fn(WORD w) { WORD mark=0x8000; if(w&mark) { mark >>= 1; while( (w&mark) && mark ) mark >>= 1; if(mark==0)//w must = 0xffff,return 1 or 2 return 2;//also can return 1 if(w&(mark-1)) return 0; else return 2; } else { mark >>= 1; while( ((w&mark)==0) && mark ) mark >>= 1; if( (w&(mark-1))==(mark-1) ) return 1; else return 0; } }