//---------------------------------------------------------------------------
//
// <copyright file="SafeMILHandle.cs" company="Microsoft">
//    Copyright (C) Microsoft Corporation.  All rights reserved.
// </copyright>
// 
//
// Description: 
//      A safe way to deal with unmanaged MIL interface pointers.
//---------------------------------------------------------------------------
 
using System;
using System.IO;
using System.Security;
using System.Security.Permissions;
using System.Collections;
using System.Reflection;
using MS.Internal;
using MS.Win32;
using System.Diagnostics;
using System.Windows.Media;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;
using Microsoft.Win32.SafeHandles;
using Microsoft.Internal;
 
using UnsafeNativeMethods=MS.Win32.PresentationCore.UnsafeNativeMethods;
 
namespace System.Windows.Media
{
    internal class SafeReversePInvokeWrapper : 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>
        /// <SecurityNote>
        ///    Critical: This derives from a class that has a link demand and inheritance demand
        ///    TreatAsSafe: Ok to call constructor
        ///  </SecurityNote>
        [SecurityCritical]
        internal SafeReversePInvokeWrapper() : base(true) 
        { 
        }
 
        /// <summary>
        /// Use this constructor if the handle exists at construction time.
        /// SafeMILHandle owns the release of the parameter.
        /// </summary>
        /// <SecurityNote>
        /// Calls into native code to wrap a reverse p-invoke delegate into a CReversePInvokeDelegateWrapper.
        /// </SecurityNote>
        [SecurityCritical]
        internal SafeReversePInvokeWrapper(IntPtr delegatePtr) : base(true) 
        {
            // Wrap the reverse p-invoke into a reversePInvokeWrapper.
            IntPtr reversePInvokeWrapper;
            HRESULT.Check(UnsafeNativeMethods.MilCoreApi.MilCreateReversePInvokeWrapper(delegatePtr, out reversePInvokeWrapper));
 
            SetHandle(reversePInvokeWrapper);
        }
 
        /// <SecurityNote>
        /// Critical - calls unmanaged code, not treat as safe because you must
        ///            validate that handle is a valid COM object.
        /// </SecurityNote>
        [SecurityCritical]
        protected override bool ReleaseHandle()
        {
            if (handle != IntPtr.Zero)
            {
                UnsafeNativeMethods.MilCoreApi.MilReleasePInvokePtrBlocking(handle);
            }
            UnsafeNativeMethods.MILUnknown.ReleaseInterface(ref handle);
 
            return true;
        }
    }
}