ceph/src/boost/libs/locale/doc/html/default_encoding_under_windows.html

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  65 <div class="title">Default Encoding under Microsoft Windows </div>  </div>
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  68 <div class="textblock"><p>All modern operating systems use Unicode.</p>
  69 <ul>
  70 <li>Unix operating system family use UTF-8 encoding by default.</li>
  71 <li>Microsoft Windows had migrated to Wide/UTF-16 API. The narrow encodings had been deprecated and the native OS API became so called "Wide API"</li>
  72 </ul>
  73 <p>As a result of radically different approaches, it is very hard to write portable Unicode aware applications.</p>
  74 <p>Boost Locale fully supports both narrow and wide API. The default character encoding is assumed to be UTF-8 on Windows.</p>
  75 <p>So if the default operating system Locale is "English_USA.1252" the default locale for Boost.Locale on Windows would be "en_US.UTF-8".</p>
  76 <p>When the created locale object is installed globally then any libraries that use <code>std::codecvt</code> for conversion between narrow API and the native wide API would handle UTF-8 correctly.</p>
  77 <p>A good example of such library is Boost.Filesystem v3.</p>
  78 <p>For example</p>
  79 <div class="fragment"><div class="line"><span class="preprocessor">#include &lt;boost/locale.hpp&gt;</span></div>
  80 <div class="line"><span class="preprocessor">#include &lt;boost/filesystem/path.hpp&gt;</span></div>
  81 <div class="line"><span class="preprocessor">#include &lt;boost/filesystem/fstream.hpp&gt;</span></div>
  82 <div class="line"></div>
  83 <div class="line"><span class="keywordtype">int</span> main()</div>
  84 <div class="line">{</div>
  85 <div class="line">    <span class="comment">// Create and install global locale</span></div>
  86 <div class="line">    std::locale::global(<a class="code" href="classboost_1_1locale_1_1generator.html">boost::locale::generator</a>().generate(<span class="stringliteral">&quot;&quot;</span>));</div>
  87 <div class="line">    <span class="comment">// Make boost.filesystem use it</span></div>
  88 <div class="line">    boost::filesystem::path::imbue(std::locale());</div>
  89 <div class="line">    <span class="comment">// Now Works perfectly fine with UTF-8!</span></div>
  90 <div class="line">    boost::filesystem::ofstream hello(<span class="stringliteral">&quot;שלום.txt&quot;</span>); </div>
  91 <div class="line">}</div>
  92 </div><!-- fragment --><p>However such behavior may break existing software that assumes that the current encoding is single byte encodings like code page 1252.</p>
  93 <p><a class="el" href="classboost_1_1locale_1_1generator.html">boost::locale::generator</a> class has a property <a class="el" href="classboost_1_1locale_1_1generator.html#a9afb2b0791abbabd39c800e08d9c9717">use_ansi_encoding()</a> that allows to change the behavior to legacy one and select an ANSI code page as default system encoding.</p>
  94 <p>So, when the current locale is "English_USA.1252" and the <code>use_ansi_encoding</code> is turned on then the default locale would be "en_US.windows-1252"</p>
  95 <dl class="section note"><dt>Note</dt><dd><code>winapi</code> backend does not support ANSI encodings, thus UTF-8 encoding is always used for narrow characters. </dd></dl>
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