NAME¶

std::codecvt::max_length,do_max_length - std::codecvt::max_length,do_max_length

Synopsis¶

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

1) Public member function, calls the member function do_max_length of the most
derived class.
2) Returns the maximum value that do_length(state, from, from_end, 1) can return for
any valid range [from, from_end) and any valid state.

Return value¶

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

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

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¶

// Run this code

#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";
}

Output:¶

In codecvt_utf8, the longest multibyte character is 4 bytes long
In header-consuming codecvt_utf8, the longest multibyte character is 7 bytes long
In this system's en_US.utf8, the longest multibyte character is 6 bytes long
In this system's zh_CN.gb18030, the longest multibyte character is 4 bytes long

See also¶

MB_CUR_MAX maximum number of bytes in a multibyte character in the current C locale
(macro variable)
do_encoding returns the number of ExternT characters necessary to produce one
[virtual] InternT character, if constant
(virtual protected member function)