public bool PerformComparison(MethodDef method, bool preserveOrder = true, bool allowOtherInstruction = false)
{
int groupIndex = 0;
for (var i = 0; i < method.GetInstructions().Count; ++i)
{
var instruction = method.Body.Instructions[i];
if (InstructionGroups.Count <= groupIndex && !allowOtherInstruction)
{
return(false);
}
else if (InstructionGroups.Count <= groupIndex)
{
break;
}
bool hasLimit = InstructionGroups[groupIndex].HowMany.HasValue;
int limit = InstructionGroups[groupIndex].HowMany.GetValueOrDefault();
//At this moment this algorithm doesn't manage:
// unrecognized -> optional -> non optional
//But only:
// optional -> unrecognized -> non optional
//(Not planning to add this use case, though)
bool isRecognized = InstructionGroups[groupIndex].RecognizedInstructions.Contains(instruction.OpCode);
while (!isRecognized && ((InstructionGroups[groupIndex].IsOptional) ||
(hasLimit && InstructionGroups[groupIndex].FoundInstructions.Count == limit) ||
(!hasLimit && InstructionGroups[groupIndex].FoundInstructions.Count > 0)))
{
//If you're here:
// Either you're skipping a not found, optional instruction,
// or you're skipping a group of instruction you've already matched in a
// previous iteration.
groupIndex++;
isRecognized = InstructionGroups[groupIndex].RecognizedInstructions.Contains(instruction.OpCode);
}
//If you're here:
// Not optional, found
// Not optional, not found
// Optional, found
if (isRecognized)
{
InstructionGroups[groupIndex].FoundInstructions.Add(i);
}
else if (allowOtherInstruction)
{
continue;
}
else if (!InstructionGroups[groupIndex].IsOptional)
{
return(false);
}
}
foreach (var group in instructionGroups)
{
if (!group.HowMany.HasValue)
{
if (!group.IsOptional && group.FoundInstructions.Count == 0)
{
return(false);
}
}
else
{
if (!group.IsOptional && group.FoundInstructions.Count != group.HowMany.Value)
{
return(false);
}
}
}
return(true);
}