[29] | 1 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> |
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| 2 | <HTML> |
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| 3 | <HEAD> |
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| 4 | <TITLE>Class Template code_converter</TITLE> |
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| 5 | <LINK REL="stylesheet" HREF="../../../../boost.css"> |
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| 6 | <LINK REL="stylesheet" HREF="../theme/iostreams.css"> |
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| 7 | </HEAD> |
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| 8 | <BODY> |
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| 9 | |
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| 10 | <!-- Begin Banner --> |
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| 11 | |
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| 12 | <H1 CLASS="title">Class Template <CODE>code_converter</CODE></H1> |
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| 13 | <HR CLASS="banner"> |
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| 14 | |
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| 15 | <!-- End Banner --> |
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| 16 | |
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| 17 | <DL class="page-index"> |
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| 18 | <DT><A href="#description">Description</A></DT> |
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| 19 | <DT><A href="#headers">Headers</A></DT> |
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| 20 | <DT><A href="#reference">Reference</A></DT> |
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| 21 | </DL> |
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| 22 | |
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| 23 | <HR> |
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| 24 | |
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| 25 | <A NAME="description"></A> |
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| 26 | <H2>Description</H2> |
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| 27 | |
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| 28 | <P> |
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| 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. |
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| 30 | </P> |
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| 31 | <P> |
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| 32 | For example, we can define a wide-character Device for reading from a memory-mapped file as follows: |
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| 33 | <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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| 34 | |
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| 35 | <SPAN CLASS="keyword">typedef</SPAN> code_converter<mapped_file_source> my_source;</PRE> |
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| 36 | |
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| 37 | Similarly, we can define a wide-character Device which writes multibyte characters to an in-memory character sequence as follows: |
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| 38 | |
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| 39 | <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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| 40 | |
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| 41 | <SPAN CLASS="keyword">typedef</SPAN> code_converter<array_sink> my_sink;</PRE> |
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| 42 | </P> |
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| 43 | <P> |
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| 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. |
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| 45 | </P> |
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| 46 | |
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| 47 | <A NAME="headers"></A> |
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| 48 | <H2>Headers</H2> |
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| 49 | |
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| 50 | <DL class="page-index"> |
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| 51 | <DT><A CLASS="header" HREF="../../../../boost/iostreams/code_converter.hpp"><CODE><boost/iostreams/code_converter.hpp></CODE></A></DT> |
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| 52 | </DL> |
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| 53 | |
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| 54 | <A NAME="reference"></A> |
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| 55 | <H2>Reference</H2> |
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| 56 | |
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| 57 | <H4>Synopsis</H4> |
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| 58 | |
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| 59 | <PRE CLASS="broken_ie"><SPAN CLASS="keyword">namespace</SPAN> boost { <SPAN CLASS="keyword">namespace</SPAN> iostreams { |
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| 60 | |
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| 61 | <SPAN CLASS="keyword">template</SPAN>< <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Device</A>, |
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| 62 | <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Codecvt</A> = <SPAN CLASS='omitted'>default_value</SPAN> |
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| 63 | <SPAN CLASS="keyword">typename</SPAN> <A CLASS="documented" HREF="#template_params">Alloc</A> = std::allocator<<CODE>char</CODE>> > |
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| 64 | <SPAN CLASS="keyword">class</SPAN> <A CLASS="documented" HREF="#template_params">code_converter</A> { |
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| 65 | <SPAN CLASS="keyword">public</SPAN>: |
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| 66 | <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="keyword">typename</SPAN> Codecvt::intern_type char_type; |
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| 67 | <SPAN CLASS="keyword">typedef</SPAN> <SPAN CLASS="omitted">implementation-defined</SPAN> category; |
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| 68 | <A CLASS="documented" HREF="#constructors">code_converter</A>(); |
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| 69 | <A CLASS="documented" HREF="#constructors">code_converter</A>( <SPAN CLASS="keyword">const</SPAN> Device& dev, |
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| 70 | std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN> ); |
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| 71 | <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#open">open</A>( <SPAN CLASS="keyword">const</SPAN> Device& dev, |
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| 72 | std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN> ); |
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| 73 | <SPAN CLASS="keyword">bool</SPAN> <A CLASS="documented" HREF="#is_open">is_open</A>() <SPAN CLASS="keyword">const</SPAN>; |
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| 74 | <SPAN CLASS="keyword">void</SPAN> <A CLASS="documented" HREF="#close">close</A>(); |
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| 75 | std::locale <A CLASS="documented" HREF="#imbue">imbue</A>(<SPAN CLASS="keyword">const</SPAN> std::locale& loc); |
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| 76 | Device& <A CLASS="documented" HREF="#operator_star">operator*</A>(); |
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| 77 | Device* <A CLASS="documented" HREF="#operator_arrow">operator-></A>(); |
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| 78 | }; |
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| 79 | |
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| 80 | } } <SPAN CLASS="comment">// End namespace boost::io</SPAN></PRE> |
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| 81 | |
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| 82 | <A NAME="template_params"></A> |
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| 83 | <H4>Template parameters</H4> |
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| 84 | |
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| 85 | <TABLE STYLE="margin-left:2em" BORDER=0 CELLPADDING=2> |
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| 86 | <TR> |
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| 87 | <TR> |
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| 88 | <TD VALIGN="top"><I>Device</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
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| 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> |
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| 90 | </TR> |
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| 91 | <TR> |
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| 92 | <TD VALIGN="top"><I>Codecvt</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
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| 93 | <TD> |
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| 94 | A standard library codecvt facet, which must be default constructible. If this parameter is not specified, |
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| 95 | an instance of <CODE>std::codecvt<wchar_t, char, std::mbstate_t></CODE> will be fetched from the global |
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| 96 | local when a <CODE>code_converter</CODE> is constructed or opened. |
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| 97 | </TD> |
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| 98 | </TR> |
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| 99 | <TR> |
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| 100 | <TD VALIGN="top"><I>Alloc</I></TD><TD WIDTH="2em" VALIGN="top">-</TD> |
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| 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> |
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| 102 | </TR> |
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| 103 | </TABLE> |
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| 104 | |
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| 105 | <A NAME="constructors"></A> |
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| 106 | <H4><CODE>code_converter::code_converter</CODE></H4> |
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| 107 | |
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| 108 | <PRE CLASS="broken_ie"> code_converter(); |
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| 109 | code_converter( <SPAN CLASS="keyword">const</SPAN> Device& dev, |
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| 110 | std::streamsize buffer_size );</PRE> |
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| 111 | |
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| 112 | <P> |
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| 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. |
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| 114 | </P> |
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| 115 | |
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| 116 | <P> |
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| 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<wchar_t, char, std::mbstate_t></CODE> will be fetched from it. |
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| 118 | </P> |
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| 119 | |
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| 120 | <A NAME="imbue"></A> |
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| 121 | <H4><CODE>code_converter::imbue</CODE></H4> |
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| 122 | |
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| 123 | <PRE CLASS="broken_ie"> std::locale imbue(<SPAN CLASS="keyword">const</SPAN> std::locale& loc);</PRE> |
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| 124 | |
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| 125 | <P> |
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| 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. |
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| 127 | </P> |
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| 128 | |
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| 129 | <P> |
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| 130 | This function is a no-op if a <CODE>std::codecvt</CODE> facet was specified as a template parameter. |
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| 131 | </P> |
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| 132 | |
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| 133 | <A NAME="open"></A> |
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| 134 | <H4><CODE>code_converter::open</CODE></H4> |
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| 135 | |
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| 136 | <PRE CLASS="broken_ie"> <SPAN CLASS="keyword">void</SPAN> open( <SPAN CLASS="keyword">const</SPAN> Device& dev, |
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| 137 | std::streamsize buffer_size = <SPAN CLASS="omitted">default_value</SPAN> );</PRE> |
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| 138 | |
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| 139 | <P> |
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| 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<wchar_t, char, std::mbstate_t></CODE> will be fetched from it. |
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| 141 | </P> |
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| 142 | |
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| 143 | <A NAME="is_open"></A> |
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| 144 | <H4><CODE>code_converter::is_open</CODE></H4> |
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| 145 | |
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| 146 | <PRE CLASS="broken_ie"> <SPAN CLASS="keyword">bool</SPAN> is_open() <SPAN CLASS="keyword">const</SPAN>;</PRE> |
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| 147 | |
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| 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> |
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| 149 | |
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| 150 | <A NAME="close"></A> |
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| 151 | <H4><CODE>code_converter::close</CODE></H4> |
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| 152 | |
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| 153 | <PRE CLASS="broken_ie"> <SPAN CLASS="keyword">void</SPAN> close();</PRE> |
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| 154 | |
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| 155 | <P> |
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| 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>. |
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| 157 | </P> |
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| 158 | |
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| 159 | <A NAME="operator_star"></A> |
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| 160 | <H4><CODE>code_converter::operator*</CODE></H4> |
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| 161 | |
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| 162 | <PRE CLASS="broken_ie"> Device& operator*();</PRE> |
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| 163 | |
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| 164 | <P> |
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| 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>. |
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| 166 | </P> |
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| 167 | |
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| 168 | <A NAME="operator_arrow"></A> |
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| 169 | <H4><CODE>code_converter::operator-></CODE></H4> |
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| 170 | |
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| 171 | <PRE CLASS="broken_ie"> Device* operator->();</PRE> |
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| 172 | |
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| 173 | <P> |
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| 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>. |
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| 175 | </P> |
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| 176 | |
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| 177 | <!-- Begin Footer --> |
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| 178 | |
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| 179 | <HR> |
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| 180 | <P CLASS="copyright">Revised |
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| 181 | <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B, %Y" startspan --> |
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| 182 | 20 May, 2004 |
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| 183 | <!--webbot bot="Timestamp" endspan i-checksum="38504" --> |
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| 184 | </P> |
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| 185 | |
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| 186 | <P CLASS="copyright">© Copyright <A HREF="http://www.kangaroologic.com" TARGET="_top">Jonathan Turkanis</A>, 2004</P> |
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| 187 | <P CLASS="copyright"> |
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| 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>) |
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| 189 | </P> |
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| 190 | |
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| 191 | <!-- End Footer --> |
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| 192 | |
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| 193 | </BODY> |
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