Add virtual method table hooking class.

* github.com/aixxe/vmthook (8f0479b)

Signed-off-by: aixxe <me@aixxe.net>

include/vmthook/vmthook.h

@@ -0,0 +1,66 @@
+#pragma once
+
+#include <cstdint>
+#include <cstddef>
+#include <cstring>
+#include <memory>
+
+class VMTHook {
+	private:
+		std::uintptr_t** baseclass = nullptr;
+		std::unique_ptr<std::uintptr_t[]> current_vft = nullptr;
+		std::uintptr_t* original_vft = nullptr;
+		std::size_t total_functions = 0;
+	public:
+		VMTHook(void) = default;
+
+		VMTHook(void* baseclass) {
+			this->baseclass = static_cast<std::uintptr_t**>(baseclass);
+
+			while (static_cast<std::uintptr_t*>(*this->baseclass)[this->total_functions])
+				++this->total_functions;
+
+			const std::size_t table_size = this->total_functions * sizeof(std::uintptr_t);
+
+			this->original_vft = *this->baseclass;
+			this->current_vft = std::make_unique<std::uintptr_t[]>(this->total_functions);
+
+			std::memcpy(this->current_vft.get(), this->original_vft, table_size);
+
+			*this->baseclass = this->current_vft.get();
+		};
+
+		~VMTHook() {
+			*this->baseclass = this->original_vft;
+		};
+
+		inline void* GetOriginalFunction(std::size_t function_index) {
+			return reinterpret_cast<void*>(this->original_vft[function_index]);
+		}
+
+		template <typename Function> inline const Function GetOriginalFunction(std::size_t function_index) {
+			return reinterpret_cast<Function>(this->original_vft[function_index]);
+		}
+
+		inline bool HookFunction(void* new_function, const std::size_t function_index) {
+			if (function_index > this->total_functions)
+				return false;
+
+			this->current_vft[function_index] = reinterpret_cast<std::uintptr_t>(new_function);
+
+			return true;
+		}
+
+		inline bool UnhookFunction(const std::size_t function_index) {
+			if (function_index > this->total_functions)
+				return false;
+
+			this->current_vft[function_index] = this->original_vft[function_index];
+
+			return true;
+		}
+
+		inline std::size_t GetTotalFunctions() {
+			return this->total_functions;
+		}
+};