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149 lines
8.4 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<html>
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<head>
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<title>Boost.Regex: Algorithm regex_split (deprecated)</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<link rel="stylesheet" type="text/css" href="../../../boost.css">
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</head>
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<body>
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<P>
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<TABLE id="Table1" cellSpacing="1" cellPadding="1" width="100%" border="0">
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<TR>
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<td valign="top" width="300">
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<h3><a href="../../../index.htm"><img height="86" width="277" alt="C++ Boost" src="../../../c++boost.gif" border="0"></a></h3>
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</td>
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<TD width="353">
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<H1 align="center">Boost.Regex</H1>
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<H2 align="center">Algorithm regex_split (deprecated)</H2>
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</TD>
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<td width="50">
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<h3><a href="index.html"><img height="45" width="43" alt="Boost.Regex Index" src="uarrow.gif" border="0"></a></h3>
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</td>
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</TR>
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</TABLE>
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</P>
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<HR>
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<p></p>
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<P>The algorithm regex_split has been deprecated in favor of the iterator <A href="regex_token_iterator.html">
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regex_token_iterator</A> which has a more flexible and powerful interface,
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as well as following the more usual standard library "pull" rather than "push"
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semantics.</P>
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<P>Code which uses regex_split will continue to compile, the following
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documentation is taken from the previous boost.regex version:</P>
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<H3><A name="regex_split"></A>Algorithm regex_split</H3>
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<PRE>#include <<A href="../../../boost/regex.hpp">boost/regex.hpp</A>> </PRE>
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<P>Algorithm regex_split performs a similar operation to the perl split operation,
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and comes in three overloaded forms:
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</P>
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<PRE><B>template</B> <<B>class</B> OutputIterator, <B>class</B> charT, <B>class</B> Traits1, <B>class</B> Alloc1, <B>class</B> Traits2, <B>class</B> Alloc2>
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std::size_t regex_split(OutputIterator out,
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std::basic_string<charT, Traits1, Alloc1>& s,
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<B> const</B> basic_regex<charT, Traits2, Alloc2>& e,
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<B> unsigned</B> flags,
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std::size_t max_split);
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<B>template</B> <<B>class</B> OutputIterator, <B>class</B> charT, <B>class</B> Traits1, <B>class</B> Alloc1, <B>class</B> Traits2, <B>class</B> Alloc2>
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std::size_t regex_split(OutputIterator out,
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std::basic_string<charT, Traits1, Alloc1>& s,
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<B> const</B> basic_regex<charT, Traits2, Alloc2>& e,
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<B>unsigned</B> flags = match_default);
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<B>template</B> <<B>class</B> OutputIterator, <B>class</B> charT, <B>class</B> Traits1, <B>class</B> Alloc1>
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std::size_t regex_split(OutputIterator out,
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std::basic_string<charT, Traits1, Alloc1>& s);</PRE>
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<P><STRONG>Effects: </STRONG>Each version of the algorithm takes an
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output-iterator for output, and a string for input. If the expression contains
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no marked sub-expressions, then the algorithm writes one string onto the
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output-iterator for each section of input that does not match the expression.
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If the expression does contain marked sub-expressions, then each time a match
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is found, one string for each marked sub-expression will be written to the
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output-iterator. No more than <I>max_split </I>strings will be written to the
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output-iterator. Before returning, all the input processed will be deleted from
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the string <I>s</I> (if <I>max_split </I>is not reached then all of <I>s</I> will
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be deleted). Returns the number of strings written to the output-iterator. If
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the parameter <I>max_split</I> is not specified then it defaults to UINT_MAX.
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If no expression is specified, then it defaults to "\s+", and splitting occurs
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on whitespace.
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</P>
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<P><STRONG>Throws:</STRONG> <CODE>std::runtime_error</CODE> if the complexity of
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matching the expression against an N character string begins to exceed O(N<SUP>2</SUP>),
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or if the program runs out of stack space while matching the expression (if
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Boost.regex is <A href="configuration.html">configured</A> in recursive mode),
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or if the matcher exhausts it's permitted memory allocation (if Boost.regex is <A href="configuration.html">
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configured</A> in non-recursive mode).</P>
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<P><A href="../example/snippets/regex_split_example_1.cpp">Example</A>: the
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following function will split the input string into a series of tokens, and
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remove each token from the string <I>s</I>:
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</P>
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<PRE><B>unsigned</B> tokenise(std::list<std::string>& l, std::string& s)
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{
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<B> return</B> boost::regex_split(std::back_inserter(l), s);
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}</PRE>
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<P><A href="../example/snippets/regex_split_example_2.cpp">Example</A>: the
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following short program will extract all of the URL's from a html file, and
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print them out to <I>cout</I>:
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</P>
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<PRE><FONT color=#008000>#include <list>
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#include <fstream>
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#include <iostream>
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#include <boost/regex.hpp>
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</FONT>
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boost::regex e(<FONT color=#000080>"<\\s*A\\s+[^>]*href\\s*=\\s*\"([^\"]*)\""</FONT>,
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boost::regbase::normal | boost::regbase::icase);
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<B>void</B> load_file(std::string& s, std::istream& is)
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{
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s.erase();
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<FONT color=#000080>//
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// attempt to grow string buffer to match file size,
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// this doesn't always work...
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</FONT> s.reserve(is.rdbuf()-&gtin_avail());
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<B>char</B> c;
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<B>while</B>(is.get(c))
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{
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<FONT color=#000080>// use logarithmic growth stategy, in case
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// in_avail (above) returned zero:
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</FONT> <B>if</B>(s.capacity() == s.size())
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s.reserve(s.capacity() * 3);
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s.append(1, c);
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}
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}
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<B>int</B> main(<B>int</B> argc, <B>char</B>** argv)
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{
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std::string s;
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std::list<std::string> l;
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<B>for</B>(<B>int</B> i = 1; i < argc; ++i)
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{
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std::cout << <FONT color=#000080>"Findings URL's in "</FONT> << argv[i] << <FONT color=#000080>":"</FONT> << std::endl;
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s.erase();
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std::ifstream is(argv[i]);
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load_file(s, is);
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boost::regex_split(std::back_inserter(l), s, e);
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<B>while</B>(l.size())
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{
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s = *(l.begin());
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l.pop_front();
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std::cout << s << std::endl;
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}
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}
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<B>return</B> 0;
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}</PRE>
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<HR>
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<p>Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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17 May 2003
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<!--webbot bot="Timestamp" endspan i-checksum="39359" -->
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</p>
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<P><I><EFBFBD> Copyright <a href="mailto:jm@regex.fsnet.co.uk">John Maddock</a> 1998-<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%Y" startspan --> 2003<!--webbot bot="Timestamp" endspan i-checksum="39359" --></I></P>
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<P align="left"><I>Permission to use, copy, modify, distribute and sell this software
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and its documentation for any purpose is hereby granted without fee, provided
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that the above copyright notice appear in all copies and that both that
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copyright notice and this permission notice appear in supporting documentation.
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Dr John Maddock makes no representations about the suitability of this software
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for any purpose. It is provided "as is" without express or implied warranty.</I></P>
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</body>
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</html>
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