深入解析钩子和动态链接库（中）

    你必须做的第一件事是创建共有的数据段。所以我们使用# pragma data_seg声明。使用某一好记的数据段名字(它必须是没有比8 个字符长) 。我想强调名字是任意的，这里使用了我自己的名字。我发现如果我使用好的名字象.SHARE 或.SHR 或.SHRDATA，别人会认为名字有特殊的意义。但是，我要说NO。

# pragma data_seg(".JOE")

HANDLE hWnd = NULL;

# pragma dta_seg()

# pragma comment(linker ，"/section:.JOE,rws ")

    # pragma声明一个数据段，在此范围内声明的变量在初始化后将被指派到该数据段，假设他们初始化. 如未初始化，变量将被分配到缺省数据段，而# pragma  不起作用。

      初看起来, 这将阻止你在共有的数据段使用一些C++ 对象，因为你无法初始化C++中用户定义的对象。这看来是一个根本局限。

      # pragma comment使连接器有命令行开关被显示增加到链接步骤。你可以进入VC++ 项目| 设置并且改变连接器命令行。

      你可以预定某一机制设置窗口句柄，例如

void SetWindow(HWND w) {hWnd = w; }

      但更经常的是如下所示的与钩子结合。

Sample: A Mouse Hook

header file (myhook.h)

      函数setMyHook并且clearMyHook必须在此被声明。这在我的另一文章中有详细论述。“The Ultimate DLL Header File.”

             _T("UMW_MOUSEHOOK-" /

            "{B30856F0-D3DD-11d4-A00B-006067718D04}")

source file (myhook.cpp)

#include "stdafx.h"

#include "myhook.h"

#pragma data_seg(".JOE")

HWND hWndServer = NULL;

#pragma data_seg()

#pragma comment("linker, /section:.JOE,rws")

HINSTANCE hInstance;

UINT HWM_MOUSEHOOK;

HHOOK hook;

// Forward declaration

static LRESULT CALLBACK msghook(int nCode, WPARAM wParam, LPARAM lParam);

/****************************************************************

*        DllMain

*        Inputs:

*       HINSTANCE hInst: Instance handle for the DLL

*       DWORD Reason: Reason for call

*       LPVOID reserved: ignored

*        Result: BOOL

*       TRUE if successful

*       FALSE if there was an error (never returned)

*       Effect:

*       Initializes the DLL.

****************************************************************/

BOOL DllMain(HINSTANCE hInst, DWORD Reason, LPVOID reserved)

{

  switch(Reason)

   {   /* reason */

      //**********************************************

      // PROCESS_ATTACH

      //**********************************************

    case DLL_PROCESS_ATTACH:

          // Save the instance handle because we need it to set the hook later

          hInstance = hInst;

          // This code initializes the hook notification message

          UWM_MOUSEHOOK = RegisterWindowMessage(UWM_MOUSEHOOK_MSG);

          return TRUE;

    //**********************************************

    // PROCESS_DETACH

    //**********************************************

   case DLL_PROCESS_DETACH:

          // If the server has not unhooked the hook, unhook it as we unload

         if(hWndServer != NULL)

                clearMyHook(hWndServer);

         return TRUE;

  } /* reason */

/****************************************************************

*       setMyHook

*        Inputs:

*       HWND hWnd: Window whose hook is to be set

*       Result: BOOL

*       TRUE if the hook is properly set

*       FALSE if there was an error, such as the hook already

*       being set

*       Effect:

*       Sets the hook for the specified window.

*       This sets a message-intercept hook (WH_GETMESSAGE)

*       If the setting is successful, the hWnd is set as the

*       server window.

****************************************************************/

__declspec(dllexport) BOOL WINAPI setMyHook(HWND hWnd)

 {

    if(hWndServer != NULL)

        return FALSE;

    hook = SetWindowsHookEx(

                          WH_GETMESSAGE,

                           (HOOKPROC)msghook,

                           hInstance,

                           0 );

   if(hook != NULL)

     {        /* success */

             hWndServer = hWnd;

              return TRUE;

     }       /* success */

   return FALSE;

 }    // SetMyHook

#define   UWM_MOUSEHOOK_MSG /