Re: COM object passing - COM Discussion Boards

Mazdak8-Apr-02 4:29

8-Apr-02 4:29

Anonymous wrote:
I have a C++ dll that interfaces with a main VB program

What is that dll? Is that one of standard dll's like msado15.dll or you wrote it yourself?

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

8-Apr-02 14:53

I wrote the dll myself, it has a specific (and time consuming) processing task, that the VB program utilises.

-dave

Mazdak9-Apr-02 1:19

9-Apr-02 1:19

ADO connection is an string.you can pass it as simple string to your dll,But all of it depends on how you implement yout methods.

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

el davo9-Apr-02 18:54

el davo

9-Apr-02 18:54

I mean, the actual ADO Connection object (in vb, dim connObj as ADODB.Connection for example of the object i'm talking about.)

The current situation is: both the vb code and the dll using the same database (out of necessity), each connecting separately. I would like to let vb create an open ado database connection (supply it a connection string and go .open), then have the vb code pass the open connection COM object (or a pointer to it?) to the C++ dll.

Cheers,

Dave

Sam Strachan10-Apr-02 3:16

Sam Strachan

10-Apr-02 3:16

Ok, I've not tried this, but import the ADO type library doing something like this...

#import "c:/program files/common files/system/ado/msado15.dll" no_namespace rename("EOF", "EndOfFile")

Then you need an input parameter to hold the pointer to it. I suppose you could use an IUnknown pointer, but then why not just use a _Connection pointer instead (you'll see it at the top of the msado15.tlh).

So, in your IDL should be a line like...

[id(2), helpstring("method GetField")] HRESULT GetField([in] _Connection * pAdoCn, [in] BSTR bsFieldname, [out, retval] BSTR * pbsVal);

Then you can just use that pointer. (Attach the COM Smart Pointer to it though and your life will be easier... ConnectionPtr.Attach(...))

In the event that that doesn't work though, try it with IUnknown * pUnk instead, then do a QueryInterface() on it, passing the Connection Interface to it.

Good luck,

S

el davo10-Apr-02 19:24

el davo

10-Apr-02 19:24

I am trying the first _Connection method you suggest, so what should i pass from the vb side?

If i implemented your suggestion, would the vb side be something like this?

dim fred as new adodb.connection
fred.open blah blah blah
somestring = getfield(fred, anotherstring)

Cheers,

Dave

Creating Search Engine Component for Intranet

Sam Strachan10-Apr-02 22:36

Sam Strachan

10-Apr-02 22:36

Dave,

Yes, that should do the trick. If it fails then you have a few options including...

1) Making it IUnknown in C++ then in VB do this

dim fred as new adodb.connection
dim oFred as Object
fred.open blah blah blah
set oFred = fred
somestring = getfield(oFred, anotherstring)

(Set in VB is much akin to QueryInterface in C++)

2) Make it a Variant in C++ containing either IUnknown or IDispatch then do the same as above but Dim oFred as a Variant instead.

I haven't done exactly this before (I've done it with my own custom objects) but the principal should be the same.

Also, make sure that you do a _Connection.AddRef() at the beginning and .Release() at the end of your processing in C++ as you will be a COM Client in this case. Not doing this may yield all sorts of nastiness if VB decides it can let go of the Connection in the mean time.

Good luck,

Sam

ITextDocument??? UGH!!!

Dave_7-Apr-02 12:36

Dave_

7-Apr-02 12:36

This may not be a true COM question, but I am trying every source I can find to try to solve this one:

I am completely frustrated!

I have read from several sources, that you can use the GetIRichEditOle() function to get to the ITextDocument interface for a CRichEditCtrl.

I am using VC 6, and the RichEdit version looks like it is 3.0.

I am using the following code:

ITextDocument *pTextDoc = NULL;
IRichEditOle * ire = m_RichEdit.GetIRichEditOle();
if ((ire == NULL) || (ire->QueryInterface(IID_ITextDocument, (void**) &pTextDoc) != S_OK) || (pTextDoc == NULL)){
DWORD dwErr = GetLastError();
if (ire != NULL)
ire->Release();
TRACE("Failed ITextDoc\n");
}

The pTextDoc is always NULL. The GetLastError() returns 0.

I have also tried the method specified in MSDN, but it fails also. The method they use is very similar to the above code, so that's no surprise.

I am getting desperate! I need to get the ITextDocument interface to do some things like set the line spacing.

Please, if anyone knows how to do this, let me know.

Thank you very much,
David

6-Apr-02 19:57

I want to create search engine which will be used for searching xls,ppt,txt,htm,pdf,doc files base on search keyword.

For this specification i would like to create component as inprocess server and it should operate on companies intranet. So anybody guide me how to create the component weather by using IFilter index server of microsoft. If you have any guidance about IFilter or any other will be very useful for me.

How to access method in other object in COM

chq126-Apr-02 11:13

chq12

6-Apr-02 11:13

I want to build three objects, one is common and want to be used by other two objects. How can i access from one object to another object Confused | :confused:

Mazdak6-Apr-02 17:52

6-Apr-02 17:52

Reusing COM objects
.

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

chq127-Apr-02 8:32

chq12

7-Apr-02 8:32

Can you tell me something in detail. I want to access from one object to other objects.
What mechanism it is and What API i need?

Mazdak7-Apr-02 9:21

7-Apr-02 9:21

I suggest you Containment that is easier.Do you know how to use your COM object in client application?Thats exactly the same.Use CreateInstance() in your second component to iniatilize the first component.If you have any problem to use it just ask. Smile | :)

Mazy

"The path you tread is narrow and the drop is shear and very high,
The ravens all are watching from a vantage point near by,
Apprehension creeping like a choo-train uo your spine,
Will the tightrope reach the end;will the final cuplet rhyme?"Cymbaline-Pink Floyd

CoUninitialize doesn't return

chq127-Apr-02 16:30

chq12

7-Apr-02 16:30

Mazdak, Thank you very much. I'll try on it.

sefip3-Apr-02 21:24

sefip

3-Apr-02 21:24

Hi,

I'm having a problem in COM EXE.

I create a new worker thread that loops and listens to messages. during shut down I release pointers defined in its scope, and call CoUninitialize.
but it seems to get stuck there. (The function who stops the thread waits until the worker thread is signaled, that happens only after couninitialize, which is the last line in the worker thread)

is there any deadlock associated with it? or I have not released everything? I checked and it seems i have released all.

can you supply me with directions for thought what is wrong there?

Thanks.

Sefi p.

enable delegation to work

David Dal Zot3-Apr-02 3:38

David Dal Zot

3-Apr-02 3:38

Hi all,

in the code below, hToken is an impersonation token which I
duplicate into a primary token in order to use with
CreateProcessAsUser. I ask the new token to have the
DELEGATION level of impersonation but I get error 1346 :
ERROR_BAD_IMPERSONATION_LEVEL. NTLM is running on W2K as
the SSP provider, but it seem that delegation is not supported. Is it possible to have the impersonation level with CLOAKING enabled with NTLM ? does this provide a
one hop machine-cross delegation level (which is sufficient for my server) ? All this is done with a calling from an ASP page, how can i set the impersonation level for the client ?. All this confuse me, thank to bring some light ...;)

if ( !DuplicateTokenEx(
hToken, // handle to token to duplicate
TOKEN_ALL_ACCESS | TOKEN_QUERY |
TOKEN_ASSIGN_PRIMARY | TOKEN_DUPLICATE,
NULL,
SecurityDelegation,
TokenPrimary,
&hDup ) ) {
err = GetLastError();}

What does this code do?

Gerald Schwab1-Apr-02 16:57

Gerald Schwab

1-Apr-02 16:57

Sorry for the duplicate post but the first one stripped off the template args. Look near the bottom of the code snippet. I'm not sure what the code is doing, can someone explain.

template<typename _IIID> class _com_ptr_t {
public:
    typedef _IIID ThisIIID;
    typedef typename _IIID::Interface Interface;
    static const IID& GetIID() throw()
    { 
        return ThisIIID::GetIID(); 
    }

     template<typename _OtherIID> _com_ptr_t(const _com_ptr_t<_OtherIID>& p) throw(_com_error)
        : m_pInterface(NULL)
    {
        HRESULT hr = _QueryInterface(p);

        if (FAILED(hr) && (hr != E_NOINTERFACE)) {
            _com_issue_error(hr);
        }
    }
    template<typename _InterfaceType> _com_ptr_t(_InterfaceType* p) throw(_com_error)
        : m_pInterface(NULL)
    {
        HRESULT hr = _QueryInterface(p);

        if (FAILED(hr) && (hr != E_NOINTERFACE)) {
            _com_issue_error(hr);
        }
    }
    template<> _com_ptr_t(LPSTR str) throw(_com_error)
    {
        new(this) _com_ptr_t(static_cast<LPCSTR> (str), NULL);
    }
    ...
}

Michael Dunn1-Apr-02 21:15

Michael Dunn

1-Apr-02 21:15

Gerald Schwab wrote:
template<> _com_ptr_t(LPSTR str) throw(_com_error)
{
new(this) _com_ptr_t(static_cast<LPCSTR>(str), NULL);
}

That is calling one constructor from another. Since the constructor that takes an LPCSTR is marked explicit, a different constructor was needed that takes an LPSTR. (explicit means that the constructor parameter must exactly match LPCSTR, no implicit conversions (such as adding a const qualification to convert an LPSTR to an LPCSTR) are allowed.)
This totally negates the purpose of having the explicit constructor, but oh well.
The new(this) calls an operator new defined in new.h, which is #include'd at the top of comip.h.

--Mike--
"Jobs that don't allow you to visit the Lounge 25 times a day at the minimum are not worth having anyway."
-- Nish, 3/28/2002
My really out-of-date homepage
Sonork - 100.10414 AcidHelm
Big fan of Alyson Hannigan and Jamie Salé.

Gerald Schwab2-Apr-02 5:28

Gerald Schwab

2-Apr-02 5:28

Thanks for the reply Michael. I understand the "explicit" part, but I'm still a little fuzzy on the "new" part. I stepped through the code with the debugger and it looks like this constuctor is instantiating itself using the explicit constructor. Here's what I don't quit get: when "new(this)" is called, "this" already has an address. So is this constructor calling the explicit constructor and replacing itself with the constructed value of the explicit contructor? Or is it casting from this constructor to the explicit constructor? I understand the result, I just don't quite grasp how the code gets there.

Michael Dunn5-Apr-02 16:19

Michael Dunn

5-Apr-02 16:19

The purpose of new() is usually to allocate memory and return a pointer to it, however you can overload new() to do anything. That's what that constructor does, it calls an overloaded new() that just returns the parameter passed to it. Since there is already memory allocated for this, new() returns that address, then C++ calls the constructor.
It is bloody confusing, though. Wink | ;)

--Mike--
"Jobs that don't allow you to visit the Lounge 25 times a day at the minimum are not worth having anyway."
-- Nish, 3/28/2002
My really out-of-date homepage
Sonork - 100.10414 AcidHelm
Big fan of Alyson Hannigan and Jamie Salé.