/*
* (C) Copyright 2016 Pantheon Technologies, s.r.o. and others.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.opendaylight.yangtools.triemap;
import java.io.Serializable;
import javax.annotation.Nonnull;
/**
* Internal equivalence class, similar to {@link com.google.common.base.Equivalence}, but explicitly not handling
* nulls. We use equivalence only for keys, which are guaranteed to be non-null.
*
* @author Robert Varga
*/
abstract class Equivalence<T> implements Serializable {
private static final long serialVersionUID = 1L;
private static final class Equals extends Equivalence<Object> {
private static final long serialVersionUID = 1L;
static final Equals INSTANCE = new Equals();
@Override
boolean equivalent(final Object a, final Object b) {
return a.equals(b);
}
@Override
Object readResolve() {
return INSTANCE;
}
}
private static final class Identity extends Equivalence<Object> {
private static final long serialVersionUID = 1L;
static final Identity INSTANCE = new Identity();
@Override
boolean equivalent(final Object a, final Object b) {
return a == b;
}
@Override
Object readResolve() {
return INSTANCE;
}
}
static Equivalence<Object> equals() {
return Equals.INSTANCE;
}
static Equivalence<Object> identity() {
return Identity.INSTANCE;
}
final int hash(@Nonnull final T t) {
int h = t.hashCode();
// This function ensures that hashCodes that differ only by
// constant multiples at each bit position have a bounded
// number of collisions (approximately 8 at default load factor).
h ^= (h >>> 20) ^ (h >>> 12);
h ^= (h >>> 7) ^ (h >>> 4);
return h;
}
abstract boolean equivalent(@Nonnull T a, @Nonnull T b);
abstract Object readResolve();
}