// never do this

using System;

namespace PointerStack
{
  unsafe struct Node
  {
    public Node* Next;
    public void* Value;
  }

  unsafe struct PStack
  {
    public int Count;
    public Node* Head;
  }

  unsafe class Program
  {
    static void Main( string[] args )
    {
      PStack* stack = stackalloc PStack[1];
      Node* n1 = stackalloc Node[1];
      Node* n2 = stackalloc Node[1];
      Node* n3 = stackalloc Node[1];

      char* a = stackalloc char[3];
      char* b = stackalloc char[3];
      char* c = stackalloc char[6];

      // horrible!!!!
      for( int i = 0; i < "One".Length; i++ ) a[i] = "One"[i]; 
      for( int i = 0; i < "Two".Length; i++ ) b[i] = "Two"[i];
      for( int i = 0; i < "Three".Length; i++ ) c[i] = "Three"[i];

      Console.WriteLine("Pushing");

      StackPush( stack, n1, a );
      StackPush( stack, n2, b );
      StackPush( stack, n3, c );

      Console.WriteLine( "Number of elements on stack: {0}", stack->Count );
      Console.WriteLine("Popping");

      char* v;
      while ( (v = (char*)StackPop( stack )) != null )
      {
        Console.WriteLine( "Popped value: {0}", new string(v) );
      }

      Console.WriteLine( "Number of elements on stack: {0}", stack->Count );

      Console.Read();
    }

    private static void* StackPop( PStack* pStack )
    {
      if( pStack == null )
        throw new ArgumentException();
      
      if ( pStack->Count == 0 )
        return null;

      Node* node = pStack->Head;
      pStack->Head = node->Next;

      pStack->Count--;

      return node->Value;
    }

    private static void StackPush( PStack* pStack, Node* node, void* value )
    {
      if( pStack == null || node == null || value == null )
        throw new ArgumentException();

      node->Value = value;

      if( pStack->Head != null )
        node->Next = pStack->Head;

      pStack->Head = node;
      pStack->Count++;
    }
  }
}