openGL Hook

OpenGLHook.cpp

```c
namespace OpenGLMemory
{
	template<typename T>
	T Read(DWORD address)
	{
		return *((T*)address);
	}
	template<typename T>
	void Write(DWORD address, T value)
	{
		*((T*)address) = value;
	}
	template<typename T>
	DWORD Protect(DWORD address, DWORD prot)
	{
		DWORD oldProt;
		VirtualProtect((LPVOID)address, sizeof(T), prot, &oldProt);
		return oldProt;
	}
	DWORD OpenGLJumpHook(DWORD hookAt, DWORD newFunc, int size)
	{
		DWORD newOffset = newFunc - hookAt - 5; // -5 用于写入jmp 到新函数的代码
		auto oldProtection = OpenGLMemory::Protect<DWORD[3]>(hookAt + 1, PAGE_EXECUTE_READWRITE); //改内存属性为可写
		OpenGLMemory::Write<BYTE>(hookAt, 0xE9); //JMP
		OpenGLMemory::Write<DWORD>(hookAt + 1, newOffset); //跳转到新函数地址
		for (unsigned int i = 5; i < size; i++) //NOP额外字节，因此它不会破坏任何指令
			OpenGLMemory::Write<BYTE>(hookAt + i, 0x90);
		OpenGLMemory::Protect<DWORD[3]>(hookAt + 1, oldProtection);
		return hookAt + 5;
	}
}


void hwglSwapBuffers(_In_ HDC hDc)
{
	CString hDcLogger;
	hDcLogger.Format("OpenGL HOOK: hdc: %08X",hDc);
	OutputDebugString(hDcLogger);
}

DWORD owglSwapBuffers = 0;
void __declspec(naked) SwapTrampoline()
{
	__asm {
		PUSHFD						//保存EFLAGS     
		PUSHAD						//保存寄存器    
		CALL hwglSwapBuffers		//重定向到自己的buffer
		POPAD						//恢复寄存器         
		POPFD                       //恢复EFLAGS        
		PUSH EBP					//恢复hook前的汇编代码
		MOV EBP, ESP					
		JMP[owglSwapBuffers]	//返回原本的执行位置继续执行		
	}
}
void OpenGLHook()
{       
	//DWORD AddressToHook = (DWORD)GetProcAddress(GetModuleHandle(L"opengl32.dll"),"wglSwapBuffers");
	DWORD wglSwapBuffersAddress = (DWORD)GetProcAddress(GetModuleHandle(_T("opengl32.dll")),"wglSwapBuffers"); 
	owglSwapBuffers = OpenGLMemory::OpenGLJumpHook(wglSwapBuffersAddress, (DWORD)SwapTrampoline, 5);
}

```