com.hazelcast.internal.metrics.impl.LockStripe Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2016, Hazelcast, Inc. All Rights Reserved.
*
* 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 com.hazelcast.internal.metrics.impl;
import static com.hazelcast.util.HashUtil.hashToIndex;
import static java.lang.System.identityHashCode;
/**
* A stripe of locks to synchronize on a source object.
*
* We don't want to lock an 'source' objects because we don't own them to prevent running into unnecessary lock contention
* issues.
*
* We rely on the identity hashcode of the object and not on the {@link Object#hashCode()} method to prevent running into
* faulty or thread unsafe implementations.
*/
class LockStripe {
private static final int STRIPE_LENGTH = 20;
private final Object[] stripe = new Object[STRIPE_LENGTH];
LockStripe() {
for (int k = 0; k < stripe.length; k++) {
stripe[k] = new Object();
}
}
Object getLock(Object source) {
int hash = identityHashCode(source);
return hashToIndex(hash, stripe.length);
}
}