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3 | <HEAD> | |
4 | <TITLE>Class Template basic_line_filter</TITLE> | |
5 | <LINK REL="stylesheet" HREF="../../../../boost.css"> | |
6 | <LINK REL="stylesheet" HREF="../theme/iostreams.css"> | |
7 | </HEAD> | |
8 | <BODY> | |
9 | ||
10 | <!-- Begin Banner --> | |
11 | ||
12 | <H1 CLASS="title">Class Template <CODE>basic_line_filter</CODE></H1> | |
13 | <HR CLASS="banner"> | |
14 | ||
15 | <!-- End Banner --> | |
16 | ||
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="#reference">Reference</A></DT> | |
21 | <DT><A href="#example">Example</A></DT> | |
22 | </DL> | |
23 | ||
24 | <HR> | |
25 | ||
26 | <A NAME="description"></A> | |
27 | <H2>Description</H2> | |
28 | ||
29 | <P> | |
30 | 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. | |
31 | </P> | |
32 | ||
33 | <A NAME="headers"></A> | |
34 | <H2>Headers</H2> | |
35 | ||
36 | <DL class="page-index"> | |
37 | <DT><A CLASS="header" HREF="../../../../boost/iostreams/filter/line.hpp"><CODE><boost/iostreams/filter/line.hpp></CODE></A></DT> | |
38 | </DL> | |
39 | ||
40 | <A NAME="reference"></A> | |
41 | <H2>Reference</H2> | |
42 | ||
43 | <H4>Synopsis</H4> | |
44 | ||
45 | <PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams { | |
46 | ||
47 | <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> > | |
48 | <SPAN CLASS='keyword'>class</SPAN> <A CLASS='documented' HREF='#template_params'>basic_line_filter</A> { | |
49 | <SPAN CLASS='keyword'>public:</SPAN> | |
50 | <SPAN CLASS='keyword'>typedef</SPAN> Ch char_type; | |
51 | <SPAN CLASS='keyword'>typedef</SPAN> std::basic_string< | |
52 | Ch, | |
53 | std::char_traits<char_type>, | |
54 | Alloc | |
55 | > string_type; | |
56 | <SPAN CLASS='keyword'>typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN> category; | |
57 | <SPAN CLASS='keyword'>protected:</SPAN> | |
58 | basic_line_filter(); | |
59 | <SPAN CLASS='keyword'>public:</SPAN> | |
60 | <SPAN CLASS='keyword'>virtual</SPAN> ~basic_line_filter(); | |
61 | <SPAN CLASS='keyword'>private:</SPAN> | |
62 | <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>; | |
63 | }; | |
64 | ||
65 | <SPAN CLASS='keyword'>typedef</SPAN> basic_line_filter<<SPAN CLASS='keyword'>char</SPAN>> <SPAN CLASS='defined'>line_filter</SPAN>; | |
66 | <SPAN CLASS='keyword'>typedef</SPAN> basic_line_filter<<SPAN CLASS='keyword'>wchar_t</SPAN>> <SPAN CLASS='defined'>wline_filter</SPAN>; | |
67 | ||
68 | } } <SPAN CLASS="comment">// End namespace boost::io</SPAN></PRE> | |
69 | ||
70 | <A NAME="template_params"></A> | |
71 | <H4>Template parameters</H4> | |
72 | ||
73 | <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2> | |
74 | <TR> | |
75 | <TR> | |
76 | <TD VALIGN="top"><I>Ch</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> | |
77 | <TD>The <A HREF='../guide/traits.html#char_type'>character type</A></TD> | |
78 | </TR> | |
79 | <TR> | |
80 | <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> | |
81 | <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> | |
82 | </TR> | |
83 | </TABLE> | |
84 | ||
85 | <A NAME="do_filter"></A> | |
86 | <H4><CODE>line_filter::do_filter</CODE></H4> | |
87 | ||
88 | <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> | |
89 | ||
90 | <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> | |
91 | ||
92 | <A NAME="example"></A> | |
93 | <H2>Example</H2> | |
94 | ||
95 | <P>The following example shows a <CODE>line_filter</CODE> which counts the number of lines which exceed a given length.</P> | |
96 | ||
97 | <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> | |
98 | ||
99 | <SPAN CLASS='keyword'>namespace</SPAN> io = boost::iostreams; | |
100 | ||
101 | <SPAN CLASS='keyword'>class</SPAN> long_line_counter : <SPAN CLASS='keyword'>public</SPAN> io::line_filter { | |
102 | <SPAN CLASS='keyword'>public</SPAN> | |
103 | <SPAN CLASS="keyword">explicit</SPAN> long_line_counter(<SPAN CLASS='keyword'>int</SPAN> max_length = <SPAN CLASS='numeric_literal'>80</SPAN>) | |
104 | : max_(max_length), count_(<SPAN CLASS='numeric_literal'>0</SPAN>) | |
105 | { } | |
106 | <SPAN CLASS='keyword'>int</SPAN> count() <SPAN CLASS='keyword'>const</SPAN> { <SPAN CLASS='keyword'>return</SPAN> count_; } | |
107 | <SPAN CLASS='keyword'>private:</SPAN> | |
108 | std::string do_filter(<SPAN CLASS='keyword'>const</SPAN> std::string& line) | |
109 | { | |
110 | <SPAN CLASS='keyword'>if</SPAN> (line.size() > max_) | |
111 | ++count_; | |
112 | } | |
113 | <SPAN CLASS='keyword'>int</SPAN> max_; | |
114 | <SPAN CLASS='keyword'>int</SPAN> count_; | |
115 | };</PRE> | |
116 | ||
117 | <!-- Begin Footer --> | |
118 | ||
119 | <HR> | |
120 | ||
121 | <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> | |
122 | <P CLASS="copyright"> | |
123 | 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>) | |
124 | </P> | |
125 | ||
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127 | ||
128 | </BODY> |