| Defined in header <locale> | ||
|---|---|---|
public: int max_length() const; | (1) | |
protected: virtual int do_max_length() const; | (2) |
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.
Exceptions
| (none) | (until C++11) |
noexcept specification: noexcept | (since C++11) |
Example
#include <locale>
#include <iostream>
#include <codecvt>
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) |
| [virtual] | returns the number of externT characters necessary to produce one internT character, if constant (virtual protected member function) |
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