将多字节序列转换为宽字符。将pmb指向的多字节字符转换为wchar_t类型的值，并将其存储在pwc指向的位置。该函数返回多字节字符的长度(以字节为单位)。
mbtowc有其自己的内部移位状态，只有在调用此函数时才需要更改它。用空指针作为pmb调用函数重置状态(并返回多字节字符是否与状态有关)。
此函数的行为取决于所选C语言环境(C语言本地化库)的LC_CTYPE类别。
语法：
pwc: Pointer to an object of type wchar_t.
Alternatively, this argument can be a null pointer,
in which case the function does not store the wchar_t translation,
but still returns the length in bytes of the multibyte character.
pmb: Pointer to the first byte of a multibyte character.
Alternatively, this argument can be a null pointer,
in which case the function resets its internal shift
state to the initial value and returns whether
multibyte characters have a state-dependent encoding.
max: Maximum number of bytes of pmb
to consider for the multibyte character.
Return Value: If the argument passed as pmb is not a null pointer,
the size in bytes of the multibyte character pointed by pmb is returned
when it forms a valid multibyte character and is not the terminating
null character. If it is the terminating null character, the function
returns zero, and in the case they do not form a valid multibyte character, -1 is returned.
If the argument passed as pmb is a null pointer,
the function returns a nonzero value if multibyte character
encodings are state-dependent, and zero otherwise.
// C program to illustrate mbtowc
// function
#include
#include // function containing mbtowc & wchar_t(C) function
void mbtowc_func(const char* pt, size_t max)
{
int length;
// this is a typedef of an integral type
wchar_t dest;
// reset mbtowc
mbtowc(NULL, NULL, 0);
while (max > 0) {
length = mbtowc(&dest, pt, max);
if (length < 1) {
break;
}
// printing each character in square braces
printf("[%lc]", dest);
pt += length;
max -= length;
}
}
int main()
{
const char str[] = "geeks portal";
mbtowc_func(str, sizeof(str));
return 0;
}
输出：
[g][e][e][k][s][ ][p][o][r][t][a][l]
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