main.py

import sys

# valid instructions, case insensitive
instructions = {'add'           : '0010',
                'sub'           : '0011',
                'subtract'      : '0011',
                'ldi'           : '1110',
                'loadimmediate' : '1110',
                'ld'            : '1111',
                'load'          : '1111',
                'st'            : '1011',
                'store'         : '1011',
                'mv'            : '0110',
                'mov'           : '0110',
                'move'          : '0110',
                'mult'          : '0111',
                'jmp'           : '00',
                'jump'          : '00',
                'jmpn'          : '01',
                'jumpn'         : '01'
               }

nopBin = "00000110"   # move R0,R0
nopHex = "00"         # later this will be "06"

# register number or value 0-3
operands = {'0' : '00',
            '1' : '01',
            '2' : '10',
            '3' : '11'}


# map target labels to addresses
fName = input("Program File: ")
fhandle = open(fName)
addr = 0
longestLabelLength = 0
targets = {}
for line in fhandle:
   line = line.lower().strip()							  
   # skip blank & comment lines
   if line == "" or line.startswith("#"):
      continue
   # remove comments at the end of the line
   if line.find('#') != -1:   
      line = line[:line.find('#')].strip()
   if line.find(':') != -1:
      target = line[:line.find(':')].strip()
      targets[target] = format(addr,"06b")
      if len(target) > longestLabelLength:
         longestLabelLength = len(target)
   addr += 1
fhandle.close()


# assemble program
fhandle = open(fName)
lineNum = 0
addr = 0
program = ""
print("\nOriginal Program")
for line in fhandle:
    # print("line1 --> ",line)
    lineNum += 1
    origLine = line.strip()
    # get rid of target label
    if origLine.find(':') != -1:
       origLine = origLine[origLine.find(':')+1:].strip()
    line = line.lower().strip()
    # skip empty lines or comment lines
    if line.strip() == "" or line.startswith("#"):
       print('         ' + line)
       continue
    # remove comments at the end of the line
    if line.find('#') != -1:   
       line = line[:line.find('#')].strip()
    # get rid of target label
    target2Print = ""
    if line.find(':') != -1:
       target2Print = line[:line.find(':')].strip() + ":"
       line = line[line.find(':')+1:].strip()
    # print("line2 --> ",line)
    line = line.replace('\t',' ')  # replace tabs with a space
    tokens = line.split(" ",1)
    # print("tokens --> ",tokens)
    instr = tokens[0]
    if instr == "nop":
       binaryInstr = "1111" + nopBin          # to preserve a leading 0 add '1111'at beginning which results in 'fxx' otherwise '00001110' becomes just e not 0e.
    elif instr not in instructions:
       print("ERROR!!! '" + instr + "' on line " + str(lineNum) + " is not a valid instruction")
       sys.exit()
    elif instr == "jumpn" or instr == "jmpn":
       target = tokens[1].strip()
       binaryInstr = "1111" + targets[target] + "01"  # to preserve a leading 0 add '1111'at beginning which results in 'fxx' otherwise '00001110' becomes just e not 0e.
    elif instr == "jump" or instr == "jmp":
       target = tokens[1].strip()
       if target in targets:
          binaryInstr = "1111" + targets[target] + "00"  # to preserve a leading 0 add '1111'at beginning which results in 'fxx' otherwise '00001110' becomes just e not 0e.
       else:
          print("ERROR!!! '" + instr + "' on line " + str(lineNum) + " has an invalid target.")
          sys.exit()
    else:
       opsRaw = tokens[1].replace(' ', '')
       ops = opsRaw.split(',')
       # rd operand
       rd = ops[0].replace('r','').strip()
       if rd not in operands:
           print("ERROR!!! '" + ops[0] + "' on line " + str(lineNum) + " is not a valid destination operand")
           sys.exit()
       rsOp = ops[1].replace('r','').strip()
       if rsOp not in operands:
           print("ERROR!!! '" + ops[1] + "' on line " + str(lineNum) + " is not a valid source operand")
           sys.exit()
       # to preserve a leading 0 add '1111'at beginning which results in 'fxx' otherwise '00001110' becomes just e not 0e.
       binaryInstr = "1111" + operands[rd]+operands[rsOp]+instructions[instr]
    hexInstr = hex(int(binaryInstr,2))[3:]
    print(f'[{addr:02d}] ' + hexInstr + '  ' + target2Print + (' ' *  (longestLabelLength - len(target2Print) + 2)) + origLine)
    program = program + hexInstr + ' '
    addr += 1
program = program + ((nopHex + ' ') * int(64-(len(program)/3))) # 0e is the NOP
print("\nProgram Memory (copy & paste this into your program memory")
print(program)
fhandle.close()