mbrtowc

size_t mbrtowc( wchar_t* pwc, const char* s, size_t n, mbstate_t* ps );

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 mbrtowc(NULL, "", 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
• (size_t)-2 if the next n bytes constitute an incomplete, but so far valid, multibyte character. Nothing is written to *pwc.
• (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 <stdio.h>
#include <locale.h>
#include <string.h>
#include <wchar.h>
 
// print multibyte string to wide-oriented stdout
// equivalent to wprintf(L"%s\n", ptr);
void print_mb(const char* ptr)
{
    mbstate_t state;
    memset(&state, 0, sizeof state);
    const char* end = ptr + strlen(ptr);
    int len;
    wchar_t wc;
    while((len = mbrtowc(&wc, ptr, end-ptr, &state)) > 0) {
        wprintf(L"Next %d bytes are the character %lc \n", len, wc);
        ptr += len;
    }
}
 
int main(void)
{
    setlocale(LC_ALL, "en_US.utf8");
    // UTF-8 narrow multibyte encoding
    print_mb(u8"z\u00df\u6c34\U0001F34C"); // or u8"zß水🍌"
}

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 🍌

References

• C11 standard (ISO/IEC 9899:2011):
• 7.29.6.3.2 The mbrtowc function (p: 443)
• C99 standard (ISO/IEC 9899:1999):
• 7.24.6.3.2 The mbrtowc function (p: 389)

See also