ceph/src/boost/libs/iostreams/doc/classes/grep_filter.html

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  12     <H1 CLASS="title">Class Template <CODE>basic_grep_filter</CODE></H1>
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  17 <DL class="page-index">
  18   <DT><A href="#description">Description</A></DT>
  19   <DT><A href="#headers">Headers</A></DT>
  20   <DT><A href="#installation">Installation</A></DT>
  21   <DT><A href="#reference">Reference</A></DT>
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  26 <A NAME="description"></A>
  27 <H2>Description</H2>
  28
  29 <P>
  30     The class template <CODE>basic_grep_filter</CODE> filters a character sequence line by line using a regular expression provided at construction, in a manner similar to the command-line utility <i>grep</i> (<A CLASS="bib_ref" HREF="../bibliography.html#grep">[IEEE]</A>). The filter uses regular expressions from the <A HREF="http://www.boost.org/libs/regex" TARGET="_top">Boost Regular Expression Library</A> (<A CLASS="bib_ref" HREF="../bibliography.html#maddock">[Maddock]</A>).
  31 </P>
  32 <P>
  33     By default, the filtered character sequence consists of those lines of the unfiltered sequence that contain a subsequence matching the regular expression. By specifying appropriate options at construction, <CODE>basic_grep_filter</CODE> can be made to pass through only those lines which exactly match the regular expression (as if the option <i>-x</i> had been  passed to the command-line utility) or only those lines that <i>do not</i> contain a match (as if the option <i>-v</i> had been  passed to the command-line utility).
  34 </P>
  35 <P>
  36     A running count of the lines in the filtered character sequence is available via the member function <code><a href="#count">count</a></code>.
  37 </P>
  38
  39 <A NAME="headers"></A>
  40 <H2>Headers</H2>
  41
  42 <DL class="page-index">
  43   <DT><A CLASS="header" HREF="../../../../boost/iostreams/filter/grep.hpp"><CODE>&lt;boost/iostreams/filter/grep.hpp&gt;</CODE></A></DT>
  44 </DL>
  45
  46 <A NAME="installation"></A>
  47 <H2>Installation</H2>
  48
  49 <P>
  50     The template <CODE>basic_grep_filter</CODE> uses the <A HREF="http://www.boost.org/libs/regex" TARGET="_top">Boost Regular Expression Library</A>, which must be built separately. See <A HREF="http://www.boost.org/libs/regex/doc/html/boost_regex/install.html" TARGET="_top">here</A> for details.
  51 </P>
  52
  53 <A NAME="reference"></A>
  54 <H2>Reference</H2>
  55
  56 <H4>Synopsis</H4>
  57
  58 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
  59
  60 <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/function.hpp" TARGET="_top"><SPAN CLASS="literal">&lt;boost/function.hpp&gt;</SPAN></A>
  61 <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/regex.hpp" TARGET="_top"><SPAN CLASS="literal">&lt;boost/regex.hpp&gt;</SPAN></A>
  62
  63 <SPAN CLASS="keyword">namespace</SPAN> grep {
  64
  65 <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> invert;
  66 <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">int</SPAN> whole_line;
  67
  68 }
  69
  70 <SPAN CLASS="keyword">template</SPAN>&lt; <SPAN CLASS="keyword">typename</SPAN> <A HREF="#template_params" CLASS="documented">Ch</A>,
  71           <SPAN CLASS="keyword">typename</SPAN> <A HREF="#template_params" CLASS="documented">Tr</A> = regex_traits&lt;Ch&gt;,
  72           <SPAN CLASS="keyword">typename</SPAN> <A HREF="#template_params" CLASS="documented">Alloc</A> = std::allocator&lt;Ch&gt; &gt;
  73 <SPAN CLASS="keyword">class</SPAN> <A HREF="#template_params" CLASS="documented">basic_grep_filter</A> {
  74 <SPAN CLASS="keyword">public:</SPAN>
  75     <A CLASS="documented" HREF="#constructor">basic_grep_filter</A>( <SPAN CLASS="keyword">const</SPAN> basic_regex&lt;Ch, Tr, Alloc&gt;&amp; pattern,
  76                        regex_constants::match_flag_type flags =
  77                            regex_constants::match_default,
  78                        <SPAN CLASS="keyword">int</SPAN> options = <SPAN CLASS="numeric_literal">0</SPAN> );
  79     <SPAN CLASS="keyword">int</SPAN> <A CLASS="documented" HREF="#count">count</A>() <SPAN CLASS="keyword">const</SPAN>;
  80 };
  81
  82 <SPAN CLASS="keyword">typedef</SPAN> basic_grep_filter&lt;<SPAN CLASS="keyword">char</SPAN>&gt;     <SPAN CLASS="defined">grep_filter</SPAN>;
  83 <SPAN CLASS="keyword">typedef</SPAN> basic_grep_filter&lt;<SPAN CLASS="keyword">wchar_t</SPAN>&gt;  <SPAN CLASS="defined">wgrep_filter</SPAN>;
  84
  85 } } // End namespace boost::io</PRE>
  86
  87 <A NAME="template_params"></A>
  88 <H4>Template parameters</H4>
  89
  90 <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
  91 <TR>
  92     <TR>
  93         <TD VALIGN="top"><I>Ch</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
  94         <TD>The character type</TD>
  95     </TR>
  96     <TR>
  97         <TD VALIGN="top"><I>Tr</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
  98         <TD>The <A HREF="http://www.boost.org/libs/regex/doc/html/boost_regex/ref/regex_traits.html" TARGET="_top">regular expression traits</A> type</TD>
  99     </TR>
 100     <TR>
 101         <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 102         <TD>A standard library allocator type (<A CLASS="bib_ref" HREF="../bibliography.html#iso">[ISO]</A>, 20.1.5), used to allocate character buffers</TD>
 103     </TR>
 104 </TABLE>
 105
 106 <A NAME="constructor"></A>
 107 <H4><CODE>basic_grep_filter::basic_grep_filter</CODE></H4>
 108
 109 <PRE CLASS="broken_ie">    <B>basic_grep_filter</B>( <SPAN CLASS="keyword">const</SPAN> basic_regex&lt;Ch, Tr, Alloc&gt;&amp; pattern,
 110                        regex_constants::match_flag_type flags =
 111                            regex_constants::match_default,
 112                        <SPAN CLASS="keyword">int</SPAN> options = <SPAN CLASS="numeric_literal">0</SPAN> );</PRE>
 113
 114 <P>Constructs a <CODE>basic_grep_filter</CODE> from the given regular expression, match flags, and grep options. The parameters have the following interpretations:</P>
 115
 116 <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
 117 <TR>
 118     <TR>
 119         <TD VALIGN="top"><I>pattern</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 120         <TD>The regular expression to be matched against the stream of unfiltered data</TD>
 121     </TR>
 122     <TR>
 123         <TD VALIGN="top"><I>flags</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 124         <TD>The flags passed to <A HREF="http://www.boost.org/libs/regex/doc/html/boost_regex/ref/regex_search.html" TARGET="_top">regex_search</A> or <A HREF="http://www.boost.org/libs/regex/doc/html/boost_regex/ref/regex_match.html" TARGET="_top">regex_match</A> to specify regular expression matching behavior</TD>
 125     </TR>
 126     <TR>
 127         <TD VALIGN="top"><I>options</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 128         <TD>A bitwise OR of zero or more constants from the namespace <CODE>boost::iostreams::grep</CODE>. Currently two constants are recongnized: <CODE>grep::whole_line</CODE> causes the filter to pass through only those lines which exactly match the regular expression, and <CODE>grep::invert</CODE> causes the filter to pass through only those lines that <i>do not</i> contain a match.</TD>
 129     </TR>
 130 </TABLE>
 131
 132 </P>
 133
 134 <A NAME="count"></A>
 135 <H4><CODE>basic_grep_filter::count</CODE></H4>
 136
 137 <A NAME="second_constructor"></A>
 138
 139 <PRE CLASS="broken_ie">    <SPAN CLASS="keyword">int</SPAN> count() <SPAN CLASS="keyword">const</SPAN>;</PRE>
 140
 141 <P>Returns a running count of the lines passed through from the unfiltered character sequence to the filtered character sequence. The count is reset to zero automatically when the filter begins processing a new character sequence.</P>
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 147 <P CLASS="copyright">&copy; Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a></P>
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 149     Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at <A HREF="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>)
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