private static bool OperandMatches(OperandDefinition opDef, Operand op)
{
if (op.Size != opDef.Size)
{
return(false);
}
switch (opDef)
{
case FixedOperandDefinition fixDef:
{
return(op is RegisterOperand reg && reg.Name == fixDef.Name);
}
default:
{
// if we have a register operand but the definition requires a memory operand that is a match still
if (op.Type == opDef.Type)
{
return(true);
}
return(op.Type == OperandType.Register && opDef.Type == OperandType.Memory);
}
}
}
/// <summary>
///
/// </summary>
/// <param name="operand1">Memory operand</param>
/// <param name="op1Def"></param>
/// <param name="operand2">reg operand</param>
/// <param name="op2Def"></param>
/// <returns></returns>
private static byte?CalculateModRM(Operand operand1, OperandDefinition op1Def, Operand operand2, OperandDefinition op2Def)
{
var reg1Bits = CalculateModRMRegBits(operand1, op1Def);
if (reg1Bits != null)
{
var reg1Byte = reg1Bits.Value;
var reg2Bits = CalculateModRMRegBits(operand2, op2Def);
var mod = CalculateModRmModBits(operand1, reg1Bits) << 6;
if (reg2Bits != null)
{
var reg2Byte = reg2Bits.Value;
return((byte)(mod | (reg2Byte << 3) | reg1Byte));
}
return((byte)(mod | reg1Byte));
}
return(null);
}
private static byte?CalculateModRMRegBits(Operand op, OperandDefinition opDef)
{
if (op is RegisterOperand rmReg && opDef.Type != OperandType.Fixed)
{
return((byte)(RegisterByte(rmReg.Name) & 0b111));
}
if (op is MemoryOperand mem1)
{
if (mem1.InnerOperand is RegisterOperand reg)
{
return((byte)(RegisterByte(reg.Name) & 0b111));
}
if (mem1.InnerOperand is ImmOperand)
{
return(0b100); // SP
}
}
return(null);
}