22 Localization library [localization]

22.3 Locales [locales]

22.3.3 Convenience interfaces [locale.convenience] Conversions [conversions] Buffer conversions [conversions.buffer]

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.

Class template wbuffer_convert synopsis

namespace std {
template<class Codecvt,
    class Elem = wchar_t,
    class Tr = std::char_traits<Elem> >
  class wbuffer_convert
    : public std::basic_streambuf<Elem, Tr> {
    typedef typename Codecvt::state_type state_type;

    explicit wbuffer_convert(std::streambuf* bytebuf = 0,
                             Codecvt* pcvt = new Codecvt,
                             state_type state = state_type());


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

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

    state_type state() const;

    std::streambuf* bufptr;         // exposition only
    Codecvt* cvtptr;                // exposition only
    state_type cvtstate;            // exposition only

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 std::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 std::codecvt<Elem, char, std::mbstate_t>.

An object of this class template stores:

  • bufptr — a pointer to its underlying byte stream buffer

  • cvtptr — a pointer to the allocated conversion object (which is freed when the wbuffer_convert object is destroyed)

  • cvtstate — a conversion state object

state_type state() const;

Returns: cvtstate.

std::streambuf* rdbuf() const;

Returns: bufptr.

std::streambuf* rdbuf(std::streambuf* bytebuf);

Effects: stores bytebuf in bufptr.

Returns: The previous value of bufptr.

typedef typename Codecvt::state_type state_type;

The type shall be a synonym for Codecvt::state_type.

explicit wbuffer_convert(std::streambuf* bytebuf = 0, Codecvt* pcvt = new Codecvt, state_type state = state_type());

Requires: pcvt != nullptr.

Effects: The constructor constructs a stream buffer object, initializes bufptr to bytebuf, initializes cvtptr to pcvt, and initializes cvtstate to state.


Effects: The destructor shall delete cvtptr.