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]));
}
}
}