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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <HTML> <HEAD> <TITLE>Function Template get</TITLE> <LINK REL="stylesheet" HREF="../../../../boost.css"> <LINK REL="stylesheet" HREF="../theme/iostreams.css"> </HEAD> <BODY>  <H1 CLASS="title">Function Template <CODE>get</CODE></H1> <HR CLASS="banner">  <DL class="page-index"> <DT><A href="#overview">Overview</A></DT> <DT><A href="#example">Example</A></DT> <DT><A href="#headers">Headers</A></DT> <DT><A href="#reference">Reference</A></DT> </DL> <A NAME="overview"></A> <H2>Overview</H2> <P> 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="../guide/concepts.html#filter_concepts">Filter</A> types (<I>see</I> <A HREF="#example">Example</A>). </P> <A NAME="example"></A> <H2>Example</H2> <P> 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>. </P> <PRE CLASS="broken_ie"> <SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal"><ctype.h></SPAN> <SPAN CLASS="comment">// tolower</SPAN> <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> <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, EOF, WOULD_BLOCK</SPAN> <SPAN CLASS="keyword">using</SPAN> <SPAN CLASS="keyword">namespace</SPAN> std; <SPAN CLASS="keyword">using</SPAN> <SPAN CLASS="keyword">namespace</SPAN> boost::io; <SPAN CLASS="keyword">struct</SPAN> tolower_filter : <SPAN CLASS="keyword">public</SPAN> input_filter { <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> Source> <SPAN CLASS="keyword">int</SPAN> get(Source& src) { <SPAN CLASS="keyword">int</SPAN> c; <SPAN CLASS="keyword">return</SPAN> (c = boost::iostreams::get(src)) != <SPAN CLASS='numeric_literal'>EOF</SPAN> && c != WOULD_BLOCK ? tolower((<SPAN CLASS="keyword">unsigned</SPAN> <SPAN CLASS="keyword">char</SPAN>) c) : c; } };</PRE> <A NAME="headers"></A> <H2>Headers</H2> <DL> <DT><A CLASS="header" HREF="../../../../boost/iostreams/get.hpp"><CODE><boost/iostreams/get.hpp></CODE></A></DT> <DT><A CLASS="header" HREF="../../../../boost/iostreams/operations.hpp"><CODE><boost/iostreams/operations.hpp></CODE></A></DT> </DL> <A NAME="reference"></A> <H2>Reference</H2> <A NAME="description"></A> <H4>Description</H4> <P>Attemps to extract a character from a given instance of the template parameter <CODE>Source</CODE>, returning the extracted character or one of the special values <CODE>traits_type::eof</CODE> or <A HREF="../classes/char_traits.html#would_block"><CODE>traits_type::would_block</CODE></A>, where <CODE>traits_type</CODE> is an appropriate specialization of <A HREF="../classes/char_traits.html"><CODE>boost::iostreams::char_traits</CODE></A></P> <A NAME="synopsis"></A> <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">Source</A>> <SPAN CLASS="keyword">typename</SPAN> <A CLASS='documented' HREF="../guide/traits.html#int_type_of_ref">int_type_of</A><Source>::type <A CLASS="documented" HREF="#semantics">get</A>(<A CLASS="documented" HREF="#template_params">Source</A>& <A CLASS="documented" HREF="#function_params">src</A>); } } <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>Source</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> <TD>A model of <A HREF="../concepts/source.html">Source</A>. </TR> </TABLE> <A NAME="function_params"></A> <H4>Function Parameters</H4> <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2> <TR> <TR> <TD VALIGN="top"><I>src</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> <TD>An instance of <CODE>Source</CODE></TD> </TR> </TABLE> <A NAME="semantics"></A> <H4>Semantics</H4> <PRE CLASS="broken_ie"> <SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> Source> <SPAN CLASS="keyword">typename</SPAN> int_type_of<Source>::type get(Source& src);</PRE> <P>The semantics of <CODE>get</CODE> depends on the <A HREF="../guide/traits.html#category">category</A> of <CODE>Source</CODE> as follows:</P> <TABLE STYLE="margin:0,0,2em,2em" BORDER=1 CELLPADDING=4> <TR><TH><CODE>category_of<Source>::type</CODE></TH><TH>semantics</TH></TR> <TR> <TD VALIGN="top">convertible to <A HREF="../guide/traits.html#category_tags"><CODE>direct_tag</CODE></A></TD> <TD>compile-time error</CODE></TD> </TR> <TR> <TD VALIGN="top">convertible to <A HREF="../guide/traits.html#category_tags"><CODE>istream_tag</CODE></A></TD> <TD>returns <CODE>src.get()</CODE></TD> </TR> <TR> <TD VALIGN="top">convertible to <A HREF="../guide/traits.html#category_tags"><CODE>streambuf_tag</CODE></A> but not to <A HREF="../guide/traits.html#category_tags"><CODE>istream_tag</CODE></A></TD> <TD>returns <CODE>src.sbumpc()</CODE></TD> </TR> <TR> <TD VALIGN="top">otherwise</TD> <TD> attempts to extract a single character using <CODE>src.read()</CODE>, returning the extracted character if successful and one of the special values <CODE>traits_type::eof</CODE> or <A HREF="../classes/char_traits.html#would_block"><CODE>traits_type::would_block</CODE></A> otherwise, where <CODE>traits_type</CODE> is <A HREF="../classes/char_traits.html"><CODE>boost::iostreams::char_traits<Source></CODE></A> </TD> </TR> </TABLE>  <HR> <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>  </BODY>