Request: CodeInstruction generator

[pardeike]

Request: CodeInstruction generator

[pardeike]

Part of the api I want to make public in combination with reverse patching

[FrodoOf9Fingers]

Awesome, thanks!

[BarryBadpak]

Any update on this? Would be amazing to have the CodeInstructions generator available in order to replace methods

[pardeike]

Just checked it in. The tricky part is that CodeInstructions can have local var references. And those come from registering new variables with the current ILGenerator. So I made this API:

using Harmony;
using Harmony.ILCopying;
using System;
using System.Collections.Generic;
using System.Reflection;
using System.Reflection.Emit;

namespace HarmonyConsoleApp
{
	class Program
	{
		static void Main(string[] args)
		{
			var harmony = HarmonyInstance.Create("com.company.project.product");
			harmony.PatchAll(typeof(Program).Assembly);

			var test = new Test();
			test.Call();
			Console.ReadKey();
		}
	}

	public class Test
	{
		public void Extra()
		{
			Console.WriteLine("EXTRA");
		}

		public void Call()
		{
			Console.WriteLine("ORIGINAL");
		}
	}

	[HarmonyPatch(typeof(Test))]
	[HarmonyPatch("Call")]
	static class Patch
	{
		static IEnumerable<CodeInstruction> Transpiler(ILGenerator generator, MethodBase method, IEnumerable<CodeInstruction> instructions)
		{
			var ils1 = MethodBodyReader.GetInstructions(generator, method);
			foreach (var il in ils1)
			{
				var instruction = il.GetCodeInstruction();
				if (instruction.operand as string == "ORIGINAL")
					instruction.operand = "PATCHED";
				if (instruction.opcode != OpCodes.Ret)
					yield return instruction;
			}

			var ils2 = MethodBodyReader.GetInstructions(generator, AccessTools.Method(typeof(Test), "Extra"));
			foreach (var il in ils2)
			{
				var instruction = il.GetCodeInstruction();
				if (instruction.opcode != OpCodes.Ret)
					yield return instruction;
			}

			yield return new CodeInstruction(OpCodes.Ret);
		}
	}
}

Note that in order to get the instructions, you will as a side effect generate local vars on your current generator.

[pardeike]

I am going to make a high level reverse patch operation where you can project the ill codes onto an empty static method you have in your code for easier calling inside your patch functions.