1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Unicode Regular Expression Algorithms</title> 5<link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../../index.html" title="Boost.Regex 5.1.4"> 8<link rel="up" href="../icu.html" title="Working With Unicode and ICU String Types"> 9<link rel="prev" href="unicode_types.html" title="Unicode regular expression types"> 10<link rel="next" href="unicode_iter.html" title="Unicode Aware Regex Iterators"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="unicode_types.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../icu.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="unicode_iter.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 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 <boost/regex/icu.hpp> 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"><</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">></span></code>, 52 then <code class="computeroutput"><span class="special"><</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">></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">&</span> <span class="identifier">password</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">UnicodeString</span><span class="special">&</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">&</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"><</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">></span></code>, 98 then <code class="computeroutput"><span class="special"><</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">></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">&</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"><</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">></span></code>, then <code class="computeroutput"><span class="special"><</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">></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">&</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 © 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> 173</div></td> 174</tr></table> 175<hr> 176<div class="spirit-nav"> 177<a accesskey="p" href="unicode_types.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../icu.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="unicode_iter.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 178</div> 179</body> 180</html> 181
