// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
//
// 
//
// Description: 
//      A safe way to deal with unmanaged MIL interface pointers.
 
using Microsoft.Win32.SafeHandles;
 
using UnsafeNativeMethods = MS.Win32.PresentationCore.UnsafeNativeMethods;
 
namespace System.Windows.Media
{
    internal class SafeMILHandle : SafeHandleZeroOrMinusOneIsInvalid
    {
        /// <summary>
        /// Use this constructor if the handle isn't ready yet and later
        /// set the handle with SetHandle. SafeMILHandle owns the release
        /// of the handle.
        /// </summary>
        internal SafeMILHandle() : base(true) 
        { 
        }
 
        /// <summary>
        /// Use this constructor if the handle exists at construction time.
        /// SafeMILHandle owns the release of the parameter.
        /// </summary>
        internal SafeMILHandle(IntPtr handle) : base(true) 
        {
            SetHandle(handle);
        }
 
        /// <summary>
        /// Change our size to the new size specified
        /// </summary>
        internal void UpdateEstimatedSize(long estimatedSize)
        {
            _gcPressure?.Release();
 
            //
            // estimatedSize may be 0 for small images with fewer than 8 bits per pixel,
            // attempting to call GC.AddMemoryPressure with a pressure of 0 will cause it to
            // throw, so don't add memory pressure if estimatedSize is 0.
            //
            if (estimatedSize > 0)
            {
                _gcPressure = new SafeMILHandleMemoryPressure(estimatedSize);
                _gcPressure.AddRef();
            }
        }
 
        internal void CopyMemoryPressure(SafeMILHandle original)
        {
            _gcPressure = original._gcPressure;
            _gcPressure?.AddRef();
        }
 
        protected override bool ReleaseHandle()
        {
            UnsafeNativeMethods.MILUnknown.ReleaseInterface(ref handle);
            _gcPressure?.Release();
            _gcPressure = null;
 
            return true;
        }
 
        // Estimated size of the unmanaged memory
        private SafeMILHandleMemoryPressure _gcPressure; 
    }
}