C++ 参考手册

定义于头文件 <cwchar>
int wctob( std::wint_t c );

窄化宽字符 c ,若其多字节字符等价版本在初始迁移状态为单字节。

这典型地对来自 ASCII 字符集的字符可行,因为大多数多字节编码(例如 UTF-8 )用单字节编码那些字符。

参数

c - 要窄化的宽字符

返回值

c 在初始迁移状态不表示长度为 1 的多字节字符则为 EOF

否则,为作为 unsigned charc 的单字节表示,转换为 int

示例

#include <clocale>
#include <cwchar>
#include <iostream>
 
void try_narrowing(wchar_t c)
{
    int cn = std::wctob(c);
    if(cn != EOF)
        std::cout << '\'' << c << "' narrowed to " << +cn << '\n';
    else
        std::cout << '\'' << c << "' could not be narrowed\n";
}
 
int main()
{
    std::setlocale(LC_ALL, "th_TH.utf8");
    std::cout << std::hex << std::showbase << "In Thai UTF-8 locale:\n";
    try_narrowing(L'a');
    try_narrowing(L'๛');
 
    std::setlocale(LC_ALL, "th_TH.tis620");
    std::cout << "In Thai TIS-620 locale:\n";
    try_narrowing(L'a');
    try_narrowing(L'๛');
}

输出:

In Thai UTF-8 locale:
'0x61' narrowed to 0x61
'0xe5b' could not be narrowed
In Thai TIS-620 locale:
'0x61' narrowed to 0x61
'0xe5b' narrowed to 0xfb

参阅

若可能,则加宽单字节窄字符为宽字符
(函数)
窄化字符
(std::basic_ios<CharT,Traits> 的公开成员函数)
调用 do_narrow
(std::ctype<CharT> 的公开成员函数)