//
// Copyright (c) Microsoft Corporation.  All rights reserved.
//

using System.GCs;
using System.Runtime.CompilerServices;

namespace System {
  /// <summary>
  /// Abstraction for information about the stack height.  This is currently
  /// only used by the logging undo code for determining if a pointer write
  /// occurred in stack space allocated after the tryall section began.
  ///
  /// StackHeight does not record information about the call stack.
  ///
  /// The current implementation is hardwired to a stack model where the stack
  /// is a single contiguous piece of memory that grows by putting smaller
  /// values into the stack pointer.
  /// </summary>
  [RequiredByBartok]
  public struct StackHeight {
      /// <summary>
      /// Interpret the pointer as a stack pointer to determine the stack
      /// height.
      /// </summary>
      /// <param name="stackPointer">Pointer into the stack.</param>
      /// <returns>The stack height of the location pointed to by the
      /// argument.</returns>
      public StackHeight(UIntPtr stackPointer);

      /// <summary>
      /// Interpret the pointer as a stack pointer to determine the stack
      /// height.
      /// </summary>
      /// <param name="stackPointer">Pointer into the stack.</param>
      /// <returns>The stack height of the location pointed to by the
      /// argument.</returns>
      public static explicit operator StackHeight(UIntPtr stackPointer);

      /// <summary>
      /// Get the current stack height.
      /// </summary>
      /// <returns>The current stack height.</returns>
      //[Intrinsic]
      // [MethodImplAttribute(MethodImplOptions.PublicCall)]
      public static StackHeight GetStackHeight();

      /// <summary>
      /// Check if the first stack height represents a deeper location on the
      /// stack.
      /// </summary>
      /// <param name="first">The first stack height to compare.</param>
      /// <param name="second">The second stack height to compare.</param>
      /// <returns>True iff the first height is deeper in the stack than the
      /// second height.</returns>
      public static bool Deeper(StackHeight first, StackHeight second);

      /// <summary>
      /// The value of the stack pointer when the stack height was taken.
      /// </summary>
      private UIntPtr stackPointer;
  }
}