13:39
What could be done to implement weak references would be to have a weak
reference pointer in an object. Make it atomic and just make the same
object be returned if such a reference already exists. The only issue
with this is WeakReference is constructed using a new object. So I
would say that it would point to a special sub-object. When the reference
has been garbage collected, has a different object pointer, or if the
usage index is different then it was removed. So basically it would be a
simple struct with two fields:
int useindex-- The number of times the raw reference index has been used, this is used to potentially recycle those references.Object object-- The object it refers to.
If WeakReference looks at the struct then if
useindex != myindex || object == null then null will be returned
otherwise the object pointer will be returned. When a object is to be
deallocated due to being garbage collected then, first any references for
that object are cleared by just incrementing the index atomically if it
matches the object reference index. Then object deallocation continues.