一个Win32 C++ 动态连接库的模板 --- 调用方可管理DLL分配的内存

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-Win32CPPDllTemplate
//cheungmine
//underlicenceBSD
//2007
//
#ifndef_DLLCPPTMPL_H_
#define_DLLCPPTMPL_H_

//
//DllExport
//
#ifdefDLLCPPTMPL_DLLEXPORT
#defineDLLCPPTMPL_DLL__declspec(dllexport)
#elifdefined(DLLCPPTMPL_IMPORTS)
#defineDLLCPPTMPL_DLL__declspec(dllimport)
#else
#defineDLLCPPTMPL_DLL
#endif

//
//公共头文件
//
#include<string>
usingnamespacestd;

#include<new>//fornew_handler

#defineDLLCPPTMPL_API__cdecl

typedefvoid*(DLLCPPTMPL_API*PtrNew)(size_t);
typedefvoid(DLLCPPTMPL_API*PtrDelete)(void*);
typedefvoid(DLLCPPTMPL_API*PtrGetNewAndDelete)(PtrNew&,PtrDelete&);
typedefnew_handler(DLLCPPTMPL_API*PtrSetNewHandler)(new_handler);
typedefvoid(DLLCPPTMPL_API*PtrSetNewAndDelete)(PtrNew,PtrDelete,PtrSetNewHandler);

//
//DLLCPPTMPL_IMPORTS
//
#ifdefDLLCPPTMPL_IMPORTS
#ifdef_DLL
//causeCRTDLLtobeinitializedbeforeCrypto++sothatwecanusemallocandfreeduringDllMain()
#ifdefNDEBUG
#pragmacomment(lib,"msvcrt")
#else
#pragmacomment(lib,"msvcrtd")
#endif
#endif

#if!(defined(_MSC_VER)&&(_MSC_VER<1300))
usingstd::new_handler;
#endif


//WhenDllCppTmplattachestoanewprocess,itsearchesallmodulesloaded
//intotheprocessspaceforexportedfunctions"GetNewAndDeleteFor_DllCppTmpl"
//and"SetNewAndDeleteFrom_DllCppTmpl".Ifoneofthesefunctionsisfound,
//Crypto++usesmethods1or2,respectively,bycallingthefunction.
//Otherwise,method3isused.
staticPtrNew_s_pNew=NULL;
staticPtrDelete_s_pDelete=NULL;

extern"C"__declspec(dllexport)void__cdeclSetNewAndDeleteFrom_DllCppTmpl(PtrNewpNew,PtrDeletepDelete,PtrSetNewHandlerpSetNewHandler)
...{
_s_pNew=pNew;
_s_pDelete=pDelete;
}

void*__cdecloperatornew(size_tsize)
...{
return_s_pNew(size);
}

void__cdecloperatordelete(void*p)
...{
_s_pDelete(p);
}
#endif//DLLCPPTMPL_IMPORTS


//
//DLL接口方法
//
namespaceDllCppTmpl
...{

voidDLLCPPTMPL_DLLTest1(constchar*in,char**out);

voidDLLCPPTMPL_DLLTest2(conststring&in,string&out);

};//Canbeignored!
/**///////////////////////////////////////////////////////////////////////////////////
#endif/*ndef_DLLCPPTMPL_H_*/

文件2：DllCppTmpl.cpp

#defineDLLCPPTMPL_DLLEXPORT__declspec(dllexport)

#include"DllCppTmpl.h"

#include<string.h>

#include<iostream>
#include<time.h>
#include<windows.h>


#if(_MSC_VER>=1000)
#include<crtdbg.h>//forthedebugheap
#endif


/**/////////////////////////////////////////////////////
//如果使用动态库:DllCppTmpl
usingnamespaceDllCppTmpl;

//
//DLL标准输出
//
#ifdefDLLCPPTMPL_EXPORTS
#if!(defined(_MSC_VER)&&(_MSC_VER<1300))
usingstd::new_handler;
usingstd::set_new_handler;
#endif

void_CallNewHandler()
...{
new_handlernewHandler=set_new_handler(NULL);
if(newHandler)
set_new_handler(newHandler);

if(newHandler)
newHandler();
else
throwstd::bad_alloc();
}

staticPtrNew_s_pNew=NULL;
staticPtrDelete_s_pDelete=NULL;

staticvoid*New(size_tsize)
...{
void*p;
while(!(p=malloc(size)))
_CallNewHandler();

returnp;
}

staticvoidSetNewAndDeleteFunctionPointers()
...{
void*p=NULL;
HMODULEhModule=NULL;
MEMORY_BASIC_INFORMATIONmbi;

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);

PtrGetNewAndDeletepGetNewAndDelete=(PtrGetNewAndDelete)GetProcAddress(hModule,"GetNewAndDeleteFor_DllCppTmpl");
if(pGetNewAndDelete)
...{
pGetNewAndDelete(_s_pNew,_s_pDelete);
return;
}

PtrSetNewAndDeletepSetNewAndDelete=(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");//operatornew
_s_pDelete=(PtrDelete)GetProcAddress(hModule,"??3@YAXPAX@Z");//operatordelete
return;
}

OutputDebugString("DllCppTmplwasnotabletoobtainnewanddeletefunctionpointers. ");
throw0;
}

void*operatornew(size_tsize)
...{
if(!_s_pNew)
SetNewAndDeleteFunctionPointers();

return_s_pNew(size);
}

voidoperatordelete(void*p)
...{
_s_pDelete(p);
}

void*operatornew[](size_tsize)
...{
returnoperatornew(size);
}

voidoperatordelete[](void*p)
...{
operatordelete(p);
}
#endif//#ifdefDLLCPPTMPL_EXPORTS


/**//////////////////////////////////////////
//Test
voidDLLCPPTMPL_DLLDllCppTmpl::Test1(constchar*in,char**out)
...{
*out=newchar[strlen(in)+20];
strcpy(*out,"Hello");
strcat(*out,in);
}

voidDLLCPPTMPL_DLLDllCppTmpl::Test2(conststring&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>

#defineDLLCPPTMPL_IMPORTS//必须定义在前

#include"../DllCppTmpl/DllCppTmpl.h"
#pragmacomment(lib,"../DllCppTmpl/Debug/DllCppTmpl.lib")

/**///////////////////////////////////////////////////////////////////////
usingnamespaceDllCppTmpl;
/**/////////////////////////////////////////////////////////
int_tmain(intargc,_TCHAR*argv[])
...{
charin[]="cheungmine";
char*out=0;

DllCppTmpl::Test1(in,&out);

printf("Test1:%s ",out);
deleteout;


stringin2="cheungmine";
stringout2;

DllCppTmpl::Test2(in2,out2);

printf("Test2:%s ",out2.c_str());


return0;
}

注意路径的正确，和DllCppTmpl.dll要放到system32下。