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> mbrtoc8<span class="br0">(</span> char8_t<span class="sy2">*</span> pc8,<br /></span>
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<p> <span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> s,<br />
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<a href="cpp-types-size_t.html"><span class="kw100">std::<span class="me2">size_t</span></span></a> n,<br /></p>
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<a href="cpp-string-multibyte-mbstate_t.html"><span class="kw1179">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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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
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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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<p>转换窄多字节字符为 UTF-8 编码。</p>
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<p>若 <code>s</code> 不是空指针，则审视始于 <code>s</code> 所指向字符的多字节字符串的至多 <code>n</code> 个字节，以确定完成下个多字节字符所需的字节数（包含任何迁移序列）。若函数确定 <code>s</code> 中的下个多字节字符完整且合法，则将它转换成 UTF-8 并存储首个 UTF-8 编码单元于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>pc8</span></span> （若 <code>pc8</code> 非空）。</p>
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<p>若 <code>*s</code> 中的多字节字符的 UTF-8 编码由多于一个 UTF-8 编码单元组成，则在首次调用此函数后更新 <code>*ps</code> ，以使得下次调用 <code>mbrtoc8</code> 会写出另外的 UTF-8 编码单元，而不考虑 <code>*s</code> 。</p>
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<p>若 <code>s</code> 为空指针，则忽略 <code>n</code> 与 <code>pc8</code> 的值，而调用等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp">std<span class="sy4">::</span><span class="me2">mbrtoc8</span><span class="br0">(</span><a href="cpp-types-NULL.html"><span class="kw103">NULL</span></a>, <span class="st0">""</span>, <span class="nu0">1</span>, ps<span class="br0">)</span></span></span> 。</p>
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<p>若产生的 UTF-8 编码单元为 <span class="t-c"><span class="mw-geshi cpp source-cpp">u8<span class="st0">'<span class="es5">\0</span>'</span></span></span> ，则转换状态 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>ps</span></span> 代表初始迁移状态。</p>
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<p>此函数所用的多字节编码由当前活跃的 C 本地环境指定。</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>pc8</td>
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<td>-</td>
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<td>指向将写入生成的 UTF-8 编码单元的位置的指针</td>
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</tr>
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<tr class="t-par">
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<td>s</td>
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<td>-</td>
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<td>指向用作输入的多字节字符串的指针</td>
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</tr>
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<tr class="t-par">
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<td>n</td>
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<td>-</td>
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<td><code>s</code> 中能检验的字节数上的限制</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>指向转译多字节字符串时使用的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>下列的首个成立者：</p>
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<ul>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp">​<span class="nu0">0</span>​</span></span> ，若从 <code>s</code> 转换（而若 <span class="t-c"><span class="mw-geshi cpp source-cpp">pc8</span></span> 非空则存储于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>pc8</span></span> ）的字符是空字符。</li>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="br0">[</span><span class="nu0">1</span>...<span class="me1">n</span><span class="br0">]</span></span></span> ，从 <code>s</code> 成功转换的多字节字符的字节数。</li>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">-</span><span class="nu0">3</span></span></span> ，若现在已将来自由多个编码单元组成的字符的下个 UTF-8 编码单元写入 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>pc8</span></span> 。此情况下不处理来自输入的字节。</li>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">-</span><span class="nu0">2</span></span></span> ，若下 <code>n</code> 个字节组成不完整但到此仍合法的多字节字符。不写入任何内容到 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>pc8</span></span> 。</li>
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<li><span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">-</span><span class="nu0">1</span></span></span> ，若编码错误出现。不写入任何内容到 <code>*pc8</code> ，存储值 <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> ，而 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>ps</span></span> 的值未指定。</li>
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</ul>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<table class="metadata plainlinks ambox mbox-small-left ambox-notice" style="">
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<tr>
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<td class="mbox-empty-cell"></td>
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<td class="mbox-text" style="">本节未完成<br />
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原因：暂无示例</td>
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</table>
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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-c8rtomb.html"><span class="t-lines"><span>c8rtomb</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
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</div>
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</td>
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<td>转换 UTF-8 字符串为窄多字节编码<br />
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<span class="t-mark">(函数)</span></td>
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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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</body>
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