The wcsrtombs function converts a string of wide characters indirectly pointed to by src to a corresponding multibyte character string stored in the array pointed to by dst. No more than len bytes are written to dst.
If dst is NULL, no characters are stored.
If dst is not NULL, the pointer pointed to by src is updated to point to the character after the one that conversion stopped at. If conversion stops because a null character is encountered, *src is set to NULL.
.Vt mbstate_t argument, ps, is used to keep track of the shift state. If it is NULL, wcsrtombs uses an internal, static
.Vt mbstate_t object, which is initialized to the initial conversion state at program startup.
The wcsnrtombs function behaves identically to wcsrtombs, except that conversion stops after reading at most nwc characters from the buffer pointed to by src.
The wcsrtombs and wcsnrtombs functions return the number of bytes stored in the array pointed to by dst (not including any terminating null), if successful, otherwise it returns (Vt size_t-1).
The wcsrtombs and wcsnrtombs functions will fail if: