Determine conversion object status.
Standard Library (libc.a)
#include <wchar.h>
int mbsinit (const mbstate_t * p) ;
If ps is not a null pointer, the mbsinit function determines whether the object pointed to by ps describes an initial conversion state.
The mbsinit function returns non-zero if ps is a null pointer, or if the pointed-to object describes an initial conversion state; otherwise, it returns zero.
If an mbstate_t object is altered by any of the functions described as restartable, and is then used with a different character sequence, or in the other conversion direction, or with a different LC_CTYPE category setting than on earlier function calls, the behavior is undefined.
The mbstate_t object is used to describe the current conversion state from a particular character sequence to a wide-character sequence (or vice versa) under the rules of a particular setting of the LC_CTYPE category of the current locale.
The initial conversion state corresponds, for a conversion in either direction, to the beginning of a new character sequence in the initial shift state. A zero valued mbstate_t object is at least one way to describe an initial conversion state. A zero valued mbstate_t object can be used to initiate conversion involving any character sequence, in any LC_CTYPE category setting.
The mbrlen subroutine, mbrtowc subroutine, wctomb subroutine, mbsrtowcs subroutine, wcsrtombs subroutine.
The wchar.h file.