class DecoderException(Exception):
	pass

class Decoder(object):
	D = (
		14, 12, 13, 15,
		28, 29, 11, 10,
		34, 35, 50, 51,
		48, 49, 42, 43,
		40, 41, 46, 32,
		33,  7, 24, 25,
		38, 39, 54, 55,
		52, 53, 44, 45,
		47, 36, 37,  8,
		 3, 26, 27
	)
	X = (
		 28, 60,  0, 32,
		 26,758, 86,470,
		 54,278,246,1014,
		310,438,854,284,
		954,922,264, 32,
		982,119, 87,631,
		599,567,535,375,
		343,790,311,279,
		597,533, 20,534,
		 55, 23, 64,512,
		 19, 83,595,316,
		146,210,242,476,
		124,444,412, 24,
		792,824,536,247,
		215,759,727,983,
		695,663,918,439,
		407,725,661,662,
		150,183,151,598,
		370,306,566,  4,
		264, 32,  0, 14,
		 15, 72,136, 40,
		 12, 64,583, 70,
		 38,134,659
	)
	
	def decode(self, inst):
		opcd = inst & 0x3F
		
		if opcd == 18: # bx -- I form
			return (
				opcd, # OPCD
				(inst & 0x3fffffc0) >>  6, # LI
				(inst & 0x40000000) >> 30, # AA
				 inst               >> 31  # LK
			)
		elif opcd == 16: # bcx -- B form
			return (
				opcd, # OPCD
				(inst & 0x000007c0) >>  6, # BO
				(inst & 0x0000f800) >> 11, # BI
				(inst & 0x3fff0000) >> 16, # BD
				(inst & 0x40000000) >> 30, # AA
				 inst               >> 31  # LK
			)
		elif opcd == 17 and ((inst & 0x40000000) >> 30) == 1: # sc -- SC form
			return (
				opcd, # OPCD
			)
		elif opcd in self.D: # D form
			return (
				opcd, # OPCD
				(inst & 0x000007c0) >>  6, # D/S/(crfD|0|L)/TO
				(inst & 0x0000f800) >> 11, # A
				 inst               >> 16  # SIMM/UIMM/d
			)
		elif opcd in self.X: # X form
			opcd |= (inst & 0x7fe00000) >> 15
			return (
				opcd, # OPCD
				(inst & 0x000007c0) >>  6, # D/S/(crfD|0|L)/TO
				(inst & 0x0000f800) >> 11, # A
				(inst & 0x001f0000) >> 16, # B/NB/SH/IMM
				 inst               >> 31  # Rc/0/1
			)
		else:
			raise DecoderException('Bad instruction %08x' % inst)