BF_LONG_LOG2
#ifndef BF_LONG_LOG2
#define BF_M (0xFF<<BF_LONG_LOG2)
#define BF_0 (24-BF_LONG_LOG2)
#define BF_1 (16-BF_LONG_LOG2)
#define BF_2 ( 8-BF_LONG_LOG2)
#define BF_3 BF_LONG_LOG2 /* left shift */