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159 lines
6.6 KiB
HTML
Executable File
159 lines
6.6 KiB
HTML
Executable File
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML>
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<HEAD>
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<TITLE>Function Template get</TITLE>
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<LINK REL='stylesheet' HREF='../../../../boost.css'>
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<LINK REL='stylesheet' HREF='../theme/iostreams.css'>
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</HEAD>
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<BODY>
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<!-- Begin Banner -->
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<H1 CLASS='title'>Function Template <CODE>get</CODE></H1>
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<HR CLASS='banner'>
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<!-- End Banner -->
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<DL class='page-index'>
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<DT><A href='#overview'>Overview</A></DT>
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<DT><A href='#example'>Example</A></DT>
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<DT><A href='#headers'>Headers</A></DT>
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<DT><A href='#reference'>Reference</A></DT>
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</DL>
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<A NAME='overview'>
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<H2>Overview</H2>
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<P>
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The function template <CODE>get</CODE> provides a uniform interface for reading a character from a <A HREF='../concepts/source.html'>Source</A>, for use in the definitions of new <A HREF='../concepts.html#filter_concepts'>Filter</A> types (<I>see</I> <A HREF='#example'>Example</A>).
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</P>
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<A NAME='example'>
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<H2>Example</H2>
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<P>
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The following code illustrates the use of the function <CODE>get</CODE> in the definition of an <A HREF='../concepts/input_filter.html'>InputFilter</A>.
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</P>
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<PRE CLASS='broken_ie'> <SPAN CLASS='preprocessor'>#include</SPAN> <SPAN CLASS='literal'><ctype.h></SPAN> <SPAN CLASS='comment'>// tolower</SPAN>
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<SPAN CLASS='preprocessor'>#include</SPAN> <A CLASS='header' HREF='../../../../boost/iostreams/concepts.hpp'><SPAN CLASS='literal'><boost/iostreams/concepts.hpp></SPAN></A> <SPAN CLASS='comment'>// input_filter</SPAN>
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<SPAN CLASS='preprocessor'>#include</SPAN> <A CLASS='header' HREF='../../../../boost/iostreams/operations.hpp'><SPAN CLASS='literal'><boost/iostreams/operations.hpp></SPAN></A> <SPAN CLASS='comment'>// get</SPAN>
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<SPAN CLASS="keyword">using</SPAN> <SPAN CLASS="keyword">namespace</SPAN> std;
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<SPAN CLASS="keyword">using</SPAN> <SPAN CLASS="keyword">namespace</SPAN> boost::io;
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<SPAN CLASS="keyword">struct</SPAN> tolower_filter : <SPAN CLASS="keyword">public</SPAN> input_filter {
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<SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> Source>
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<SPAN CLASS="keyword">int</SPAN> get(Source& src)
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{
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<SPAN CLASS="keyword">return</SPAN> tolower(boost::iostreams::get(src));
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}
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};</PRE>
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<A NAME='headers'>
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<H2>Headers</H2>
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<DL>
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<DT><A CLASS='header' HREF='../../../../boost/iostreams/operations.hpp'><CODE><boost/iostreams/operations.hpp></CODE></A></DT>
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</DL>
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<A NAME='reference'>
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<H2>Reference</H2>
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<A NAME='description'>
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<H4>Description</H4>
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<P>Attemps to extract a character from a given instance of the template parameter <CODE>Source</CODE>, returning the extracted character if successful and an end-of-file indicator otherwise.</P>
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<A NAME='synopsis'>
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<H4>Synopsis</H4>
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<PRE CLASS='broken_ie'><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
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<SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Source</A>>
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<A STYLE='text-decoration:none' HREF='#return_type'><SPAN CLASS='omitted'>[int type]</SPAN></A> <A CLASS="documented" HREF="#semantics">get</A>(<A CLASS="documented" HREF="#template_params">Source</A>& <A CLASS="documented" HREF="#function_params">src</A>);
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} } <SPAN CLASS='comment'>// End namespace boost::io</SPAN></PRE>
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<A NAME='template_params'></A>
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<H4>Template Parameters</H4>
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<TABLE STYLE='margin-left:2em' BORDER=0 CELLPADDING=2>
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<TR>
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<TR>
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<TD VALIGN='top'><I>Source</I></TD><TD WIDTH='2em' VALIGN='top'>-</TD>
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<TD>A model of <A HREF='../concepts/source.html'>Source</A> or a standard input stream or stream buffer type.
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</TR>
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</TABLE>
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<A NAME='function_params'></A>
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<H4>Function Parameters</H4>
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<TABLE STYLE='margin-left:2em' BORDER=0 CELLPADDING=2>
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<TR>
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<TR>
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<TD VALIGN='top'><I>src</I></TD><TD WIDTH='2em' VALIGN='top'>-</TD>
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<TD>An instance of <CODE>Source</CODE></TD>
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</TR>
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</TABLE>
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<A NAME='return_type'></A>
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<H4>Return Type</H4>
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<P>An integral type large enough to represent every element of the <A HREF='../traits.html#char_type'>character type</A> of <CODE>Source</CODE> plus an end-of-file indicator. Specifically:
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<PRE CLASS='broken_ie'> <SPAN CLASS="keyword">typename</SPAN> std::char_traits<<SPAN CLASS="keyword">typename</SPAN> io_char<Source>::type>::int_type</PRE>
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<A NAME='return_value'></A>
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<H4>Return Value</H4>
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<P>The next character in the filtered sequence, or <CODE>traits_type::eof()</CODE>, where <CODE>traits_type</CODE> is</P>
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<PRE CLASS='broken_ie'> std::char_traits<<SPAN CLASS="keyword">typename</SPAN> io_char<Source>::type></PRE>
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<A NAME='semantics'></A>
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<H4>Semantics</H4>
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<PRE CLASS='broken_ie'> <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> Source>
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<SPAN CLASS='omitted'>[int type]</SPAN> get(Source& src);</PRE>
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<P>The semantics of <CODE>get</CODE> depends on the <A HREF="../traits.html#category">category</A> of <CODE>Source</CODE> as follows:</P>
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<TABLE STYLE='margin:0,0,2em,2em' BORDER=1 CELLPADDING=4>
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<TR><TH><CODE>io_category<Source>::type</CODE></TH><TH>semantics</TH></TR>
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<TR>
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<TD VALIGN='top'>convertible to <A HREF='../traits.html#category_tags'><CODE>direct_tag</CODE></A></TD>
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<TD>compile-time error</CODE></TD>
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</TR>
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<TR>
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<TD VALIGN='top'>convertible to <A HREF='../traits.html#category_tags'><CODE>istream_tag</CODE></A></TD>
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<TD>returns <CODE>src.get()</CODE></TD>
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</TR>
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<TR>
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<TD VALIGN='top'>convertible to <A HREF='../traits.html#category_tags'><CODE>streambuf_tag</CODE></A> but not to <A HREF='../traits.html#category_tags'><CODE>istream_tag</CODE></A></TD>
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<TD>returns <CODE>src.sbumpc()</CODE></TD>
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</TR>
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<TR>
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<TD VALIGN='top'>otherwise</TD>
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<TD>
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attempts to extract a single character using <CODE>src.read()</CODE>, returning the extracted character if successful and an end-of-file indicator otherwise
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</TD>
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</TR>
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</TABLE>
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<!-- Begin Footer -->
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<HR>
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<P CLASS='copyright'>Revised
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<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
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20 May, 2004
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<!--webbot bot="Timestamp" endspan i-checksum="38504" -->
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</P>
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<P CLASS='copyright'>© Copyright Jonathan Turkanis, 2004</P>
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<P CLASS='copyright'>
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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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</P>
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