/// <summary>Creates a SafeHandle class.</summary>
protected SafeHandle(IntPtr invalidHandleValue, bool ownsHandle)
{
handle = invalidHandleValue;
_state = StateBits.RefCountOne; // Ref count 1 and not closed or disposed.
_ownsHandle = ownsHandle;
if (!ownsHandle)
{
GC.SuppressFinalize(this);
}
#if DEBUG
else if (s_logFinalization)
{
int lastError = Marshal.GetLastPInvokeError();
_ctorStackTrace = Environment.StackTrace;
Marshal.SetLastPInvokeError(lastError);
}
#endif
_fullyInitialized = true;
}
private void Cleanup()
{
if (IsClosed)
{
return;
}
_isClosed = true;
if (IsInvalid)
{
return;
}
// Save last error from P/Invoke in case the implementation of
// ReleaseHandle trashes it (important because this ReleaseHandle could
// occur implicitly as part of unmarshaling another P/Invoke).
int lastError = Marshal.GetLastPInvokeError();
ReleaseHandle();
Marshal.SetLastPInvokeError(lastError);
GC.SuppressFinalize(this);
}
private void InternalRelease(bool disposeOrFinalizeOperation)
{
Debug.Assert(_fullyInitialized || disposeOrFinalizeOperation);
// See AddRef above for the design of the synchronization here. Basically we
// will try to decrement the current ref count and, if that would take us to
// zero refs, set the closed state on the handle as well.
bool performRelease = false;
// Might have to perform the following steps multiple times due to
// interference from other AddRef's and Release's.
int oldState, newState;
do
{
// First step is to read the current handle state. We use this cached
// value to predicate any modification we might decide to make to the
// state).
oldState = _state;
// If this is a Dispose operation we have additional requirements (to
// ensure that Dispose happens at most once as the comments in AddRef
// detail). We must check that the dispose bit is not set in the old
// state and, in the case of successful state update, leave the disposed
// bit set. Silently do nothing if Dispose has already been called.
if (disposeOrFinalizeOperation && ((oldState & StateBits.Disposed) != 0))
{
return;
}
// We should never see a ref count of zero (that would imply we have
// unbalanced AddRef and Releases). (We might see a closed state before
// hitting zero though -- that can happen if SetHandleAsInvalid is
// used).
if ((oldState & StateBits.RefCount) == 0)
{
throw new ObjectDisposedException(nameof(SafeHandle), SR.ObjectDisposed_SafeHandleClosed);
}
// If we're proposing a decrement to zero and the handle is not closed
// and we own the handle then we need to release the handle upon a
// successful state update. If so we need to check whether the handle is
// currently invalid by asking the SafeHandle subclass. We must do this before
// transitioning the handle to closed, however, since setting the closed
// state will cause IsInvalid to always return true.
performRelease = ((oldState & (StateBits.RefCount | StateBits.Closed)) == StateBits.RefCountOne) &&
_ownsHandle &&
!IsInvalid;
// Attempt the update to the new state, fail and retry if the initial
// state has been modified in the meantime. Decrement the ref count by
// substracting StateBits.RefCountOne from the state then OR in the bits for
// Dispose (if that's the reason for the Release) and closed (if the
// initial ref count was 1).
newState = oldState - StateBits.RefCountOne;
if ((oldState & StateBits.RefCount) == StateBits.RefCountOne)
{
newState |= StateBits.Closed;
}
if (disposeOrFinalizeOperation)
{
newState |= StateBits.Disposed;
}
} while (Interlocked.CompareExchange(ref _state, newState, oldState) != oldState);
// If we get here we successfully decremented the ref count. Additionally we
// may have decremented it to zero and set the handle state as closed. In
// this case (providng we own the handle) we will call the ReleaseHandle
// method on the SafeHandle subclass.
if (performRelease)
{
// Save last error from P/Invoke in case the implementation of ReleaseHandle
// trashes it (important because this ReleaseHandle could occur implicitly
// as part of unmarshaling another P/Invoke).
int lastError = Marshal.GetLastPInvokeError();
ReleaseHandle();
Marshal.SetLastPInvokeError(lastError);
}
}
