Re: Overwriting COM - COM Discussion Boards

yuval30-Jun-02 21:02

30-Jun-02 21:02

Hi All,
I encountered the following problem:
I succeeded using an ocx file through one exe file, while didn't succeed doing it through another exe.

In Details:
I wrote an exe file, that addresses a dll. This dll consists of a dialog, on which I added an ActiveX component (as a control). This activeX component is an OCX file.
It all worked very well: I managed interacting with that ocx. Everything was perfect.

Now the problems begin:
I wrote another exe, which, using the same principle, addresses the dll (mentioned above). But the program crashed.

While debugging, I see the there's no problem getting from the exe to the DIALOG on that dll, but the program fails when trying to address the OCX on the dialog.
I also saw that the problem relates to the CONTAINING and WRAPPING of the ocx:
Two pointers: COleControlContainer* m_pCtrlCont, and COleControlSite* m_pCtrlSite have NULL value
(both members of class CWnd, in file afxwin.h).

What seems to be the problem? Why can't I address that ocx from the other application?

I work Visual C++ 6.0, Windows NT.

Thanks a lot.
Unsure | :~

Re: How to use an OCX

Ernest Laurentin1-Jul-02 8:49

Ernest Laurentin

1-Jul-02 8:49

Call AfxEnableControlContainer(); in CYourApp::InitInstance.

Last Article:
Client/Server Socket class

Change path of an open Windows File Open/Save common dialog

Jonatan Dahl30-Jun-02 12:33

Jonatan Dahl

30-Jun-02 12:33

Hi!

How do I do start, which method do I use if I want an already open Windows file Open/Save dialog to change path?

Thanks!

/Jii

Enlist the Transaction of two transactional com+ object

Lizp28-Jun-02 22:51

Lizp

28-Jun-02 22:51

Object A was configged as "Requer Transaction" property and Object B(Actually is a databass access object to oracle and use ado to access to the datasource) was configged as "Supported Transaction" one.now A will invoke B and B must run in the Transaction context.is that practical and how to write the implement code of enlist the two transaction? thank you.

Scratch

Overwriting COM

28-Jun-02 4:38

Hi, i appologise if this question has been asked be before but its got me stummped, i need to overwrite one of the function pointers in a COM interface, i dont have access to the COM source nor can i modify it, i simply need to overwrite the pointer, i keep getting access violations.??

Goes something like this.

IInterface * MyInterface= MakeInterface();
unsigned * vTbl = ((unsigned**)MyInterface)[0];
vTbl[THE_FUNCTION_INDEX] = NewFunction;

Hope that gives you the idea of what i want, kinda like hooking a COM interface, i have yet to find an easy/any soloution like simply overwriting the functions pointer.

Re: Overwriting COM

soptest28-Jun-02 9:20

soptest

28-Jun-02 9:20

Implement interface you want to overwright.
1. You can use ATL to implement Interface.
2. Or see this example:

#include "stdafx.h"
#include "windows.h"
#import "testObj.dll"
/*
// testObj.idl : IDL source for testObj.dll

import "oaidl.idl";
import "ocidl.idl";
	[
		object,
		uuid(C795331D-0C56-11D6-A0FD-00B0D0C3D9BD),
		dual,
		helpstring("Itest Interface"),
		pointer_default(unique)
	]
	interface Itest : IDispatch
	{
		[id(1), helpstring("method f")] HRESULT f();
		[id(2), helpstring("method In")] HRESULT In([in] BSTR wsIn);
	};

[
	uuid(C7953311-0C56-11D6-A0FD-00B0D0C3D9BD),
	version(1.0),
	helpstring("testObj 1.0 Type Library")
]
library TESTOBJLib
{
	importlib("stdole32.tlb");
	importlib("stdole2.tlb");

	[
		uuid(C795331E-0C56-11D6-A0FD-00B0D0C3D9BD),
		helpstring("test Class")
	]
	coclass test
	{
		[default] interface Itest;
		interface Itest2;
	};
};

*/

#include "comdef.h"
class MyNew: public ::TESTOBJLib::ItestPtr
{
public:
	MyNew()
	{
		::CoInitialize(0);
		::TESTOBJLib::ItestPtr p;
		(*((::TESTOBJLib::ItestPtr*)this)).CreateInstance(L"TestObj.test");

	}
	~MyNew()
	{
		this->Release();
		::CoUninitialize();
	}

	HRESULT In( _bstr_t wsIn )
	{//call default function
		(*((::TESTOBJLib::ItestPtr*)this))->In(wsIn);
		return S_OK;
	};

	HRESULT f()
	{//overwritten function
		::OutputDebugString("this my function.");
		return S_OK;
	}
};

int main(int argc, char* argv[])
{
	MyNew p;

	p.f();
	p.In("test");
	
	return 0;
}

soptest

Re: Overwriting COM

28-Jun-02 18:31

Ok forgive me, im not familiar "yet", with COM and ATL etc, but from what i can gather that would require implementing every method and making it call the base (default) method for all methods i want to keep, unfortunatly the interfaces are pretty big reaching into the hundreds of methods and implementing each method to call its base method would be very time consuming.

Re: Overwriting COM

Ramu Pulipati29-Jun-02 4:15

Ramu Pulipati

29-Jun-02 4:15

COM supports two kinds of object orientation over binary components with C++. They are Containment and Aggregation.

Containment: This is traditional C++ wrapping up style where the new CoClass will implement the desired interface and internally use the Binary component to perform the operations.

Aggregation: The new CoClass will delegate the implemented interafce requests to the binary component and any request to the CoClass from binary component will be delegated back. This is a kinda tricky thing and has got restrictions. Like, the component being aggregated should be an In-Proc Server and should support component aggregation.

Advantage of Containment Over Aggregation: It doesnt have any restrictions.
Advantage of Aggregation Over Containment: You dont have to implement all interface methods by youself in the component. You'll just delegate, this will be handy if interface has lot of methods.

Check out COM books for further details.

Thanks,
Ramu

Re: Overwriting COM

Sam Hobbs1-Jul-02 13:50

Sam Hobbs

1-Jul-02 13:50

You are probably German. I think only Germans use the word "overwrite" like this. In the past I have tried to explain that the correct English word probably is "override" but Germans insist they are correct and I am mistaken.

Perhaps you really want to override the function pointer, and if so then perhaps you will get help if you state the problem that way.

ATL - Class Factory and Interface Implementation Seperation

Marc Bednar27-Jun-02 9:57

Marc Bednar

27-Jun-02 9:57

Hi All,

ATL forces the developer to implement the Call Factory (IClassFactory) and the Interface(s) implementation as part of the same C++ class (done through their template classes).

My question is: Is it possible to actually implement them (like in the old days) as seperate classes? This of course while using ATL. If so, what is the trick.

Any help is greatly appreciated.

Regards,
...Marc

marc.bednar@cactus.ca

Firing an event from an MFC ActiveX control

twomagiclovers27-Jun-02 8:59

twomagiclovers

27-Jun-02 8:59

Hi all,

I've been digging through tons of documentation but as of yet, I still haven't found an answer to a simple question.

When an MFC ActiveX control fires an event, does it return immediately or does it return only after the container's event handler is finished?

Thanks!

Re: Firing an event from an MFC ActiveX control

Ernest Laurentin27-Jun-02 19:29

Ernest Laurentin

27-Jun-02 19:29

After container's event handler is finished.

Last Article:
Client/Server Socket class

Simple Srting Conversion

Ryan B.27-Jun-02 5:19

Ryan B.

27-Jun-02 5:19

Im doing a simple non-MFC application.. I need to convert an ASCII string into an OLECHAR array. I want to pass my string into a SysAllocString(); function call like this:

<br />
char string[] = "ASCII STRING";<br />
(t+f)->str = SysAllocString(string);<br />

Of course this doesnt work because, SysAllocString is expecting an OLECHAR FAR*. The function works fine when I do:

<br />
(t+f)->str = SysAllocString(OLESTR("Test String"));<br />

Im actually passing in an array of UDTypes with variable length strings from VB and populating each element of the array / structure.

Im not very familiar with this whole ATL/COM string stuff.. =) Ill be honest, Im a C programmer, so Im out of my element. What can I do.. Please Help.

Ryan Baillargeon
Software Specialist
Fuel Cell Technologies Inc.

Re: Simple Srting Conversion

Ernest Laurentin27-Jun-02 19:27

Ernest Laurentin

27-Jun-02 19:27

Use CComBSTR class!

Last Article:
Client/Server Socket class

Re: Simple Srting Conversion

Stuart Dootson3-Jul-02 14:37

Stuart Dootson

3-Jul-02 14:37

If you #include <atlbase.h> & <atlconv.h>, you can use the ATL string conversion macros. These convert strings 'on-the-fly':

const char* s;
BSTR s = ::SysAllocString(A2COLE(s));
LPCTSTR ts;
BSTR s = ::SysAllocString(T2COLE(ts));

They 'do the right' thing wrt conversion to/from Unicode & ASCII & use the stack for temporary string allocation (so are reasonably efficient and deallocate the temporaries automatically).

Alternatively, the CComBSTR or _bstr_t classes seem to work pretty well (I tend to use _bstr_t because it's got char* & wchar_t* extraction operators). The following code should properly allocate a BSTR for use in a C struct

struct {
....
BSTR bs;
....
} thing;
char* s;
thing.bs = CComBSTR(s).Detach();

Just remember to make sure that the BSTR is properly deallocated - using SysFreeString if you do it yourself. For this reason, you'd be better having a CComBSTR in your struct if that's at all practical, as the CComBSTR will deallocate the BSTR in it's destructor.

HTH

Stuart Dootson

'Java, Basic, who cares - it's all a bunch of tree-hugging hippy cr*p'

Re: Simple Srting Conversion

Jeremy Pullicino4-Jul-02 4:57

Jeremy Pullicino

4-Jul-02 4:57

Just take care of the conversion macros like A2W, W2A, A2COLE, etc.. for 2 reasons:

1) They dynamically allocate memory ON THE STACK. This is good because it is fast and memory autmatically gets freed when the stack goes out of scope. However, there are memory limitations, so big strings could cause nasty things....

2) CComBSTR (or any other BSTR strings) support EMBEDDED NULLs. For those who do not know what embedded nulls are - basically, a BSTR could be: "Hello\0World" (notice the 0 in the middle.). When a BSTR is counted using SysStringLen(), the proper lenght is taken (SysAllocString stores the lenght of the string). However, if strlenW is used, it will stop after the "Hello" and not count the "World" part. A2W, W2A, A2COLE etc.. use strlenW to get the lenght of the string and not SysStringLen... this causes a converted string to be truncated when it encounters and embedded NULL.

Jeremy.

"Hey man, Taliban, Tali me Banana."

No Matching DLGINIT

ssirisha27-Jun-02 4:35

ssirisha

27-Jun-02 4:35

I have a dialog resource within a COM object and have added a thirdparty ActiveX control to the dialog box.

During execution, while loading the dialog resource I get the following error message..
"Dialog has OLE controls, but not matching DLGINIT resource"
I checked the .rc file and there is DLGINIT resource defined.

Any clue. Thanks

Re: No Matching DLGINIT

Prem Kumar28-Jun-02 4:39

Prem Kumar

28-Jun-02 4:39

Hi,

I have seen and replied to an earlier post of yours.
I think there is no problem in your programming and
the fault lies with the ActiveX control.

The ActiveX control should support specific interfaces
for saving information during design time, so as to enable
the Application to load it during runtime.

I think that your AciveX control is having specific
Run-time validation which is not fullfilled by the
default behavior of Dialog start up.(ActiveX Control Support).

What you need to do now is create the Active X control at
runtime and then place it in the specific position
on the dialog programmatically.

Look into the documentation for the ActiveX control.
During the creation you can pass the specific liscensing requirement.
PS: Can you tell me what control is it ?

Re: No Matching DLGINIT

ssirisha28-Jun-02 6:29

ssirisha

28-Jun-02 6:29

It's MSChart Control.

Hope I mentioned that, The dialog resource is in a COM DLL. The control loads properly in an EXE just fine.
Thanks.

SAFEARRAY in Variant

Hans Ruck26-Jun-02 5:18

Hans Ruck

26-Jun-02 5:18

I pass a SAFEARRAY through a Variant in VB.
Now i have the Variant and i don't know how to extract the SAFEARRAY from it.

rechi

Re: SAFEARRAY in Variant

Ramu Pulipati26-Jun-02 6:24

Ramu Pulipati

26-Jun-02 6:24

STDMETHODIMPL MyCOMClass::VBMethod(VARIANT * vt)
{
SAFEARRAY *psa;

if(vt == NULL)
return E_POINTER;

//assuming safearray consists BSTR. if not change to appropriate sa datatype
if(vt->vt != VT_BSTR | VT_ARRAY)
{
return E_INVALIDARG;
}

psa = vt->parray;
ATLASSERT(psa != NULL);

//use safe array here

return S_OK;
}

Hth,
Ramu

DCOM port restriction

MrGlover24-Jun-02 13:46

MrGlover

24-Jun-02 13:46

This is more of a configuration question.

I have a firewall between me and a DCOM component that is only letting allowing DCOM traffic (or more specifically I guess RPC traffic) through ports 135 and 40000-40001.

I have followed instructions on how to achieve this from such entertaining articles such as "Using Distributed COM with Firewalls" (from MSDN) but to no avail. My component is still trying to establish a connection through any random port it likes.

Although I'm well versed in details of TCP and the like I am a bit lost as to how to diagnose the problem here.

A nod in the right direction would really be appreciated. Typically, most of the article I'm coming across are knee deep in most details but then skip quickly over the art of configuring the security aspects.

TIA

JBoy

COM Exe that "stays"

[Shadow]24-Jun-02 2:28

[Shadow]

24-Jun-02 2:28

I made a COM exe that i create from other applications, but when i close the application that created it, it goes away. How can i make it so that the COM exe stays even when the program that created it closes?

Thanks Rose | [Rose]

Re: COM Exe that "stays"

Ernest Laurentin24-Jun-02 4:29

Ernest Laurentin

24-Jun-02 4:29

Hi Shadow,
That's the correct implementation, it should go away when the application that creates it
goes away! But if you are looking for a quick and dirty way to do that, look at CExeModule::MonitorShutdown() or comment the SetEvent call in CExeModule::Unlock. I assumed you are using ATL. But why do you want
your server to remain?

Last Article:
Client/Server Socket class

Re: COM Exe that "stays"

Jason Henderson24-Jun-02 9:16

Jason Henderson

24-Jun-02 9:16

I added a bool (bOKToShutdown) that gets set to true only if the user closes the app (from a tray icon).

void CExeModule::MonitorShutdown()
{
    while (1)
    {
        WaitForSingleObject(hEventShutdown, INFINITE);
        DWORD dwWait=0;
        do
        {
            bActivity = false;
 			dwWait = WaitForSingleObject(hEventShutdown, dwTimeOut);
        } while (dwWait == WAIT_OBJECT_0);

        // timed out
        if (!bActivity && m_nLockCnt == 0 && bOKToShutDown) // if no activity let's really bail
        {
#if _WIN32_WINNT >= 0x0400 & defined(_ATL_FREE_THREADED)
            CoSuspendClassObjects();
            if (!bActivity && m_nLockCnt == 0)
#endif
                break;
        }
    }
    CloseHandle(hEventShutdown);
    PostThreadMessage(dwThreadID, WM_QUIT, 0, 0);
}

Jason Henderson
_{quasi-homepage}
^articles
_{"Like it or not, I'm right!"}

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