python下如何调用dll

http://blog.csdn.net/hong201/article/details/4499998

dll调用的来龙去脉

分类： C++ Python 2009-08-30 17:04 360人阅读 评论(0) 收藏 举报

dll api thread python null c

 关于dll的介绍可以在这里看到http://support.microsoft.com/kb/815065/zh-cn，这个算是官方解释了。

 

1.dll生成

dll的入口如下，就像应用程序的main函数一样，其中DLL_PROCESS_ATTACH是dll被调用的执行处理，DLL_PROCESS_DETACH是被卸载的时候的调用。

 

BOOL APIENTRY DllMain( HANDLE hModule,
                       DWORD  ul_reason_for_call,
                       LPVOID lpReserved
                     )
{
    switch (ul_reason_for_call)
    {
        case DLL_PROCESS_ATTACH:
        case DLL_THREAD_ATTACH:
        case DLL_THREAD_DETACH:
        case DLL_PROCESS_DETACH:
            break;
    }
    return TRUE;
}

 

 

先定义一些dll导出的接口，__declspec(dllexport)对dll来说，是需要导出的接口，当然了也可以用def文件来定义导出接口；__declspec(dllimport)是对调用该dll的程序来说，是需要导入。

 #dllcase.h

 

#ifdef DLLTEST_EXPORTS
#define DLLTEST_API_C extern "C" __declspec(dllexport)
#define DLLTEST_API __declspec(dllexport)
#else
#define DLLTEST_API_C extern "C" __declspec(dllimport)
#define DLLTEST_API __declspec(dllimport)
#endif

class DLLTEST_API CDllCase
{
public:
    CDllCase();
    virtual ~CDllCase();

public:
    int GetSub(int nLeft, int nRight);
    void GetStr(char* pszDst, const char* pszSrc);

};

DLLTEST_API_C int g_nDlltest;

DLLTEST_API_C int fnDlltest(int nLeft, int nRight);
DLLTEST_API_C void fnGetStr(char* pszDst, const char* pszSrc);

 

该头文件的实现文件，简单的一些例子

#dllcase.cpp

int g_nDlltest = 0;

int fnDlltest(int nLeft, int nRight)
{
    g_nDlltest = nLeft + nRight;
    return g_nDlltest;
}

void fnGetStr(char* pszDst, const char* pszSrc)
{
    ::strcpy(pszDst, pszSrc);
}

CDllCase::CDllCase()
{

}

CDllCase::~CDllCase()
{

}

int CDllCase::GetSub(int nLeft, int nRight)
{
    return nLeft - nRight;
}

void CDllCase::GetStr(char* pszDst, const char* pszSrc)
{
    ::strcpy(pszDst, pszSrc);
}

 

编译完该dll文件之后，dumpbin -exports dlltest.dll，就可以看到该dll导出的接口了。

 

2.dll调用

2.1 C++调用，隐式调用

需要dll文件，lib文件，头文件

包含头文件，#include "DllCase.h"，链接lib文件#pragma comment(lib, "dlltest.lib")，dll文件一般和应用程序放在同一个目录

 

std::cout << "fnDlltest(1, 2): " << fnDlltest(1, 2) << std::endl;
std::cout << "g_nDlltest: " << g_nDlltest << std::endl;

CDllCase c;
std::cout << "CDllCase::GetSub(2,8): " << c.GetSub(2,8) << std::endl;

char* pszSrc = "Hello dll.";
char szDst[sizeof(pszSrc) + 1] = {0x00};
c.GetStr(szDst, pszSrc);

std::cout << "CDllCase::GetStr: " << szDst << std::endl;

 

2.2C++调用，显示调用，只需要dll文件就可以了，放置在应用程序目录下

typedef int* nDlltest;
typedef int (*AddFunc)(int, int);

void usedllShow()
{
    AddFunc _AddFunc;
    HINSTANCE hInstLibrary = ::LoadLibrary("dlltest.dll");
    if (NULL == hInstLibrary)
    {
        ::FreeLibrary(hInstLibrary);
        return;
    }

    _AddFunc = (AddFunc)::GetProcAddress(hInstLibrary, "fnDlltest");
    nDlltest n = (nDlltest)::GetProcAddress(hInstLibrary, "g_nDlltest");
    if (NULL == _AddFunc || NULL == n)
    {
        ::FreeLibrary(hInstLibrary);
        return;
    }

    std::cout << "fnDlltest(1, 2): " << _AddFunc(1, 12) << std::endl;
    std::cout << "g_nDlltest: " << *n << std::endl;

    ::FreeLibrary(hInstLibrary);

}
i

 

2.2 python调用dll文件

在其他语言中只能用显示调用了，其他语言没有办法和C++头文件交互。

import ctypes

def dll_read_1(dll_name):
    ''''' __cdecl'''
    dll = ctypes.cdll.LoadLibrary(dll_name)
    print "first dll func [fnDlltest]", dll.fnDlltest(2, 8)

    s1 = "Hello, python and C++."
    s2 = ctypes.create_string_buffer("", len(s1))
    dll.fnGetStr(s2, s1)
    print "second dll func [fnGetStr]", s2.value

def dll_read_2(dll_name):
    '''''__stdcall '''
    dll = ctypes.windll.LoadLibrary(dll_name)

    test  = dll.fnDlltest
    test.argtypes = [ctypes.c_int, ctypes.c_int]
    test.restypes = ctypes.c_int
    nRst = test(1, 3)
    print nRst

if __name__ == '__main__':
    dll_read_1("dlltest.dll")
#    dll_read_2("dlltest.dll")