Dissasembler for simplified version of motorolla 68000

dissassembler.py

#!/usr/bin/python

import optparse

def add(opcode,memory=None):
   dest     = ((opcode >> 9) & int(   "111",2))
   src      = ((opcode >> 0) & int(   "111",2))
   mode     = ((opcode >> 3) & int("111111",2))

   destType = 'd' if mode == int("001000",2) else 'a'
   srcType  = 'd'

   print "add\t%s%d,%s%d"%(srcType, src, destType, dest)
   return True

def sub(opcode,memory=None):
   dest     = ((opcode >> 9) & int(   "111",2))
   src      = ((opcode >> 0) & int(   "111",2))

   destType = 'd'
   srcType  = 'd'

   print "sub\t%s%d,%s%d"%(srcType, src, destType, dest)
   return True
   
def div(opcode,memory=None):
   dest     = ((opcode >> 9) & int(   "111",2))
   src      = ((opcode >> 0) & int(   "111",2))

   destType = 'd'
   srcType  = 'd'

   print "div\t%s%d,%s%d"%(srcType, src, destType, dest)
   return True

def mul(opcode,memory=None):
   dest     = ((opcode >> 9) & int(   "111",2))
   src      = ((opcode >> 0) & int(   "111",2))

   destType = 'd'
   srcType  = 'd'

   print "mul\t%s%d,%s%d"%(srcType, src, destType, dest)
   return True

def move(opcode, memory=None):
   def makeOperand(mode, number):
      if mode == 0: return "d%d" % number
      if mode == 1: return "a%d" % number
      if mode == 5: return "$%s(a%d)" % (hex(memory.next())[2:].upper().zfill(4), number)
      return "ERR"

   dest     = ((opcode >> 9) & int(   "111",2))
   src      = ((opcode >> 0) & int(   "111",2))

   destMode = ((opcode >> 6) & int(   "111",2))
   srcMode = ((opcode >> 3) & int(   "111",2))

   dest = makeOperand(destMode, dest)
   src  = makeOperand(srcMode, src)

   operand = "movea" if destMode == 1 or srcMode == 1 else "move"

   print "%s\t%s,%s"%(operand,src, dest)
   return True

def branch(opcode, memory=None):
   mode = (opcode >> 8) & int("1111",2)
   mode = {0:"bra", 7:"beq", 14:"bgt", 13:"blt"}[mode]

   displacement = hex(opcode & int("11111111",2))[2:].upper().zfill(2)

   print "%s\t$%s" % (mode, displacement)
   return True

def stop(opcode, memory=None):
   mode = (opcode >> 9) & int("111",2)
   if mode == 7:
      print "stop"
      return False
   elif mode == 4:
      print "swap\td%d" % (opcode & 7)
      return True

def declareData(opcode, memory=None):
   print "dc\t$%s" % hex(opcode)[2:].upper().zfill(4)
   return False

opcodes = {
   int("1101",2) << 12:add,
   int("1001",2) << 12:sub,
   int("1100",2) << 12:mul,
   int("1000",2) << 12:div,
   int("1011",2) << 12:"!comp",
   int("0100",2) << 12:stop,
   int("0011",2) << 12:move,
   int("0110",2) << 12:branch
}

def main(memory):
   # keep track of whether or not we've reached a stop instruction
   inProgram = True
   while 1:
      try:
         instruction = memory.next()
      except StopIteration:# end of input
         break
      if inProgram:
         try:
            try:
               inProgram = opcodes[instruction & (15 << 12)](instruction, memory)
            except TypeError: # 'str' object is not callable
               print opcodes[instruction & (15 << 12)]
         except KeyError: # operation doesn't exist/is not known/is not implemented
            print hex(instruction)
      else:
            declareData(instruction)

if __name__ == '__main__':
   parser = optparse.OptionParser("usage: %prog [-b|--base<n>] [-a|--addresses] filename")
   parser.add_option("-b", "--base",type="int", default=2)
   parser.add_option("-a", "--addresses", action="store_true", default=False)

   (options, args) = parser.parse_args()

   base = options.base
   addresses = options.addresses

   if len(args) == 1:
      filename = args[0]
      memory = reduce(\
                      lambda x, y: x + y, \
                      (\
                          list(int(d,base) for d in c.split()[int(addresses):])\
                      for c in open(filename).read().splitlines() if len(c) > 0)\
                     )

      main(iter(memory))
   else:
      print parser.get_usage()

test.asm

; test output from the disassembler
sub     d0,d0
movea   d0,a1
movea   a1,a0
move    $4052(a1),d1
swap    d0
movea   $4050(a1),a0
move    d1,d3
add     d3,d3
move    d3,d2
mul     d0,d2
sub     d3,d2
add     d2,a0
sub     d2,d2
sub     d3,d2
div     d3,d0
movea   $403E(a0),a3
movea   $403E(a1),a2
movea   a3,$403E(a1)
movea   a2,$403E(a0)
add     d2,a0
add     d3,a1
sub     d1,d0
bgt     $EC
move    $4054(a0),d0
stop
dc      $000A
dc      $000B
dc      $000C
dc      $000D
dc      $000E
dc      $0000
dc      $0001
dc      $0002
dc      $0003
dc      $0009
dc      $0001
dc      $0003