using System;

public unsafe class ByteBuffer
{
  byte* p;
  int length;

  public ByteBuffer(byte* p, int length)
  {
    this.p = p;
    this.length = length;
  }

  public void ReadScatter(int[] indexes, byte[] buf)
  {
    indexes = (int[])indexes.Clone();
    Array.Sort(indexes);
    if(indexes[0] < 0 || indexes[indexes.Length - 1] >= length)
      throw new IndexOutOfRangeException();
    for(int i = 0; i < indexes.Length; i++)
      buf[i] = p[indexes[i]];
  }
}

public class Test
{
  static unsafe void Main()
  {
    byte[] buf = new byte[42];
    fixed(byte* p = buf)
    {
      ByteBuffer bb = new ByteBuffer(p, buf.Length);
      UntrustedCode(bb);      
    }
  }

  static void UntrustedCode(ByteBuffer bb)
  {
    byte[] buf = new byte[2];
    bb.ReadScatter((int[])(object)new uint[] { 0, unchecked((uint)-4) }, buf);
    Console.WriteLine("the original array length was: " + buf[1]);
  }
}