public IteratorResult next
Get the next item from the iterator in
Only when this function returns OK,
elem will contain a
valid value. For iterators that return refcounted objects, the returned object will have its refcount increased and should therefore be unreffed
When this function returns DONE, no more elements can be retrieved
A return value of RESYNC indicates that the element list was
concurrently updated. The user of
it should call resync to
get the newly updated list.
A return value of ERROR indicates an unrecoverable fatal error.
||pointer to hold next element
|The result of the iteration. Unref
elem after usage if this is a refcounted object. MT safe.