From b38e50d520ecc5ac6acccd6cfdb112a278f6fb1f Mon Sep 17 00:00:00 2001
From: Federico Cecchetto <fedecek3@gmail.com>
Date: Sat, 29 May 2021 23:35:47 +0200
Subject: [PATCH] Add replaceFunc function

---
 src/component/gsc.cpp       | 73 +++++++++++++++++++++++++++++++++++++
 src/component/scripting.cpp |  4 ++
 src/component/scripting.hpp |  2 +
 3 files changed, 79 insertions(+)

diff --git a/src/component/gsc.cpp b/src/component/gsc.cpp
index d42e599..5f77bd1 100644
--- a/src/component/gsc.cpp
+++ b/src/component/gsc.cpp
@@ -1,6 +1,7 @@
 #include <stdinc.hpp>
 #include "loader/component_loader.hpp"
 #include "scheduler.hpp"
+#include "scripting.hpp"
 
 #include "game/scripting/event.hpp"
 #include "game/scripting/execution.hpp"
@@ -169,6 +170,62 @@ namespace gsc
 				retn
 			}
 		}
+
+		unsigned int replaced_pos = 0;
+
+		void get_replaced_pos(unsigned int pos)
+		{
+			if (scripting::replaced_functions.find(pos) != scripting::replaced_functions.end())
+			{
+				replaced_pos = scripting::replaced_functions[pos];
+			}
+		}
+
+		__declspec(naked) void vm_execute_stub()
+		{
+			__asm
+			{
+				pushad
+				push esi
+				call get_replaced_pos
+				pop esi
+				popad
+
+				cmp replaced_pos, 0
+				jne set_pos
+
+				movzx eax, byte ptr[esi]
+				inc esi
+
+				jmp loc_1
+			loc_1:
+				mov [ebp - 0x18], eax
+				mov [ebp - 0x8], esi
+
+				push ecx
+
+				mov ecx, 0x20B8E28
+				mov [ecx], eax
+
+				mov ecx, 0x20B4A5C
+				mov[ecx], esi
+
+				pop ecx
+
+				cmp eax, 0x98
+
+				push 0x56B740
+				retn
+			set_pos:
+				mov esi, replaced_pos
+				mov replaced_pos, 0
+
+				movzx eax, byte ptr[esi]
+				inc esi
+
+				jmp loc_1
+			}
+		}
 	}
 
 	namespace function
@@ -204,8 +261,24 @@ namespace gsc
 				return {};
 			});
 
+			function::add("replacefunc", [](function_args args) -> scripting::script_value
+			{
+				const auto what = args[0].get_raw();
+				const auto with = args[1].get_raw();
+
+				if (what.type != game::SCRIPT_FUNCTION || with.type != game::SCRIPT_FUNCTION)
+				{
+					throw std::runtime_error("Invalid type");
+				}
+
+				scripting::replaced_functions[what.u.uintValue] = with.u.uintValue;
+
+				return {};
+			});
+
 			utils::hook::jump(0x56C8EB, call_builtin_stub);
 			utils::hook::jump(0x56CBDC, call_builtin_method_stub);
+			utils::hook::jump(0x56B726, vm_execute_stub);
 		}
 	};
 }
diff --git a/src/component/scripting.cpp b/src/component/scripting.cpp
index 782de82..27c33ac 100644
--- a/src/component/scripting.cpp
+++ b/src/component/scripting.cpp
@@ -12,6 +12,8 @@ namespace scripting
 	std::unordered_map<int, std::unordered_map<std::string, int>> fields_table;
 	std::unordered_map<std::string, std::unordered_map<std::string, char*>> script_function_table;
 
+	std::unordered_map<unsigned, unsigned> replaced_functions;
+
 	namespace
 	{
 		utils::hook::detour vm_notify_hook;
@@ -67,6 +69,8 @@ namespace scripting
 
 		void g_shutdown_game_stub(const int free_scripts)
 		{
+			replaced_functions.clear();
+
 			g_shutdown_game_hook.invoke<void>(free_scripts);
 		}
 
diff --git a/src/component/scripting.hpp b/src/component/scripting.hpp
index 21e9445..b8fc942 100644
--- a/src/component/scripting.hpp
+++ b/src/component/scripting.hpp
@@ -2,6 +2,8 @@
 
 namespace scripting
 {
+	extern std::unordered_map<unsigned, unsigned> replaced_functions;
+
 	extern std::unordered_map<int, std::unordered_map<std::string, int>> fields_table;
 	extern std::unordered_map<std::string, std::unordered_map<std::string, char*>> script_function_table;
 }
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