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     <H1 CLASS="title">Null Devices</H1>
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 <DL class="page-index">
   <DT><A href="#overview">Overview</A></DT>
   <DT><A href="#acknowledgments">Acknowledgments</A></DT>
   <DT><A href="#headers">Headers</A></DT>
   <DT><A href="#reference">Reference</A>
     <DL>
       <DT><A href="#null_source">Class template <CODE>basic_null_source</CODE></A></DT>
       <DT><A href="#null_sink">Class template <CODE>basic_null_sink</CODE></A></DT>
       <DT><A href="#null_device">Class template <CODE>basic_null_device</CODE></A></DT>
     </DL>
   </DT>
 </DL>

 <HR>

 <A NAME="overview"></A>
 <H2>Overview</H2>

 <P>
     The class templates <CODE>basic_null_source</CODE>, <CODE>basic_null_sink</CODE> and <CODE>basic_null_device</CODE> are models of Device whose member functions all have trivial implementations. A <CODE>basic_null_source</CODE> is a <A HREF="../concepts/source.html">Source</A> whose member function <CODE>read</CODE> returns <CODE>-1</CODE>, indicating end-of-sequence. A <CODE>basic_null_sink</CODE> is a <A HREF="../concepts/sink.html">Sink</A> whose member function <CODE>write</CODE> consumes and ignores the characters passed to it. A <CODE>basic_null_device</CODE> combines &#8212; depending on its template parameter <A HREF="#null_device_params"><CODE>Mode</CODE></A> &#8212; the trivial <CODE>read</CODE> and <CODE>write</CODE> functions just described with a member <CODE>seek</CODE> that always returns an invalid stream position.
 </P>

 <P>
     In addition, each of the above templates is <A HREF='../concepts/closable.html'>Closable</A>, with a no-op implementation of <CODE>close</CODE>.
 </P>

 <A NAME="acknowledgments"></A>
 <H2>Acknowledgments</H2>

 <P>
     The templates described here were inspired by <A HREF="http://www.boost.org/people/daryle_walker.html" TARGET="_top">Daryle Walker's</A> <CODE>basic_nullbuf</CODE> template. <I>See</I> <A HREF="http://cvs.sourceforge.net/viewcvs.py/boost-sandbox/boost-sandbox/libs/io/doc/null_stream.html" TARGET="_top">Disconnected Streams</A>.
 </P>

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

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

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

 <A NAME="null_source"></A>
 <H3>Class template <CODE>basic_null_source</CODE></H3>

 <H4>Description</H4>

 <P>Model of <A HREF="../concepts/source.html">Source</A> whose member function <CODE>read</CODE> returns <CODE>-1</CODE>, indicating end-of-sequence.</P>

 <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="#null_source_params">Ch</A>&gt;
 <SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#null_source_params">basic_null_source</A> {
 <SPAN CLASS="keyword">public</SPAN>:
     <SPAN CLASS="keyword">typedef</SPAN> Ch                        char_type;
     <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN>  category;

     <A CLASS="documented" HREF="#null_source_ctor">basic_null_source</A>();
     std::streamsize <A CLASS="documented" HREF="#null_source_read">read</A>(char_type* s, std::streamsize n);
     <SPAN CLASS='keyword'>void</SPAN> <A CLASS='documented' HREF='#null_source_close'>close</A>();
 };

 <SPAN CLASS='keyword'>typedef</SPAN> basic_null_source&lt;<SPAN CLASS='keyword'>char</SPAN>&gt;     <SPAN CLASS='defined'>null_source</SPAN>;
 <SPAN CLASS='keyword'>typedef</SPAN> basic_null_source&lt;<SPAN CLASS='keyword'>wchar_t</SPAN>&gt;  <SPAN CLASS='defined'>wnull_source</SPAN>;

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

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

 <TABLE STYLE="margin-left:2em">
 <TR>
     <TD><P><I>Ch</I></TD><TD VALIGN="top">-</TD>
     <TD><P>The <A HREF='../guide/traits.html#char_type'>character type</A> type.</TD>
 </TR>
 </TABLE>

 <A NAME="null_source_ctor"></A>

 <H4><CODE>basic_null_source::basic_null_source</CODE></H4>

 <PRE CLASS="broken_ie">    basic_null_source();</PRE>

 <P>Constructs a <CODE>basic_null_source</CODE>.</P>

 <A NAME="null_source_read"></A>
 <H4><CODE>basic_null_source::read</CODE></H4>

 <PRE CLASS="broken_ie">    std::streamsize read(char_type* s, std::streamsize n);</PRE>

 <P>Returns <CODE>-1</CODE>.</P>

 <A NAME="null_source_close"></A>
 <H4><CODE>basic_null_source::close</CODE></H4>

 <PRE CLASS="broken_ie">    <SPAN CLASS='keyword'>void</SPAN> close();</PRE>

 <P>No-op.</P>

 <A NAME="null_sink"></A>
 <H3>Class template <CODE>basic_null_sink</CODE></H3>

 <H4>Description</H4>

 <P>Model of <A HREF="../concepts/sink.html">Sink</A> whose member function <CODE>write</CODE> consumes and ignores the contents of the character buffer passed to it.

 <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="#null_sink_params">Ch</A>&gt;
 <SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#null_sink_params">basic_null_sink</A> {
 <SPAN CLASS="keyword">public</SPAN>:
     <SPAN CLASS="keyword">typedef</SPAN> Ch                        char_type;
     <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN>  category;

     <A CLASS="documented" HREF="#null_sink_ctor">basic_null_sink</A>();
     std::streamsize <A CLASS="documented" HREF="#null_sink_write">write</A>(<SPAN CLASS='keyword'>const</SPAN> char_type* s, std::streamsize n);
     <SPAN CLASS='keyword'>void</SPAN> <A CLASS='documented' HREF='#null_sink_close'>close</A>();
 };

 <SPAN CLASS='keyword'>typedef</SPAN> basic_null_sink&lt;<SPAN CLASS='keyword'>char</SPAN>&gt;     <SPAN CLASS='defined'>null_sink</SPAN>;
 <SPAN CLASS='keyword'>typedef</SPAN> basic_null_sink&lt;<SPAN CLASS='keyword'>wchar_t</SPAN>&gt;  <SPAN CLASS='defined'>wnull_sink</SPAN>;

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

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

 <TABLE STYLE="margin-left:2em">
 <TR>
     <TD><P><I>Ch</I></TD><TD VALIGN="top">-</TD>
     <TD><P>The <A HREF='../guide/traits.html#char_type'>character type</A> type.</TD>
 </TR>
 </TABLE>

 <A NAME="null_sink_ctor"></A>

 <H4><CODE>basic_null_sink::basic_null_sink</CODE></H4>

 <PRE CLASS="broken_ie">    basic_null_sink();</PRE>

 <P>Constructs a <CODE>basic_null_sink</CODE>.</P>

 <A NAME="null_sink_write"></A>
 <H4><CODE>basic_null_sink::write</CODE></H4>

 <PRE CLASS="broken_ie">    std::streamsize write(<SPAN CLASS='keyword'>const</SPAN> char_type* s, std::streamsize n);</PRE>

 <P>Returns <CODE>n</CODE>.</P>

 <A NAME="null_sink_close"></A>
 <H4><CODE>basic_null_sink::close</CODE></H4>

 <PRE CLASS="broken_ie">    <SPAN CLASS='keyword'>void</SPAN> close();</PRE>

 <P>No-op.</P>

 <A NAME="null_device"></A>
 <H3>Class template <CODE>basic_null_device</CODE></H3>

 <H4>Description</H4>

 <P>Model of <A HREF="../concepts/seekable_device.html">Device</A> whose mode is specified as a template parameter, and whose member functions have trivial implementations, as follows:</P>
 <UL>
 <LI><CODE>read</CODE> returns <CODE>-1</CODE>, indicating end-of-sequence
 <LI><CODE>write</CODE> consumes but ignores the entire contents of the character buffer passed to it
 <LI><CODE>seek</CODE> returns an invalid stream position
 </UL>

 <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="#null_device_params">Ch</A>, <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#null_device_params">Mode</A>&gt;
 <SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#null_device_params">basic_null_device</A> {
 <SPAN CLASS="keyword">public</SPAN>:
     <SPAN CLASS="keyword">typedef</SPAN> Ch                        char_type;
     <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN>  category;

     <A CLASS="documented" HREF="#null_device_ctor">basic_null_device</A>();
     std::streamsize <A CLASS="documented" HREF="#null_device_read">read</A>(char_type* s, std::streamsize n);
     std::streamsize <A CLASS="documented" HREF="#null_device_write">write</A>(<SPAN CLASS='keyword'>const</SPAN> char_type* s, std::streamsize n);
     <A CLASS='documented' HREF='../functions/positioning.html#synopsis'>stream_offset</A> <A CLASS='documented' HREF='#null_device_seek'>seek</A>( <A CLASS='documented' HREF='../functions/positioning.html#synopsis'>stream_offset</A> off, std::ios_base::seekdir way,
                         std::ios_base::openmode which =
                             std::ios_base::in | std::ios_base::out );
     <SPAN CLASS='keyword'>void</SPAN> <A CLASS='documented' HREF='#null_device_close'>close</A>();
 };

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

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

 <TABLE STYLE="margin-left:2em">
 <TR>
     <TD><P><I>Ch</I></TD><TD VALIGN="top">-</TD>
     <TD><P>The <A HREF='../guide/traits.html#char_type'>character type</A>.</TD>
 </TR>
 <TR>
     <TD><P><I>Mode</I></TD><TD VALIGN="top">-</TD>
     <TD><P>The <A HREF='../guide/modes.html'>mode</A>.</TD>
 </TR>
 </TABLE>

 <A NAME="null_device_ctor"></A>
 <H4><CODE>basic_null_device::basic_null_device</CODE></H4>

 <PRE CLASS="broken_ie">    basic_null_device();</PRE>

 <P>Constructs a <CODE>basic_null_device</CODE>.</P>

 <A NAME="null_device_read"></A>
 <H4><CODE>basic_null_device::read</CODE></H4>

 <PRE CLASS="broken_ie">    std::streamsize read(char_type* s, std::streamsize n);</PRE>

 <P>Returns <CODE>-1</CODE>. Enabled if <CODE>Mode</CODE> refines <A HREF='../guide/modes.html#mode_tags'><CODE>input</CODE></A>.</P>

 <A NAME="null_device_write"></A>
 <H4><CODE>basic_null_device::write</CODE></H4>

 <PRE CLASS="broken_ie">    std::streamsize write(<SPAN CLASS='keyword'>const</SPAN> char_type* s, std::streamsize n);</PRE>

 <P>Returns <CODE>n</CODE>. Enabled if <CODE>Mode</CODE> refines <A HREF='../guide/modes.html#mode_tags'><CODE>output</CODE></A>.</P>

 <A NAME="null_device_seek"></A>
 <H4><CODE>basic_null_device::seek</CODE></H4>

 <PRE CLASS="broken_ie">     <A CLASS='documented' HREF='../functions/positioning.html#synopsis'>stream_offset</A> seek( <A CLASS='documented' HREF='../functions/positioning.html#synopsis'>stream_offset</A> off, std::ios_base::seekdir way,
                          std::ios_base::openmode which =
                              std::ios_base::in | std::ios_base::out );</PRE>

 <P>Returns an invalid stream position. Enabled if <CODE>Mode</CODE> permits random access.</P>

 <A NAME="null_device_close"></A>
 <H4><CODE>basic_null_device::close</CODE></H4>

 <PRE CLASS="broken_ie">    <SPAN CLASS='keyword'>void</SPAN> close();</PRE>

 <P>No-op.</P>

 <!-- 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>Null Devices</TITLE>
	<LINK REL="stylesheet" HREF="../../../../boost.css">
	<LINK REL="stylesheet" HREF="../theme/iostreams.css">
	</HEAD>
	<BODY>

	<!-- Begin Banner -->

	<H1 CLASS="title">Null Devices</H1>
	<HR CLASS="banner">

	<!-- End Banner -->

	<DL class="page-index">
	<DT><A href="#overview">Overview</A></DT>
	<DT><A href="#acknowledgments">Acknowledgments</A></DT>
	<DT><A href="#headers">Headers</A></DT>
	<DT><A href="#reference">Reference</A>
	<DL>
	<DT><A href="#null_source">Class template <CODE>basic_null_source</CODE></A></DT>
	<DT><A href="#null_sink">Class template <CODE>basic_null_sink</CODE></A></DT>
	<DT><A href="#null_device">Class template <CODE>basic_null_device</CODE></A></DT>
	</DL>
	</DT>
	</DL>

	<HR>

	<A NAME="overview"></A>
	<H2>Overview</H2>

	<P>
	The class templates <CODE>basic_null_source</CODE>, <CODE>basic_null_sink</CODE> and <CODE>basic_null_device</CODE> are models of Device whose member functions all have trivial implementations. A <CODE>basic_null_source</CODE> is a <A HREF="../concepts/source.html">Source</A> whose member function <CODE>read</CODE> returns <CODE>-1</CODE>, indicating end-of-sequence. A <CODE>basic_null_sink</CODE> is a <A HREF="../concepts/sink.html">Sink</A> whose member function <CODE>write</CODE> consumes and ignores the characters passed to it. A <CODE>basic_null_device</CODE> combines — depending on its template parameter <A HREF="#null_device_params"><CODE>Mode</CODE></A> — the trivial <CODE>read</CODE> and <CODE>write</CODE> functions just described with a member <CODE>seek</CODE> that always returns an invalid stream position.
	</P>

	<P>
	In addition, each of the above templates is <A HREF='../concepts/closable.html'>Closable</A>, with a no-op implementation of <CODE>close</CODE>.
	</P>

	<A NAME="acknowledgments"></A>
	<H2>Acknowledgments</H2>

	<P>
	The templates described here were inspired by <A HREF="http://www.boost.org/people/daryle_walker.html" TARGET="_top">Daryle Walker's</A> <CODE>basic_nullbuf</CODE> template. <I>See</I> <A HREF="http://cvs.sourceforge.net/viewcvs.py/boost-sandbox/boost-sandbox/libs/io/doc/null_stream.html" TARGET="_top">Disconnected Streams</A>.
	</P>

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

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

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

	<A NAME="null_source"></A>
	<H3>Class template <CODE>basic_null_source</CODE></H3>

	<H4>Description</H4>

	<P>Model of <A HREF="../concepts/source.html">Source</A> whose member function <CODE>read</CODE> returns <CODE>-1</CODE>, indicating end-of-sequence.</P>

	<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="#null_source_params">Ch</A>>
	<SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#null_source_params">basic_null_source</A> {
	<SPAN CLASS="keyword">public</SPAN>:
	<SPAN CLASS="keyword">typedef</SPAN> Ch char_type;
	<SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN> category;

	<A CLASS="documented" HREF="#null_source_ctor">basic_null_source</A>();
	std::streamsize <A CLASS="documented" HREF="#null_source_read">read</A>(char_type* s, std::streamsize n);
	<SPAN CLASS='keyword'>void</SPAN> <A CLASS='documented' HREF='#null_source_close'>close</A>();
	};

	<SPAN CLASS='keyword'>typedef</SPAN> basic_null_source<<SPAN CLASS='keyword'>char</SPAN>> <SPAN CLASS='defined'>null_source</SPAN>;
	<SPAN CLASS='keyword'>typedef</SPAN> basic_null_source<<SPAN CLASS='keyword'>wchar_t</SPAN>> <SPAN CLASS='defined'>wnull_source</SPAN>;

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

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

	<TABLE STYLE="margin-left:2em">
	<TR>
	<TD><P><I>Ch</I></TD><TD VALIGN="top">-</TD>
	<TD><P>The <A HREF='../guide/traits.html#char_type'>character type</A> type.</TD>
	</TR>
	</TABLE>

	<A NAME="null_source_ctor"></A>

	<H4><CODE>basic_null_source::basic_null_source</CODE></H4>

	<PRE CLASS="broken_ie"> basic_null_source();</PRE>

	<P>Constructs a <CODE>basic_null_source</CODE>.</P>

	<A NAME="null_source_read"></A>
	<H4><CODE>basic_null_source::read</CODE></H4>

	<PRE CLASS="broken_ie"> std::streamsize read(char_type* s, std::streamsize n);</PRE>

	<P>Returns <CODE>-1</CODE>.</P>

	<A NAME="null_source_close"></A>
	<H4><CODE>basic_null_source::close</CODE></H4>

	<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>void</SPAN> close();</PRE>

	<P>No-op.</P>

	<A NAME="null_sink"></A>
	<H3>Class template <CODE>basic_null_sink</CODE></H3>

	<H4>Description</H4>

	<P>Model of <A HREF="../concepts/sink.html">Sink</A> whose member function <CODE>write</CODE> consumes and ignores the contents of the character buffer passed to it.

	<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="#null_sink_params">Ch</A>>
	<SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#null_sink_params">basic_null_sink</A> {
	<SPAN CLASS="keyword">public</SPAN>:
	<SPAN CLASS="keyword">typedef</SPAN> Ch char_type;
	<SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN> category;

	<A CLASS="documented" HREF="#null_sink_ctor">basic_null_sink</A>();
	std::streamsize <A CLASS="documented" HREF="#null_sink_write">write</A>(<SPAN CLASS='keyword'>const</SPAN> char_type* s, std::streamsize n);
	<SPAN CLASS='keyword'>void</SPAN> <A CLASS='documented' HREF='#null_sink_close'>close</A>();
	};

	<SPAN CLASS='keyword'>typedef</SPAN> basic_null_sink<<SPAN CLASS='keyword'>char</SPAN>> <SPAN CLASS='defined'>null_sink</SPAN>;
	<SPAN CLASS='keyword'>typedef</SPAN> basic_null_sink<<SPAN CLASS='keyword'>wchar_t</SPAN>> <SPAN CLASS='defined'>wnull_sink</SPAN>;

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

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

	<TABLE STYLE="margin-left:2em">
	<TR>
	<TD><P><I>Ch</I></TD><TD VALIGN="top">-</TD>
	<TD><P>The <A HREF='../guide/traits.html#char_type'>character type</A> type.</TD>
	</TR>
	</TABLE>

	<A NAME="null_sink_ctor"></A>

	<H4><CODE>basic_null_sink::basic_null_sink</CODE></H4>

	<PRE CLASS="broken_ie"> basic_null_sink();</PRE>

	<P>Constructs a <CODE>basic_null_sink</CODE>.</P>

	<A NAME="null_sink_write"></A>
	<H4><CODE>basic_null_sink::write</CODE></H4>

	<PRE CLASS="broken_ie"> std::streamsize write(<SPAN CLASS='keyword'>const</SPAN> char_type* s, std::streamsize n);</PRE>

	<P>Returns <CODE>n</CODE>.</P>

	<A NAME="null_sink_close"></A>
	<H4><CODE>basic_null_sink::close</CODE></H4>

	<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>void</SPAN> close();</PRE>

	<P>No-op.</P>

	<A NAME="null_device"></A>
	<H3>Class template <CODE>basic_null_device</CODE></H3>

	<H4>Description</H4>

	<P>Model of <A HREF="../concepts/seekable_device.html">Device</A> whose mode is specified as a template parameter, and whose member functions have trivial implementations, as follows:</P>
	<UL>
	<LI><CODE>read</CODE> returns <CODE>-1</CODE>, indicating end-of-sequence
	<LI><CODE>write</CODE> consumes but ignores the entire contents of the character buffer passed to it
	<LI><CODE>seek</CODE> returns an invalid stream position
	</UL>

	<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="#null_device_params">Ch</A>, <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#null_device_params">Mode</A>>
	<SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#null_device_params">basic_null_device</A> {
	<SPAN CLASS="keyword">public</SPAN>:
	<SPAN CLASS="keyword">typedef</SPAN> Ch char_type;
	<SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS='omitted'>[implementation-defined]</SPAN> category;

	<A CLASS="documented" HREF="#null_device_ctor">basic_null_device</A>();
	std::streamsize <A CLASS="documented" HREF="#null_device_read">read</A>(char_type* s, std::streamsize n);
	std::streamsize <A CLASS="documented" HREF="#null_device_write">write</A>(<SPAN CLASS='keyword'>const</SPAN> char_type* s, std::streamsize n);
	<A CLASS='documented' HREF='../functions/positioning.html#synopsis'>stream_offset</A> <A CLASS='documented' HREF='#null_device_seek'>seek</A>( <A CLASS='documented' HREF='../functions/positioning.html#synopsis'>stream_offset</A> off, std::ios_base::seekdir way,
	std::ios_base::openmode which =
	std::ios_base::in \| std::ios_base::out );
	<SPAN CLASS='keyword'>void</SPAN> <A CLASS='documented' HREF='#null_device_close'>close</A>();
	};

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

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

	<TABLE STYLE="margin-left:2em">
	<TR>
	<TD><P><I>Ch</I></TD><TD VALIGN="top">-</TD>
	<TD><P>The <A HREF='../guide/traits.html#char_type'>character type</A>.</TD>
	</TR>
	<TR>
	<TD><P><I>Mode</I></TD><TD VALIGN="top">-</TD>
	<TD><P>The <A HREF='../guide/modes.html'>mode</A>.</TD>
	</TR>
	</TABLE>

	<A NAME="null_device_ctor"></A>
	<H4><CODE>basic_null_device::basic_null_device</CODE></H4>

	<PRE CLASS="broken_ie"> basic_null_device();</PRE>

	<P>Constructs a <CODE>basic_null_device</CODE>.</P>

	<A NAME="null_device_read"></A>
	<H4><CODE>basic_null_device::read</CODE></H4>

	<PRE CLASS="broken_ie"> std::streamsize read(char_type* s, std::streamsize n);</PRE>

	<P>Returns <CODE>-1</CODE>. Enabled if <CODE>Mode</CODE> refines <A HREF='../guide/modes.html#mode_tags'><CODE>input</CODE></A>.</P>

	<A NAME="null_device_write"></A>
	<H4><CODE>basic_null_device::write</CODE></H4>

	<PRE CLASS="broken_ie"> std::streamsize write(<SPAN CLASS='keyword'>const</SPAN> char_type* s, std::streamsize n);</PRE>

	<P>Returns <CODE>n</CODE>. Enabled if <CODE>Mode</CODE> refines <A HREF='../guide/modes.html#mode_tags'><CODE>output</CODE></A>.</P>

	<A NAME="null_device_seek"></A>
	<H4><CODE>basic_null_device::seek</CODE></H4>

	<PRE CLASS="broken_ie"> <A CLASS='documented' HREF='../functions/positioning.html#synopsis'>stream_offset</A> seek( <A CLASS='documented' HREF='../functions/positioning.html#synopsis'>stream_offset</A> off, std::ios_base::seekdir way,
	std::ios_base::openmode which =
	std::ios_base::in \| std::ios_base::out );</PRE>

	<P>Returns an invalid stream position. Enabled if <CODE>Mode</CODE> permits random access.</P>

	<A NAME="null_device_close"></A>
	<H4><CODE>basic_null_device::close</CODE></H4>

	<PRE CLASS="broken_ie"> <SPAN CLASS='keyword'>void</SPAN> close();</PRE>

	<P>No-op.</P>

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	<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>)
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