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[.net] get a pointer on Array [C#]

Started by SeeMe Sep 1, 2006 at 8:56 AM 2 replies 1.3k views

Original Post

Sep 1, 2006 at 8:56 AM

Hello, my question is very simple, I have a fonction with an "Array myArray" parameters. This array can by of differents type. How can I get a byte pointer on it ? Something like this : fixed (byte* pVD = (byte*)myArray) { } Everytime I have an error : Cannot convert type 'System.Array' to 'byte*' Is it possible ? Or even from an other Value type ! [Edited by - SeeMe on September 1, 2006 9:25:34 AM]

benryves

526

benryves

Sep 1, 2006 at 9:31 AM

Quote:
Original post by SeeMe
This array can by of differents size.
How can I get a byte pointer on it ?

You can use a GCHandle for this.

// Pin the array:GCHandle PinnedArray = GCHandle.Alloc(myArray, GCHandleType.Pinned);// Use the unsafe address of this pinned array to read data into. unsafe {    byte* pVD = (byte*)PinnedArray.AddrOfPinnedObject.ToPointer();    // *do stuff*}// Free the handle (let the GC do whatever it needs to do with the memory). PinnedArray.Free();

(Sorry, I don't have any code on me that uses fixed and I don't want to give away invalid syntax. The above will also work in languages without fixed or unsafe, excluding the part that uses an unsafe pointer, such as VB).

SeeMe

Author

SeeMe

Sep 1, 2006 at 9:43 AM

Hello, tx you for the exemple.

In fact I'm looking for the method that will give me the best performance as this fonction will be called +/- 100 times by seconds !

Does the GCHandle "copy" everytime the Array data ?
The problem is that those array are quite big.
Is it not too slow ?
Tx you !

benryves

526

benryves

Sep 1, 2006 at 9:58 AM

From what I can tell, all it allocates is a handle, and specifying GCHandleType.Pinned stops the garbage collector from moving the pinned object around - I can't see where there would be much performance loss.

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