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c#c++.netmultithreadingdll
user1314926
user1314926

Reputation: 180

.NET + pInvoked C++ Dynamic Link Library + Multithreading

Okay, I messed something up. I've written in C++ a DLL which I call from the managed code (C# .NET). The library works like diamonds and is blazingly fast.

My DLL uses its internal state i.e. allocates heaps of memory and uses myriad of variables which are not cleared off between the calls from .NET. Instead they stay there and C# code is aware of that (there is preprocessing and building data structures), actually this is required for performance.

So what is the problem? I want to add multi-threading, effectively by allowing each .NET thread access his own DLL. Without storing any data between the calls it would be easy achievable with just one DLL. But in my case, do I have to copy the *.DLL the number of times equal to the number of threads and write pInvoke wrapper for each file separately?? :O I mean [DllImport(...)] for each out of like 40 functions?

No way, there must be something more clever. Help?

Upvotes: 1

Views: 169

Answers (1)

David Heffernan
David Heffernan

Reputation: 612954

Simply put you need to stop sharing variables between threads.

Your global variables are the problem. Instead you need each different thread to have its own copy of the state that persists between calls. Typically you would put this state into a structure of some sort, perhaps a struct. Then an initial call to the DLL would return a new instance of this structure. You then pass that structure back into the DLL every time you call a function that requires access to the persistent state. When you are done, call back into the DLL to deallocate the structure. You don't need to declare the structure in the managed code. You can just treat it as an opaque pointer. Use IntPtr.

Of course, perhaps you'd just be better off with a C++/CLI assembly.

Upvotes: 1

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