/*
* Copyright 2015 The Netty Project
*
* The Netty Project 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 io.netty.util.internal;
/**
* Math utility methods.
*/
public final class MathUtil {
private MathUtil() {
}
/**
* Fast method of finding the next power of 2 greater than or equal to the supplied value.
*
* <p>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.
* <p>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.
* <p>Special cases for return values are as follows:
* <ul>
* <li>{@code <= 0} -> 1</li>
* <li>{@code >= 2^30} -> 2^30</li>
* </ul>
*/
public static int safeFindNextPositivePowerOfTwo(final int value) {
return value <= 0 ? 1 : value >= 0x40000000 ? 0x40000000 : findNextPositivePowerOfTwo(value);
}
/**
* Determine if the requested {@code index} and {@code length} will fit within {@code capacity}.
* @param index The starting index.
* @param length The length which will be utilized (starting from {@code index}).
* @param capacity The capacity that {@code index + length} is allowed to be within.
* @return {@code true} if the requested {@code index} and {@code length} will fit within {@code capacity}.
* {@code false} if this would result in an index out of bounds exception.
*/
public static boolean isOutOfBounds(int index, int length, int capacity) {
return (index | length | (index + length) | (capacity - (index + length))) < 0;
}
/**
* Compares two {@code int} values.
*
* @param x the first {@code int} to compare
* @param y the second {@code int} to compare
* @return the value {@code 0} if {@code x == y};
* {@code -1} if {@code x < y}; and
* {@code 1} if {@code x > y}
*/
public static int compare(final int x, final int y) {
// do not subtract for comparison, it could overflow
return x < y ? -1 : (x > y ? 1 : 0);
}
/**
* Compare two {@code long} values.
* @param x the first {@code long} to compare.
* @param y the second {@code long} to compare.
* @return
* <ul>
* <li>0 if {@code x == y}</li>
* <li>{@code > 0} if {@code x > y}</li>
* <li>{@code < 0} if {@code x < y}</li>
* </ul>
*/
public static int compare(long x, long y) {
return (x < y) ? -1 : (x > y) ? 1 : 0;
}
}