BIT & types definition

运算：

#define BIT_SET(var, bits) (var set to bits) ///< set the bits
#define BIT_CLR(var, bits) (var cleared of bits) ///< clear the bits
#define BIT_XOR(var, bits) (var XORed with bits) ///< perform XOR operation on the bits
#define BIT_FW(var,v,mask) (var written into the specified field using mask and value v) ///< write to a specific bit field using mask and value v

#define DIV_2(Y, X) ((Y) >> __builtin_ctz(X-1)) << 1 ///< Bitwise Division by Power of Two
#define MOD_2(Y, X) ((Y) & (X-1)) ///< Bitwise Modulus by Power of Two
#define MOD_FTL(Y, X) ((Y) % (X)) ///< Remainder Modulo O