std::codecv...do_encoding(3)

💖 NAME 💖

std::codecvt::encoding,do_encoding — std::codecvt::encoding,do_encoding

Okay bestie, welcome to std::codecv...do_encoding(3) from the C++ Standard Libary manual — and yes, that's “Libary” exactly how the header spells it, I don't make the rules 😭💅. This page is all about the member that tells you how a codecvt facet handles character counts, and it is lowkey iconic.

✨ Synopsis ✨

Defined in header <locale>
public:                                           (until C++11)
int encoding() const throw();
public:                                           (since C++11)
int encoding() const noexcept;            (1)
protected:
(until C++11)
virtual int do_encoding() const throw();      (2)
protected:
(since C++11)
virtual int do_encoding() const noexcept;

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

Heads-up, bestie: those return values are the whole vibe check here — constant count, 0 for variable, -1 for state-dependent. Periodt.

🎀 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. Slay.

💅 Example 💅

The manpage says // Run this code — so go off:

#include <iostream>
#include <locale>

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

🌈 See also 🌈

• MB_CUR_MAX — maximum number of bytes in a multibyte character in the current C locale (macro variable).
• do_max_length [virtual] — returns the maximum number of ExternT characters that could be converted into a single InternT character (virtual protected member function).

Source/version/date cuties: http://cppreference.com, 2024.06.10, and the page tag std::codecv...do_encoding(3) — mwah, that's the whole page 💖✨