File: Base\MS\Internal\Security\RightsManagement\SafeRightsManagementSessionHandle.cs
Project: wpf\src\WindowsBase.csproj (WindowsBase)
// <copyright file="SafeRightsManagementSessionHandle.cs" company="Microsoft">
//    Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// Description:
//  SafeRightsManagementSessionHandle class
// History:
//  10/12/2005: SarjanaS:  Initial implementation.
using System;
using System.Runtime.InteropServices;    
using Microsoft.Win32.SafeHandles;
using System.Security;
namespace MS.Internal.Security.RightsManagement
    internal sealed class SafeRightsManagementSessionHandle : SafeHandle
        //Although it is not obvious this constructor is being called by the interop services 
        // it throws exceptions without it 
        private SafeRightsManagementSessionHandle()
            : base(IntPtr.Zero, true)
        //  We have incompatibility between SafeHandle class hierarchy and the unmanaged 
        //  DRM SDK declarations. In the safe handle hierarchy it is assumed that the type 
        //  of handle is the IntPtr (64 or 32 bit depending on the platform). In the unmanaged
        //  SDK C++ unsigned long type is used, which is 32 bit regardless of the platform. 
        //  We have decided the safest thing would be to still use the SafeHandle classes 
        //  and subclasses and cast variable back and force under assumption that IntPtr
        //  is at least as big as unsigned long (in the managed code we generally use uint 
        //  declaration for that)  
        internal SafeRightsManagementSessionHandle(uint handle)
            : base((IntPtr)handle, true)  // "true" means "owns the handle"
        // base class expects us to override this method with the handle specific release code  
        protected override bool ReleaseHandle()
            int z = 0;
            if (!IsInvalid) 
                        // we can not use safe handle in the DrmClose... function
                        // as the SafeHandle implementation marks this instance as an invalid by the time 
                        // ReleaseHandle is called. After that marshalling code doesn't let the current instance 
                        // of the Safe*Handle sub-class to cross managed/unmanaged boundary.
                z = SafeNativeMethods.DRMCloseSession((uint)this.handle);
        #if DEBUG
                // This member might be called twice(depending on the client app). In order to 
                // prevent Unmanaged RM SDK from returning an error (Handle is already closed) 
                // we need to mark our handle as invalid after successful close call
            return (z>=0);
        // apparently there is no existing implementation that treats Zero and only Zero as an invalid value 
        // so we are sub-classing the base class and we need to override the IsInvalid property along with 
        // ReleaseHandle implementation
        public override bool IsInvalid
                return this.handle.Equals(IntPtr.Zero);