-/*
- * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
- *
- * This program and the accompanying materials are made available under the
- * terms of the Eclipse Public License v1.0 which accompanies this distribution,
- * and is available at http://www.eclipse.org/legal/epl-v10.html
- */
-package org.opendaylight.yangtools.objcache.spi;
-
-import static java.util.Objects.requireNonNull;
-
-import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.FinalizableReferenceQueue;
-import com.google.common.base.FinalizableSoftReference;
-import com.google.common.cache.Cache;
-import java.util.concurrent.ExecutionException;
-import javax.annotation.Nonnull;
-import org.opendaylight.yangtools.concepts.ProductAwareBuilder;
-import org.opendaylight.yangtools.objcache.ObjectCache;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * Abstract object cache implementation. This implementation takes care
- * of interacting with the user and manages interaction with the Garbage
- * Collector (via soft references). Subclasses are expected to provide
- * a backing {@link Cache} instance and provide the
- */
-public abstract class AbstractObjectCache implements ObjectCache {
- /**
- * Key used when looking up a ProductAwareBuilder product. We assume
- * the builder is not being modified for the duration of the lookup,
- * anything else is the user's fault.
- */
- @VisibleForTesting
- static final class BuilderKey {
- private final ProductAwareBuilder<?> builder;
-
- private BuilderKey(final ProductAwareBuilder<?> builder) {
- this.builder = requireNonNull(builder);
- }
-
- @Override
- public int hashCode() {
- return builder.productHashCode();
- }
-
- @Override
- public boolean equals(Object obj) {
- /*
- * We can tolerate null objects coming our way, but we need
- * to be on the lookout for WeakKeys, as we cannot pass them
- * directly to productEquals().
- */
- if (obj instanceof SoftKey) {
- obj = ((SoftKey<?>)obj).get();
- }
-
- return builder.productEquals(obj);
- }
- }
-
- /**
- * Key used in the underlying map. It is essentially a soft reference, with
- * slightly special properties.
- *
- * <p>
- * It acts as a proxy for the object it refers to and essentially delegates
- * to it. There are three exceptions here:
- *
- * <p>
- * 1) This key needs to have a cached hash code. The requirement is that the
- * key needs to be able to look itself up after the reference to the object
- * has been cleared (and thus we can no longer look it up from there). One
- * typical container where we are stored are HashMaps -- and they need it
- * to be constant.
- * 2) This key does not tolerate checks to see if its equal to null. While we
- * could return false, we want to catch offenders who try to store nulls
- * in the cache.
- * 3) This key inverts the check for equality, e.g. it calls equals() on the
- * object which was passed to its equals(). Instead of supplying itself,
- * it supplies the referent. If the soft reference is cleared, such check
- * will return false, which is fine as it prevents normal lookup from
- * seeing the cleared key. Removal is handled by the explicit identity
- * check.
- */
- protected abstract static class SoftKey<T> extends FinalizableSoftReference<T> {
- private final int hashCode;
-
- public SoftKey(final T referent, final FinalizableReferenceQueue queue) {
- super(requireNonNull(referent), queue);
- hashCode = referent.hashCode();
- }
-
- @Override
- public boolean equals(final Object obj) {
- if (obj == null) {
- return false;
- }
-
- // Order is important: we do not want to call equals() on ourselves!
- return this == obj || obj.equals(get());
- }
-
- @Override
- public int hashCode() {
- return hashCode;
- }
- }
-
- private static final Logger LOG = LoggerFactory.getLogger(AbstractObjectCache.class);
- private final FinalizableReferenceQueue queue;
- private final Cache<SoftKey<?>, Object> cache;
-
- protected AbstractObjectCache(final Cache<SoftKey<?>, Object> cache, final FinalizableReferenceQueue queue) {
- this.queue = requireNonNull(queue);
- this.cache = requireNonNull(cache);
- }
-
- protected <T> SoftKey<T> createSoftKey(final T object) {
- /*
- * This may look like a race (having a soft reference and not have
- * it in the cache). In fact this is protected by the fact we still
- * have a strong reference on the object in our arguments and that
- * reference survives past method return since we return it.
- */
- return new SoftKey<T>(object, queue) {
- @Override
- public void finalizeReferent() {
- /*
- * NOTE: while it may be tempting to add "object" into this
- * trace message, do not ever do that: it would retain
- * a strong reference, preventing collection.
- */
- LOG.trace("Invalidating key {}", this);
- cache.invalidate(this);
- }
- };
- }
-
- @Override
- public final <B extends ProductAwareBuilder<P>, P> P getProduct(@Nonnull final B builder) {
- throw new UnsupportedOperationException();
-// LOG.debug("Looking up product for {}", builder);
-//
-// @SuppressWarnings("unchecked")
-// final P ret = (P) cache.getIfPresent(new BuilderKey(builder));
-// return ret == null ? put(Preconditions.checkNotNull(builder.toInstance())) : ret;
- }
-
- @Override
- @SuppressWarnings("unchecked")
- public final <T> T getReference(final T object) {
- LOG.debug("Looking up reference for {}", object);
- if (object == null) {
- return null;
- }
-
- final SoftKey<T> key = createSoftKey(object);
- try {
- return (T) cache.get(key, () -> object);
- } catch (ExecutionException e) {
- throw new IllegalStateException("Failed to load value", e);
- }
- }
-}