forum.vdsworld.com

[DavidR]

I'm struggling with the best way to pass data between multiple VDS applications. If possible I'd like to avoid additional external dll's but would consider it if it's the only reasonable option. It needs to work with Win98 & XP.
Here's the application. A PC has a digital I/O card installed. The card has 48 digital I/O, each of which can be configured as either an input or an output. I have created a VDS application that can read the status of each input and can turn on/off each output. This app utilizes an external (non-vds) dll and works very well.
What I want is to create a "memory table" of both the inputs and the outputs. In the finished product my existing application will examine the inputs and update the input memory table with the status. Then it would examine the output "memory table" and set the real world outputs to match. This process would continuously scan I/O and update at (hopefully) less than 100ms. In other words 10 times per second or faster in order to avoid missing short duration inputs.
My other application(s) would then read the input table, make the appropriate decisions based on the input conditions and set the appropriate outputs or perform administrative functions.
I've considered using file I/O to store and read data but that seems very cumbersome and would result in a lot of disk activity at the scan rate I desire.
Another option is to create Registry entries and read/write to them
This seems to make more sense but I don't know how windows would handle that much registry access. Is the registry written to disk every time it's changed? This is an area I'm not too clear on.
The ideal thing would be to simply reserve a small range of memory addresses that could be accessed by each application. I've tinkered with the @addr() function but while I can get the memory location of a variable and could pass that location to another application through a registry key, I haven't been able to figure out how to get the value back into a variable in that application.
Perhaps I'm making this too complicated. I would appreciate any input and suggestions. An API function perhaps?
Thanks........
............David

[trapper]

Have you looked at VDSMEM.DLL?

[PGWARE]

You could also use VDSIPP, create a localhost server and applications would connect locally to the server application and send data back and forth - using UDP or TCP protocol.

One benefit to this is you could add a remote feature to your software which allows remote execution over the internet.

But if you don't want remote access, then you will need to add checks into your application so no outside IP's are accessing the server and manipulating any data.

[DavidR]

Thanks for the suggestions.
I looked at VSDMEM.DLL and it looks like it would work great for the small amount of data I need to pass.
What about using the registry for passing data between applications. Any ideas how much overhead/latency would be incurred using Registry functions as opposed to VDSMEM or VDSIPP?
One obvious advantage would be that it wouldn't require a dll and any application that can read or write registry keys could access the data.

Any thoughts?

...............David

[SnarlingSheep]

The registry is stored in files on your harddrive, and would be the same as using INI files in terms of overhead/disk activity.

I have used something in C, but I'm not sure if it can be done in VDS.
It uses Global Atoms, which are basically strings stored in RAM.

-Use GlobalAddAtomA to store your string, and it returns the identifier of the atom.
-Pass that atom identifier to your other program(s) with PostMessageA
-Get the message with VDS's OPTION MSGEVENT.
-Use GlobalGetAtomNameA to retrieve the string stored in the atom.
-Use GlobalDeleteAtomA to delete the atom after reading it.

This could be problematic with the way you have use @addr and the fact that VDS doesn't pass all messages to your MSGEVENT, but worth a try.

[Skit3000]

SnarlingSheep, I tried the functions you suggested. I found that there is also a GlobalFindAtomA function with which you should be able to search for text inside and atom after which a Atom identifier has to be returned. Unfortunately, I couldn't get it to work. If you comment out the specified line, it does work however.

[SnarlingSheep]

The problem with that is, GlobalFindAtom searches for the exact string, it doesn't just search for atoms with a certain prefix(That's the way I read it anyway).

Its really too bad that you can't just edit an atom once you add it. That way you could add a Global Atom, store the identifier to it in the registry/ini and continue to use that identifier to store other Atoms later.

[vdsalchemist]

Here's a few other ideas You could use DDE? Or you could also use @SendMessage() and a Message Hook with a user defined Message ID? I don't know if your programs have a Dialog or not?

I do have a GadgetX demo of how to share data between VDS applications. The demo actually shows 3 distinct ways of sharing data both encrypted and unencrypted all in memory. One of the ways GadgetX allows the sharing data does not require a Dialog. It's just a global memory buffer that all applications that attach to GadgetX has access too.

[DavidR]

[vdsalchemist]

David,
You can hide the dialogs. They don't need to be displayed.