1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2<HTML> 3<HEAD> 4 <TITLE>Tutorial</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">Tutorial</H1> 13 <HR CLASS="banner"> 14 15<!-- End Banner --> 16 17<!-- Begin Nav --> 18 19<DIV CLASS='nav'> 20 <A><IMG WIDTH=19 HEIGHT=19 SRC='../../../../doc/src/images/prev_disabled.png'></A> 21 <A HREF='tutorial.html'><IMG BORDER=0 WIDTH=19 HEIGHT=19 SRC='../../../../doc/src/images/up.png'></A> 22 <A HREF='container_source.html'><IMG BORDER=0 WIDTH=19 HEIGHT=19 SRC='../../../../doc/src/images/next.png'></A> 23</DIV> 24 25<!-- End Nav --> 26 27<A NAME="device_overview"></A> 28<H2 CLEAR='right'>2.1.1. Overview: Devices, <CODE>stream_buffer</CODE> and <CODE>stream</CODE></H2> 29 30<P>Writing a new stream or stream buffer class using the Boost Iostreams library is easy: you simply write a class modeling the <A HREF="../concepts/device.html">Device</A> concept, then use that class as the template argument to <A HREF="../guide/generic_streams.html#stream"><CODE>stream</CODE></A> or <A HREF="../guide/generic_streams.html#stream_buffer"><CODE>stream_buffer</CODE></A>: 31 32<PRE CLASS="broken_ie"><SPAN CLASS='preprocessor'>#include</SPAN> <A CLASS="HEADER" HREF="../../../../boost/iostreams/stream.hpp"><SPAN CLASS='literal'><boost/iostreams/stream.hpp></SPAN></A> 33<SPAN CLASS='preprocessor'>#include</SPAN> <A HREF="../../../../boost/iostreams/stream_buffer.hpp"><SPAN CLASS='literal'><boost/iostreams/stream_buffer.hpp></SPAN></A> 34 35<SPAN CLASS='keyword'>namespace</SPAN> io = boost::iostreams; 36 37<SPAN CLASS='keyword'>class</SPAN> my_device { <SPAN CLASS='comment'>/* */</SPAN> }; 38 39<SPAN CLASS='keyword'>typedef</SPAN> io::stream<my_device> my_stream; 40<SPAN CLASS='keyword'>typedef</SPAN> io::stream_buffer<my_device> my_streambuf;</PRE> 41 42<P>Here <CODE>io::stream_buffer<my_device></CODE> is a derived class of <CODE>std::basic_streambuf</CODE>, and <CODE>io::stream<my_device></CODE> is a derived class of <CODE>std::basic_istream</CODE>, <CODE>std::basic_ostream</CODE> or <CODE>std::basic_iostream</CODE> depending on the <A HREF="../guide/modes.html">mode</A> of my_device, <I>i.e.</I>, depending on which of the fundamental i/o operations <A HREF="../functions/read.html"><CODE>read</CODE></A>, <A HREF="../functions/write.html"><CODE>write</CODE></A> and <A HREF="../functions/seek.html"><CODE>seek</CODE></A> it supports. 43 44<P>The template <CODE>io::stream</CODE> is provided as a convenience. It's always possible to avoid <CODE>io::stream</CODE> and simply use <CODE>io::stream_buffer</CODE> together with one of the standard library stream templates. <I>E.g.</I>, 45 46<PRE CLASS="broken_ie"><SPAN CLASS='preprocessor'>#include</SPAN> <SPAN CLASS='literal'><ostream></SPAN> 47<SPAN CLASS='preprocessor'>#include</SPAN> <A CLASS="HEADER" HREF="../../../../boost/iostreams/device/file.hpp"><SPAN CLASS='literal'><boost/iostreams/device/file.hpp></SPAN></A> 48<SPAN CLASS='preprocessor'>#include</SPAN> <A CLASS="HEADER" HREF="../../../../boost/iostreams/stream.hpp"><SPAN CLASS='literal'><boost/iostreams/stream.hpp></SPAN></A> 49 50<SPAN CLASS='keyword'>namespace</SPAN> io = boost::iostreams; 51 52<SPAN CLASS='keyword'>int</SPAN> main() 53{ 54 io::stream_buffer<io::file_sink> buf(<SPAN CLASS='literal'>"log.txt"</SPAN>); 55 std::ostream out(&buf); 56 <SPAN CLASS='comment'>// out writes to log.txt</SPAN> 57}</PRE> 58 59<P>In this example, the <CODE>ostream</CODE> <CODE>out</CODE> uses the <CODE>stream_buffer</CODE> <CODE>buf</CODE> as its underlying data sink, so that data written to <CODE>out</CODE> goes to the file <I>log.txt</I>. The same effect could be achieved by default constructing <CODE>out</CODE> and telling it to use stream buffer <CODE>buf</CODE> by invoking <CODE>out.rdbuf(&buf)</CODE>. 60 61<P>Another way to define a new stream or stream buffer class using the Boost Iostreams library is to derive from <A HREF="../classes/filtering_stream.html"><CODE>filtering_stream</CODE></A> or <A HREF="../classes/filtering_streambuf.html"><CODE>filtering_streambuf</CODE></A>. 62<P>The next three items will demonstrate how to write Devices for accessing STL-compatible containers. The source code for the examples can be found in the header <A HREF="../../example/container_device.hpp"><<CODE>libs/iostreams/example/container_device.hpp</CODE>></A></P> 63 64<!-- Begin Nav --> 65 66<DIV CLASS='nav'> 67 <IMG WIDTH=19 HEIGHT=19 SRC='../../../../doc/src/images/prev_disabled.png'> 68 <A HREF='tutorial.html'><IMG BORDER=0 WIDTH=19 HEIGHT=19 SRC='../../../../doc/src/images/up.png'></A> 69 <A HREF='container_source.html'><IMG BORDER=0 WIDTH=19 HEIGHT=19 SRC='../../../../doc/src/images/next.png'></A> 70</DIV> 71 72<!-- End Nav --> 73 74<!-- Begin Footer --> 75 76<HR> 77 78 79<P CLASS="copyright">© Copyright 2008 <a href="http://www.coderage.com/" target="_top">CodeRage, LLC</a><br/>© Copyright 2004-2007 <a href="https://www.boost.org/users/people/jonathan_turkanis.html" target="_top">Jonathan Turkanis</a></P> 80<P CLASS="copyright"> 81 Use, modification, and distribution are subject to the Boost Software License, Version 2.0. (See accompanying file <A HREF="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</A> or copy at <A HREF="http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</A>) 82</P> 83<!-- End Footer --> 84 85</BODY>
