Motivation:
In later Java8 versions our Atomic*FieldUpdater are slower then the JDK implementations so we should not use ours anymore. Even worse the JDK implementations provide for example an optimized version of addAndGet(...) using intrinsics which makes it a lot faster for this use-case.
Modifications:
- Remove methods that return our own Atomic*FieldUpdaters.
- Use the JDK implementations everywhere.
Result:
Faster code.
Motivation:
Due an implementation flaw in DefaultAttributeMap it was possible that an attribute and its stored value/key could not be collected until the DefaultAttributeMap could be collected. This can lead to unexpected memory usage and strong reachability of objects that should be collected.
Modifications:
Use an special empty DefaultAttribute as head of the each bucket which will not store any key / value. With this change everything can be collected as expected as we not use any DefaultAttribute created by the user as head of a bucket.
Result:
DefaultAttributeMap does not store user data and thus the lifetime of this user data is not tied to the lifetime of the DefaultAttributeMap.
Motivation:
When remove0() is called multiple times for an DefaultAttribute it can cause corruption of the internal linked-list structure.
Modifications:
- Ensure remove0() can not cause corruption by null out prev and next references.
Result:
No more corruption possible
Motivation:
The current DefaultAttributeMap cause an infinite-loop when the user removes an attribute and create the same attribute again. This regression was introduced by c3bd7a8ff1.
Modification:
Correctly break out loop
Result:
No infinite-loop anymore.
Motivation:
The old DefaultAttributeMap impl did more synchronization then needed and also did not expose a efficient way to check if an attribute exists with a specific key.
Modifications:
* Rewrite DefaultAttributeMap to not use IdentityHashMap and synchronization on the map directly. The new impl uses a combination of AtomicReferenceArray and synchronization per chain (linked-list). Also access the first Attribute per bucket can be done without any synchronization at all and just uses atomic operations. This should fit for most use-cases pretty weel.
* Add hasAttr(...) implementation
Result:
It's now possible to check for the existence of a attribute without create one. Synchronization is per linked-list and the first entry can even be added via atomic operation.
