How do I marshal an array of bytes to a struct?

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Related Question

In the related question, I was trying to figure out the fastest way. The method I chose in that question has become a bottle neck for me. I am reading some binary data from a file and need to put it into a managed structure definition. No unmanaged code is involved so I'm thinking there is a better way than allocating the GCHandle.

Is there a way to just cast an array of bytes to a structure of the same size?

Answer 1

I have a method like this:

static public T ReadStructure<T>(byte[] bytes)
    where T : struct
{
    int len = Marshal.SizeOf(typeof(T));
    IntPtr i = Marshal.AllocHGlobal(len);

    try
    {
        Marshal.Copy(bytes, 0, i, len);
        return (T)Marshal.PtrToStructure(i, typeof(T));
    }
    finally
    {
        Marshal.FreeHGlobal(i);
    }
}

Admittedly, it's not very fast--but it doesn't need to be, in my case. Is this your current solution, and you're finding that the alloc/copy/release overhead is too slow?

Answer 2

You could check out such code:

struct Foo
{
  public int x;
}

public unsafe static void Main()
{
  byte[] x = new byte[] { 1, 1, 0, 0 };
  Foo f;

  fixed (byte* xPtr = x)
  {
    f = *((Fpp*)xPtr);
  }

  Console.WriteLine(f.x);
}

It's definitely very unsafe, ad you could have problems if the structure contains some more complex types.