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  26 <div class="titlepage"><div><div><h5 class="title">
  27 <a name="boost_regex.ref.non_std_strings.icu.unicode_algo"></a><a class="link" href="unicode_algo.html" title="Unicode Regular Expression Algorithms">Unicode
  28           Regular Expression Algorithms</a>
  29 </h5></div></div></div>
  30 <p>
  31             The regular expression algorithms <a class="link" href="../../regex_match.html" title="regex_match"><code class="computeroutput"><span class="identifier">regex_match</span></code></a>, <a class="link" href="../../regex_search.html" title="regex_search"><code class="computeroutput"><span class="identifier">regex_search</span></code></a> and <a class="link" href="../../regex_replace.html" title="regex_replace"><code class="computeroutput"><span class="identifier">regex_replace</span></code></a> all expect that
  32             the character sequence upon which they operate, is encoded in the same
  33             character encoding as the regular expression object with which they are
  34             used. For Unicode regular expressions that behavior is undesirable: while
  35             we may want to process the data in UTF-32 "chunks", the actual
  36             data is much more likely to encoded as either UTF-8 or UTF-16. Therefore
  37             the header &lt;boost/regex/icu.hpp&gt; provides a series of thin wrappers
  38             around these algorithms, called <code class="computeroutput"><span class="identifier">u32regex_match</span></code>,
  39             <code class="computeroutput"><span class="identifier">u32regex_search</span></code>, and
  40             <code class="computeroutput"><span class="identifier">u32regex_replace</span></code>. These
  41             wrappers use iterator-adapters internally to make external UTF-8 or UTF-16
  42             data look as though it's really a UTF-32 sequence, that can then be passed
  43             on to the "real" algorithm.
  44           </p>
  45 <h5>
  46 <a name="boost_regex.ref.non_std_strings.icu.unicode_algo.h0"></a>
  47             <span class="phrase"><a name="boost_regex.ref.non_std_strings.icu.unicode_algo.u32regex_match"></a></span><a class="link" href="unicode_algo.html#boost_regex.ref.non_std_strings.icu.unicode_algo.u32regex_match">u32regex_match</a>
  48           </h5>
  49 <p>
  50             For each <a class="link" href="../../regex_match.html" title="regex_match"><code class="computeroutput"><span class="identifier">regex_match</span></code></a>
  51             algorithm defined by <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">regex</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>,
  52             then <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">regex</span><span class="special">/</span><span class="identifier">icu</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code> defines an overloaded algorithm that
  53             takes the same arguments, but which is called <code class="computeroutput"><span class="identifier">u32regex_match</span></code>,
  54             and which will accept UTF-8, UTF-16 or UTF-32 encoded data, as well as
  55             an ICU UnicodeString as input.
  56           </p>
  57 <p>
  58             Example: match a password, encoded in a UTF-16 UnicodeString:
  59           </p>
  60 <pre class="programlisting"><span class="comment">//</span>
  61 <span class="comment">// Find out if *password* meets our password requirements,</span>
  62 <span class="comment">// as defined by the regular expression *requirements*.</span>
  63 <span class="comment">//</span>
  64 <span class="keyword">bool</span> <span class="identifier">is_valid_password</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UnicodeString</span><span class="special">&amp;</span> <span class="identifier">password</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">UnicodeString</span><span class="special">&amp;</span> <span class="identifier">requirements</span><span class="special">)</span>
  65 <span class="special">{</span>
  66    <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">u32regex_match</span><span class="special">(</span><span class="identifier">password</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">make_u32regex</span><span class="special">(</span><span class="identifier">requirements</span><span class="special">));</span>
  67 <span class="special">}</span>
  68 </pre>
  69 <p>
  70             Example: match a UTF-8 encoded filename:
  71           </p>
  72 <pre class="programlisting"><span class="comment">//</span>
  73 <span class="comment">// Extract filename part of a path from a UTF-8 encoded std::string and return the result</span>
  74 <span class="comment">// as another std::string:</span>
  75 <span class="comment">//</span>
  76 <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">get_filename</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">&amp;</span> <span class="identifier">path</span><span class="special">)</span>
  77 <span class="special">{</span>
  78    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">u32regex</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">make_u32regex</span><span class="special">(</span><span class="string">"(?:\\A|.*\\\\)([^\\\\]+)"</span><span class="special">);</span>
  79    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">smatch</span> <span class="identifier">what</span><span class="special">;</span>
  80    <span class="keyword">if</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">u32regex_match</span><span class="special">(</span><span class="identifier">path</span><span class="special">,</span> <span class="identifier">what</span><span class="special">,</span> <span class="identifier">r</span><span class="special">))</span>
  81    <span class="special">{</span>
  82       <span class="comment">// extract $1 as a std::string:</span>
  83       <span class="keyword">return</span> <span class="identifier">what</span><span class="special">.</span><span class="identifier">str</span><span class="special">(</span><span class="number">1</span><span class="special">);</span>
  84    <span class="special">}</span>
  85    <span class="keyword">else</span>
  86    <span class="special">{</span>
  87       <span class="keyword">throw</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">runtime_error</span><span class="special">(</span><span class="string">"Invalid pathname"</span><span class="special">);</span>
  88    <span class="special">}</span>
  89 <span class="special">}</span>
  90 </pre>
  91 <h5>
  92 <a name="boost_regex.ref.non_std_strings.icu.unicode_algo.h1"></a>
  93             <span class="phrase"><a name="boost_regex.ref.non_std_strings.icu.unicode_algo.u32regex_search"></a></span><a class="link" href="unicode_algo.html#boost_regex.ref.non_std_strings.icu.unicode_algo.u32regex_search">u32regex_search</a>
  94           </h5>
  95 <p>
  96             For each <a class="link" href="../../regex_search.html" title="regex_search"><code class="computeroutput"><span class="identifier">regex_search</span></code></a>
  97             algorithm defined by <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">regex</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>,
  98             then <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">regex</span><span class="special">/</span><span class="identifier">icu</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code> defines an overloaded algorithm that
  99             takes the same arguments, but which is called <code class="computeroutput"><span class="identifier">u32regex_search</span></code>,
 100             and which will accept UTF-8, UTF-16 or UTF-32 encoded data, as well as
 101             an ICU UnicodeString as input.
 102           </p>
 103 <p>
 104             Example: search for a character sequence in a specific language block:
 105           </p>
 106 <pre class="programlisting"><span class="identifier">UnicodeString</span> <span class="identifier">extract_greek</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UnicodeString</span><span class="special">&amp;</span> <span class="identifier">text</span><span class="special">)</span>
 107 <span class="special">{</span>
 108    <span class="comment">// searches through some UTF-16 encoded text for a block encoded in Greek,</span>
 109    <span class="comment">// this expression is imperfect, but the best we can do for now - searching</span>
 110    <span class="comment">// for specific scripts is actually pretty hard to do right.</span>
 111    <span class="comment">//</span>
 112    <span class="comment">// Here we search for a character sequence that begins with a Greek letter,</span>
 113    <span class="comment">// and continues with characters that are either not-letters ( [^[:L*:]] )</span>
 114    <span class="comment">// or are characters in the Greek character block ( [\\x{370}-\\x{3FF}] ).</span>
 115    <span class="comment">//</span>
 116    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">u32regex</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">make_u32regex</span><span class="special">(</span>
 117          <span class="identifier">L</span><span class="string">"[\\x{370}-\\x{3FF}](?:[^[:L*:]]|[\\x{370}-\\x{3FF}])*"</span><span class="special">);</span>
 118    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">u16match</span> <span class="identifier">what</span><span class="special">;</span>
 119    <span class="keyword">if</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">u32regex_search</span><span class="special">(</span><span class="identifier">text</span><span class="special">,</span> <span class="identifier">what</span><span class="special">,</span> <span class="identifier">r</span><span class="special">))</span>
 120    <span class="special">{</span>
 121       <span class="comment">// extract $0 as a UnicodeString:</span>
 122       <span class="keyword">return</span> <span class="identifier">UnicodeString</span><span class="special">(</span><span class="identifier">what</span><span class="special">[</span><span class="number">0</span><span class="special">].</span><span class="identifier">first</span><span class="special">,</span> <span class="identifier">what</span><span class="special">.</span><span class="identifier">length</span><span class="special">(</span><span class="number">0</span><span class="special">));</span>
 123    <span class="special">}</span>
 124    <span class="keyword">else</span>
 125    <span class="special">{</span>
 126       <span class="keyword">throw</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">runtime_error</span><span class="special">(</span><span class="string">"No Greek found!"</span><span class="special">);</span>
 127    <span class="special">}</span>
 128 <span class="special">}</span>
 129 </pre>
 130 <h5>
 131 <a name="boost_regex.ref.non_std_strings.icu.unicode_algo.h2"></a>
 132             <span class="phrase"><a name="boost_regex.ref.non_std_strings.icu.unicode_algo.u32regex_replace"></a></span><a class="link" href="unicode_algo.html#boost_regex.ref.non_std_strings.icu.unicode_algo.u32regex_replace">u32regex_replace</a>
 133           </h5>
 134 <p>
 135             For each <a class="link" href="../../regex_replace.html" title="regex_replace"><code class="computeroutput"><span class="identifier">regex_replace</span></code></a> algorithm defined
 136             by <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">regex</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>, then <code class="computeroutput"><span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">regex</span><span class="special">/</span><span class="identifier">icu</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
 137             defines an overloaded algorithm that takes the same arguments, but which
 138             is called <code class="computeroutput"><span class="identifier">u32regex_replace</span></code>,
 139             and which will accept UTF-8, UTF-16 or UTF-32 encoded data, as well as
 140             an ICU UnicodeString as input. The input sequence and the format string
 141             specifier passed to the algorithm, can be encoded independently (for
 142             example one can be UTF-8, the other in UTF-16), but the result string
 143             / output iterator argument must use the same character encoding as the
 144             text being searched.
 145           </p>
 146 <p>
 147             Example: Credit card number reformatting:
 148           </p>
 149 <pre class="programlisting"><span class="comment">//</span>
 150 <span class="comment">// Take a credit card number as a string of digits, </span>
 151 <span class="comment">// and reformat it as a human readable string with "-"</span>
 152 <span class="comment">// separating each group of four digit;, </span>
 153 <span class="comment">// note that we're mixing a UTF-32 regex, with a UTF-16</span>
 154 <span class="comment">// string and a UTF-8 format specifier, and it still all </span>
 155 <span class="comment">// just works:</span>
 156 <span class="comment">//</span>
 157 <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">u32regex</span> <span class="identifier">e</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">make_u32regex</span><span class="special">(</span>
 158       <span class="string">"\\A(\\d{3,4})[- ]?(\\d{4})[- ]?(\\d{4})[- ]?(\\d{4})\\z"</span><span class="special">);</span>
 159 <span class="keyword">const</span> <span class="keyword">char</span><span class="special">*</span> <span class="identifier">human_format</span> <span class="special">=</span> <span class="string">"$1-$2-$3-$4"</span><span class="special">;</span>
 160
 161 <span class="identifier">UnicodeString</span> <span class="identifier">human_readable_card_number</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">UnicodeString</span><span class="special">&amp;</span> <span class="identifier">s</span><span class="special">)</span>
 162 <span class="special">{</span>
 163    <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">u32regex_replace</span><span class="special">(</span><span class="identifier">s</span><span class="special">,</span> <span class="identifier">e</span><span class="special">,</span> <span class="identifier">human_format</span><span class="special">);</span>
 164 <span class="special">}</span>
 165 </pre>
 166 </div>
 167 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 168 <td align="left"></td>
 169 <td align="right"><div class="copyright-footer">Copyright &#169; 1998-2013 John Maddock<p>
 170         Distributed under the Boost Software License, Version 1.0. (See accompanying
 171         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
 172       </p>
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