Converting byte[] to fixed byte[]

[O.B.]

Given the following bit of code, the PtrToStructure is not correctly
copying the data into the PDU class. After it executes, the
pdu.buffer[] array looks nothing like the data[] array that I tried to
copy from. Help?



[StructLayout(La youtKind.Explic it)]
public unsafe struct PDU {
public const int MAX_PDU_SIZE = 1400;
[FieldOffset(0)]
public fixed byte buffer[MAX_PDU_SIZE];
[FieldOffset(0)]
public Header header;
}

class Manager {
unsafe public void processData(byt e[] data) {
//
// Convert data to a PDU
//
PDU pdu;
IntPtr arrayPtr = Marshal.UnsafeA ddrOfPinnedArra yElement(
data, PDU.MAX_PDU_SIZ E);
pdu = (PDU)Marshal.Pt rToStructure(ar rayPtr, typeof(PDU));

// More processing ...
}
}

static void Main(string[] args) {
// Testing...
Manager manager = new Manager();
byte[] data = new byte[1400];
for (int i = 0; i < 1400; i++) {
data[i] = (byte)((i + 1)%256);
}
manager.process Data(data);
}

[Mattias Sjögren]

Re: Converting byte[] to fixed byte[]

IntPtr arrayPtr = Marshal.UnsafeA ddrOfPinnedArra yElement(

data, PDU.MAX_PDU_SIZ E);

Here you get the address of the _last_ element in the array. So what
you're processing is whatever is in memory after the array. The second
parameter should probably be 0 in your case.

Also, you never pin the data array. Therefore the address may become
invalid at any time.


Mattias

--
Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
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[O.B.]

Re: Converting byte[] to fixed byte[]

Mattias Sjögren wrote:

> IntPtr arrayPtr = Marshal.UnsafeA ddrOfPinnedArra yElement(
> data, PDU.MAX_PDU_SIZ E);

>
Here you get the address of the _last_ element in the array. So what
you're processing is whatever is in memory after the array. The second
parameter should probably be 0 in your case.
>
Also, you never pin the data array. Therefore the address may become
invalid at any time.
>
>
Mattias
>

Thank you.