public MachineOperand GetOperand(ImageReader rdr, string args, PrimitiveType dataWidth) { if (i >= args.Length) return null; for (; ; ) { if (args[i] == ',') ++i; Address addr; switch (args[i++]) { case 'A': // Address register A0-A7 encoded in in instrution return new RegisterOperand(AddressRegister(opcode, GetOpcodeOffset(args[i++]))); case 'c': // CCR register return new RegisterOperand(Registers.ccr); case 'D': // Data register D0-D7 encoded in instruction return DataRegisterOperand(opcode, GetOpcodeOffset(args[i++])); case 'E': // Effective address (EA) return ParseOperand(opcode, GetOpcodeOffset(args[i++]), dataWidth, rdr); case 'e': // Effective address with 3-bit halves swapped return ParseSwappedOperand(opcode, GetOpcodeOffset(args[i++]), dataWidth, rdr); case 'I': // Immediate operand return GetImmediate(rdr, GetSizeType(0, args[i++], dataWidth)); case 'J': // PC Relative jump addr = rdr.Address; int offset = opcode & 0xFF; if (offset == 0xFF) offset = rdr.ReadBeInt32(); else if (offset == 0x00) offset = rdr.ReadBeInt16(); else offset = (sbyte) offset; return new M68kAddressOperand(addr + offset); case 'M': // Register bitset return new RegisterSetOperand(rdr.ReadBeUInt16()); case 'n': // cache bitset bitSet = rdr.ReadBeUInt16(); break; case 'm': // Register bitset reversed return RegisterSetOperand.CreateReversed(bitSet); case 'q': // "Small" quick constant (3-bit part of the opcode) return GetQuickImmediate(GetOpcodeOffset(args[i++]), 0x07, 8, PrimitiveType.Byte); case 'Q': // "Large" quick constant (8-bit part of the opcode) return GetQuickImmediate(GetOpcodeOffset(args[i++]), 0xFF, 0, PrimitiveType.SByte); case 'R': // relative addr = rdr.Address; int relative = 0; switch (args[i++]) { case 'w': relative = rdr.ReadBeInt16(); break; case 'l': relative = rdr.ReadBeInt32(); break; default: throw new NotImplementedException(); } return new M68kAddressOperand(addr + relative); case 's': // SR register return new RegisterOperand(Registers.sr); case '+': // Postincrement operator; following character specifies bit offset of the address register code. return new PostIncrementMemoryOperand(dataWidth, AddressRegister(opcode, GetOpcodeOffset(args[i++]))); case '-': // Predecrement operator; following character specifies bit offset of the address register code. return new PredecrementMemoryOperand(dataWidth, AddressRegister(opcode, GetOpcodeOffset(args[i++]))); default: throw new FormatException(string.Format("Unknown argument type {0}.", args[--i])); } } }