opdecode

# Chip 8 OpCode Reader

# Loads a chip 8 rom and reads the opcodes
# Displays a human readable discribtion of the opcode


rom = open("pong", "rb")
data = []

simple_codes = [1,2,3,4,5,6,7,9,10,11,12,13]
for num, line in enumerate(rom.read()):
    if num % 2 == 0:
        part = format(ord(line), '02x')
    else:
        data.append(part+format(ord(line), '02x'))

for num, opcode in enumerate(data):
    print format(num+512, '04x'),
    first_nib = int(opcode[0], 16)
    if first_nib in simple_codes:
        if first_nib == 1:
            print opcode, "JUMP TO", opcode[1:]
        elif first_nib == 2:
            print opcode, "CALL SUB AT", opcode[1:]
        elif first_nib == 3:
            print opcode, "SKIP IF REG", opcode[1], "==", opcode[2:]
        elif first_nib == 4:
            print opcode, "SKIP IF REG", opcode[1], "!=", opcode[2:]
        elif first_nib == 5:
            print opcode, "SKIP IF REG", opcode[1], "== REG", opcode[2]
        elif first_nib == 6:
            print opcode, "SET REG", opcode[1], "==", opcode[2:]
        elif first_nib == 7:
            print opcode, "ADD", opcode[2:], "TO REG", opcode[1]
        elif first_nib == 9:
            print opcode, "SKIP IF !="
        elif first_nib == 10:
            print opcode, "SET INSTR TO ADDR", opcode[1:]
        elif first_nib == 11:
            print opcode, "JUMP PLUS"
        elif first_nib == 12:
            print opcode, "RNDOM"
        elif first_nib == 13:
            print opcode, "DRAW"
        else:
            opcode, "SIMPLE"
    else:
        first_nib = int(opcode[0], 16)
        last_nib = int(opcode[3], 16)
        if opcode == "00e0":
            print opcode, "CLEAR"
        elif opcode == "00ee":
            print opcode, "RETURN SUB"
        elif first_nib == 0:
            print opcode, "CALL RCA 1802"

        elif first_nib == 8 and last_nib == 0:
            print opcode, "SET"
        elif first_nib == 8 and last_nib == 1:
            print opcode, "SET OR"
        elif first_nib == 8 and last_nib == 2:
            print opcode, "SET AND"
        elif first_nib == 8 and last_nib == 3:
            print opcode, "SET XOR"
        elif first_nib == 8 and last_nib == 4:
            print opcode, "ADD"
        elif first_nib == 8 and last_nib == 5:
            print opcode, "SUBTRACT"
        elif first_nib == 8 and last_nib == 6:
            print opcode, "SHIFT"
        elif first_nib == 8 and last_nib == 7:
            print opcode, "SUBTRACT"
        elif first_nib == 8 and last_nib == 14:
            print opcode, "SHIFT"

        elif first_nib == 14 and last_nib == 14:
            print opcode, "SKIP IF PRESS"
        elif first_nib == 14 and last_nib == 1:
            print opcode, "SKIP IF NOT PRESS"

        elif first_nib == 15 and last_nib == 7:
            print opcode, "SET TO DELAY"
        elif first_nib == 15 and last_nib == 10:
            print opcode, "WAIT FOR KEY"
        elif first_nib == 15 and last_nib == 5:
            print opcode, "SET DELAY"
        elif first_nib == 15 and last_nib == 8:
            print opcode, "SET SOUND"
        elif first_nib == 15 and last_nib == 14:
            print opcode, "ADD TO INSTR"
        elif first_nib == 15 and last_nib == 9:
            print opcode, "DRAW INSTR"
        elif first_nib == 15 and last_nib == 3:
            print opcode, "SET BIN CODE"
        else:
            print opcode, "COMPLEX"