API hooking revealed

//---------------------------------------------------------------------------
//
// ApplicationScope.h
//
// SUBSYSTEM:   Hook system
//				
// MODULE:      Hook server
//
// DESCRIPTION: Declares interface for the CApplicationScope class. 
//              This class is designed to provide single interface for 
//              all hook related activities.
// 				
//             
// AUTHOR:		Ivo Ivanov (ivopi@hotmail.com)
// DATE:		2001 December v1.00
//
//---------------------------------------------------------------------------

#if !defined(_APPLICATIONSCOPE_H_)
#define _APPLICATIONSCOPE_H_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

#include "..\Common\LockMgr.h"
#include "..\Common\CustomMessages.h"

//---------------------------------------------------------------------------
//
// Global variables
// 
//---------------------------------------------------------------------------
//
// A global guard object used for protecting singelton's instantiation 
//
static CCSWrapper g_AppSingeltonLock;

//---------------------------------------------------------------------------
//
// Prototype of the main hook function
//
//---------------------------------------------------------------------------
typedef BOOL (WINAPI *PFN_INSTALLHOOK)(
	BOOL bActivate, 
	HWND hWndServer
	);


//---------------------------------------------------------------------------
//
// class CApplicationScope 
//
//---------------------------------------------------------------------------
class CApplicationScope  
{
private:
	//
	// Intentionally hide the defualt constructor,
	// copy constructor and assignment operator 
	//

	//
	// Default constructor
	//
	CApplicationScope();
	//
	// Copy constructor
	//
	CApplicationScope(const CApplicationScope& rhs);
	//
	// Assignment operator
	//
	CApplicationScope& operator=(const CApplicationScope& rhs);
public:
	//
	// Destructor - we must declare it as public in order to provide
	// enough visibility for the GetInstance().
	// However the destructor shouldn't be called directly by the 
	// application's code.
	//
	virtual ~CApplicationScope();
	//
	// Implements the "double-checking" locking pattern combined with 
	// Scott Meyers single instance
	// For more details see - 
	// 1. "Modern C++ Design" by Andrei Alexandrescu - 6.9 Living in a 
	//     Multithreaded World
	// 2. "More Effective C++" by Scott Meyers - Item 26
	//
	static CApplicationScope& GetInstance();
	//
	// Delegates the call to the DLL InstallHook function
	//
	void InstallHook(BOOL bActivate, HWND hwndServer);
	//
	// Fired when a process loads hooktool dll
	//
	void OnDllLoaded(DWORD dwProcessId);
	//
	// Fired when a process unloads hooktool dll
	//
	void OnDllUnLoaded(DWORD dwProcessId);
private:
	//
	// Instance's pointer holder
	//
	static CApplicationScope* sm_pInstance;
	//
	// HookTool handle
	//
	HMODULE m_hmodHookTool;
	//
	//
	//
	PFN_INSTALLHOOK m_pfnInstallHook;
};

#endif // !defined(_APPLICATIONSCOPE_H_)

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