ICopyHook是一个用于创建拷贝钩子处理程序COM接口，它决定一个文件夹或者打印机对象是否可以被移动，拷贝，重命名或删除。Shell在执行这些操作之前，会调用ICopyHook接口的CopyCallback方法对它们进行验证。CopyCallback返回一个int值指示Shell是否应该继续执行这个操作。返回值IDYES表示继续，而返回值IDNO和IDCANCEL则表示终止。
一个文件夹对象可以安装多个拷贝钩子处理程序。如果出现这种情况，Shell会依次调用每个处理程序。只有当每个处理程序都返回IDYES时，Shell才真正执行用户请求的操作。
拷贝钩子处理程序的作用是在上述四种操作执行前对它们进行验证，但是Shell并不会把操作的结果通知给拷贝钩子处理程序。而windows提供的API函数FindFirstChangeNotification和FindNextChangeNotification却可以实现这个功能。因此，只有把这种两种方法结合起来，才能对一个文件夹的状态进行完全的监控。
拷贝钩子处理程序实现并不困难，首先创建一个作为进程内组件的COM对象，它只需要暴露一个ICopyHook接口（当然还有IUnknown）。然后用regsrv32.exe注册这个COM组件。最后一步是向Shell注册你的这个拷贝钩子处理程序，方法是在注册表HKEY_CLASSES_ROOT\Directory\Shellex\CopyHookHandlers下创建一个名称任意的sub key，在此sub key中创建一个类型为REG_SZ的项并将你的COM对象的CLSID作为它的默认值就可以了。
下面就是一个拷贝钩子的实现程序(注：以下代码经老妖改动并添加了详细操作过程，在BCB6中成功编译并通过测试)
1. 从ICopyHook接口创建TCopyHook，从IClassFactory接口创建TClassFactory:
// TCopyHook.h
// TCopyHook类实现了ICopyHook接口，TClassFactory实现了IClassFactory接口
//---------------------------------------------------------------------------
#define NO_WIN32_LEAN_AND_MEAN
#include <shlobj.h>
//---------------------------------------------------------------------------
class TCopyHook: public ICopyHook
{
public:
TCopyHook():m_refcnt(0) {}
STDMETHODIMP QueryInterface(REFIID iid,void **ppvObject);
STDMETHODIMP_(ULONG) AddRef();
STDMETHODIMP_(ULONG) Release();
STDMETHODIMP_(UINT) CopyCallback(HWND hwnd, UINT wFunc, UINT wFlags,
LPCTSTR pszSrcFile, DWORD dwSrcAttribs,
LPCTSTR pszDestFile, DWORD dwDestAttribs);
private:
int m_refcnt;
};
//---------------------------------------------------------------------------
class TClassFactory : public IClassFactory
{
public:
TClassFactory():m_refcnt(0) {}
STDMETHODIMP QueryInterface(REFIID iid, void **ppvObject);
STDMETHODIMP_(ULONG) AddRef();
STDMETHODIMP_(ULONG) Release();
STDMETHODIMP CreateInstance(IUnknown *pUnkOuter, REFIID riid, void **ppvObject);
STDMETHODIMP LockServer(BOOL fLock);
private:
int m_refcnt;
};
// TCopyHook.cpp
// TCopyHook对象和TClassFactory对象的实现文件
#include <stdio.h>
#include "TCopyHook.h"
//---------------------------------------------------------------------------
extern LONG nLocks; // 对象计数，用于DllCanUnloadNow
ULONG __stdcall TCopyHook::AddRef()
{
if(m_refcnt == 0)
nLocks++;
m_refcnt++;
return m_refcnt;
}
//---------------------------------------------------------------------------
ULONG __stdcall TCopyHook::Release()
{
int nNewCnt = --m_refcnt;
if(nNewCnt <= 0)
{
nLocks--;
delete this;
}
return nNewCnt;
}
//---------------------------------------------------------------------------
HRESULT __stdcall TCopyHook::QueryInterface(REFIID dwIID, void **ppvObject)
{
if(dwIID == IID_IUnknown)
*ppvObject = static_cast<IUnknown*>(this);
else
if(dwIID == IID_IShellCopyHook)
*ppvObject = static_cast<ICopyHook*>(this);
else
return E_NOINTERFACE;
reinterpret_cast<IUnknown*>(*ppvObject)->AddRef();
return S_OK;
}
//---------------------------------------------------------------------------
// 这就是CopyCallback方法，拷贝钩子的所有功能由它实现。参数的具体值参看MSDN
UINT __stdcall TCopyHook::CopyCallback(HWND hwnd, UINT wFunc, UINT wFlags,
LPCTSTR pszSrcFile, DWORD dwSrcAttribs,
LPCTSTR pszDestFile, DWORD dwDestAttribs)
{
char szMessage[MAX_PATH+14];
sprintf(szMessage, "对%s进行的操作，是否继续？", pszSrcFile);
return MessageBox(NULL, szMessage, "确认", MB_YESNO | MB_ICONEXCLAMATION);
}
//---------------------------------------------------------------------------
ULONG __stdcall TClassFactory::AddRef()
{
if(m_refcnt==0)
nLocks++;
m_refcnt++;
return m_refcnt;
}
//---------------------------------------------------------------------------
ULONG __stdcall TClassFactory::Release()
{
int nNewCnt = --m_refcnt;
if(nNewCnt <= 0)
{
nLocks--;
delete this;
}
return nNewCnt;
}
//---------------------------------------------------------------------------
HRESULT __stdcall TClassFactory::QueryInterface(REFIID dwIID, void **ppvObject)
{
if(dwIID == IID_IUnknown)
*ppvObject = static_cast<IUnknown*>(this);
else
if(dwIID == IID_IClassFactory)
*ppvObject = static_cast<IClassFactory*>(this);
else
return E_NOINTERFACE;
reinterpret_cast<IUnknown*>(*ppvObject)->AddRef();
return S_OK;
}
//---------------------------------------------------------------------------
HRESULT __stdcall TClassFactory::CreateInstance(IUnknown* pUnkownOuter,
REFIID riid, void** ppvObj)
{
if(pUnkownOuter != NULL)
return CLASS_E_NOAGGREGATION;
TCopyHook *pObj = new TCopyHook;
pObj->AddRef();
HRESULT hr = pObj->QueryInterface(riid, ppvObj);
pObj->Release();
return hr;
}
//---------------------------------------------------------------------------
HRESULT __stdcall TClassFactory::LockServer(BOOL fLock)
{
if(fLock)
nLocks++;
else
nLocks--;
return S_OK;
}