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# mbrtowc

From cppreference.com
< c‎ | string‎ | multibyte

Defined in header `<wchar.h>` |  |
size_t mbrtowc( wchar_t* pwc, const char* s, size_t n, mbstate_t* ps ); |  | (since C95)

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.

### [edit] Parameters

pwc | - | pointer to the location where the resulting wide character will be written
s | - | pointer to the multibyte character string used as input
n | - | limit on the number of bytes in s that can be examined
ps | - | pointer to the conversion state used when interpreting the multibyte string

### [edit] 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.

### [edit] Example

Run this code

    #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🍌"
    }

Output:

    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 🍌

### [edit] 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)

### [edit] See also

mbtowc | converts the next multibyte character to wide character (function) [edit]
wcrtombwcrtomb_s (C95)(C11) | converts a wide character to its multibyte representation, given state (function) [edit]
C++ documentation for mbrtowc

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