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# std::codecvt::encoding, do_encoding

From cppreference.com
< cpp‎ | locale‎ | codecvt

Defined in header `<locale>` |  |
public: int encoding() const; | (1) |
protected: virtual int do_encoding() const; | (2) |

1) public member function, calls the member function `do_encoding` of the most derived class.
2) if the encoding represented by this codecvt facet maps each internal character to the same, constant number of external characters, returns that number. If the encoding is variable-length (e.g. UTF-8 or UTF-16), returns ​0​. If the encoding is state-dependent, returns -1.

### [edit] Return value

The exact number of `externT` characters that correspond to one `internT` character, if constant. ​0​ if the number varies, -1 if the encoding is state-dependent.

The non-converting specialization std::codecvt<char, char, std::mbstate_t> returns 1

### [edit] Exceptions

(none) | (until C++11)
`noexcept` specification: noexcept | (since C++11)

### [edit] Example

Run this code

    #include <locale>
    #include <iostream>

    int main()
    {
        std::cout << "en_US.utf8 is a variable-length encoding, encoding() returns "
                  << std::use_facet<std::codecvt<wchar_t, char, std::mbstate_t>>(
                        std::locale("en_US.utf8")
                  ).encoding() << '\n';

        std::cout << "zh_CN.gb18030 is also variable-length, encoding() == "
                  << std::use_facet<std::codecvt<wchar_t, char, std::mbstate_t>>(
                        std::locale("zh_CN.gb18030")
                  ).encoding() << '\n';

        std::cout << "ru_RU.koi8r is a single-byte encoding encoding() == "
                  << std::use_facet<std::codecvt<wchar_t, char, std::mbstate_t>>(
                        std::locale("ru_RU.koi8r")
                  ).encoding() << '\n';
    }

Output:

    en_US.utf8 is a variable-length encoding, encoding() returns 0
    zh_CN.gb18030 is also variable-length, encoding() == 0
    ru_RU.koi8r is a single-byte encoding encoding() == 1

### [edit] See also

MB_CUR_MAX | maximum number of bytes in a multibyte character in the current C locale (macro variable) [edit]
do_max_length [virtual] | returns the maximum number of externT characters that could be converted into a single internT character (virtual protected member function) [edit]

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