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1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
2<HTML>
3<HEAD>
4    <TITLE>Class Template code_converter</TITLE>
5    <LINK REL="stylesheet" HREF="../../../../boost.css">
6    <LINK REL="stylesheet" HREF="../theme/iostreams.css">
7</HEAD>
8<BODY>
9
10<!-- Begin Banner -->
11
12    <H1 CLASS="title">Class Template <CODE>code_converter</CODE></H1>
13    <HR CLASS="banner">
14
15<!-- End Banner -->
16
17<DL class="page-index">
18  <DT><A href="#description">Description</A></DT>
19  <DT><A href="#headers">Headers</A></DT>
20  <DT><A href="#reference">Reference</A></DT>
21</DL>
22
23<HR>
24
25<A NAME="description"></A>
26<H2>Description</H2>
27
28<P>
29    The class templates <CODE>code_converter</CODE> is a <SPAN CLASS="term">Device adapter</SPAN> which takes a Device with a narrow <A HREF="../guide/traits.html#char_type">character type</A> — typically <CODE>char</CODE> — and produces a Device with wide character type — typically <CODE>wchar_t</CODE> — by introducing a layer of <A HREF="../guide/code_conversion.html">code conversion</A>. The code conversion is performed using a <CODE>std::codecvt</CODE> facet which can either be specified as a template parameter or be fetched from a <CODE>std::locale</CODE> provided at runtime.
30</P>
31<P>
32    For example, we can define a wide-character Device for reading from a memory-mapped file as follows:
33    <PRE CLASS="broken_ie">    <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/device/mapped_file.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/maped_file.hpp&gt;</SPAN></A>
34
35    <SPAN CLASS="keyword">typedef</SPAN> code_converter&lt;mapped_file_source&gt; my_source;</PRE>
36
37    Similarly, we can define a wide-character Device which writes multibyte characters to an in-memory character sequence as follows:
38
39    <PRE CLASS="broken_ie">    <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/device/array.hpp"><SPAN CLASS="literal">&lt;boost/iostreams/device/array.hpp&gt;</SPAN></A>
40
41    <SPAN CLASS="keyword">typedef</SPAN> code_converter&lt;array_sink&gt; my_sink;</PRE>
42</P>
43<P>
44    The <A HREF="../guide/modes.html">mode</A> of a specialization of <CODE>code_converter</CODE> is determined as follows. If a narrow character Device is read-only, the resulting specialization of <CODE>code_converter</CODE> has mode <A HREF="../guide/modes.html#input">input</A>. If a narrow character Device is write-only, the resulting specialization of <CODE>code_converter</CODE> has mode <A HREF="../guide/modes.html#output">output</A>. If a narrow character Device performs input and output using two distinct sequences (<I>see</I> <A HREF="../guide/modes.html">Modes</A>), the resulting specialization of <CODE>code_converter</CODE> has mode <A HREF="../guide/modes.html#bidirectional">bidirectional</A>. Otherwise, attempting to spcialize <CODE>code_converter</CODE> results in a compile-time error.
45</P>
46
47<A NAME="headers"></A>
48<H2>Headers</H2>
49
50<DL class="page-index">
51  <DT><A CLASS="header" HREF="../../../../boost/iostreams/code_converter.hpp"><CODE>&lt;boost/iostreams/code_converter.hpp&gt;</CODE></A></DT>
52</DL>
53
54<A NAME="reference"></A>
55<H2>Reference</H2>
56
57<H4>Synopsis</H4>
58
59<PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams {
60
61<SPAN CLASS="keyword">template</SPAN>&lt; <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Device</A>,
62          <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Codecvt</A> = <SPAN CLASS='omitted'>default_value</SPAN>
63          <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Alloc</A> = std::allocator&lt;<CODE>char</CODE>&gt; &gt;
64<SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#template_params">code_converter</A> {
65<SPAN CLASS="keyword">public</SPAN>:
66    <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">typename</SPAN> Codecvt::intern_type  char_type;
67    <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="omitted">implementation-defined</SPAN>         category;
68    <A CLASS="documented" HREF="#constructors">code_converter</A>();
69    <A CLASS="documented" HREF="#constructors">code_converter</A>( <SPAN CLASS="keyword">const</SPAN> Device& dev,
70                    std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN> );
71    <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#open">open</A>( <SPAN CLASS="keyword">const</SPAN> Device& dev,
72               std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN> );
73    <SPAN CLASS="keyword">bool</SPAN> <A CLASS="documented" HREF="#is_open">is_open</A>() <SPAN CLASS="keyword">const</SPAN>;
74    <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#close">close</A>();
75    std::locale <A CLASS="documented" HREF="#imbue">imbue</A>(<SPAN CLASS="keyword">const</SPAN> std::locale& loc);
76    Device& <A CLASS="documented" HREF="#operator_star">operator*</A>();
77    Device* <A CLASS="documented" HREF="#operator_arrow">operator-&gt;</A>();
78};
79
80} } <SPAN CLASS="comment">// End namespace boost::io</SPAN></PRE>
81
82<A NAME="template_params"></A>
83<H4>Template parameters</H4>
84
85<TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2>
86<TR>
87    <TR>
88        <TD VALIGN="top"><I>Device</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
89        <TD>A model of one of the <A HREF="../guide/concepts.html#device_concepts">Device</A> concepts; typically has <A HREF="../guide/traits.html#char_type">character type</A> <CODE>char</CODE>.</TD>
90    </TR>
91    <TR>
92        <TD VALIGN="top"><I>Codecvt</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
93        <TD>
94            A standard library codecvt facet, which must be default constructible. If this parameter is not specified,
95            an instance of <CODE>std::codecvt&lt;wchar_t, char, std::mbstate_t&gt;</CODE> will be fetched from the global
96            local when a <CODE>code_converter</CODE> is constructed or opened.
97        </TD>
98    </TR>
99    <TR>
100        <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD>
101        <TD>A standard library allocator type (<A CLASS="bib_ref" HREF="../bibliography.html#iso">[ISO]</A>, 20.1.5), used to allocate character buffers</TD>
102    </TR>
103</TABLE>
104
105<A NAME="constructors"></A>
106<H4><CODE>code_converter::code_converter</CODE></H4>
107
108<PRE CLASS="broken_ie">    code_converter();
109    code_converter( <SPAN CLASS="keyword">const</SPAN> Device& dev,
110                    std::streamsize buffer_size );</PRE>
111   
112<P>
113    The first member constructs a <CODE>code_converter</CODE> with no associated instance of the Device type <CODE>Device</CODE>. Before the instance can be used for i/o, the member function <CODE>open()</CODE> must be invoked.
114</P>
115   
116<P>
117    The second member constructs a <CODE>code_converter</CODE> based on the given instance of <CODE>Device</CODE>. The second parameter determines the size of the buffers or buffers used for code conversion. If a <CODE>std::codecvt</CODE> was specified as a template parameter, an instance of it will be default constructed. Otherwise, a copy of the global <CODE>locale</CODE> will be made, and an instance of <CODE>std::codecvt&lt;wchar_t, char, std::mbstate_t&gt;</CODE> will be fetched from it.
118</P>
119
120<A NAME="imbue"></A>
121<H4><CODE>code_converter::imbue</CODE></H4>
122
123<PRE CLASS="broken_ie">    std::locale imbue(<SPAN CLASS="keyword">const</SPAN> std::locale& loc);</PRE>
124
125<P>
126    Used to specify a locale from which a <CODE>std::codecvt</CODE> facet will be fetched to perform code conversion. The effect of invoking imbue while code conversion is in progress is undefined.
127</P>
128
129<P>
130    This function is a no-op if a <CODE>std::codecvt</CODE> facet was specified as a template parameter.
131</P>
132
133<A NAME="open"></A>
134<H4><CODE>code_converter::open</CODE></H4>
135
136<PRE CLASS="broken_ie">     <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">const</SPAN> Device& dev,
137                std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN> );</PRE>
138
139<P>
140    Assocaites the given instance of <CODE>Device</CODE> with <CODE>this</CODE> instance of <CODE>code_converter</CODE>, if there is no such instance currently associated; otherwise, throws <CODE>std::ios_base::failure</CODE>. The second parameter determines the size of the buffer or buffers used for code conversion. If a <CODE>std::codecvt</CODE> was specified as a template parameter, an instance of it will be default constructed. Otherwise, a copy of the global <CODE>locale</CODE> will be made, and an instance of <CODE>std::codecvt&lt;wchar_t, char, std::mbstate_t&gt;</CODE> will be fetched from it.
141</P>
142
143<A NAME="is_open"></A>
144<H4><CODE>code_converter::is_open</CODE></H4>
145
146<PRE CLASS="broken_ie">    <SPAN CLASS="keyword">bool</SPAN> is_open() <SPAN CLASS="keyword">const</SPAN>;</PRE>
147
148<P>Returns true if there is an instance of the Device type <CODE>Device</CODE> associated with <CODE>this</CODE> instance of <CODE>code_converter</CODE>.</P>
149
150<A NAME="close"></A>
151<H4><CODE>code_converter::close</CODE></H4>
152
153<PRE CLASS="broken_ie">    <SPAN CLASS="keyword">void</SPAN> close();</PRE>
154
155<P>
156    Disassociates from <CODE>this</CODE> instance of <CODE>code_converter</CODE> any instance of the Device type <CODE>Device</CODE> currently associated with it, calling cleanup functions as appropriate and destroying the associated instance of <CODE>Device</CODE>.
157</P>
158
159<A NAME="operator_star"></A>
160<H4><CODE>code_converter::operator*</CODE></H4>
161
162<PRE CLASS="broken_ie">    Device& operator*();</PRE>
163
164<P>
165     Returns a reference to the instance of Device associated with this instance of <CODE>code_converter</CODE>, which must be <A HREF="#is_open">open</A>.
166</P>
167
168<A NAME="operator_arrow"></A>
169<H4><CODE>code_converter::operator-></CODE></H4>
170
171<PRE CLASS="broken_ie">    Device* operator->();</PRE>
172
173<P>
174    Returns a pointer to the instance of Device associated with this instance of <CODE>code_converter</CODE>, which must be <A HREF="#is_open">open</A>.
175</P>
176   
177<!-- Begin Footer -->
178
179<HR>
180<P CLASS="copyright">Revised
181<!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan -->
18220 May, 2004
183<!--webbot bot="Timestamp" endspan i-checksum="38504" -->
184</P>
185
186<P CLASS="copyright">&copy; Copyright <A HREF="http://www.kangaroologic.com" TARGET="_top">Jonathan Turkanis</A>, 2004</P>
187<P CLASS="copyright"> 
188    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>)
189</P>
190
191<!-- End Footer -->
192
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