bool IEqualityComparer.Equals(object x, object y)
{
if (x == null)
{
return(y == null);
}
if (y != null && x.GetHashCode() == y.GetHashCode())
{
EqualityWeakReference wX = x as EqualityWeakReference;
EqualityWeakReference wY = y as EqualityWeakReference;
//Both WeakReferences are gc'd and they both had the same hash
//Since this is only used in Weak Hash table races are not really an issue.
if (wX != null && wY != null && !wY.IsAlive && !wX.IsAlive)
{
return(true);
}
if (wX != null)
{
x = wX.Target;
}
if (wY != null)
{
y = wY.Target;
}
return(object.ReferenceEquals(x, y));
}
return(false);
}
private void WrapKey(ref object key)
{
if (key != null && !key.GetType().IsValueType)
{
key = new EqualityWeakReference(key);
}
}
/// <devdoc>
/// This method checks to see if it is necessary to
/// scavenge keys, and if it is it performs a scan
/// of all keys to see which ones are no longer valid.
/// To determine if we need to scavenge keys we need to
/// try to track the current GC memory. Our rule of
/// thumb is that if GC memory is decreasing and our
/// key count is constant we need to scavenge. We
/// will need to see if this is too often for extreme
/// use cases like the CompactFramework (they add
/// custom type data for every object at design time).
/// </devdoc>
private void ScavengeKeys()
{
int hashCount = Count;
if (hashCount == 0)
{
return;
}
if (_lastHashCount == 0)
{
_lastHashCount = hashCount;
return;
}
long globalMem = GC.GetTotalMemory(false);
if (_lastGlobalMem == 0)
{
_lastGlobalMem = globalMem;
return;
}
float memDelta = (float)(globalMem - _lastGlobalMem) / (float)_lastGlobalMem;
float hashDelta = (float)(hashCount - _lastHashCount) / (float)_lastHashCount;
if (memDelta < 0 && hashDelta >= 0)
{
// Perform a scavenge through our keys, looking
// for dead references.
ArrayList cleanupList = null;
foreach (object o in Keys)
{
EqualityWeakReference wr = o as EqualityWeakReference;
if (wr != null && !wr.IsAlive)
{
if (cleanupList == null)
{
cleanupList = new ArrayList();
}
cleanupList.Add(wr);
}
}
if (cleanupList != null)
{
foreach (object o in cleanupList)
{
Remove(o);
}
}
}
_lastGlobalMem = globalMem;
_lastHashCount = hashCount;
}
bool IEqualityComparer.Equals(object x, object y)
{
if (x == null)
{
return(y == null);
}
if (y != null && x.GetHashCode() == y.GetHashCode())
{
EqualityWeakReference wX = x as EqualityWeakReference;
EqualityWeakReference wY = y as EqualityWeakReference;
if (wX != null)
{
if (!wX.IsAlive)
{
return(false);
}
x = wX.Target;
}
if (wY != null)
{
if (!wY.IsAlive)
{
return(false);
}
y = wY.Target;
}
return(object.ReferenceEquals(x, y));
}
return(false);
}
public object UnwrapKey(object key)
{
EqualityWeakReference keyRef = key as EqualityWeakReference;
return((keyRef != null) ? keyRef.Target : key);
}
