std::codecvt<InternT,ExternT,StateT>::max_length, do_max_length

Since C++11

Header: <locale>

Public member function, calls the member function do_max_length of the most derived class.

# Declarations

public:
int max_length() const throw();

(until C++11)

public:
int max_length() const noexcept;

(since C++11)

protected:
virtual int do_max_length() const throw();

(until C++11)

protected:
virtual int do_max_length() const noexcept;

(since C++11)

# Return value

The maximum number of ExternT characters that could be consumed if converted by in() to produce one InternT character.

# Notes

If the encoding is state-dependent (encoding() == -1), then more than max_length() external characters may be consumed to produce one internal character.

# Example

#include <codecvt>
#include <iostream>
#include <locale>
 
int main()
{
    std::cout << "In codecvt_utf8, the longest multibyte character is "
              << std::codecvt_utf8<wchar_t>().max_length() << " bytes long\n";
 
    std::cout << "In header-consuming codecvt_utf8, the longest multibyte character is "
              << std::codecvt_utf8<wchar_t,
                                   0x10ffff,
                                   std::consume_header>().max_length() << " bytes long\n";
 
    std::cout << "In this system's en_US.utf8, the longest multibyte character is "
              << std::use_facet<std::codecvt<wchar_t, char, std::mbstate_t>>(
                     std::locale("en_US.utf8")
                 ).max_length() << " bytes long\n";
 
    std::cout << "In this system's zh_CN.gb18030, the longest multibyte character is "
              << std::use_facet<std::codecvt<wchar_t, char, std::mbstate_t>>(
                     std::locale("zh_CN.gb18030")
                 ).max_length() << " bytes long\n";
}

# See also

do_encoding