C / C++ / MFC

George_George29-Aug-07 22:57

29-Aug-07 22:57

Thanks nave,

Naveen.R wrote:
A single will load the dll only once.

I mean for a specific process, if it invokes LoadLibrary multiple times without invoking unLoadLibrary, the DLL will be loaded multiple times or once one time?

Naveen.R wrote:
If you have create only class, the costructor will never be called. You have to create an object of the class.

Sure, I create object (instance) of a class. I want to know if I make the class a singleton class, if the DLL is loaded by multiple processes, each process will have a separate copy of the singleton class object?

regards,
George

Naveen29-Aug-07 23:06

29-Aug-07 23:06

George_George wrote:
the DLL will be loaded multiple times or once one time?

One time only.

George_George wrote:
if the DLL is loaded by multiple processes, each process will have a separate copy of the singleton class object?

Offcourse multiple copy.

nave

[OpenedFileFinder]

George_George29-Aug-07 23:17

29-Aug-07 23:17

Thanks nave,

So, making a class singleton does not make an instance (object) shared between multiple process, right?

I have read through the article you recommended. And I learned that we can use #pragma data_seg to make a shared data segment. But I have not found any information about how to synchronize the acces of the data between multiple process (lockig?)? Any reference or samples?

regards,
George

Naveen29-Aug-07 23:31

29-Aug-07 23:31

May be you have to synchronize it using some mutex. Samples.. have to search

nave

[OpenedFileFinder]

George_George29-Aug-07 23:41

29-Aug-07 23:41

Thanks nave,

I noticed when using #pragma data_seg, all the shared data are global data. But when we use mutex, we need to use it in a function. I do not know how to use mutex outside a function and apply mutex to global data.

Any comments or ideas?

regards,
George

Naveen29-Aug-07 23:48

29-Aug-07 23:48

I hope you have a singleton class. create a member varibable say HANDLE m_hMutex in that class. In the constructor create the mutex( CreateMutex()) and destructor close it( CloseHandle()). Add some function to set/get the data to the shared segment. In that functions before getting/setting the datas wait for the mutex using the WaitForSingleObject() function and in the end of that function call ReleaseMutex().

nave

[OpenedFileFinder]

George_George29-Aug-07 23:53

29-Aug-07 23:53

Thanks nave,

I can understand that in your method, we can make function level synchronization through mutex, like get/set functions.

But where to put statement, like #pragma data_seg? I think you mean put #pragma data_seg inside get/set function? Could you show me a sample about where to put #pragma data_seg please?

regards,
George

Naveen30-Aug-07 0:02

30-Aug-07 0:02

Put them as global itself. you can access global varaible from the member functions isn't it?

#pragma data_seg("SHARED")<br />
char c;<br />
#pragma data_seg()          <br />
<br />
<br />
     SingleTon::Set()<br />
     {<br />
          //acuqire mutex<br />
          c = '1';<br />
          // Release mutex<br />
     }<br />
<br />
     SingleTon::get()<br />
     {<br />
          //acuqire mutex         <br />
          char temp = c;<br />
          // Release mutex<br />
     }

nave

[OpenedFileFinder]

George_George30-Aug-07 0:06

30-Aug-07 0:06

Cool!

regards,
George

VC++ dll to C++ Builder

smsmfe29-Aug-07 21:06

29-Aug-07 21:06

Hi all,

I'm desperately trying to create a dll-file in visual studio and use the file in Borland C++ Builder. Anyone with experience of that?
I've started vc++ and made a console application (dll) with exports. Then I've done the implib thing on it to get a lib-file for use in borland. Included the lib-file in borland, and the .h-file made in visual studio. But I always get this error (the class declared in the vc-dll is called CSHA):
[Linker Error] Unresolved external 'CSHA::CSHA()' referenced from C:\TMP\SHA\UNIT1.OBJ
Looks like Borland is unable to understand the lib-file or something. HELP!! D'Oh! | :doh:

eli1502197929-Aug-07 21:53

eli15021979

29-Aug-07 21:53

Hi,

Are you trying to use a class from that DLL?
Becaue in order to do so , you can't just create an instance of that class from your application,
because the constructor of that class is not being exported.
In order to use class from the DLL,your DLL should export a function which create that instance
and return a pointer to the created object.
For example,if you are trying to use a class called MyDllClass,then you need to export the following method:

MyDllClass *CreateMyDllClass()
{
    return new MyDllClass;
}

Goodluck,
Eli

smsmfe29-Aug-07 22:34

29-Aug-07 22:34

Eli, thanks for your (fast) reply!!
But I still got the same linking-error message.

Ok, this is what the cpp-file in vc++ looks like:

#include "stdafx.h"
#include "SHA.h"
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;
}

// This is an example of an exported variable
SHA_API int nSHA=0;

// This is an example of an exported function.
SHA_API int fnSHA(void)
{
return 42;
}

// This is the constructor of a class that has been exported.
// see SHA.h for the class definition
CSHA::CSHA()
{
return;
}
CSHA *CSHA::New()
{
return new CSHA();
}
//--------------------------------------------------
This is the h-file (which I also use in my borland project):
#ifdef SHA_EXPORTS
#define SHA_API __declspec(dllexport)
#else
#define SHA_API __declspec(dllimport)
#endif

// This class is exported from the SHA.dll
class SHA_API CSHA {
public:
CSHA(void);
CSHA* New(void);
// TODO: add your methods here.
};

extern SHA_API int nSHA;

SHA_API int fnSHA(void);

//--------------------------------------------------
Borland cpp-file:

#include <vcl.h>
#pragma hdrstop
#include "sha.h"

CSHA* dll();

#pragma argsused
int main(int argc, char* argv[])
{
CSHA test;
CSHA* h = test.New();
return 0;
}

eli1502197930-Aug-07 0:00

eli15021979

30-Aug-07 0:00

First,In the header of the DLL,put all exported functions and veriables inside the following block:

#ifdef __cplusplus
extern "C" {
#endif

     // Put here the exported functions and veriables

#ifdef __cplusplus
}
#endif

For example:

#ifdef __cplusplus
extern "C" {
#endif

// This class is exported from the SHA.dll
class SHA_API CSHA {
public:
CSHA(void);
CSHA* New(void);
// TODO: add your methods here.
};

extern SHA_API int nSHA;

SHA_API int fnSHA(void);

#ifdef __cplusplus
}
#endif

In addition,your DLL solution should contain also a "*.def" file.
in that file you should add all the exported functions according to the following
example :

EXPORTS
 fnSHA                     @1
 Another exported function @2

Now,build your DLL again,and make sure that your application links to the correct dll/lib file.

Eli

smsmfe30-Aug-07 1:02

30-Aug-07 1:02

I used the code you sent me, but I get compile error (C2470) You don't happen to have a working example of a cpp-file, h-file and def-file I could check?

And once again, thanks alot for you help!

/Martin

eli1502197930-Aug-07 1:13

eli15021979

30-Aug-07 1:13

Hi Martin,

smsmfe wrote:
I used the code you sent me, but I get compile error (C2470)

From MSDN :

Visual C++ Concepts: Building a C/C++ Program
Compiler Error C2470
'function' : looks like a function definition, but there is no formal parameter list; skipping apparent body

A function definition is missing its argument list. The following sample generates C2470:

// C2470.cpp
int MyFunc {
// ...
};

int main(){
MyFunc();  // C2470 expected
}

This error may also be issued on a brace-enclosed initialization that is missing an =.

int arr[] { 1, 2, 3, 4, 5 };

Instead, you should use:
int arr[] = { 1, 2, 3, 4, 5 };

Can you post your source code after using my code?
Maybe I can see something you missed?

Regards,
Eli

smsmfe30-Aug-07 1:18

30-Aug-07 1:18

h-file:

#ifdef __cplusplus
extern "C" {
#endif
// This class is exported from the SHA.dll
class SHA_API CSHA {
public:
CSHA(void);
CSHA* New(void);
// TODO: add your methods here.
};
extern SHA_API int nSHA;
SHA_API int fnSHA(void);
#ifdef __cplusplus
}
#endif

cpp-file:
// SHA.cpp : Defines the entry point for the DLL application.
//

#include "stdafx.h"
#include "SHA.h"
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;
}

// This is an example of an exported variable
SHA_API int nSHA=0;

// This is an example of an exported function.
SHA_API int fnSHA(void)
{
return 42;
}
CSHA::CSHA()
{
return;
}

SHA_API CSHA* New()
{
return new CSHA();
}

smsmfe29-Aug-07 23:33

how to compare char * and WCHAR *

29-Aug-07 23:33

I also can't call the function fnSHA()

Same err: [linker error] unresolved external 'fnSHA()' referenced from... Frown | :(

GauranG Shah29-Aug-07 20:58

GauranG Shah

29-Aug-07 20:58

Hello Friends.

I need to compare two string in which one is of type WCHAR * and other is of type char * . D'Oh! | :doh:

if anybody know how to do it. please tell me.

Re: how to compare char * and WCHAR *

Nishad S29-Aug-07 21:12

Nishad S

29-Aug-07 21:12

I think its better to convert char* to wchar* and then compare...

- NS -

Re: how to compare char * and WCHAR *

Suneet.0329-Aug-07 23:14

Suneet.03

29-Aug-07 23:14

Convert your char* to wchar* using MultiByteToWideChar

and then use wcscmp to compare these two strings...

Excel automation

__yash__29-Aug-07 20:47

__yash__

29-Aug-07 20:47

Hello people,
I wish to save an excel sheet programmatically
I tried using the following:

_Application app;<br />
.<br />
.<br />
COleVariant strFile(_T("C:\\Temp\\Disc.xls"));<br />
app.SaveWorkspace(strFile);

BUt this does not save it by itself, it instead opens a 'Save As' box when i had expected it save it automatically as Disc.xls at location C:\Temp\

Is there something wrong in waht i m doing?? Or how do i achieve it...

Roger Broomfield29-Aug-07 21:34

Roger Broomfield

29-Aug-07 21:34

There are normally 3 objects of interest when automating excel the Application, the Workbook, and the Worksheet. Instead of trying to save the Workspace why not save the Worksheet or Workbook. Both of those objects have a SaveAs method.

__yash__29-Aug-07 22:55

__yash__

29-Aug-07 22:55

i tried using workbook.SaveAs()....but i am not getting the hang of parameters i need to pass...i tried searching on the net too.....didnt find anything...can you help??
All i want to do is save in a specified path as a specified type..
Can you provide me an example??

Roger Broomfield29-Aug-07 23:25

Roger Broomfield

29-Aug-07 23:25

Try this

<br />
COleVariant varFile(_T("C:\\Temp\\Disc.xls"));<br />
COleVariant varFileFormat((long)0xFFFFEFD1/*xlWorkbookNormal*/);<br />
COleVariant varTRUE((short)-1,VT_BOOL);<br />
COleVariant varFALSE((short)0,VT_BOOL);<br />
COleVariant varOptional((long)DISP_E_PARAMNOTFOUND,VT_ERROR);<br />
workbook.SaveAs(varFile, varFileFormat, varOptional/*password*/, varOptional/*WriteResPassword*/, varTRUE/*ReadOnlyRecommended*/, varFALSE/*CreateBackup*/, 1/*xlNoChange*//*AccessMode*/, varOptional/*ConflictResolution*/, varTRUE/*AddToMRU*/, varOptional/*TextCodePage*/, varOptional/*TextVisualLayout*/);<br />