一个Win32 C++ 动态连接库的模板
cheungmine
一般情形下，使用C++编写动态库（DLL），在方法参数中不能输出STL对象类型， 如 std::string，这给我们的工作带来极大的麻烦。我参考一些资料，写了个C++ DLL模板，专门解决了这个问题。
使用VS2003新建一个Win32 DLL工程——DllCppTmpl，选择空项目，即什么也不自动创建。然后把下面2个文件加入到你的工程中，编译之。
文件1：DllCppTmpl.h
//
//
DllCppTmpl.h - Win32 CPP Dll Template
//
cheungmine
//
under licence BSD
//
2007
//
#ifndef _DLLCPPTMPL_H_
#define
_DLLCPPTMPL_H_
//
//
DllExport
//
#ifdef DLLCPPTMPL_DLLEXPORT
#define
DLLCPPTMPL_DLL __declspec(dllexport)
#elif
defined(DLLCPPTMPL_IMPORTS)
#define
DLLCPPTMPL_DLL __declspec(dllimport)
#else
#define
DLLCPPTMPL_DLL
#endif
//
//
公共头文件
//
#include
<
string
>
using
namespace
std;
#include
<
new
>
//
for new_handler
#define
DLLCPPTMPL_API __cdecl
typedef
void
*
(DLLCPPTMPL_API
*
PtrNew)(size_t);
typedef
void
(DLLCPPTMPL_API
*
PtrDelete)(
void
*
);
typedef
void
(DLLCPPTMPL_API
*
PtrGetNewAndDelete)(PtrNew
&
, PtrDelete
&
);
typedef new_handler (DLLCPPTMPL_API
*
PtrSetNewHandler)(new_handler);
typedef
void
(DLLCPPTMPL_API
*
PtrSetNewAndDelete)(PtrNew, PtrDelete, PtrSetNewHandler);
//
//
DLLCPPTMPL_IMPORTS
//
#ifdef DLLCPPTMPL_IMPORTS
#ifdef _DLL
//
cause CRT DLL to be initialized before Crypto++ so that we can use malloc and free during DllMain()
#ifdef NDEBUG
#pragma
comment(lib, "msvcrt")
#else
#pragma
comment(lib, "msvcrtd")
#endif
#endif
#if
!(defined(_MSC_VER) && (_MSC_VER < 1300))
using
std::new_handler;
#endif
//
When DllCppTmpl attaches to a new process, it searches all modules loaded
//
into the process space for exported functions "GetNewAndDeleteFor_DllCppTmpl"
//
and "SetNewAndDeleteFrom_DllCppTmpl". If one of these functions is found,
//
Crypto++ uses methods 1 or 2, respectively, by calling the function.
//
Otherwise, method 3 is used.
static
PtrNew _s_pNew
=
NULL;
static
PtrDelete _s_pDelete
=
NULL;
extern
"
C
"
__declspec(dllexport)
void
__cdecl SetNewAndDeleteFrom_DllCppTmpl(PtrNew pNew, PtrDelete pDelete, PtrSetNewHandler pSetNewHandler)
...
{
_s_pNew = pNew;
_s_pDelete = pDelete;
}
void
*
__cdecl
operator
new
(size_t size)
...
{
return _s_pNew(size);
}
void
__cdecl
operator
delete (
void
*
p)
...
{
_s_pDelete(p);
}
#endif
//
DLLCPPTMPL_IMPORTS
//
//
DLL接口方法
//
namespace
DllCppTmpl
...
{
void DLLCPPTMPL_DLL Test1(const char *in, char** out);
void DLLCPPTMPL_DLL Test2(const string& in, string& out);
}
;
//
Can be ignored!
/**/
//
#endif
/* ndef _DLLCPPTMPL_H_ */
文件2：DllCppTmpl.cpp
#define DLLCPPTMPL_DLLEXPORT __declspec(dllexport)
#include "
DllCppTmpl.h
"
#include <
string
.h
>
#include <
iostream
>
#include <
time.h
>
#include <
windows.h
>
#if
(_MSC_VER >= 1000)
#include <
crtdbg.h
>
//
for the debug heap
#endif
/**/
////
// 如果使用动态库: DllCppTmpl
using
namespace
DllCppTmpl;
//
//
DLL标准输出
//
#ifdef DLLCPPTMPL_EXPORTS
#if
!(defined(_MSC_VER) && (_MSC_VER < 1300))
using
std::new_handler;
using
std::set_new_handler;
#endif
void
_CallNewHandler()
...
{
new_handler newHandler = set_new_handler(NULL);
if (newHandler)
set_new_handler(newHandler);
if (newHandler)
newHandler();
else
throw std::bad_alloc();
}
static
PtrNew _s_pNew
=
NULL;
static
PtrDelete _s_pDelete
=
NULL;
static
void
*
New (size_t size)
...
{
void *p;
while (!(p = malloc(size)))
_CallNewHandler();
return p;
}
static
void
SetNewAndDeleteFunctionPointers()
...
{
void *p = NULL;
HMODULE hModule = NULL;
MEMORY_BASIC_INFORMATION mbi;
while (true)
...{
VirtualQuery(p, &mbi, sizeof(mbi));
if (p >= (char *)mbi.BaseAddress + mbi.RegionSize)
break;
p = (char *)mbi.BaseAddress + mbi.RegionSize;
if (!mbi.AllocationBase || mbi.AllocationBase == hModule)
continue;
hModule = HMODULE(mbi.AllocationBase);
PtrGetNewAndDelete pGetNewAndDelete = (PtrGetNewAndDelete)GetProcAddress(hModule, "GetNewAndDeleteFor_DllCppTmpl");
if (pGetNewAndDelete)
...{
pGetNewAndDelete(_s_pNew, _s_pDelete);
return;
}
PtrSetNewAndDelete pSetNewAndDelete = (PtrSetNewAndDelete)GetProcAddress(hModule, "SetNewAndDeleteFrom_DllCppTmpl");
if (pSetNewAndDelete)
...{
_s_pNew = &New;
_s_pDelete = &free;
pSetNewAndDelete(_s_pNew, _s_pDelete, &set_new_handler);
return;
}
}
hModule = GetModuleHandle("msvcrtd");
if (!hModule)
hModule = GetModuleHandle("msvcrt");
if (hModule)
...{
_s_pNew = (PtrNew)GetProcAddress(hModule, "??2@YAPAXI@Z"); // operator new
_s_pDelete = (PtrDelete)GetProcAddress(hModule, "??3@YAXPAX@Z"); // operator delete
return;
}
OutputDebugString("DllCppTmpl was not able to obtain new and delete function pointers. ");
throw 0;
}
void
*
operator
new
(size_t size)
...
{
if (!_s_pNew)
SetNewAndDeleteFunctionPointers();
return _s_pNew(size);
}
void
operator
delete (
void
*
p)
...
{
_s_pDelete(p);
}
void
*
operator
new
[] (size_t size)
...
{
return operator new (size);
}
void
operator
delete [] (
void
*
p)
...
{
operator delete (p);
}
#endif
//
#ifdef DLLCPPTMPL_EXPORTS
/**/
/////
// Test
void
DLLCPPTMPL_DLL DllCppTmpl::Test1(
const
char
*
in
,
char
**
out
)
...
{
*out = new char[strlen(in) + 20];
strcpy(*out, "Hello ");
strcat(*out, in);
}
void
DLLCPPTMPL_DLL DllCppTmpl::Test2(
const
string
&
in
,
string
&
out
)
...
{
out = "hello ";
out += in;
}
好了，开始写客户端。建一个Win32 console项目，如下：
// testDllCppTmpl.cpp : 定义控制台应用程序的入口点。
//
#include " stdafx.h
"
#include < windows.h
>
#define
DLLCPPTMPL_IMPORTS
//
必须定义在前
#include " ../DllCppTmpl/DllCppTmpl.h
"
#pragma
comment(lib, "../DllCppTmpl/Debug/DllCppTmpl.lib")
/**/
//
using namespace
DllCppTmpl;
/**/
////
int _tmain( int
argc, _TCHAR
*
argv[])
...
{
char in[] = "cheungmine";
char* out = 0;
DllCppTmpl::Test1(in, &out);
printf("Test1: %s ", out);
delete out;
string in2="cheungmine";
string out2;
DllCppTmpl::Test2(in2, out2);
printf("Test2: %s ", out2.c_str());
return 0;
}
注意路径的正确，和DllCppTmpl.dll要放到system32下。
