//
// System.Runtime.InteropServices.SafeHandle
//
// Copyright (C) 2005 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
// Notes:
// This code is only API complete, but it lacks the runtime support
// for CriticalFinalizerObject and any P/Invoke wrapping that might
// happen.
//
// For details, see:
// http://blogs.msdn.com/cbrumme/archive/2004/02/20/77460.aspx
//
// On implementing SafeHandles:
// http://blogs.msdn.com/bclteam/archive/2005/03/15/396335.aspx
//
// Issues:
// The System.Runtime.ConstrainedExecution.ReliabilityContractAttribute has
// not been applied to any APIs here yet.
//
// TODO: Although DangerousAddRef has been implemented, I need to
// find out whether the runtime performs the P/Invoke if the
// handle has been disposed already.
//
//
using System;
using System.Runtime.InteropServices;
using System.Runtime.ConstrainedExecution;
using System.Threading;
namespace System.Runtime.InteropServices{
public abstract class SafeHandle : CriticalFinalizerObject, IDisposable {
//
// Warning: the offset of handle is mapped inside the runtime
// if you move this, you must updated the runtime definition of
// MonoSafeHandle
//
protected IntPtr handle;
IntPtr invalid_handle_value;
int refcount = 0;
bool owns_handle;
#if NET_2_1
protected SafeHandle ()
{
throw new NotImplementedException ();
}
#endif
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.MayFail)]
protected SafeHandle (IntPtr invalidHandleValue, bool ownsHandle)
{
invalid_handle_value = invalidHandleValue;
owns_handle = ownsHandle;
refcount = 1;
}
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
public void Close ()
{
if (refcount == 0)
throw new ObjectDisposedException (GetType ().FullName);
int newcount, current;
do {
current = refcount;
newcount = current-1;
} while (Interlocked.CompareExchange (ref refcount, newcount, current) != current);
if (newcount == 0 && owns_handle && !IsInvalid){
ReleaseHandle ();
handle = invalid_handle_value;
refcount = -1;
}
}
//
// I do not know when we could not be able to increment the
// reference count and set success to false. It might just
// be a convention used for the following code pattern:
//
// bool release = false
// try { x.DangerousAddRef (ref release); ... }
// finally { if (release) x.DangerousRelease (); }
//
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.MayFail)]
public void DangerousAddRef (ref bool success)
{
if (refcount <= 0)
throw new ObjectDisposedException (GetType ().FullName);
int newcount, current;
do {
current = refcount;
newcount = current + 1;
if (current <= 0){
//
// In MS, calling sf.Close () followed by a call
// to P/Invoke with SafeHandles throws this, but
// am left wondering: when would "success" be
// set to false?
//
throw new ObjectDisposedException (GetType ().FullName);
}
} while (Interlocked.CompareExchange (ref refcount, newcount, current) != current);
success = true;
}
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
public IntPtr DangerousGetHandle ()
{
if (refcount <= 0){
throw new ObjectDisposedException (GetType ().FullName);
}
return handle;
}
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
public void DangerousRelease ()
{
if (refcount <= 0)
throw new ObjectDisposedException (GetType ().FullName);
int newcount, current;
do {
current = refcount;
newcount = current-1;
} while (Interlocked.CompareExchange (ref refcount, newcount, current) != current);
if (newcount == 0 && owns_handle && !IsInvalid){
ReleaseHandle ();
handle = invalid_handle_value;
}
}
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
public void Dispose ()
{
Dispose (true);
GC.SuppressFinalize (this);
}
//
// See documentation, this invalidates the handle without
// closing it.
//
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
public void SetHandleAsInvalid ()
{
handle = invalid_handle_value;
}
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
protected virtual void Dispose (bool disposing)
{
if (disposing)
Close ();
else {
//
// The docs say `never call this with disposing=false',
// the question is whether:
// * The runtime will ever call Dipose(false) for SafeHandles (special runtime case)
// * Whether we should just call ReleaseHandle regardless?
//
}
}
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
protected abstract bool ReleaseHandle ();
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
protected void SetHandle (IntPtr handle)
{
this.handle = handle;
}
public bool IsClosed {
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
get {
return refcount <= 0;
}
}
public abstract bool IsInvalid {
[ReliabilityContract (Consistency.WillNotCorruptState, Cer.Success)]
get;
}
~SafeHandle ()
{
if (owns_handle && !IsInvalid){
ReleaseHandle ();
handle = invalid_handle_value;
}
}
}
}
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