org.aspectbench.tm.runtime.internal
Class MaybeWeakRef

java.lang.Object
  java.lang.ref.Reference<T>
      java.lang.ref.WeakReference
          org.aspectbench.tm.runtime.internal.MyWeakRef
              org.aspectbench.tm.runtime.internal.MaybeWeakRef

public class MaybeWeakRef
extends MyWeakRef

Weak ref implementation that allows the reference to be strengthened if necessary. Equality is reference identity of referents. Hashcode is identityHashCode of referent, even after referent expires. Weak references are canonicalised to guarantee they all expire at the same time and only appear in the reference queue (if any) once.

Author:

Pavel Avgustinov

Field Summary

Fields inherited from class org.aspectbench.tm.runtime.internal.MyWeakRef

expiredQueue

Constructor Summary

protected	MaybeWeakRef(java.lang.Object ref)
protected	MaybeWeakRef(java.lang.Object ref, java.lang.ref.ReferenceQueue q)

Method Summary

void	cleanup()
boolean	equals(java.lang.Object obj) Only one PersistentWeakRef is ever constructed for a particular object.
static MyWeakRef	getWeakRef(java.lang.Object o) Really, we want these to be canonical.
void	strengthen(java.lang.Object obj) Strengthen a weak ref by keeping a strong ref in addition.
void	weaken() Weaken the reference by dropping the strong link to the referent.

Methods inherited from class org.aspectbench.tm.runtime.internal.MyWeakRef

addContainer, checkExpired, hashCode, isExpired, notifyContainers, removeContainer

Methods inherited from class java.lang.ref.Reference

clear, enqueue, get, isEnqueued

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MaybeWeakRef

protected MaybeWeakRef(java.lang.Object ref)

MaybeWeakRef

protected MaybeWeakRef(java.lang.Object ref,
                       java.lang.ref.ReferenceQueue q)

Method Detail

getWeakRef

public static MyWeakRef getWeakRef(java.lang.Object o)

Really, we want these to be canonical. Of course, it just so happens that the current codegen guarantees them to be canonical (they are constructed once per ITD object, which is guaranteed fresh), so we can dispense with the expensive map.

equals

public boolean equals(java.lang.Object obj)

Only one PersistentWeakRef is ever constructed for a particular object. Thus, this PWR is equal to obj iff they are the same weak reference, or if obj is the referent of this.

Overrides:

equals in class MyWeakRef

strengthen

public void strengthen(java.lang.Object obj)

Strengthen a weak ref by keeping a strong ref in addition. Referent must be passed as an argument to avoid race conditions with the GC.

weaken

public void weaken()

Weaken the reference by dropping the strong link to the referent.

cleanup

public void cleanup()

Overrides:

cleanup in class MyWeakRef