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4 | <TITLE>Function Template write</TITLE> | |
5 | <LINK REL="stylesheet" HREF="../../../../boost.css"> | |
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7 | </HEAD> | |
8 | <BODY> | |
9 | ||
10 | <!-- Begin Banner --> | |
11 | ||
12 | <H1 CLASS="title">Function Template <CODE>write</CODE></H1> | |
13 | <HR CLASS="banner"> | |
14 | ||
15 | <!-- End Banner --> | |
16 | ||
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"><algorithm></SPAN> <SPAN CLASS="comment">// reverse</SPAN> | |
43 | <SPAN CLASS="preprocessor">#include</SPAN> <SPAN CLASS="literal"><vector></SPAN> | |
44 | <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> | |
45 | <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> | |
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><<SPAN CLASS="keyword">typename</SPAN> Sink> | |
52 | std::streamsize write(Sink& 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><<SPAN CLASS="keyword">typename</SPAN> Sink> | |
58 | <SPAN CLASS="keyword">void</SPAN> close(Sink& snk) | |
59 | { | |
60 | std::reverse(data.begin(), data.end()); | |
61 | boost::iostreams::write(&data[0], (streamsize) data.size()); | |
62 | data.clear(); | |
63 | } | |
64 | std::vector<<SPAN CLASS="keyword">char</SPAN>> 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><boost/iostreams/operations.hpp></CODE></A></DT> | |
72 | <DT><A CLASS="header" HREF="../../../../boost/iostreams/write.hpp"><CODE><boost/iostreams/write.hpp></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><<SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">T</A>> | |
89 | std::streamsize | |
90 | <A CLASS="documented" HREF="#write_device">write</A>( T& <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><T>::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><<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>> | |
95 | std::streamsize | |
96 | <A CLASS="documented" HREF="#write_filter">write</A>( T& <A CLASS="documented" HREF="#function_params">t</A>, | |
97 | Sink& <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><T>::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 — Device Types</H4> | |
143 | ||
144 | <PRE CLASS="broken_ie"><SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> T> | |
145 | std::streamsize | |
146 | write( T& t, | |
147 | <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">typename</SPAN> char_type_of<T>::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<T>::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 — Filter Types</H4> | |
170 | ||
171 | <PRE CLASS="broken_ie"><SPAN CLASS="keyword">template</SPAN><<SPAN CLASS="keyword">typename</SPAN> T, <SPAN CLASS="keyword">typename</SPAN> Sink> | |
172 | std::streamsize | |
173 | write( T& t, | |
174 | Sink& snk, | |
175 | <SPAN CLASS="keyword">const</SPAN> <SPAN CLASS="keyword">typename</SPAN> char_type_of<T>::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<T>::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> | |
191 | ||
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195 | ||
196 | <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> | |
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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