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<H1 CLASS="title">Function Template <CODE>write</CODE></H1>
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<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 two overloads of the function template <CODE>write</CODE> provide a uniform interface for writing a sequence of characters to a <A HREF="../concepts/source.html">Sink</A> or <A HREF="../concepts/output_filter.html">OutputFilter</A>.
<UL>
<LI>The first overload can be used directly in the definitions of new Filter types (<I>see</I> <A HREF="#example">Example</A>), and figures in the specification of the <A HREF="../guide/concepts.html#device_concepts">Device</A> concepts.
<LI>The second overload is primarily for internal use by the library.
</UL>
</P>
<A NAME="example"></A>
<H2>Example</H2>
<P>
The following code illustrates the use of the function <CODE>write</CODE> in the definition of an <A HREF="../concepts/output_filter.html">OutputFilter</A> which reverses its controlled sequence.
</P>
<PRE CLASS="broken_ie"> <SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal"><algorithm></SPAN> <SPAN CLASS="comment">// reverse</SPAN>
<SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal"><vector></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">// output_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">// write</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> reversing_filter : <SPAN CLASS="keyword">public</SPAN> multichar_output_filter {
<SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> Sink>
std::streamsize write(Sink& snk, <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">char</SPAN>* s, streamsize n)
{
data.insert(data.end(), s, s + n);
<SPAN CLASS="keyword">return</SPAN> n;
}
<SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> Sink>
<SPAN CLASS="keyword">void</SPAN> close(Sink& snk)
{
std::reverse(data.begin(), data.end());
boost::iostreams::write(&data[0], (streamsize) data.size());
data.clear();
}
std::vector<<SPAN CLASS="keyword">char</SPAN>> data;
};</PRE>
<A NAME="headers"></A>
<H2>Headers</H2>
<DL>
<DT><A CLASS="header" HREF="../../../../boost/iostreams/operations.hpp"><CODE><boost/iostreams/operations.hpp></CODE></A></DT>
<DT><A CLASS="header" HREF="../../../../boost/iostreams/write.hpp"><CODE><boost/iostreams/write.hpp></CODE></A></DT>
</DL>
<A NAME="reference"></A>
<H2>Reference</H2>
<A NAME="description"></A>
<H4>Description</H4>
<P>Attempts to write a sequence of characters to a given instance of the template parameter <CODE>T</CODE>, returning the number of characters written.</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">T</A>>
std::streamsize
<A CLASS="documented" HREF="#write_device">write</A>( T& <A CLASS="documented" HREF="#function_params">t</A>,
<SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="../guide/traits.html#char_type_of_ref">char_type_of</A><T>::type* <A CLASS="documented" HREF="#function_params">s</A>,
std::streamsize <A CLASS="documented" HREF="#function_params">n</A> );
<SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">T</A>, <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Sink</A>>
std::streamsize
<A CLASS="documented" HREF="#write_filter">write</A>( T& <A CLASS="documented" HREF="#function_params">t</A>,
Sink& <A CLASS="documented" HREF="#function_params">snk</A>,
<SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="../guide/traits.html#char_type_of_ref">char_type_of</A><T>::type* <A CLASS="documented" HREF="#function_params">s</A>,
std::streamsize <A CLASS="documented" HREF="#function_params">n</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>T</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>For the first overload, a model of <A HREF="../concepts/sink.html">Sink</A>. For the second overload, a model of <A HREF="../concepts/output_filter.html">OutputFilter</A>.
</TR>
<TR>
<TD VALIGN="top"><I>Sink</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>A model of <A HREF="../concepts/sink.html">Sink</A> with the same <A HREF="../guide/traits.html#char_type">character type</A> as <CODE>T</CODE> whose <A HREF="../guide/modes.html">mode</A> refines that of <CODE>T</CODE>.
</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>t</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>An instance of T</CODE></TD>
</TR>
<TR>
<TD VALIGN="top"><I>s</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>A buffer containing characters to write</TD>
</TR>
<TR>
<TD VALIGN="top"><I>n</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>The number of characters to write</TD>
</TR>
<TR>
<TD VALIGN="top"><I>snk</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
<TD>An instance of <CODE>Sink</CODE>.
</TR>
</TABLE>
<A NAME="write_device"></A>
<H4>Semantics — Device Types</H4>
<PRE CLASS="broken_ie"><SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> T>
std::streamsize
write( T& t,
<SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">typename</SPAN> char_type_of<T>::type* s,
std::streamsize n );</PRE>
<P>The semantics of <CODE>write</CODE> depends on the <A HREF="../guide/traits.html#category">category</A> of <CODE>T</CODE> as follows:</P>
<TABLE STYLE="margin-left:2em" BORDER=1 CELLPADDING=4>
<TR><TH><CODE>category_of<T>::type</CODE></TH><TH>semantics</TH></TR>
<TR>
<TD VALIGN="top">convertible to <CODE>ostream_tag</CODE></TD>
<TD>returns <CODE>t.rdbuf()->sputn(s, n)</CODE></TD>
</TR>
<TR>
<TD VALIGN="top">convertible to <CODE>streambuf_tag</CODE> but not to <CODE>ostream_tag</CODE></TD>
<TD>returns <CODE>t.sputn(s, n)</CODE></TD>
</TR>
<TR>
<TD VALIGN="top">otherwise</TD>
<TD>returns <CODE>t.write(s, n)</CODE></TD>
</TR>
</TABLE>
<A NAME="write_filter"></A>
<H4>Semantics — Filter Types</H4>
<PRE CLASS="broken_ie"><SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> T, <SPAN CLASS="keyword">typename</SPAN> Sink>
std::streamsize
write( T& t,
Sink& snk,
<SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">typename</SPAN> char_type_of<T>::type* s,
std::streamsize n );</PRE>
<P>The semantics of <CODE>write</CODE> depends on the <A HREF="../guide/traits.html#category">category</A> of <CODE>T</CODE> as follows:</P>
<TABLE STYLE="margin:0,0,2em,2em" BORDER=1 CELLPADDING=4>
<TR><TH><CODE>category_of<T>::type</CODE></TH><TH>semantics</TH></TR>
<TR>
<TD VALIGN="top">convertible to <CODE>multichar_tag</CODE></TD>
<TD>returns <CODE>t.write(snk, s, n)</CODE></TD>
</TR>
<TR>
<TD VALIGN="top"><I>otherwise</I></TD>
<TD>Attempts to write <CODE>n</CODE> characters from <CODE>s</CODE> by invoking <CODE>t.put(snk, s[m])</CODE> for each value <CODE>m</CODE> in the interval <CODE>[0, n)</CODE>, halting if <CODE>put</CODE> returns <CODE>false</CODE>. Returns the number of characters written.</TD>
</TR>
</TABLE>
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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>
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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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