Manual Pages  — MBRLEN

mbrlen – get number of bytes in a character (restartable)

LIBRARY SYNOPSIS DESCRIPTION RETURN VALUES EXAMPLES ERRORS SEE ALSO STANDARDS

Standard C Library (libc, -lc)

#include <wchar.h>

size_t
mbrlen(const char * restrict s, size_t n, mbstate_t * restrict ps);

The mbrlen() function inspects at most n bytes pointed to by s to determine the number of bytes needed to complete the next multibyte character.

The mbstate_t argument, ps, is used to keep track of the shift state. If it is NULL, mbrlen() uses an internal, static mbstate_t object, which is initialized to the initial conversion state at program startup.

It is equivalent to:

    mbrtowc(NULL, s, n, ps);

Except that when ps is a NULL pointer, mbrlen() uses its own static, internal mbstate_t object to keep track of the shift state.

The mbrlen() functions returns:

0	The next n or fewer bytes represent the null wide character (L'\0').
>0	The next n or fewer bytes represent a valid character, mbrlen() returns the number of bytes used to complete the multibyte character.
(size_t )-2
	The next n contribute to, but do not complete, a valid multibyte character sequence, and all n bytes have been processed.
(size_t )-1
	An encoding error has occurred. The next n or fewer bytes do not contribute to a valid multibyte character.

A function that calculates the number of characters in a multibyte character string:

size_t
nchars(const char *s)
{
        size_t charlen, chars;
        mbstate_t mbs;

        chars = 0;
        memset(&mbs, 0, sizeof(mbs));
        while ((charlen = mbrlen(s, MB_CUR_MAX, &mbs)) != 0 &&
            charlen != (size_t)-1 && charlen != (size_t)-2) {
                s += charlen;
                chars++;
        }

        return (chars);
}

The mbrlen() function will fail if:

[EILSEQ]
	An invalid multibyte sequence was detected.
[EINVAL]
	The conversion state is invalid.

The mbrlen() function conforms to ISO/IEC 9899:1999 ("ISO C99").