Dll receiving strings from another application

Question

3.00/5 (2 votes)

See more:

I have another program that will sent strings to another application. This application will load my dll as plugin, how do I receive the strings with my dll using WM_COPYDATA ? how do I declare WM_COPYDATA inside my dll?

C++

BOOL APIENTRY DllMain (HINSTANCE hInst,DWORD reason,LPVOID reserved )
{
switch (reason)
    {
		case DLL_PROCESS_ATTACH:
			 CreateThread(0, 0, (LPTHREAD_START_ROUTINE)main, 0, 0, 0);
		break;
    }

    return TRUE;
}

What I have tried:

I don't know how to use WM_COPYDATA inside the dll.

Posted 13-Apr-16 1:39am

Derek Kaos

Updated 13-Apr-16 3:00am

Add a Solution

Comments

Richard MacCutchan 13-Apr-16 8:06am

You cannot send messages to a DLL as it does not have a message pump. You need to use some other mechanism.

Sergey Alexandrovich Kryukov 13-Apr-16 8:51am

It makes no sense. If you develop plug-in, develop appropriate plug-in interfaces.
—SA

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Jochen Arndt · Accepted Answer · 2016-04-13T02:14:00

Solution 1

To pass a string to a DLL just pass a const char* or const wchar_t* pointer when calling a DLL function. The DLL function may then create a local copy of the string if necessary.

Sending WM_COPYDATA messages requires a destination window handle and a message loop which may be not present in a DLL.

Posted 13-Apr-16 2:14am

Jochen Arndt

Comments

Sergey Alexandrovich Kryukov 13-Apr-16 9:02am

Sure, a 5.
And, on the positive side, I depicted the whole brief sketch of proper plug-in architecture in Solution 2.
—SA

Jochen Arndt 13-Apr-16 9:24am

Thank you Sergey.
My 5 too for your solution about plug-ins.

Sergey Alexandrovich Kryukov 13-Apr-16 9:31am

Thank you, Jochen.
—SA

Sergey Alexandrovich Kryukov · Accepted Answer · 2016-04-13T03:00:00

Please see my comment and Solution 1, which correctly explains another reason why it all makes no sense.

If you define the system with plug-ins, first define some plug-in interfaces. Plug-in model is interesting. Normally, the host application provides its own plug-in interface which each plug-in can use in its implementation, and expects all plug-ins to implement one or more interfaces, which are fixed; you can consider then as "contract" between the host application and plug-in modules.

I would strongly advice to make plug-in DLL "entry-free", or, better, the architecture to be "entry-agnostic". I would advice to export only one method from all plug-in, such as "get interface", which returns the instance of an object implementing the plug-in interface. Actually, you can develop the system implementing more than one plug-in in a single DLL module, through some interface listing several objects each implementing its own plug-in interface.

By "interface", you can use, say, a class without data with pure-virtual functions (COM interfaces were actually modeled after such structures), and the "implementation" would be a class overriding all these functions.

Now, when you build appropriate plug-in architecture, you can pass anything via the interface functions in any directions, strings or anything else.

—SA