# mbrlen

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< c‎ | string‎ | multibyte

Defined in header `<wchar.h>` |  |
size_t mbrlen( const char *s, size_t n, mbstate_t *ps ); |  | (since C95) (until C99)
size_t mbrlen( const char *restrict s, size_t n, mbstate_t *restrict ps ); |  | (since C99)

Determines the size, in bytes, of the representation of a multibyte character.

This function is equivalent to the call mbrtowc(nullptr, s, n, ps?ps:&internal) for some hidden object `internal` of type mbstate_t, except that the expression `ps` is evaluated only once.

### Parameters

s | - | pointer to an element of a multibyte character string
n | - | limit on the number of bytes in s that can be examined
ps | - | pointer to the variable holding the conversion state

### Return value

The first of the following that applies:

- ​0​ if the next `n` or fewer bytes complete the null character or if `s` is a null pointer. Both cases reset the conversion state.
- the number of bytes [1...n] that complete a valid multibyte character
- (size_t)-2 if the next `n` bytes are part of a possibly valid multibyte character, which is still incomplete after examining all `n` bytes
- (size_t)-1 if encoding error occurs. The value of errno is `EILSEQ`; the conversion state is unspecified.

### Example

Run this code

    #include <locale.h>
    #include <string.h>
    #include <stdio.h>
    #include <wchar.h>

    int main(void)
    {
        // allow mbrlen() to work with UTF-8 multibyte encoding
        setlocale(LC_ALL, "en_US.utf8");
        // UTF-8 narrow multibyte encoding
        const char* str = u8"水";
        size_t sz = strlen(str);

        mbstate_t mb;
        memset(&mb, 0, sizeof mb);
        int len1 = mbrlen(str, 1, &mb);
        if(len1 == -2)
            printf("The first 1 byte of %s is an incomplete multibyte char"
                   " (mbrlen returns -2)\n", str);

        int len2 = mbrlen(str+1, sz-1, &mb);
        printf("The remaining %zu  bytes of %s hold %d bytes of the multibyte"
               " character\n", sz-1, str, len2);

        printf("Attempting to call mbrlen() in the middle of %s while in initial"
               " shift state returns %zd\n", str, mbrlen(str+1, sz-1, &mb));
    }

Output:

    The first 1 byte of 水 is an incomplete multibyte char (mbrlen returns -2)
    The remaining 2  bytes of 水 hold 2 bytes of the multibyte character
    Attempting to call mbrlen() in the middle of 水 while in initial shift state returns -1

### References

- C11 standard (ISO/IEC 9899:2011):

  - 7.29.6.3.1 The mbrlen function (p: 442)

- C99 standard (ISO/IEC 9899:1999):

  - 7.24.6.3.1 The mbrlen function (p: 388)

### See also

mbrtowc (C95) | converts the next multibyte character to wide character, given state (function)
mblen | returns the number of bytes in the next multibyte character (function)

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