curator-master/curator-recipes/src/main/java/org/apache/curator/framework/recipes/atomic/CachedAtomicLong.java
/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.curator.framework.recipes.atomic;

/**
 * Uses an {@link DistributedAtomicNumber} and allocates values in chunks for better performance
 */
public class CachedAtomicLong {
    private final DistributedAtomicLong number;
    private final long cacheFactor;

    private AtomicValue<Long> currentValue = null;
    private int currentIndex = 0;

    /**
     * @param number the number to use
     * @param cacheFactor the number of values to allocate at a time
     */
    public CachedAtomicLong(DistributedAtomicLong number, int cacheFactor) {
        this.number = number;
        this.cacheFactor = cacheFactor;
    }

    /**
     * Returns the next value (incrementing by 1). If a new chunk of numbers is needed, it is
     * requested from the number
     *
     * @return next increment
     * @throws Exception errors
     */
    public AtomicValue<Long> next() throws Exception {
        MutableAtomicValue<Long> result = new MutableAtomicValue<Long>(0L, 0L);

        if (currentValue == null) {
            currentValue = number.add(cacheFactor);
            if (!currentValue.succeeded()) {
                currentValue = null;
                result.succeeded = false;
                return result;
            }
            currentIndex = 0;
        }

        result.succeeded = true;
        result.preValue = currentValue.preValue() + currentIndex;
        result.postValue = result.preValue + 1;

        if (++currentIndex >= cacheFactor) {
            currentValue = null;
        }

        return result;
    }
}
