std:: mbrtowc

Converts a narrow multibyte character to a wide character.

If s is not a null pointer, inspects at most n bytes of the multibyte character string, beginning with the byte pointed to by s to determine the number of bytes necessary to complete the next multibyte character (including any shift sequences). If the function determines that the next multibyte character in s is complete and valid, converts it to the corresponding wide character and stores it in * pwc (if pwc is not null).

If s is a null pointer, the values of n and pwc are ignored and call is equivalent to std :: mbrtowc ( nullptr, "" , 1 , ps ) .

If the wide character produced is the null character, the conversion state stored in * ps is the initial shift state.

Parameters

Return value

The first of the following that applies:

• ​ 0 ​ if the character converted from s (and stored in pwc if non-null) was the null character.
• the number of bytes [ 1 ... n ] of the multibyte character successfully converted from s .
• static_cast < std:: size_t > ( - 2 ) if the next n bytes constitute an incomplete, but so far valid, multibyte character. Nothing is written to * pwc .
• static_cast < std:: size_t > ( - 1 ) if encoding error occurs. Nothing is written to * pwc , the value EILSEQ is stored in errno and the value of * ps is left unspecified.

Example

#include <clocale>
#include <cstring>
#include <cwchar>
#include <iostream>
 
void print_mb(const char* ptr)
{
    std::mbstate_t state = std::mbstate_t(); // initial state
    const char* end = ptr + std::strlen(ptr);
    int len;
    wchar_t wc;
    while ((len = std::mbrtowc(&wc, ptr, end-ptr, &state)) > 0)
    {
        std::wcout << "Next " << len << " bytes are the character " << wc << '\n';
        ptr += len;
    }
}
 
int main()
{
    std::setlocale(LC_ALL, "en_US.utf8");
    // UTF-8 narrow multibyte encoding
    const char* str = "z\u00df\u6c34\U0001d10b"; // or u8"zß水𝄋"
                      // or "\x7a\xc3\x9f\xe6\xb0\xb4\xf0\x9d\x84\x8b";
    print_mb(str);
}

Next 1 bytes are the character z
Next 2 bytes are the character ß
Next 3 bytes are the character 水
Next 4 bytes are the character 𝄋

See also