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using dnlib.DotNet;
using dnlib.DotNet.Emit;
using Obfuz.Emit;
using System.Collections.Generic;

namespace Obfuz.ObfusPasses
{
    public abstract class BasicBlockObfuscationPassBase : ObfuscationMethodPassBase
    {
        protected virtual bool ComputeBlockInLoop => true;

        protected abstract bool TryObfuscateInstruction(MethodDef callingMethod, Instruction inst, BasicBlock block, int instructionIndex,
            IList<Instruction> globalInstructions, List<Instruction> outputInstructions, List<Instruction> totalFinalInstructions);

        protected override void ObfuscateData(MethodDef method)
        {
            BasicBlockCollection bbc = new BasicBlockCollection(method, ComputeBlockInLoop);

            IList<Instruction> instructions = method.Body.Instructions;

            var outputInstructions = new List<Instruction>();
            var totalFinalInstructions = new List<Instruction>();
            for (int i = 0; i < instructions.Count; i++)
            {
                Instruction inst = instructions[i];
                BasicBlock block = bbc.GetBasicBlockByInstruction(inst);
                outputInstructions.Clear();
                if (TryObfuscateInstruction(method, inst, block, i, instructions, outputInstructions, totalFinalInstructions))
                {
                    // current instruction may be the target of control flow instruction, so we can't remove it directly.
                    // we replace it with nop now, then remove it in CleanUpInstructionPass
                    inst.OpCode = outputInstructions[0].OpCode;
                    inst.Operand = outputInstructions[0].Operand;
                    totalFinalInstructions.Add(inst);
                    for (int k = 1; k < outputInstructions.Count; k++)
                    {
                        totalFinalInstructions.Add(outputInstructions[k]);
                    }
                }
                else
                {
                    totalFinalInstructions.Add(inst);
                }
            }

            instructions.Clear();
            foreach (var obInst in totalFinalInstructions)
            {
                instructions.Add(obInst);
            }
        }
    }
}