Convert a byte array to a class containing a byte array in C#

Question

I've got a C# function that converts a byte array to a class, given it's type:

IntPtr buffer = Marshal.AllocHGlobal(rawsize);
Marshal.Copy(data, 0, buffer, rawsize);
object result = Marshal.PtrToStructure(buffer, type);
Marshal.FreeHGlobal(buffer);

I use sequential structs:

[StructLayout(LayoutKind.Sequential)]
public new class PacketFormat : Packet.PacketFormat { }

This worked fine, until I tried to convert to a struct/class containing a byte array.

[StructLayout(LayoutKind.Sequential)]
public new class PacketFormat : Packet.PacketFormat
{
  public byte header;
  public byte[] data = new byte[256];
}

Marshal.SizeOf(type) returns 16, which is too low (should be 257) and causes Marshal.PtrToStructure to fail with the following error:

Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

I'm guessing that using a fixed array would be a solution, but can it also be done without having to resort to unsafe code?

Could you use a binary serializer/deserializer instead? mikehadlow.blogspot.com/2006/11/… — Raj Kaimal
– Raj Kaimal, Commented May 2, 2010 at 23:22
Can you give a little more background to what you are doing? If possible, using the built-in serialization classes will save you a lot of headache. — ChaosPandion
– ChaosPandion, Commented May 2, 2010 at 23:29

arul · Accepted Answer · 2010-05-02 23:24:22Z

6

No need for unsafe code:

[StructLayout(LayoutKind.Sequential)]
public struct PacketFormat
{
  public byte header;
  [MarshalAs(UnmanagedType.ByValArray, SizeConst = 256)] public byte[] data;
}

answered May 2, 2010 at 23:24

arul

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ChaosPandion · Accepted Answer · 2010-05-02 23:20:29Z

4

You need to use a fixed size byte array.

[StructLayout(LayoutKind.Sequential)]
public unsafe struct PacketFormat
{
  public byte header;
  public fixed byte data[256];
}

answered May 2, 2010 at 23:20

ChaosPandion

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1 Comment

Matt Over a year ago

My question was whether it could be done without unsafe code.

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