/*
 * Licensed to Elasticsearch B.V. under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch B.V. 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.
 */
/*
 * Copyright 2014-2019 Real Logic Ltd.
 *
 * 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
 *
 * https://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 co.elastic.apm.agent.profiler.collections;

/**
 * Utility functions for collection objects.
 */
public class CollectionUtil
{
    /**
     * Validate that a load factor is in the range of 0.1 to 0.9.
     * <p>
     * Load factors in the range 0.5 - 0.7 are recommended for open-addressing with linear probing.
     *
     * @param loadFactor to be validated.
     */
    public static void validateLoadFactor(final float loadFactor)
    {
        if (loadFactor < 0.1f || loadFactor > 0.9f)
        {
            throw new IllegalArgumentException("load factor must be in the range of 0.1 to 0.9: " + loadFactor);
        }
    }

    /**
     * Fast method of finding the next power of 2 greater than or equal to the supplied value.
     * <p>
     * If the value is &lt;= 0 then 1 will be returned.
     * <p>
     * This method is not suitable for {@link Integer#MIN_VALUE} or numbers greater than 2^30. When provided
     * then {@link Integer#MIN_VALUE} will be returned.
     *
     * @param value from which to search for next power of 2.
     * @return The next power of 2 or the value itself if it is a power of 2.
     */
    public static int findNextPositivePowerOfTwo(final int value)
    {
        return 1 << (Integer.SIZE - Integer.numberOfLeadingZeros(value - 1));
    }

    /**
     * Fast method of finding the next power of 2 greater than or equal to the supplied value.
     * <p>
     * If the value is &lt;= 0 then 1 will be returned.
     * <p>
     * This method is not suitable for {@link Long#MIN_VALUE} or numbers greater than 2^62. When provided
     * then {@link Long#MIN_VALUE} will be returned.
     *
     * @param value from which to search for next power of 2.
     * @return The next power of 2 or the value itself if it is a power of 2.
     */
    public static long findNextPositivePowerOfTwo(final long value)
    {
        return 1L << (Long.SIZE - Long.numberOfLeadingZeros(value - 1));
    }
}
