#include <fontconfig/fontconfig.h>
FcBool FcUtf16Len (FcChar8 *src, FcEndian endian, int len, int *nchar, int *wchar);

Counts the number of Unicode chars in len bytes of src. Bytes of src are combined into 16-bit units according to endian. Places that count in nchar. wchar contains 1, 2 or 4 depending on the number of bytes needed to hold the largest Unicode char counted. The return value indicates whether string is a well-formed UTF16 string.