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| <H1 CLASS="title">Class Template <CODE>code_converter</CODE></H1> |
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| <DT><A href="#description">Description</A></DT> |
| <DT><A href="#headers">Headers</A></DT> |
| <DT><A href="#reference">Reference</A></DT> |
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| <A NAME="description"></A> |
| <H2>Description</H2> |
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| <P> |
| 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. |
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| <P> |
| For example, we can define a wide-character Device for reading from a memory-mapped file as follows: |
| <PRE CLASS="broken_ie"> <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/device/mapped_file.hpp"><SPAN CLASS="literal"><boost/iostreams/maped_file.hpp></SPAN></A> |
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| <SPAN CLASS="keyword">typedef</SPAN> code_converter<mapped_file_source> my_source;</PRE> |
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| Similarly, we can define a wide-character Device which writes multibyte characters to an in-memory character sequence as follows: |
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| <PRE CLASS="broken_ie"> <SPAN CLASS="preprocessor">#include</SPAN> <A CLASS="header" HREF="../../../../boost/iostreams/device/array.hpp"><SPAN CLASS="literal"><boost/iostreams/device/array.hpp></SPAN></A> |
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| <SPAN CLASS="keyword">typedef</SPAN> code_converter<array_sink> my_sink;</PRE> |
| </P> |
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| 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. |
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| <H2>Headers</H2> |
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| <DL class="page-index"> |
| <DT><A CLASS="header" HREF="../../../../boost/iostreams/code_converter.hpp"><CODE><boost/iostreams/code_converter.hpp></CODE></A></DT> |
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| <A NAME="reference"></A> |
| <H2>Reference</H2> |
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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">Device</A>, |
| <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Codecvt</A> = <SPAN CLASS='omitted'>default_value</SPAN> |
| <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Alloc</A> = std::allocator<<CODE>char</CODE>> > |
| <SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#template_params">code_converter</A> { |
| <SPAN CLASS="keyword">public</SPAN>: |
| <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">typename</SPAN> Codecvt::intern_type char_type; |
| <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="omitted">implementation-defined</SPAN> category; |
| <A CLASS="documented" HREF="#constructors">code_converter</A>(); |
| <A CLASS="documented" HREF="#constructors">code_converter</A>( <SPAN CLASS="keyword">const</SPAN> Device& dev, |
| std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN> ); |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#open">open</A>( <SPAN CLASS="keyword">const</SPAN> Device& dev, |
| std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN> ); |
| <SPAN CLASS="keyword">bool</SPAN> <A CLASS="documented" HREF="#is_open">is_open</A>() <SPAN CLASS="keyword">const</SPAN>; |
| <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#close">close</A>(); |
| std::locale <A CLASS="documented" HREF="#imbue">imbue</A>(<SPAN CLASS="keyword">const</SPAN> std::locale& loc); |
| Device& <A CLASS="documented" HREF="#operator_star">operator*</A>(); |
| Device* <A CLASS="documented" HREF="#operator_arrow">operator-></A>(); |
| }; |
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| } } <SPAN CLASS="comment">// End namespace boost::io</SPAN></PRE> |
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| <A NAME="template_params"></A> |
| <H4>Template parameters</H4> |
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| <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2> |
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| <TR> |
| <TD VALIGN="top"><I>Device</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <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> |
| </TR> |
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| <TD VALIGN="top"><I>Codecvt</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
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| A standard library codecvt facet, which must be default constructible. If this parameter is not specified, |
| an instance of <CODE>std::codecvt<wchar_t, char, std::mbstate_t></CODE> will be fetched from the global |
| local when a <CODE>code_converter</CODE> is constructed or opened. |
| </TD> |
| </TR> |
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| <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
| <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> |
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| </TABLE> |
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| <A NAME="constructors"></A> |
| <H4><CODE>code_converter::code_converter</CODE></H4> |
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| <PRE CLASS="broken_ie"> code_converter(); |
| code_converter( <SPAN CLASS="keyword">const</SPAN> Device& dev, |
| std::streamsize buffer_size );</PRE> |
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| <P> |
| 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. |
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| <P> |
| 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<wchar_t, char, std::mbstate_t></CODE> will be fetched from it. |
| </P> |
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| <A NAME="imbue"></A> |
| <H4><CODE>code_converter::imbue</CODE></H4> |
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| <PRE CLASS="broken_ie"> std::locale imbue(<SPAN CLASS="keyword">const</SPAN> std::locale& loc);</PRE> |
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| <P> |
| 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. |
| </P> |
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| <P> |
| This function is a no-op if a <CODE>std::codecvt</CODE> facet was specified as a template parameter. |
| </P> |
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| <A NAME="open"></A> |
| <H4><CODE>code_converter::open</CODE></H4> |
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| <PRE CLASS="broken_ie"> <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">const</SPAN> Device& dev, |
| std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN> );</PRE> |
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| <P> |
| 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<wchar_t, char, std::mbstate_t></CODE> will be fetched from it. |
| </P> |
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| <A NAME="is_open"></A> |
| <H4><CODE>code_converter::is_open</CODE></H4> |
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| <PRE CLASS="broken_ie"> <SPAN CLASS="keyword">bool</SPAN> is_open() <SPAN CLASS="keyword">const</SPAN>;</PRE> |
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| <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> |
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| <A NAME="close"></A> |
| <H4><CODE>code_converter::close</CODE></H4> |
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| <PRE CLASS="broken_ie"> <SPAN CLASS="keyword">void</SPAN> close();</PRE> |
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| <P> |
| 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>. |
| </P> |
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| <A NAME="operator_star"></A> |
| <H4><CODE>code_converter::operator*</CODE></H4> |
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| <PRE CLASS="broken_ie"> Device& operator*();</PRE> |
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| <P> |
| 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>. |
| </P> |
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| <A NAME="operator_arrow"></A> |
| <H4><CODE>code_converter::operator-></CODE></H4> |
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| <PRE CLASS="broken_ie"> Device* operator->();</PRE> |
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| <P> |
| 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>. |
| </P> |
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| <P CLASS="copyright">Revised 02 Feb 2008</P> |
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| <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> |
| <P CLASS="copyright"> |
| 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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