ceph/src/boost/libs/iostreams/doc/functions/write.html

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   4     <TITLE>Function Template write</TITLE>
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  12     <H1 CLASS="title">Function Template <CODE>write</CODE></H1>
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  17 <DL class="page-index">
  18   <DT><A href="#overview">Overview</A></DT>
  19   <DT><A href="#example">Example</A></DT>
  20   <DT><A href="#headers">Headers</A></DT>
  21   <DT><A href="#reference">Reference</A></DT>
  22 </DL>
  23
  24 <A NAME="overview"></A>
  25 <H2>Overview</H2>
  26
  27 <P>
  28     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>.
  29     <UL>
  30         <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.
  31         <LI>The second overload is primarily for internal use by the library.
  32     </UL>
  33 </P>
  34
  35 <A NAME="example"></A>
  36 <H2>Example</H2>
  37
  38 <P>
  39     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.
  40 </P>
  41
  42 <PRE CLASS="broken_ie">    <SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal">&lt;algorithm&gt;</SPAN>                      <SPAN CLASS="comment">// reverse</SPAN>
  43     <SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal">&lt;vector&gt;</SPAN>
  44     <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/concepts.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/concepts.hpp&gt;</SPAN></A>   <SPAN CLASS="comment">// output_filter</SPAN>
  45     <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/operations.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/operations.hpp&gt;</SPAN></A> <SPAN CLASS="comment">// write</SPAN>
  46
  47     <SPAN CLASS="keyword">using</SPAN> <SPAN CLASS="keyword">namespace</SPAN> std;
  48     <SPAN CLASS="keyword">using</SPAN> <SPAN CLASS="keyword">namespace</SPAN> boost::io;
  49
  50     <SPAN CLASS="keyword">struct</SPAN> reversing_filter : <SPAN CLASS="keyword">public</SPAN> multichar_output_filter {
  51         <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Sink&gt;
  52         std::streamsize write(Sink&amp; snk, <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">char</SPAN>* s, streamsize n)
  53         {
  54             data.insert(data.end(), s, s + n);
  55             <SPAN CLASS="keyword">return</SPAN> n;
  56         }
  57         <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> Sink&gt;
  58         <SPAN CLASS="keyword">void</SPAN> close(Sink&amp; snk)
  59         {
  60             std::reverse(data.begin(), data.end());
  61             boost::iostreams::write(&amp;data[0], (streamsize) data.size());
  62             data.clear();
  63         }
  64         std::vector&lt;<SPAN CLASS="keyword">char</SPAN>&gt; data;
  65     };</PRE>
  66
  67 <A NAME="headers"></A>
  68 <H2>Headers</H2>
  69
  70 <DL>
  71   <DT><A CLASS="header" HREF="../../../../boost/iostreams/operations.hpp"><CODE>&lt;boost/iostreams/operations.hpp&gt;</CODE></A></DT>
  72   <DT><A CLASS="header" HREF="../../../../boost/iostreams/write.hpp"><CODE>&lt;boost/iostreams/write.hpp&gt;</CODE></A></DT>
  73 </DL>
  74
  75 <A NAME="reference"></A>
  76 <H2>Reference</H2>
  77
  78 <A NAME="description"></A>
  79 <H4>Description</H4>
  80
  81 <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>
  82
  83 <A NAME="synopsis"></A>
  84 <H4>Synopsis</H4>
  85
  86 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
  87
  88 <SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">T</A>&gt;
  89 std::streamsize
  90 <A CLASS="documented" HREF="#write_device">write</A>( T&amp; <A CLASS="documented" HREF="#function_params">t</A>,
  91        <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>&lt;T&gt;::type* <A CLASS="documented" HREF="#function_params">s</A>,
  92        std::streamsize <A CLASS="documented" HREF="#function_params">n</A> );
  93
  94 <SPAN CLASS="keyword">template</SPAN>&lt;<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>&gt;
  95 std::streamsize
  96 <A CLASS="documented" HREF="#write_filter">write</A>( T&amp; <A CLASS="documented" HREF="#function_params">t</A>,
  97        Sink&amp; <A CLASS="documented" HREF="#function_params">snk</A>,
  98        <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>&lt;T&gt;::type* <A CLASS="documented" HREF="#function_params">s</A>,
  99        std::streamsize <A CLASS="documented" HREF="#function_params">n</A> );
 100
 101 } } <SPAN CLASS="comment">// End namespace boost::io</SPAN></PRE>
 102
 103 <A NAME="template_params"></A>
 104 <H4>Template Parameters</H4>
 105
 106 <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
 107 <TR>
 108     <TR>
 109         <TD VALIGN="top"><I>T</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 110         <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>.
 111     </TR>
 112     <TR>
 113         <TD VALIGN="top"><I>Sink</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 114         <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>.
 115     </TR>
 116 </TABLE>
 117
 118 <A NAME="function_params"></A>
 119 <H4>Function Parameters</H4>
 120
 121 <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
 122 <TR>
 123     <TR>
 124         <TD VALIGN="top"><I>t</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 125         <TD>An instance of T</CODE></TD>
 126     </TR>
 127     <TR>
 128         <TD VALIGN="top"><I>s</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 129         <TD>A buffer containing characters to write</TD>
 130     </TR>
 131     <TR>
 132         <TD VALIGN="top"><I>n</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 133         <TD>The number of characters to write</TD>
 134     </TR>
 135     <TR>
 136         <TD VALIGN="top"><I>snk</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
 137         <TD>An instance of <CODE>Sink</CODE>.
 138     </TR>
 139 </TABLE>
 140
 141 <A NAME="write_device"></A>
 142 <H4>Semantics &#8212; Device Types</H4>
 143
 144 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> T&gt;
 145 std::streamsize
 146 write( T&amp; t,
 147        <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">typename</SPAN> char_type_of&lt;T&gt;::type* s,
 148        std::streamsize n );</PRE>
 149
 150 <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>
 151
 152 <TABLE STYLE="margin-left:2em" BORDER=1 CELLPADDING=4>
 153     <TR><TH><CODE>category_of&lt;T&gt;::type</CODE></TH><TH>semantics</TH></TR>
 154     <TR>
 155         <TD VALIGN="top">convertible to <CODE>ostream_tag</CODE></TD>
 156         <TD>returns <CODE>t.rdbuf()->sputn(s, n)</CODE></TD>
 157     </TR>
 158     <TR>
 159         <TD VALIGN="top">convertible to <CODE>streambuf_tag</CODE> but not to <CODE>ostream_tag</CODE></TD>
 160         <TD>returns <CODE>t.sputn(s, n)</CODE></TD>
 161     </TR>
 162     <TR>
 163         <TD VALIGN="top">otherwise</TD>
 164         <TD>returns <CODE>t.write(s, n)</CODE></TD>
 165     </TR>
 166 </TABLE>
 167
 168 <A NAME="write_filter"></A>
 169 <H4>Semantics &#8212; Filter Types</H4>
 170
 171 <PRE CLASS="broken_ie"><SPAN CLASS="keyword">template</SPAN>&lt;<SPAN CLASS="keyword">typename</SPAN> T, <SPAN CLASS="keyword">typename</SPAN> Sink&gt;
 172 std::streamsize
 173 write( T&amp; t,
 174        Sink&amp; snk,
 175        <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">typename</SPAN> char_type_of&lt;T&gt;::type* s,
 176        std::streamsize n );</PRE>
 177
 178 <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>
 179
 180 <TABLE STYLE="margin:0,0,2em,2em" BORDER=1 CELLPADDING=4>
 181     <TR><TH><CODE>category_of&lt;T&gt;::type</CODE></TH><TH>semantics</TH></TR>
 182     <TR>
 183         <TD VALIGN="top">convertible to <CODE>multichar_tag</CODE></TD>
 184         <TD>returns <CODE>t.write(snk, s, n)</CODE></TD>
 185     </TR>
 186     <TR>
 187         <TD VALIGN="top"><I>otherwise</I></TD>
 188         <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>
 189     </TR>
 190 </TABLE>
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 196 <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>
 197 <P CLASS="copyright">
 198     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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