passing pointers between the process

Hi,
I need to pass the character array or char* to the another process through BroadcastSystemMessage() API. If I use WPARAM for this, I get the junk address in the recieving process.I am doing something like this
Sender

Code:

---

..
char szTemp[32]={0};
strcpy(szTemp,"TEST");
ULONG uiMsg = RegisterWindowMessage(KP_EXPORT_STATUS_MSG);
                DWORD dwRecipients                = BSM_APPLICATIONS;
                DWORD dwFlags                        = BSF_FORCEIFHUNG | BSF_POSTMESSAGE;
               
BroadcastSystemMessage(        BSF_FORCEIFHUNG|BSF_POSTMESSAGE,
                                                &dwRecepients,
                                                iServerFileFailure,
                                        (WPARAM)temp,
                                                0);
...

---

Reciever

Code:

---

ULONG uiMsg = RegisterWindowMessage(KP_EXPORT_STATUS_MSG);
                DWORD dwRecipients
LRESULT CALLBACK WndMainProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
        if(        message ==        uiMsg )
        {
                char* szTemp = (char*)wParam;
                                //szTemp is junk here
        }

---

Later I figured out that, pointers are meaningless between two processes as they will be having different process space. But it works if i send an interger as WPARAM instead of pointer.
I need to pass a string to another process. Is there any workaround for this problem??

Thanks

Like you figured out yourself, you cannot send a pointer since it is only meaningful in 1 process.
Since it seems you are writing both applications, try to use WM_COPYDATA.
Make sure you read the remarks in that article!

There are several forms of Interprocess Communication on Windows Platforms.

Another option is a Win32 dll with a share data segment. The dll provides a pair of GetSet methods and you put a string buffer into the shared seg area of the dll. You would have to load the dll in both processes.

One of the options mentioned in the link above is a memory mapped file. I use this technique in one of my articles in my subject line (Win32.. Part II). There is a Log Send and Log Receive sample that uses a MMF to send a structure containing a string buffer between two processes.

As Arjay wrote there are many ways to send data between processes, and as Marc G pointed out using WM_COPYDATA is one of the simplest ones providing that both processes are on the same machine/desktop. But there could be also some problems with WM_COPYDATA if someone else (not your sender process) broadcasts it! See this essay:Using WM_COPYDATA

Quote:

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Originally Posted by Marc G

Like you figured out yourself, you cannot send a pointer since it is only meaningful in 1 process.
Since it seems you are writing both applications, try to use WM_COPYDATA.
Make sure you read the remarks in that article!

---

Thanks a lot for the reply..
I gone through the link regarding WM_COPYDATA, But I dont have the handle for the window. That is why I am broadcasting the custom message. So I am afraid I cant use WM_COPYDATA.

However I am not getting why this works in the case of integers.

Thanks

Because in the case of integers you send the real integer and not some pointer.

Thanks Arjay and VictorN for reply..

Hello Mark G, I see that WPARAM is defined as UINT_PTR, so its a pointer. Doesnt it means that we are sending pointer and not the integer.

I am little confused abt it.

Thanks anyway.

No, UINT_PTR is defined as follows:

Code:

---

#if defined(_WIN64)
 typedef unsigned __int64 UINT_PTR;
#else
 typedef unsigned int UINT_PTR;
#endif

---

So, it's a 32 bit uint when building 32 bit version and it's 64 bit when building 64 bit version. It is called _PTR because it could be used to store pointers since it will have the correct size.

Quote:

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Originally Posted by sachin871

But I dont have the handle for the window.

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But, is it possible for you to get a handle to the window , say using FindWindow/Ex ?

If it is a string of known length, check to see if this post about atom tables is a viable option. http://www.codeguru.com/forum/showpo...7&postcount=14

Thanks a lot for all ur replies..
Meanwhile I came across this tutorial on MSDN which is regarding the use of shared memory. I think its pretty easy and I can use that in future as well.

Here is the link

:thumb: