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     <H1 CLASS="title">Class Template <CODE>basic_line_filter</CODE></H1>
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   <DT><A href="#description">Description</A></DT>
   <DT><A href="#headers">Headers</A></DT>
   <DT><A href="#reference">Reference</A></DT>
   <DT><A href="#example">Example</A></DT>
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 <A NAME="description"></A>
 <H2>Description</H2>

 <P>
     The class template <CODE>basic_line_filter</CODE> is a <A HREF='../concepts/dual_use_filter.html'>DualUseFilter</A> for use as a base class by Filters which filter a character sequence one line at a time. Derived classes override the <CODE>private</CODE> <CODE>virtual</CODE> function <CODE>do_filter</CODE>, which takes a line of unfiltered text as argument returns the result of filtering the line.
 </P>

 <A NAME="headers"></A>
 <H2>Headers</H2>

 <DL class="page-index">
   <DT><A CLASS="header" HREF="../../../../boost/iostreams/filter/line.hpp"><CODE>&lt;boost/iostreams/filter/line.hpp&gt;</CODE></A></DT>
 </DL>

 <A NAME="reference"></A>
 <H2>Reference</H2>

 <H4>Synopsis</H4>

 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {

 <SPAN CLASS='keyword'>template</SPAN>&lt;<SPAN CLASS='keyword'>typename</SPAN> <A CLASS='documented' HREF='#template_params'>Ch</A>, <SPAN CLASS='keyword'>typename</SPAN> <A CLASS='documented' HREF='#template_params'>Alloc</A> = std::allocator&lt;Ch&gt; &gt;
 <SPAN CLASS='keyword'>class</SPAN> <A CLASS='documented' HREF='#template_params'>basic_line_filter</A>  {
 <SPAN CLASS='keyword'>public:</SPAN>
     <SPAN CLASS='keyword'>typedef</SPAN> Ch                                char_type;
     <SPAN CLASS='keyword'>typedef</SPAN> std::basic_string&lt;
                 Ch,
                 std::char_traits&lt;char_type&gt;,
                 Alloc
             &gt;                                 string_type;
     <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN>          category;
 <SPAN CLASS='keyword'>protected:</SPAN>
     basic_line_filter();
 <SPAN CLASS='keyword'>public:</SPAN>
     <SPAN CLASS='keyword'>virtual</SPAN> ~basic_line_filter();
 <SPAN CLASS='keyword'>private:</SPAN>
     <SPAN CLASS='keyword'>virtual</SPAN> string_type <A CLASS='documented' HREF='#do_filter'>do_filter</A>(<SPAN CLASS='keyword'>const</SPAN> string_type& line) <SPAN CLASS='numeric_literal'>= 0</SPAN>;
 };

 <SPAN CLASS='keyword'>typedef</SPAN> basic_line_filter&lt;<SPAN CLASS='keyword'>char</SPAN>&gt;     <SPAN CLASS='defined'>line_filter</SPAN>;
 <SPAN CLASS='keyword'>typedef</SPAN> basic_line_filter&lt;<SPAN CLASS='keyword'>wchar_t</SPAN>&gt;  <SPAN CLASS='defined'>wline_filter</SPAN>;

 } } <SPAN CLASS="comment">// End namespace boost::io</SPAN></PRE>

 <A NAME="template_params"></A>
 <H4>Template parameters</H4>

 <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
 <TR>
     <TR>
         <TD VALIGN="top"><I>Ch</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
         <TD>The <A HREF='../guide/traits.html#char_type'>character type</A></TD>
     </TR>
     <TR>
         <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
         <TD>A standard library allocator type (<A CLASS="bib_ref" HREF="../bibliography.html#iso">[ISO]</A>, 20.1.5), used to allocate a character buffer</TD>
     </TR>
 </TABLE>

 <A NAME="do_filter"></A>
 <H4><CODE>line_filter::do_filter</CODE></H4>

 <PRE CLASS="broken_ie">    <SPAN CLASS='keyword'>virtual</SPAN> string_type do_filter(<SPAN CLASS='keyword'>const</SPAN> string_type& line) <SPAN CLASS='numeric_literal'>= 0</SPAN>;</PRE>

 <P>The argument <CODE>line</CODE> represents a single line of unfiltered text, not including any terminal newline character. Returns the result of filtering <CODE>line</CODE>.</P>

 <A NAME="example"></A>
 <H2>Example</H2>

 <P>The following example shows a <CODE>line_filter</CODE> which counts the number of lines which exceed a given length.</P>

 <PRE CLASS="broken_ie"><SPAN CLASS='preprocessor'>#include</SPAN> <A CLASS='header' HREF='../../../../boost/iostreams/filter/line.hpp'><SPAN CLASS='literal'>&lt;boost/iostreams/filter/line.hpp&gt;</SPAN></A>

 <SPAN CLASS='keyword'>namespace</SPAN> io = boost::iostreams;

 <SPAN CLASS='keyword'>class</SPAN> long_line_counter : <SPAN CLASS='keyword'>public</SPAN> io::line_filter {
 <SPAN CLASS='keyword'>public</SPAN>
     <SPAN CLASS="keyword">explicit</SPAN> long_line_counter(<SPAN CLASS='keyword'>int</SPAN> max_length = <SPAN CLASS='numeric_literal'>80</SPAN>)
         : max_(max_length), count_(<SPAN CLASS='numeric_literal'>0</SPAN>)
         { }
     <SPAN CLASS='keyword'>int</SPAN> count() <SPAN CLASS='keyword'>const</SPAN> { <SPAN CLASS='keyword'>return</SPAN> count_; }
 <SPAN CLASS='keyword'>private:</SPAN>
     std::string do_filter(<SPAN CLASS='keyword'>const</SPAN> std::string& line)
     {
         <SPAN CLASS='keyword'>if</SPAN> (line.size() &gt; max_)
             ++count_;
     }
     <SPAN CLASS='keyword'>int</SPAN> max_;
     <SPAN CLASS='keyword'>int</SPAN> count_;
 };</PRE>

 <!-- Begin Footer -->

 <HR>
 <P CLASS="copyright">Revised 02 Feb 2008</P>

 <P CLASS="copyright">&copy; Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>&copy; Copyright 2004-2007 <a href="http://www.coderage.com/turkanis/" target="_top">Jonathan Turkanis</a></P>
 <P CLASS="copyright">
     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>)
 </P>

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 </BODY>
	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
	<HTML>
	<HEAD>
	<TITLE>Class Template basic_line_filter</TITLE>
	<LINK REL="stylesheet" HREF="../../../../boost.css">
	<LINK REL="stylesheet" HREF="../theme/iostreams.css">
	</HEAD>
	<BODY>

	<!-- Begin Banner -->

	<H1 CLASS="title">Class Template <CODE>basic_line_filter</CODE></H1>
	<HR CLASS="banner">

	<!-- End Banner -->

	<DL class="page-index">
	<DT><A href="#description">Description</A></DT>
	<DT><A href="#headers">Headers</A></DT>
	<DT><A href="#reference">Reference</A></DT>
	<DT><A href="#example">Example</A></DT>
	</DL>

	<HR>

	<A NAME="description"></A>
	<H2>Description</H2>

	<P>
	The class template <CODE>basic_line_filter</CODE> is a <A HREF='../concepts/dual_use_filter.html'>DualUseFilter</A> for use as a base class by Filters which filter a character sequence one line at a time. Derived classes override the <CODE>private</CODE> <CODE>virtual</CODE> function <CODE>do_filter</CODE>, which takes a line of unfiltered text as argument returns the result of filtering the line.
	</P>

	<A NAME="headers"></A>
	<H2>Headers</H2>

	<DL class="page-index">
	<DT><A CLASS="header" HREF="../../../../boost/iostreams/filter/line.hpp"><CODE><boost/iostreams/filter/line.hpp></CODE></A></DT>
	</DL>

	<A NAME="reference"></A>
	<H2>Reference</H2>

	<H4>Synopsis</H4>

	<PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {

	<SPAN CLASS='keyword'>template</SPAN><<SPAN CLASS='keyword'>typename</SPAN> <A CLASS='documented' HREF='#template_params'>Ch</A>, <SPAN CLASS='keyword'>typename</SPAN> <A CLASS='documented' HREF='#template_params'>Alloc</A> = std::allocator<Ch> >
	<SPAN CLASS='keyword'>class</SPAN> <A CLASS='documented' HREF='#template_params'>basic_line_filter</A> {
	<SPAN CLASS='keyword'>public:</SPAN>
	<SPAN CLASS='keyword'>typedef</SPAN> Ch char_type;
	<SPAN CLASS='keyword'>typedef</SPAN> std::basic_string<
	Ch,
	std::char_traits<char_type>,
	Alloc
	> string_type;
	<SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN> category;
	<SPAN CLASS='keyword'>protected:</SPAN>
	basic_line_filter();
	<SPAN CLASS='keyword'>public:</SPAN>
	<SPAN CLASS='keyword'>virtual</SPAN> ~basic_line_filter();
	<SPAN CLASS='keyword'>private:</SPAN>
	<SPAN CLASS='keyword'>virtual</SPAN> string_type <A CLASS='documented' HREF='#do_filter'>do_filter</A>(<SPAN CLASS='keyword'>const</SPAN> string_type& line) <SPAN CLASS='numeric_literal'>= 0</SPAN>;
	};

	<SPAN CLASS='keyword'>typedef</SPAN> basic_line_filter<<SPAN CLASS='keyword'>char</SPAN>> <SPAN CLASS='defined'>line_filter</SPAN>;
	<SPAN CLASS='keyword'>typedef</SPAN> basic_line_filter<<SPAN CLASS='keyword'>wchar_t</SPAN>> <SPAN CLASS='defined'>wline_filter</SPAN>;

	} } <SPAN CLASS="comment">// End namespace boost::io</SPAN></PRE>

	<A NAME="template_params"></A>
	<H4>Template parameters</H4>

	<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
	<TR>
	<TR>
	<TD VALIGN="top"><I>Ch</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
	<TD>The <A HREF='../guide/traits.html#char_type'>character type</A></TD>
	</TR>
	<TR>
	<TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
	<TD>A standard library allocator type (<A CLASS="bib_ref" HREF="../bibliography.html#iso">[ISO]</A>, 20.1.5), used to allocate a character buffer</TD>
	</TR>
	</TABLE>

	<A NAME="do_filter"></A>
	<H4><CODE>line_filter::do_filter</CODE></H4>

	<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>virtual</SPAN> string_type do_filter(<SPAN CLASS='keyword'>const</SPAN> string_type& line) <SPAN CLASS='numeric_literal'>= 0</SPAN>;</PRE>

	<P>The argument <CODE>line</CODE> represents a single line of unfiltered text, not including any terminal newline character. Returns the result of filtering <CODE>line</CODE>.</P>

	<A NAME="example"></A>
	<H2>Example</H2>

	<P>The following example shows a <CODE>line_filter</CODE> which counts the number of lines which exceed a given length.</P>

	<PRE CLASS="broken_ie"><SPAN CLASS='preprocessor'>#include</SPAN> <A CLASS='header' HREF='../../../../boost/iostreams/filter/line.hpp'><SPAN CLASS='literal'><boost/iostreams/filter/line.hpp></SPAN></A>

	<SPAN CLASS='keyword'>namespace</SPAN> io = boost::iostreams;

	<SPAN CLASS='keyword'>class</SPAN> long_line_counter : <SPAN CLASS='keyword'>public</SPAN> io::line_filter {
	<SPAN CLASS='keyword'>public</SPAN>
	<SPAN CLASS="keyword">explicit</SPAN> long_line_counter(<SPAN CLASS='keyword'>int</SPAN> max_length = <SPAN CLASS='numeric_literal'>80</SPAN>)
	: max_(max_length), count_(<SPAN CLASS='numeric_literal'>0</SPAN>)
	{ }
	<SPAN CLASS='keyword'>int</SPAN> count() <SPAN CLASS='keyword'>const</SPAN> { <SPAN CLASS='keyword'>return</SPAN> count_; }
	<SPAN CLASS='keyword'>private:</SPAN>
	std::string do_filter(<SPAN CLASS='keyword'>const</SPAN> std::string& line)
	{
	<SPAN CLASS='keyword'>if</SPAN> (line.size() > max_)
	++count_;
	}
	<SPAN CLASS='keyword'>int</SPAN> max_;
	<SPAN CLASS='keyword'>int</SPAN> count_;
	};</PRE>

	<!-- Begin Footer -->

	<HR>
	<P CLASS="copyright">Revised 02 Feb 2008</P>

	<P CLASS="copyright">© Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>© Copyright 2004-2007 <a href="http://www.coderage.com/turkanis/" target="_top">Jonathan Turkanis</a></P>
	<P CLASS="copyright">
	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>)
	</P>

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