std::codecvt<InternT,ExternT,StateT>::max_length, do_max_length
来自 cppreference.cn
| 定义于头文件 <locale> |
||
| (1) | ||
public: int max_length() const throw(); |
(直到 C++11) | |
| public: int max_length() const noexcept; |
(自 C++11 起) | |
| (2) | ||
protected: virtual int do_max_length() const throw(); |
(直到 C++11) | |
| protected: virtual int do_max_length() const noexcept; |
(自 C++11 起) | |
1) 公有成员函数，调用最派生类的成员函数
do_max_length。2) 返回 do_length(state, from, from_end, 1) 对于任何有效的范围
[from, from_end) 和任何有效的 state 可以返回的最大值。目录 |
[编辑] 返回值
如果通过 in() 转换以产生一个 InternT 字符，则可能消耗的最大 ExternT 字符数。
非转换特化 std::codecvt<char, char, std::mbstate_t> 返回 1。
[编辑] 注释
如果编码是依赖状态的 ( encoding() == -1 )，则可能消耗多于 max_length() 个外部字符来产生一个内部字符。
[编辑] 示例
运行此代码
#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"; }
输出
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
[编辑] 参见
| MB_CUR_MAX |
当前 C 区域设置中多字节字符的最大字节数 (宏变量) |
| [虚函数] |
如果恒定，则返回产生一个 InternT 字符所需的 ExternT 字符数(虚保护成员函数) |
