深入浅出Dll(介绍函数导出、类导出、钓子dll、不同语言混合编程方法、插件等的实现方法)
所有代码均经过测试，如有问题可留言
一。简单的dll函数调用有两种方式:
1。显式调用2。隐式调用.如下例子
//xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
// dlltest.cpp : Dll 撰写
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#include <windows.h>
#include <stdio.h>
extern "C" __declspec(dllexport) int Add(int n1, int n2);
BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved)
{
if(ul_reason_for_call==DLL_PROCESS_ATTACH)
{
//TRACE0("DLL Initializing!\n");
}
else if(ul_reason_for_call=DLL_PROCESS_DETACH)
{
//TRACE0("DLL Terminating!\n");
}
return TRUE;
}
__declspec(dllexport) Add(int n1, int n2)
{
char szTxt[1024];
sprintf(szTxt,"%d + %d =%d",n1,n2,n1+n2);
MessageBox(0,szTxt,"Dll Respond here:",0);
return 1;
}
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// usedll.cpp : Dll 调用测试
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#include <windows.h>
//#define USESTATELIB
// 隐式链接方式:
#ifdef USESTATELIB
#pragma comment(lib,"lib\\dlltest.lib")
extern "C" __declspec(dllimport) int Add(int n1, int n2);
#endif
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
#ifndef USESTATELIB
// 显式调用方式:
HINSTANCE hIns=LoadLibrary("dlltest.dll");
if(!hIns)
{
MessageBox(0,"couldn't find dlltest.dll","error:",0);
return 0;
}
typedef int (DLL_Add)(int , int );
DLL_Add *testit=(DLL_Add*) GetProcAddress(hIns,"Add");
if(testit)
{
(*testit)(1,2);
}else
{
MessageBox(0,"couldn't find Add from dlltest.dll","error:",0);
return 0;
}
FreeLibrary(GetModuleHandle("dlltest.dll"));
#else
//隐式链接方式:
int nres= Add(1, 2);
#endif
return 0;
}
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// 二。 导出类
// 注意CTest类应该定义在文件头，dllexport最好用宏作判断定义，
// 而这里仅作测试。
//xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
1。dll生成:
// tdll.cpp : Defines the entry point for the DLL application.
//
#include "stdafx.h"
class __declspec(dllexport) CTest
{
private:
int m_nvalue;
public:
CTest() : m_nvalue(0) {}
int Getvalue() const;
};
int CTest::Getvalue() const
{
return m_nvalue;
}
BOOL APIENTRY DllMain( HANDLE hModule,
DWORD ul_reason_for_call,
LPVOID lpReserved
)
{
return TRUE;
}
2。调用(记得把上述生成的tdll.dll及tdll.lib拷过来):
#pragma comment(lib, "tdll.lib")
class __declspec(dllimport) CTest
{
private:
int m_nvalue;
public:
CTest() : m_nvalue(1) {}
int Getvalue() const;
};
int main(int argc, char* argv[])
{
CTest a;
int kk = a.Getvalue();
return 0;
}
运行正确。
有趣的现象是:
当我把应用端的dllimport错误的改成dllexport,程序依然可以build通过
（不过注释了#pragma comment(lib, "tdll.lib")就不行），运行时结果
是1（为区别于dll中初始值0，我把应用端的初始为1）。
嗯，这是因为编译器在处理应用端的CTest时，编译确实看得见类结构，而链接时
在tdll.lib中也可找Getvalue()相应符号，所以build成功，运行时既然应用端自己
的CTest是dllexport，当然就是直接运行它了。
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//三。使用钓子的dll
// 1.参见我的QQ本马程序:
// http://blog.gameres.com/thread.asp?BlogID=386&;threadid=13701;threadid=13701
// 2.另一个用于按F3弹出dll框供输出debug信息的dll,代码如下:
// 用vc创建一个win32dll,并在菜单中选择insert下的resource,插入一个dialog按ctrl+s存盘,并编写内容如下：
// logdll.h内容:
#ifdef LOGDLL_EXPORTS
#define LOGDLL_API __declspec(dllexport)
#else
#define LOGDLL_API __declspec(dllimport)
#endif
extern "C" LOGDLL_API void LG( const char* szTxt );
// logdll.cpp 内容:
//
#include <windows.h>
#include "logdll.h"
#include "resource.h"
// global data:
#pragma comment( linker, "section:Shared,rws" )
#pragma data_seg( "Shared" )
HHOOK g_hhook = NULL;
HINSTANCE g_hInstance = NULL;
HWND g_pLogDlg = NULL;
BOOL g_bShowDlg = FALSE;
#pragma data_seg()
//------------------------------------------------------------------------
void Init();
void Finish();
BOOL CreateLogDlg();
BOOL ShowLogDlg();
void InstallHook();
void UninstallHook();
LRESULT CALLBACK KeyboardProc( int, WPARAM, LPARAM );
INT_PTR CALLBACK LgDlgProc( HWND, UINT, WPARAM, LPARAM );
//------------------------------------------------------------------------
/*
*/
BOOL CreateLogDlg()
{
if( g_pLogDlg ) return TRUE;
if( FALSE == g_hInstance ) return FALSE;
g_pLogDlg = CreateDialog( g_hInstance, MAKEINTRESOURCE(IDD_DIALOG1), NULL, (DLGPROC)LgDlgProc );
return TRUE;
}
//------------------------------------------------------------------------
/*
*/
BOOL ShowLogDlg()
{
if( NULL == g_pLogDlg )
{
if( FALSE == CreateLogDlg() )
return FALSE;
}
return ShowWindow( g_pLogDlg, (g_bShowDlg = !g_bShowDlg) ? SW_SHOW : SW_HIDE );
}
//------------------------------------------------------------------------
/*
*/
void InstallHook()
{
if( g_hhook == NULL ) {
g_hhook = SetWindowsHookEx( WH_KEYBOARD, (HOOKPROC)KeyboardProc, g_hInstance, 0 );
}
}
//------------------------------------------------------------------------
/*
*/
void UninstallHook()
{
if( g_hhook ) {
UnhookWindowsHookEx(g_hhook);
g_hhook = NULL;
}
}
//------------------------------------------------------------------------
/*
*/
LOGDLL_API void LG( const char* szTxt )
{
// here set the text info to your dialog's text ctrl
}
void Init()
{
InstallHook();
}
void Finish()
{
UninstallHook();
if( g_pLogDlg )
{
DestroyWindow( g_pLogDlg );
g_pLogDlg = NULL;
}
}
//------------------------------------------------------------------------
/*
*/
BOOL APIENTRY DllMain( HANDLE hModule, DWORD ul_reason_for_call, LPVOID lpReserved )
{
g_hInstance = (HINSTANCE) hModule;
switch( ul_reason_for_call )
{
case DLL_PROCESS_ATTACH:
Init();
break;
case DLL_THREAD_ATTACH:
Init();
break;
case DLL_THREAD_DETACH:
Finish();
break;
case DLL_PROCESS_DETACH:
Finish();
break;
}
return TRUE;
}
//------------------------------------------------------------------------
/*
*/
LRESULT CALLBACK KeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)
{
LRESULT res = CallNextHookEx( g_hhook, nCode, wParam, lParam);
if( (lParam & (1 << 31)) && (wParam == VK_F3) && (nCode == HC_ACTION) )
{
ShowLogDlg();
}
return res;
}
//------------------------------------------------------------------------
/*
*/
INT_PTR CALLBACK LgDlgProc( HWND hDlg, UINT msg, WPARAM wParam, LPARAM lParam )
{
switch ( msg )
{
case WM_INITDIALOG:
return TRUE;
case WM_COMMAND:
switch( LOWORD(wParam) )
{
case IDCANCEL:
case IDOK:
EndDialog( hDlg, TRUE );
g_bShowDlg = FALSE;
return TRUE;
}
break;
case WM_DESTROY:
break;
}
return FALSE;
}
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//xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
// 四。不同语言混合编程方法
// 标题太夸张了点，这里只是通过一种语言编写dll给另一种语言使用而已。例如：在VC中写dll而在vb中调用。这个在我转载的文章中已有祥细例子，我就不多说了，参见:（引用别人的“库”，又少写了很多“代码”，呵呵）
http://blog.gameres.com/thread.asp?BlogID=386&;threadid=13945
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//xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
// 五。插件dll相关撰写
// (我写了以下例子来说明3dmax的导出插件是如何编写与实现,
// 源码简单就不说明了)
//xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
这里我们的程序我用app.h和app.cpp实现，而别人写的插件我用plugtest.h与plugtest.cpp实现.
1.先写我们的程序(用建立普通win32程序方法创建)
// app.h头文件内容:
#include <windows.h>
// extern "C"
// Define USING_IMPORT by app's project setting that this head file local at
#ifdef USING_IMPORT
#define THIS_CLASS_EXPORT __declspec(dllimport)
#else
#define THIS_CLASS_EXPORT __declspec(dllexport)
#endif
class THIS_CLASS_EXPORT TestExport
{
public:
TestExport() {};
virtual ~TestExport() {};
virtual int DoExport() = 0;
};
class THIS_CLASS_EXPORT ClassDesc
{
public:
virtual HINSTANCE HInstance() = 0;
virtual void* Create() = 0; // { return new TestExport's Derive class }
};
// app.cpp 文件内容:
//
#include "app.h"
#include <stdio.h>
#include <IO.H>
typedef ClassDesc* (*PFN_DESC)();
void TestCall( const char* szName )
{
HINSTANCE hDll = LoadLibrary( szName );
PFN_DESC pPlugDesc = (PFN_DESC)GetProcAddress( hDll, "Get_PlugDesc" );
ClassDesc* pDesc = (*pPlugDesc)();
if( pDesc )
{
TestExport* pExp = (TestExport*)pDesc->Create();
if( pExp )
{
pExp->DoExport();
}
}
}
int APIENTRY WinMain(HINSTANCE hInstance,
HINSTANCE hPrevInstance,
LPSTR lpCmdLine,
int nCmdShow)
{
// search all dll:
struct _finddata_t c_file;
long hFile;
/* Find first .c file in current directory */
if( (hFile = _findfirst( "*.dll", &c_file )) == -1L )
printf( "No *.dll files in current directory!\n" );
else
{
TestCall( c_file.name );
/* Find the rest of the .c files */
while( _findnext( hFile, &c_file ) == 0 )
{
TestCall( c_file.name );
}
_findclose( hFile );
}
return 0;
}
下面写一个插件来测试一下:
可在vc中用普通win32 dll的创建方法来创建以下一个dll内容:
// plugtest.cpp内容
//
#include <windows.h>
#include "../app/app.h"
//#pragma comment(lib, "app.lib")
HINSTANCE g_hInstance;
// example:
// notic: must not define USING_IMPORT(because this example using for client)
class Dll_Plug : public TestExport
{
int DoExport()
{
MessageBox(0, "test ok", "ok", 0);
return 1;
}
};
class Test_plusClassDesc : public ClassDesc
{
HINSTANCE HInstance()
{
return g_hInstance;
}
void* Create()
{
return new Dll_Plug;
}
};
static Test_plusClassDesc test_plusDesc;
extern "C" THIS_CLASS_EXPORT ClassDesc* Get_PlugDesc()
{
return &test_plusDesc;
}
BOOL APIENTRY DllMain( HANDLE hModule,
DWORD ul_reason_for_call,
LPVOID lpReserved
)
{
g_hInstance = (HINSTANCE)hModule;
return TRUE;
}
[注:]
1. 函数调用有不同的约定方式，其中带extern "C"的是c约定与不带
的是不同的，具体体现在输出的符号上，一般c约定的符号与函数名相同，
c++的则带xx@xxxx之类(这可用dll查看工具查看)，主要是区别参数的不同（为了处理类似重载等）,相关文章可参见我转载的文章:
http://blog.gameres.com/thread.asp?BlogID=386&;threadid=13945
2. dll查看工具推荐: process explorer.exe、 dependency walker.exe
这些工具非常有用，如果你的项目经常与一堆dll打交道的话就知道
怎么用它们来查出不同dll工程之间关系，查出找不到符号的原因。
相关有关工具参见:
http://blog.gameres.com/show.asp?BlogID=386&;column=469
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