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/*
* 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 com.datastax.oss.driver.internal.core.util;
import edu.umd.cs.findbugs.annotations.NonNull;
import java.util.concurrent.ThreadLocalRandom;
public class ArrayUtils {
public static void swap(@NonNull ElementT[] elements, int i, int j) {
if (i != j) {
ElementT tmp = elements[i];
elements[i] = elements[j];
elements[j] = tmp;
}
}
/**
* Moves an element towards the beginning of the array, shifting all the intermediary elements to
* the right (no-op if {@code targetIndex >= sourceIndex}).
*/
public static void bubbleUp(
@NonNull ElementT[] elements, int sourceIndex, int targetIndex) {
for (int i = sourceIndex; i > targetIndex; i--) {
swap(elements, i, i - 1);
}
}
/**
* Moves an element towards the end of the array, shifting all the intermediary elements to the
* left (no-op if {@code targetIndex <= sourceIndex}).
*/
public static void bubbleDown(
@NonNull ElementT[] elements, int sourceIndex, int targetIndex) {
for (int i = sourceIndex; i < targetIndex; i++) {
swap(elements, i, i + 1);
}
}
/**
* Shuffles the first n elements of the array in-place.
*
* @param elements the array to shuffle.
* @param n the number of elements to shuffle; must be {@code <= elements.length}.
* @see Modern
* Fisher-Yates shuffle
*/
public static void shuffleHead(@NonNull ElementT[] elements, int n) {
shuffleHead(elements, n, ThreadLocalRandom.current());
}
/**
* Shuffles the first n elements of the array in-place.
*
* @param elements the array to shuffle.
* @param n the number of elements to shuffle; must be {@code <= elements.length}.
* @param random the {@link ThreadLocalRandom} instance to use. This is mainly intended to
* facilitate tests.
* @see Modern
* Fisher-Yates shuffle
*/
public static void shuffleHead(
@NonNull ElementT[] elements, int n, @NonNull ThreadLocalRandom random) {
if (n > elements.length) {
throw new ArrayIndexOutOfBoundsException(
String.format(
"Can't shuffle the first %d elements, there are only %d", n, elements.length));
}
if (n > 1) {
for (int i = n - 1; i > 0; i--) {
int j = random.nextInt(i + 1);
swap(elements, i, j);
}
}
}
/** Rotates the elements in the specified range by the specified amount (round-robin). */
public static void rotate(
@NonNull ElementT[] elements, int startIndex, int length, int amount) {
if (length >= 2) {
amount = amount % length;
// Repeatedly shift by 1. This is not the most time-efficient but the array will typically be
// small so we don't care, and this avoids allocating a temporary buffer.
for (int i = 0; i < amount; i++) {
bubbleDown(elements, startIndex, startIndex + length - 1);
}
}
}
}