How to get a sub-array from an existing array in C# without copying?

Question

My question is similar to Getting a sub-array from an existing array although a little different notion is very important in my case - I can't use memory copying.

Let's say I have array X of 10000 elements, I need array Y that would contains 9000 elements from X, starting from X's index 500.

But I don't want to copy part of X to new array Y, so I don't want to use Array.Copy, Array.Clone, System.Block.Copy, IEnumerables etc. I want Y to be reference to X - Y[0] would be in fact X[500], Y[1] corresponds to X[501], ..., Y[9000] is X[9500].

Thus, for example changing value of X[100] would at the same time change value of Y[600]. How can I achieve this in C#?

Answer 1

You could wrap it in another object with something like this:

class View<T>
{
     private T[] _array;
     private long _start;
     private long _length;
     public View(T[] array, long start, long length) { ... }
     public T this[long index] 
     {
         get 
         {
             if (/*do bounds check here*/) 
             {
                 return _array[_start + index];
             }    
         }
     }
}

This won't be an array, but a projection of one.