do_max_length
STD：：编解码器：：MAX[医]长度，做[医]马克斯[医]长度
| Defined in header | | |
|---|---|---|
| public: int max_length() const; | (1) | |
| protected: virtual int do_max_length() const; | (2) | |
1%29公共成员函数，调用成员函数do_max_length最派生的类。
2%29返回最大值do_length(state, from, from_end, 1)可以返回任何有效范围。[from, from_end)任何有效的state...
返回值
最大数目ExternT转换时可以使用的字符。in()生产一个InternT性格。
非转换专业化std::codecvt<char, char,std::mbstate_t>回报1...
注记
如果编码是状态相关的%28encoding() == -1%29，然后超过max_length()外部字符可以被消耗以产生一个内部字符。
例外
| (none) | (until C++11) |
|---|---|
| noexcept specification: noexcept | (since C++11) |
例
二次
#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";
}
二次
产出：
二次
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
二次
另见
| MB_CUR_MAX | maximum number of bytes in a multibyte character in the current C locale(macro variable) |
|---|---|
| do_encoding virtual | returns the number of externT characters necessary to produce one internT character, if constant (virtual protected member function) |
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