#include <wchar.h> size_t mbrlen(const char *restrict s, size_t n, mbstate_t *restrict ps);
If s is not a null pointer, mbrlen() determines the number of bytes constituting the character pointed to by s. It is equivalent to:
mbstate_t internal; mbrtowc(NULL, s, n, ps != NULL ? ps : &internal);
If ps is a null pointer, the mbrlen() function uses its own internal mbstate_t object, which is initialized at program startup to the initial conversion state. Otherwise, the mbstate_t object pointed to by ps is used to completely describe the current conversion state of the associated character sequence. Solaris will behave as if no function defined in the Solaris Reference Manual calls mbrlen().
The behavior of this function is affected by the LC_CTYPE category of the current locale. See environ(5).
The mbrlen() function returns the first of the following that applies:
If the next n or fewer bytes complete the character that corresponds to the null wide-character.
If the next n or fewer bytes complete a valid character; the value returned is the number of bytes that complete the character.
If the next n bytes contribute to an incomplete but potentially valid character, and all n bytes have been processed. When n has at least the value of the MB_CUR_MAX macro, this case can only occur if s points at a sequence of redundant shift sequences (for implementations with state-dependent encodings).
If an encoding error occurs, in which case the next n or fewer bytes do not contribute to a complete and valid character. In this case, EILSEQ is stored in errno and the conversion state is undefined.
The mbrlen() function may fail if:
The ps argument points to an object that contains an invalid conversion state.
Invalid character sequence is detected.
See attributes(5) for descriptions of the following attributes:
If ps is not a null pointer, mbrlen() uses the mbstate_t object pointed to by ps and the function can be used safely in multithreaded applications, as long as setlocale(3C) is not being called to change the locale. If ps is a null pointer, mbrlen() uses its internal mbstate_t object and the function is Unsafe in multithreaded applications.