170 lines
16 KiB
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170 lines
16 KiB
HTML
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<title>std::codecvt<InternT,ExternT,State>::in, std::codecvt<InternT,ExternT,State>::do_in</title>
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<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::codecvt<InternT,ExternT,State>::</span>in, <span style="font-size:0.7em; line-height:130%">std::codecvt<InternT,ExternT,State>::</span>do_in</h1>
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<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-locale.html">locale</a>‎ | <a href="cpp-locale-codecvt.html">codecvt</a></span></div>
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<div>定义于头文件 <code><a href="cpp-header-locale.html"><locale></a></code></div>
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<td></td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">public</span><span class="sy4">:</span><br /></span>
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<p>result in<span class="br0">(</span> StateT<span class="sy3">&</span> state,<br />
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<span class="kw4">const</span> ExternT<span class="sy2">*</span> from,<br />
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<span class="kw4">const</span> ExternT<span class="sy2">*</span> from_end,<br />
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<span class="kw4">const</span> ExternT<span class="sy2">*</span><span class="sy3">&</span> from_next,<br />
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InternT<span class="sy2">*</span> to,<br />
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InternT<span class="sy2">*</span> to_end,<br /></p>
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InternT<span class="sy2">*</span><span class="sy3">&</span> to_next <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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<td>(1)</td>
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<div><span class="mw-geshi cpp source-cpp"><span class="kw1">protected</span><span class="sy4">:</span><br /></span>
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<p><span class="kw1">virtual</span> result do_in<span class="br0">(</span> StateT<span class="sy3">&</span> state,<br />
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<span class="kw4">const</span> ExternT<span class="sy2">*</span> from,<br />
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<span class="kw4">const</span> ExternT<span class="sy2">*</span> from_end,<br />
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<span class="kw4">const</span> ExternT<span class="sy2">*</span><span class="sy3">&</span> from_next,<br />
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InternT<span class="sy2">*</span> to,<br />
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InternT<span class="sy2">*</span> to_end,<br /></p>
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InternT<span class="sy2">*</span><span class="sy3">&</span> to_next <span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></div>
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<td>(2)</td>
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<td class="t-dcl-nopad"></td>
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<td></td>
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<div class="t-li1"><span class="t-li">1)</span> 公开成员函数，调用最终导出类的成员函数 <code>do_in</code> 。</div>
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<div class="t-li1"><span class="t-li">2)</span> 若此 <code>codecvt</code> 平面定义一个转换，则翻译来自源范围 <code>[from, from_end)</code> 的外部字符为内部字符，将结果置始于 <code>to</code> 的后继位置。不转换多于 <span class="t-c"><span class="mw-geshi cpp source-cpp">from_end <span class="sy2">-</span> from</span></span> 个外部字符，不写入多于 <span class="t-c"><span class="mw-geshi cpp source-cpp">to_end <span class="sy2">-</span> to</span></span> 个内部字符。令 <code>from_next</code> 和 <code>to_next</code> 指向最后成功转换元素的后一位置。</div>
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<p>若此 <code>codecvt</code> 平面不定义转换，则不转换字符。设置 <code>to_next</code> 等于 <code>to</code> ，不更改 <code>state</code> ，并返回 <span class="t-lc"><a href="cpp-locale-codecvt_base.html">std::codecvt_base::noconv</a></span> 。</p>
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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><span class="t-lc"><a href="cpp-locale-codecvt_base.html">std::codecvt_base::result</a></span> 类型值，按以下方式指示成功状况：</p>
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<table class="t-dsc-begin">
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<td><code>ok</code></td>
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<td>转换完成</td>
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<td><code>partial</code></td>
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<td>输出缓冲区的中空间不足，或源缓冲的未期待结尾</td>
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<td><code>error</code></td>
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<td>遇到无法转换的字符</td>
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<td><code>noconv</code></td>
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<td>此平面为非转换，不写入输出</td>
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<p>非转换特化 <span class="t-c"><span class="mw-geshi cpp source-cpp"><a href="cpp-locale-codecvt.html"><span class="kw1939">std::<span class="me2">codecvt</span></span></a><span class="sy1"><</span><span class="kw4">char</span>, <span class="kw4">char</span>, <a href="cpp-string-multibyte-mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="sy1">></span></span></span> 始终返回 <span class="t-lc"><a href="cpp-locale-codecvt_base.html">std::codecvt_base::noconv</a></span> 。</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>要求 <span class="t-c"><span class="mw-geshi cpp source-cpp">from <span class="sy1"><=</span> from_end <span class="sy3">&&</span> to <span class="sy1"><=</span> to_end</span></span> 且 <code>state</code> 要么表示初始迁移状态，要么以转换序列中前趋的字符获得。</p>
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<p><code>state</code> 上的效果是有意未指定的。标准平面中，它用于维护像是调用 <span class="t-lc"><a href="cpp-string-multibyte-mbsrtowcs.html">std::mbsrtowcs</a></span> 时的状态，从而被更新为反映最后被处理外部字符后的转换状态，但是用户定义平面可以自由地用它维护任何其他状态，例如计量遇到的特殊字符数。</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 <string></span>
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<span class="co2">#include <locale></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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std<span class="sy4">::</span><span class="me2">locale</span><span class="sy4">::</span><span class="me2">global</span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="st0">"en_US.utf8"</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">auto</span><span class="sy3">&</span> f <span class="sy1">=</span> <a href="cpp-locale-use_facet.html"><span class="kw1897">std::<span class="me2">use_facet</span></span></a><span class="sy1"><</span><a href="cpp-locale-codecvt.html"><span class="kw1939">std::<span class="me2">codecvt</span></span></a><span class="sy1"><</span><span class="kw4">wchar_t</span>, <span class="kw4">char</span>, <a href="cpp-string-multibyte-mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="sy1">>></span><span class="br0">(</span><a href="cpp-locale-locale.html"><span class="kw1894">std::<span class="me2">locale</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-string-basic_string.html"><span class="kw1230">std::<span class="me2">string</span></span></a> external <span class="sy1">=</span> u8<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 u8"zß水𝄋"</span>
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<span class="co1">// 或 "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9d\x84\x8b";</span>
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<span class="co1">// 注意 wstring_convert 能进行下列内容</span>
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<a href="cpp-string-multibyte-mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a> mb <span class="sy1">=</span> <a href="cpp-string-multibyte-mbstate_t.html"><span class="kw1179">std::<span class="me2">mbstate_t</span></span></a><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> <span class="co1">// 初始迁移状态</span>
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<a href="cpp-string-basic_string.html"><span class="kw1232">std::<span class="me2">wstring</span></span></a> internal<span class="br0">(</span>external.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span>, <span class="st0">'<span class="es5">\0</span>'</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> from_next<span class="sy4">;</span>
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<span class="kw4">wchar_t</span><span class="sy2">*</span> to_next<span class="sy4">;</span>
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f.<span class="me1">in</span><span class="br0">(</span>mb, <span class="sy3">&</span>external<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span>, <span class="sy3">&</span>external<span class="br0">[</span>external.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">]</span>, from_next,
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<span class="sy3">&</span>internal<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span>, <span class="sy3">&</span>internal<span class="br0">[</span>internal.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">]</span>, to_next<span class="br0">)</span><span class="sy4">;</span>
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<span class="co1">// 为简略跳过错误检查</span>
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internal.<span class="me1">resize</span><span class="br0">(</span>to_next <span class="sy2">-</span> <span class="sy3">&</span>internal<span class="br0">[</span><span class="nu0">0</span><span class="br0">]</span><span class="br0">)</span><span class="sy4">;</span>
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<a href="cpp-io-cout.html"><span class="kw1759">std::<span class="me2">wcout</span></span></a> <span class="sy1"><<</span> L<span class="st0">"The string in wide encoding: "</span> <span class="sy1"><<</span> internal <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></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 string in wide encoding: zß水𝄋</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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<div class="t-dsc-member-div">
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<div><a href="cpp-io-basic_filebuf-underflow.html"><span class="t-lines"><span>underflow</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>从关联文件读取<br />
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<span class="t-mark">(<code>std::basic_filebuf<CharT,Traits></code> 的虚受保护成员函数)</span></td>
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<div class="t-dsc-member-div">
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<div><a href="cpp-locale-wstring_convert-from_bytes.html"><span class="t-lines"><span>from_bytes</span></span></a></div>
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</div>
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</td>
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<td>转换字节字符串为宽字符串<br />
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<span class="t-mark">(<code>std::wstring_convert<Codecvt,Elem,Wide_alloc,Byte_alloc></code> 的公开成员函数)</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-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">(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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