144 lines
15 KiB
HTML
144 lines
15 KiB
HTML
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<title>c16rtomb</title>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_string_multibyte_c16rtomb 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">c16rtomb</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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<td>
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<div>定义于头文件 <code><uchar.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-c11">
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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> c16rtomb<span class="br0">(</span> <span class="kw4">char</span> <span class="sy2">*</span> <span class="kw4">restrict</span> s, char16_t c16, <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>
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<td class="t-dcl-nopad"></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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<p>从变长 16 位宽字符表示（典型地为 UTF-16 ）转换单个编码点到其多字节窄字符表示。</p>
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<p>若 <code>s</code> 不是空指针且 <code>c16</code> 是合法的编码点变长编码中的最后一个 16 位编码单元，则函数确定存储该编码点所需的字节数（包含任何迁移序列，并考虑当前多字节转换状态 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>ps</span></span> ），并存储多字节表示于首元素为 <code>s</code> 所指向的字符数组，若必要则更新 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>ps</span></span> 。此函数最能写入 <span class="t-c"><span class="mw-geshi c source-c">MB_CUR_MAX</span></span> 个字节。</p>
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<p>若 <code>s</code> 是空指针，则调用等价于对于某内部缓冲区 <code>buf</code> 的 <span class="t-c"><span class="mw-geshi c source-c">c16rtomb<span class="br0">(</span>buf, u<span class="st0">'<span class="es5">\0</span>'</span>, ps<span class="br0">)</span></span></span> 。</p>
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<p>若 <code>c16</code> 是空宽字符 <span class="t-c"><span class="mw-geshi c source-c">u<span class="st0">'<span class="es5">\0</span>'</span></span></span> ，则存储空字节，前附恢复到初始迁移状态所需的任何迁移序列，并更新 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>ps</span></span> 以表示初始迁移状态。</p>
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<p>若 <code>c16</code> 不是宽字符的 16 位表示中最终编码单元，则不写入 <code>s</code> 所指向的数组，只更新 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>ps</span></span> 。</p>
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<p>若定义宏 <span class="t-c"><span class="mw-geshi c source-c">__STDC_UTF_16__</span></span> ，则此函数所用的 16 位编码是 UTF-16 ；否则，它是实现定义的。任何情况下，此函数所用的宽字符编码为当前活跃的 C 本地环境所指定。</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>s</td>
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<td>-</td>
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<td>指向将存储多字节字符的窄字符数组的指针</td>
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</tr>
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<tr class="t-par">
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<td>c16</td>
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<td>-</td>
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<td>要转换的 16 位宽字符</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所用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>s</code> 所指向的字符数组的字节数（包含任何迁移序列）。此值可以是 <span class="t-c"><span class="mw-geshi c source-c">​<span class="nu0">0</span>​</span></span> ，例如在处理多 <span class="t-c"><span class="mw-geshi c source-c">char16_t</span></span> 单元序列的前导 <span class="t-c"><span class="mw-geshi c source-c">char16_t</span></span> 单元时（在处理 UTF-16 代理对中的前导代理时出现）。</p>
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<p>失败时（若 <span class="t-c"><span class="mw-geshi c source-c">c16</span></span> 不是合法的 16 位编码单元），则返回 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">-</span><span class="nu0">1</span></span></span> ，并存储 <span class="t-lc"><a href="c-error-errno_macros.html">EILSEQ</a></span> 于 <span class="t-lc"><a href="c-error-errno.html">errno</a></span> ，把 <span class="t-c"><span class="mw-geshi c source-c"><span class="sy2">*</span>ps</span></span> 置于未指定状态。</p>
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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>在 C11 刚发布时，不同于转换变宽多字节（如 UTF-8 ）到变宽 16 位（如 UTF-16 ）编码的 <span class="t-lc"><a href="c-string-multibyte-mbrtoc16.html">mbrtoc16</a></span> ，此函数只能转换单个单元的 16 位编码，这表示尽管此函数的原目的如此，它仍不能转换 UTF-16 到 UTF-8 。这为 C11 后的缺陷报告 <a rel="nofollow" class="external text" href="http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2059.htm#dr_488">DR488</a> 所更正。</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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<p>注意：此示例假设应用缺陷报告 488 的修复</p>
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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 <locale.h></span>
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<span class="co2">#include <uchar.h></span>
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<span class="co2">#include <stdlib.h></span>
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<a href="c-string-multibyte-mbstate_t.html"><span class="kw591">mbstate_t</span></a> state<span class="sy4">;</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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<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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char16_t in<span class="br0">[</span><span class="br0">]</span> <span class="sy1">=</span> u<span class="st0">"zß水🍌"</span><span class="sy4">;</span> <span class="co1">// 或 "z\u00df\u6c34\U0001F34C"</span>
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<a href="c-types-size_t.html"><span class="kw100">size_t</span></a> in_sz <span class="sy1">=</span> <span class="kw4">sizeof</span> in <span class="sy2">/</span> <span class="kw4">sizeof</span> <span class="sy2">*</span>in<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">"Processing %zu UTF-16 code units: [ "</span>, in_sz<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> n <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span> n <span class="sy1"><</span> in_sz<span class="sy4">;</span> <span class="sy2">++</span>n<span class="br0">)</span> <a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"%#x "</span>, in<span class="br0">[</span>n<span class="br0">]</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-puts.html"><span class="kw835">puts</span></a><span class="br0">(</span><span class="st0">"]"</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">char</span> out<span class="br0">[</span>MB_CUR_MAX <span class="sy2">*</span> in_sz<span class="br0">]</span><span class="sy4">;</span>
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<span class="kw4">char</span> <span class="sy2">*</span>p <span class="sy1">=</span> out<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> n <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span> n <span class="sy1"><</span> in_sz<span class="sy4">;</span> <span class="sy2">++</span>n<span class="br0">)</span> <span class="br0">{</span>
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<a href="c-types-size_t.html"><span class="kw100">size_t</span></a> rc <span class="sy1">=</span> c16rtomb<span class="br0">(</span>p, in<span class="br0">[</span>n<span class="br0">]</span>, <span class="sy3">&</span>state<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">if</span><span class="br0">(</span>rc <span class="sy1">==</span> <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 class="br0">)</span> <span class="kw1">break</span><span class="sy4">;</span>
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p <span class="sy2">+</span><span class="sy1">=</span> rc<span class="sy4">;</span>
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<span class="br0">}</span>
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<a href="c-types-size_t.html"><span class="kw100">size_t</span></a> out_sz <span class="sy1">=</span> p <span class="sy2">-</span> out<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">"into %zu UTF-8 code units: [ "</span>, out_sz<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> x <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span> x <span class="sy1"><</span> out_sz<span class="sy4">;</span> <span class="sy2">++</span>x<span class="br0">)</span> <a href="c-io-fprintf.html"><span class="kw850">printf</span></a><span class="br0">(</span><span class="st0">"%#x "</span>, <span class="sy2">+</span><span class="br0">(</span><span class="kw4">unsigned</span> <span class="kw4">char</span><span class="br0">)</span>out<span class="br0">[</span>x<span class="br0">]</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-puts.html"><span class="kw835">puts</span></a><span class="br0">(</span><span class="st0">"]"</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">Processing 6 UTF-16 code units: [ 0x7a 0xdf 0x6c34 0xd83c 0xdf4c 0 ]
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into 11 UTF-8 code units: [ 0x7a 0xc3 0x9f 0xe6 0xb0 0xb4 0xf0 0x9f 0x8d 0x8c 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>7.28.1.2 The c16rtomb function (p: 399-400)</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-mbrtoc16.html"><span class="t-lines"><span>mbrtoc16</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>从窄多字节字符串生成下一个16位宽字符<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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</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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