170 lines
12 KiB
HTML
170 lines
12 KiB
HTML
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<title>mbrlen</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_string_multibyte_mbrlen 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">mbrlen</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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<div>定义于头文件 <code><wchar.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 class="t-dcl t-since-c95 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> mbrlen<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span>s, <a href="c-types-size_t.html"><span class="kw100">size_t</span></a> n, <a href="c-string-multibyte-mbstate_t.html"><span class="kw591">mbstate_t</span></a> <span class="sy2">*</span>ps <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-c95">(C95 起)</span><br />
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<span class="t-mark-rev t-until-c99">(C99 前)</span></td>
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<tr class="t-dcl t-since-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> mbrlen<span class="br0">(</span> <span class="kw4">const</span> <span class="kw4">char</span> <span class="sy2">*</span><span class="kw4">restrict</span> s, <a href="c-types-size_t.html"><span class="kw100">size_t</span></a> n, <a href="c-string-multibyte-mbstate_t.html"><span class="kw591">mbstate_t</span></a> <span class="sy2">*</span><span class="kw4">restrict</span> ps <span class="br0">)</span><span class="sy4">;</span></span></div>
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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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<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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<p>给定当前转换状态 <code>ps</code> ，确定 <code>s</code> 所指向的剩余多字节字符的字节大小。</p>
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<p>此函数等价于对于某个隐藏的 <span class="t-lc"><a href="c-string-multibyte-mbstate_t.html">mbstate_t</a></span> 类型对象 <code>internal</code> 调用 <span class="t-c"><span class="mw-geshi c source-c"><a href="c-string-multibyte-mbrtowc.html"><span class="kw583">mbrtowc</span></a><span class="br0">(</span><a href="c-types-NULL.html"><span class="kw103">NULL</span></a>, s, n, ps<span class="sy4">?</span>ps<span class="sy4">:</span><span class="sy3">&</span>internal<span class="br0">)</span></span></span> ，除了只求值 <code>ps</code> 一次。</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>s</td>
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<td>-</td>
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<td>指向多字节字符串首元素的指针</td>
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</tr>
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<tr class="t-par">
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<td>n</td>
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<td>-</td>
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<td>s 中能检验的字节数限制</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>指向保有转换状态的对象的指针</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>应用下个首个可用者：</p>
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<ul>
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<li><span class="t-c"><span class="mw-geshi c source-c">​<span class="nu0">0</span>​</span></span> ，若接下来 <code>n</code> 个或更少字节组成空字符，或 <code>s</code> 为空指针。两种情况下都重置转换状态。</li>
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<li>字节数 <span class="t-c"><span class="mw-geshi c source-c"><span class="br0">[</span><span class="nu0">1</span>...<span class="me1">n</span><span class="br0">]</span></span></span> ，这些字节组成合法的多字节字符。</li>
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<li><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">2</span></span></span> ，若接下来 <code>n</code> 个字节是可能合法的多字节字符的一部分，但在检验所有 <code>n</code> 个字节后仍不完整</li>
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<li><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> ，若出现编码错误。设置 <span class="t-lc"><a href="c-error-errno.html">errno</a></span> 的值为 <code>EILSEQ</code> ；转换状态未指定。</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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<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 <locale.h></span>
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<span class="co2">#include <string.h></span>
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<span class="co2">#include <stdio.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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<span class="co1">// 允许 mbrlen() 以 UTF-8 多字节编码工作</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="co1">// UTF-8 窄多字节编码</span>
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<span class="kw4">const</span> <span class="kw4">char</span><span class="sy2">*</span> str <span class="sy1">=</span> u8<span class="st0">"水"</span><span class="sy4">;</span>
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<a href="c-types-size_t.html"><span class="kw100">size_t</span></a> sz <span class="sy1">=</span> <a href="c-string-byte-strlen.html"><span class="kw558">strlen</span></a><span class="br0">(</span>str<span class="br0">)</span><span class="sy4">;</span>
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<a href="c-string-multibyte-mbstate_t.html"><span class="kw591">mbstate_t</span></a> mb<span class="sy4">;</span>
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<a href="c-string-byte-memset.html"><span class="kw571">memset</span></a><span class="br0">(</span><span class="sy3">&</span>mb, <span class="nu0">0</span>, <span class="kw4">sizeof</span> mb<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">int</span> len1 <span class="sy1">=</span> mbrlen<span class="br0">(</span>str, <span class="nu0">1</span>, <span class="sy3">&</span>mb<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span><span class="br0">(</span>len1 <span class="sy1">==</span> <span class="sy2">-</span><span class="nu0">2</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">"The first 1 byte of %s is an incomplete multibyte char"</span>
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<span class="st0">" (mbrlen returns -2)<span class="es1">\n</span>"</span>, str<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">int</span> len2 <span class="sy1">=</span> mbrlen<span class="br0">(</span>str<span class="sy2">+</span><span class="nu0">1</span>, sz<span class="sy2">-</span><span class="nu0">1</span>, <span class="sy3">&</span>mb<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">"The remaining %zu bytes of %s hold %d bytes of the multibyte"</span>
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<span class="st0">" character<span class="es1">\n</span>"</span>, sz<span class="sy2">-</span><span class="nu0">1</span>, str, len2<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">"Attempting to call mbrlen() in the middle of %s while in initial"</span>
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<span class="st0">" shift state returns %zd<span class="es1">\n</span>"</span>, str, mbrlen<span class="br0">(</span>str<span class="sy2">+</span><span class="nu0">1</span>, sz<span class="sy2">-</span><span class="nu0">1</span>, <span class="sy3">&</span>mb<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">The first 1 byte of 水 is an incomplete multibyte char (mbrlen returns -2)
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The remaining 2 bytes of 水 hold 2 bytes of the multibyte character
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Attempting to call mbrlen() in the middle of 水 while in initial shift state returns -1</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>7.29.6.3.1 The mbrlen function (p: 442)</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>7.24.6.3.1 The mbrlen function (p: 388)</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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<div class="t-dsc-member-div">
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<div><a href="c-string-multibyte-mbrtowc.html"><span class="t-lines"><span>mbrtowc</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></div>
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</div>
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</td>
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<td>给定状态，将下一个多字节字符转换成宽字符<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="c-string-multibyte-mblen.html"><span class="t-lines"><span>mblen</span></span></a></div>
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</div>
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</td>
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<td>返回下一个多字节字符的字节数<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 class="visualClear"></div>
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</div>
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</body>
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