Annex D (normative) Compatibility features [depr]

D.21 Deprecated convenience conversion interfaces [depr.conversions]

D.21.2 Class template wbuffer_­convert [depr.conversions.buffer]

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Class template wbuffer_­convert looks like a wide stream buffer, but performs all its I/O through an underlying byte stream buffer that you specify when you construct it.
Like class template wstring_­convert, it lets you specify a code conversion facet to perform the conversions, without affecting any streams or locales.
namespace std {
  template<class Codecvt, class Elem = wchar_t, class Tr = char_traits<Elem>>
    class wbuffer_convert : public basic_streambuf<Elem, Tr> {
    public:
      using state_type = typename Codecvt::state_type;

      wbuffer_convert() : wbuffer_convert(nullptr) {}
      explicit wbuffer_convert(streambuf* bytebuf,
                               Codecvt* pcvt = new Codecvt,
                               state_type state = state_type());

      ~wbuffer_convert();

      wbuffer_convert(const wbuffer_convert&) = delete;
      wbuffer_convert& operator=(const wbuffer_convert&) = delete;

      streambuf* rdbuf() const;
      streambuf* rdbuf(streambuf* bytebuf);

      state_type state() const;

    private:
      streambuf* bufptr;            // exposition only
      Codecvt* cvtptr;              // exposition only
      state_type cvtstate;          // exposition only
  };
}
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The class template describes a stream buffer that controls the transmission of elements of type Elem, whose character traits are described by the class Tr, to and from a byte stream buffer of type streambuf.
Conversion between a sequence of Elem values and multibyte sequences is performed by an object of class Codecvt, which shall meet the requirements of the standard code-conversion facet codecvt<Elem, char, mbstate_­t>.
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An object of this class template stores:
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state_type state() const;
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Returns: cvtstate.
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streambuf* rdbuf() const;
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Returns: bufptr.
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streambuf* rdbuf(streambuf* bytebuf);
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Effects: Stores bytebuf in bufptr.
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Returns: The previous value of bufptr.
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using state_type = typename Codecvt::state_type;
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The type shall be a synonym for Codecvt​::​state_­type.
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explicit wbuffer_convert( streambuf* bytebuf, Codecvt* pcvt = new Codecvt, state_type state = state_type());
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Requires: pcvt != nullptr.
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Effects: The constructor constructs a stream buffer object, initializes bufptr to bytebuf, initializes cvtptr to pcvt, and initializes cvtstate to state.
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~wbuffer_convert();
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Effects: The destructor shall delete cvtptr.