com.microsoft.z3.IDecRefQueue Maven / Gradle / Ivy
/**
Copyright (c) 2012-2014 Microsoft Corporation
Module Name:
IDecRefQueue.java
Abstract:
Author:
@author Christoph Wintersteiger (cwinter) 2012-03-15
Notes:
**/
package com.microsoft.z3;
import java.lang.ref.PhantomReference;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.util.IdentityHashMap;
import java.util.Map;
/**
* A queue to handle management of native memory.
*
* Mechanics: once an object is created, a metadata is stored for it in
* {@code referenceMap}, and a {@link PhantomReference} is created with a
* reference to {@code referenceQueue}.
* Once the object becomes strongly unreachable, the phantom reference gets
* added by JVM to the {@code referenceQueue}.
* After each object creation, we iterate through the available objects in
* {@code referenceQueue} and decrement references for them.
*
* @param Type of object stored in queue.
*/
public abstract class IDecRefQueue {
private final ReferenceQueue referenceQueue = new ReferenceQueue<>();
private final Map, Long> referenceMap =
new IdentityHashMap<>();
protected IDecRefQueue() {}
/**
* An implementation of this method should decrement the reference on a
* given native object.
* This function should always be called on the {@code ctx} thread.
*
* @param ctx Z3 context.
* @param obj Pointer to a Z3 object.
*/
protected abstract void decRef(Context ctx, long obj);
public void storeReference(Context ctx, T obj) {
PhantomReference ref = new PhantomReference<>(obj, referenceQueue);
referenceMap.put(ref, obj.getNativeObject());
clear(ctx);
}
/**
* Clean all references currently in {@code referenceQueue}.
*/
protected void clear(Context ctx)
{
Reference ref;
while ((ref = referenceQueue.poll()) != null) {
long z3ast = referenceMap.remove(ref);
decRef(ctx, z3ast);
}
}
/**
* Clean all references stored in {@code referenceMap},
* regardless of whether they are in {@code referenceMap} or not.
*/
public void forceClear(Context ctx) {
for (long ref : referenceMap.values()) {
decRef(ctx, ref);
}
}
}