Marshal.PtrToStructure (and back again) and generic solution for endianness swapping
- by cgyDeveloper
I have a system where a remote agent sends serialized structures (from and embedded C system) for me to read and store via IP/UDP. In some cases I need to send back the same structure types. I thought I had a nice setup using Marshal.PtrToStructure (receive) and Marshal.StructureToPtr (send). However, a small gotcha is that the network big endian integers need to be converted to my x86 little endian format to be used locally. When I'm sending them off again, big endian is the way to go.
Here are the functions in question:
private static T BytesToStruct<T>(ref byte[] rawData) where T: struct
{
T result = default(T);
GCHandle handle = GCHandle.Alloc(rawData, GCHandleType.Pinned);
try
{
IntPtr rawDataPtr = handle.AddrOfPinnedObject();
result = (T)Marshal.PtrToStructure(rawDataPtr, typeof(T));
}
finally
{
handle.Free();
}
return result;
}
private static byte[] StructToBytes<T>(T data) where T: struct
{
byte[] rawData = new byte[Marshal.SizeOf(data)];
GCHandle handle = GCHandle.Alloc(rawData, GCHandleType.Pinned);
try
{
IntPtr rawDataPtr = handle.AddrOfPinnedObject();
Marshal.StructureToPtr(data, rawDataPtr, false);
}
finally
{
handle.Free();
}
return rawData;
}
And a quick example structure that might be used like this:
byte[] data = this.sock.Receive(ref this.ipep);
Request request = BytesToStruct<Request>(ref data);
Where the structure in question looks like:
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi, Pack = 1)]
private struct Request
{
public byte type;
public short sequence;
[MarshalAs(UnmanagedType.ByValArray, SizeConst = 5)]
public byte[] address;
}
What (generic) way can I swap the endianness when marshalling the structures? My need is such that the locally stored 'public short sequence' in this example will be little-endian for displaying to the user. I don't want to have to swap the endianness on a structure-specific way.
My first thought was to use Reflection, but I'm not very familiar with that feature. Also, I hoped that there would be a better solution out there that somebody could point me towards. Thanks in advance :)
