C# and Pointers - experienced question

axd33

I know c# isn't a great place to do pointer arithmetic, but I am writing an app that interacts with a server that returns a great deal of data with pointers actually in the returned data. The data is predictable for the first few fields, but after a little while, the dynamic part of the data stream comes into play. The data stream consists of the data requested and then a pointer to the start of the data points associated with it. My only problem is that there is no good way for me to jump straight to the address pointed to by this pointer they included. And it is not an offset, it is literally a pointer in that if we were programming in c/c++, we could assign a pointer this value and it would jump straight to the data. Any ideas? I've tried IntPtr, casting the Int32 to an object and then to Int32[], and a couple other things, but nothing's working. I always get an invalid cast exception. Thanks!

7 Replies

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david 022y ago
Any production environment which doew not block unsafe code ( and a large number of other features) as a general policy is asking for trouble. You should assume that this will always be blocked [it can be unblocked for a specific registered, strong-named assembly, and you MAY get permission to get that enabled]. If you are going to stay with this approach, then keep the code that does this work in its own small assembly to minimize the risk/exposure. That being said, if you are performing com-interop then you are ALREADY using unsafe code!
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axd3322y ago
Here is the code: [ StructLayout( LayoutKind.Sequential )] public struct server_record { public Int32 numrecords; public Int32 types; public Int32 fields; public Int32 [] data; } public unsafe override void HandleData(Char [] data) { fixed(char* inbuf=data) { errors--> server_record* history=(server_record*)inbuf; ... } } The 2 errors: c:\work\Serverdata\Server.cs(120,22): error CS0208: Cannot take the address or size of a variable of a managed type ('Serverdata.Server.server_record') c:\work\Serverdata\Server.cs(120,46): error CS0208: Cannot take the address or size of a variable of a managed type ('Serverdata.Server.server_record') ANYONE? This has been a royal PITA. Thanks for your help!
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axd3322y ago
Looks like it will work. However, I am coming up with a problem using the structures that map all this data. I declared them in the same class and it is giving me an error message about using managed structures in a fixed statement. How do i let my unsafe function use my structures?
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axd3322y ago
I am under the impression that an executable with unsafe code may be prevented from running via a PolicyException - when the local security settings are more restrictive than what the unsafe code/executable requires. I have never used unsafe code so I'm not sure how far-reaching this is. I will give it a try and post back later.
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Mykonine22y ago
Security issues? Sorry if I seem a bit slow here, I'm not familiar with .NET security.
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axd3322y ago
I'd rather not have the security issues.
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Mykonine22y ago
You could always use an unsafe code block, jump back into C++ mode, and do the pointer work there.
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