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200 lines
9.4 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 write</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>write</CODE></H1>
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<HR CLASS='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 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>.
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<UL>
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<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='../concepts.html#device_concepts'>Device</A> concepts.
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<LI>The second overload is primarily for internal use by the library.
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</UL>
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</P>
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<P>
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Although <CODE>write</CODE> is designed to be overloaded or specialized for new Filter and Device types, the default implementation should be suitable for most purposes.</P>
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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>write</CODE> in the definition of an <A HREF='../concepts/output_filter.html'>OutputFilter</A> which reverses its controlled sequence.
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</P>
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<PRE CLASS='broken_ie'> <SPAN CLASS='preprocessor'>#include</SPAN> <SPAN CLASS='literal'><algorithm></SPAN> <SPAN CLASS='comment'>// reverse</SPAN>
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<SPAN CLASS='preprocessor'>#include</SPAN> <SPAN CLASS='literal'><vector></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'>// output_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'>// write</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> reversing_filter : <SPAN CLASS="keyword">public</SPAN> multichar_output_filter {
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<SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> Sink>
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<SPAN CLASS="keyword">void</SPAN> write(Sink& snk, <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">char</SPAN>* s, streamsize n)
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{
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data.insert(data.end(), s, s + n);
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}
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<SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> Sink>
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<SPAN CLASS="keyword">void</SPAN> close(Sink& snk)
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{
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std::reverse(data.begin(), data.end());
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boost::iostreams::write(&data[0], (streamsize) data.size());
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data.clear();
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}
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std::vector<<SPAN CLASS="keyword">char</SPAN>> data;
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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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Writes a sequence of characters to a given instance of the template parameter <CODE>T</CODE>.
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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">T</A>>
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void <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='../traits.html#io_char_ref'>io_char</A><T>::type* <A CLASS="documented" HREF="#function_params">s</A>, std::streamsize <A CLASS="documented" HREF="#function_params">n</A> );
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<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>>
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void <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='../traits.html#io_char_ref'>io_char</A><T>::type* <A CLASS="documented" HREF="#function_params">s</A>, std::streamsize <A CLASS="documented" HREF="#function_params">n</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>T</I></TD><TD WIDTH='2em' VALIGN='top'>-</TD>
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<TD>For the first overload, a model of <A HREF='../concepts/sink.html'>Sink</A> or a standard output stream or stream buffer type. For the second overload, a model of <A HREF='../concepts/output_filter.html'>OutputFilter</A>.
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</TR>
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<TR>
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<TD VALIGN='top'><I>Sink</I></TD><TD WIDTH='2em' VALIGN='top'>-</TD>
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<TD>A model of <A HREF='../concepts/sink.html'>Sink</A> with the same <A HREF='../traits.html#char_type'>character type</A> as <CODE>T</CODE> whose <A HREF='../modes.html'>i/o mode</A> refines that of <CODE>T</CODE>.
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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>t</I></TD><TD WIDTH='2em' VALIGN='top'>-</TD>
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<TD>An instance of the <A HREF='../concepts/sink.html'>Sink</A> type<CODE> T</CODE></TD>
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</TR>
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<TR>
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<TD VALIGN='top'><I>s</I></TD><TD WIDTH='2em' VALIGN='top'>-</TD>
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<TD>A buffer containing characters to write</TD>
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</TR>
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<TR>
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<TD VALIGN='top'><I>n</I></TD><TD WIDTH='2em' VALIGN='top'>-</TD>
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<TD>The number of characters to write</TD>
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</TR>
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<TR>
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<TD VALIGN='top'><I>snk</I></TD><TD WIDTH='2em' VALIGN='top'>-</TD>
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<TD>An instance of <CODE>Sink</CODE>.
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</TR>
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</TABLE>
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<A NAME='write_device'></A>
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<H4>Semantics — Device Types</H4>
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<PRE CLASS='broken_ie'><SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> T>
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void write( T& t, <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">typename</SPAN> io_char<T>::type* s, std::streamsize n );</PRE>
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<P>The semantics of <CODE>write</CODE> depends on the <A HREF="../traits.html#category">category</A> of <CODE>T</CODE> as follows:</P>
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<TABLE STYLE='margin-left:2em' BORDER=1 CELLPADDING=4>
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<TR><TH><CODE>io_category<T>::type</CODE></TH><TH>semantics</TH></TR>
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<TR>
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<TD VALIGN='top'>convertible to <CODE>ostream_tag</CODE></TD>
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<TD>invokes <CODE>t.write(s, n)</CODE></TD>
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</TR>
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<TR>
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<TD VALIGN='top'>convertible to <CODE>streambuf_tag</CODE> but not to <CODE>ostream_tag</CODE></TD>
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<TD>invokes <CODE>t.sputn(s, n)</CODE></TD>
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</TR>
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<TR>
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<TD VALIGN='top'>convertible to <CODE>insert_iterator_tag</CODE></TD>
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<TD>invokes <CODE>std::copy(s, s + n, t)</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>invokes <CODE>t.write(s, n)</CODE></TD>
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</TR>
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</TABLE>
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<A NAME='write_filter'></A>
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<H4>Semantics — Filter Types</H4>
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<PRE CLASS='broken_ie'><SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> T, <SPAN CLASS="keyword">typename</SPAN> Sink>
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void write( T& t, Sink& snk,
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<SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">typename</SPAN> io_char<T>::type* s, std::streamsize n );</PRE>
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<P>The semantics of <CODE>read</CODE> depends on the <A HREF="../traits.html#category">category</A> of <CODE>T</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<T>::type</CODE></TH><TH>semantics</TH></TR>
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<TR>
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<TD VALIGN='top'>convertible to <CODE>multichar_tag</CODE></TD>
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<TD>invokes <CODE>t.write(snk, s, n)</CODE></TD>
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</TR>
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<TR>
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<TD VALIGN='top'><I>otherwise</I></TD>
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<TD>writes <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></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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