// ==++==
// 
//   Copyright (c) Microsoft Corporation.  All rights reserved.
// 
// ==--==
/*============================================================
**
** Class: EventLogHandle
**
** Purpose: 
** This internal class is a SafeHandle implementation over a 
** native EVT_HANDLE - obtained from EventLog Native Methods.
**
============================================================*/
using System;
using System.Runtime.InteropServices;
using System.Security.Permissions;
 
namespace System.Diagnostics.Eventing.Reader {
 
    //
    // Marked as SecurityCritical due to link demands from inherited
    // SafeHandle members.
    //
 
    // marked as Safe since the only real operation that is performed
    // by this class is NativeWrapper.EvtClose and that is protected
    // by a full Demand() before doing any work.
    [System.Security.SecuritySafeCritical]
    internal sealed class EventLogHandle : SafeHandle {
        // Called by P/Invoke when returning SafeHandles
        private EventLogHandle()
            : base(IntPtr.Zero, true) {
        }
 
        internal EventLogHandle(IntPtr handle, bool ownsHandle)
            : base(IntPtr.Zero, ownsHandle) {
            SetHandle(handle);
        }
   
        public override bool IsInvalid {
            get {
                return IsClosed || handle == IntPtr.Zero;
            }
        }
 
        protected override bool ReleaseHandle() {
            NativeWrapper.EvtClose(handle);
            handle = IntPtr.Zero;
            return true;
        }
 
        // DONT compare EventLogHandle with EventLogHandle.Zero
        // use IsInvalid instead. Zero is provided where a NULL handle needed   
        public static EventLogHandle Zero {
            get {
                return new EventLogHandle();
            }
        }
    }
}