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/*
 * Copyright © 2018-2019 Apple Inc. and the ServiceTalk project authors
 *
 * 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 io.servicetalk.utils.internal;

/**
 * Internal math utilities.
 */
public final class MathUtils {
    private MathUtils() {
    }

    /**
     * Fast method of finding the next power of 2 greater than or equal to the supplied value.
     *
     * If the value is {@code <= 0} then 1 will be returned.
     * This method is not suitable for {@link Integer#MIN_VALUE} or numbers greater than 2^30.
     *
     * @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) {
        assert value > Integer.MIN_VALUE && value < 0x40000000;
        return 1 << (32 - Integer.numberOfLeadingZeros(value - 1));
    }

    /**
     * Fast method of finding the next power of 2 greater than or equal to the supplied value.
     * 
This method will do runtime bounds checking and call {@link #findNextPositivePowerOfTwo(int)} if within a
     * valid range.
     * @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.
     * 
Special cases for return values are as follows:
     * 

     *     {@code <= 0} to 1
     *     {@code >= 2^30} to 2^30
     * 
     */
    public static int safeFindNextPositivePowerOfTwo(final int value) {
        return value <= 0 ? 1 : value >= 0x40000000 ? 0x40000000 : findNextPositivePowerOfTwo(value);
    }
}