std::codecvt<InternT,ExternT,StateT>::max_length, do_max_length
來自 cppreference.com
| 定義於標頭檔案 <locale> |
||
| (1) | ||
public: int max_length() const throw(); |
(C++11 前) | |
| public: int max_length() const noexcept; |
(C++11 起) | |
| (2) | ||
protected: virtual int do_max_length() const throw(); |
(C++11 前) | |
| protected: virtual int do_max_length() const noexcept; |
(C++11 起) | |
1) 公有成員函式，呼叫最派生類中的成員函式
do_max_length。2) 對於任何有效的範圍
[from, from_end) 和任何有效的 state，返回 do_length(state, from, from_end, 1) 可以返回的最大值。目錄 |
[編輯] 返回值
透過 in() 轉換為生成一個 InternT 字元時，可能消耗的 ExternT 字元的最大數量。
非轉換特化 std::codecvt<char, char, std::mbstate_t> 返回 1。
[編輯] 注意
如果編碼是狀態相關的 (encoding() == -1)，則可能消耗超過 max_length() 的外部字元以生成一個內部字元。
[編輯] 示例
執行此程式碼
#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"; }
輸出
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
[編輯] 參閱
| MB_CUR_MAX |
當前 C 語言環境多位元組字元中的最大位元組數 (宏變數) |
| [虛擬函式] |
返回生成一個 InternT 字元所需的 ExternT 字元數（如果恆定）(虛保護成員函式) |
