https://source.android.com/ 
/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * 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 com.android.internal.util;


A helper class that aims to provide comparable growth performance to ArrayList, but on primitive
arrays. Common array operations are implemented for efficient use in dynamic containers.
All methods in this class assume that the length of an array is equivalent to its capacity and
NOT the number of elements in the array. The current size of the array is always passed in as a
parameter.

@hide
/**
 * A helper class that aims to provide comparable growth performance to ArrayList, but on primitive
 * arrays. Common array operations are implemented for efficient use in dynamic containers.
 *
 * All methods in this class assume that the length of an array is equivalent to its capacity and
 * NOT the number of elements in the array. The current size of the array is always passed in as a
 * parameter.
 *
 * @hide
 */
public final class GrowingArrayUtils {

    
Appends an element to the end of the array, growing the array if there is no more room.

Params:
  • array – The array to which to append the element. This must NOT be null.
  • currentSize – The number of elements in the array. Must be less than or equal to
                   array.length.
  • element – The element to append.
Returns:the array to which the element was appended. This may be different than the given
        array.
/**
     * Appends an element to the end of the array, growing the array if there is no more room.
     * @param array The array to which to append the element. This must NOT be null.
     * @param currentSize The number of elements in the array. Must be less than or equal to
     *                    array.length.
     * @param element The element to append.
     * @return the array to which the element was appended. This may be different than the given
     *         array.
     */
    public static <T> T[] append(T[] array, int currentSize, T element) {
        assert currentSize <= array.length;

        if (currentSize + 1 > array.length) {
            @SuppressWarnings("unchecked")
            T[] newArray = ArrayUtils.newUnpaddedArray(
                    (Class<T>) array.getClass().getComponentType(), growSize(currentSize));
            System.arraycopy(array, 0, newArray, 0, currentSize);
            array = newArray;
        }
        array[currentSize] = element;
        return array;
    }

    
Primitive int version of append(Object[], int, Object). 
/**
     * Primitive int version of {@link #append(Object[], int, Object)}.
     */
    public static int[] append(int[] array, int currentSize, int element) {
        assert currentSize <= array.length;

        if (currentSize + 1 > array.length) {
            int[] newArray = ArrayUtils.newUnpaddedIntArray(growSize(currentSize));
            System.arraycopy(array, 0, newArray, 0, currentSize);
            array = newArray;
        }
        array[currentSize] = element;
        return array;
    }

    
Primitive long version of append(Object[], int, Object). 
/**
     * Primitive long version of {@link #append(Object[], int, Object)}.
     */
    public static long[] append(long[] array, int currentSize, long element) {
        assert currentSize <= array.length;

        if (currentSize + 1 > array.length) {
            long[] newArray = ArrayUtils.newUnpaddedLongArray(growSize(currentSize));
            System.arraycopy(array, 0, newArray, 0, currentSize);
            array = newArray;
        }
        array[currentSize] = element;
        return array;
    }

    
Primitive boolean version of append(Object[], int, Object). 
/**
     * Primitive boolean version of {@link #append(Object[], int, Object)}.
     */
    public static boolean[] append(boolean[] array, int currentSize, boolean element) {
        assert currentSize <= array.length;

        if (currentSize + 1 > array.length) {
            boolean[] newArray = ArrayUtils.newUnpaddedBooleanArray(growSize(currentSize));
            System.arraycopy(array, 0, newArray, 0, currentSize);
            array = newArray;
        }
        array[currentSize] = element;
        return array;
    }

    
Primitive float version of append(Object[], int, Object). 
/**
     * Primitive float version of {@link #append(Object[], int, Object)}.
     */
    public static float[] append(float[] array, int currentSize, float element) {
        assert currentSize <= array.length;

        if (currentSize + 1 > array.length) {
            float[] newArray = ArrayUtils.newUnpaddedFloatArray(growSize(currentSize));
            System.arraycopy(array, 0, newArray, 0, currentSize);
            array = newArray;
        }
        array[currentSize] = element;
        return array;
    }

    
Inserts an element into the array at the specified index, growing the array if there is no
more room.

Params:
  • array – The array to which to append the element. Must NOT be null.
  • currentSize – The number of elements in the array. Must be less than or equal to
                   array.length.
  • element – The element to insert.
Returns:the array to which the element was appended. This may be different than the given
        array.
/**
     * Inserts an element into the array at the specified index, growing the array if there is no
     * more room.
     *
     * @param array The array to which to append the element. Must NOT be null.
     * @param currentSize The number of elements in the array. Must be less than or equal to
     *                    array.length.
     * @param element The element to insert.
     * @return the array to which the element was appended. This may be different than the given
     *         array.
     */
    public static <T> T[] insert(T[] array, int currentSize, int index, T element) {
        assert currentSize <= array.length;

        if (currentSize + 1 <= array.length) {
            System.arraycopy(array, index, array, index + 1, currentSize - index);
            array[index] = element;
            return array;
        }

        @SuppressWarnings("unchecked")
        T[] newArray = ArrayUtils.newUnpaddedArray((Class<T>)array.getClass().getComponentType(),
                growSize(currentSize));
        System.arraycopy(array, 0, newArray, 0, index);
        newArray[index] = element;
        System.arraycopy(array, index, newArray, index + 1, array.length - index);
        return newArray;
    }

    
Primitive int version of insert(Object[], int, int, Object). 
/**
     * Primitive int version of {@link #insert(Object[], int, int, Object)}.
     */
    public static int[] insert(int[] array, int currentSize, int index, int element) {
        assert currentSize <= array.length;

        if (currentSize + 1 <= array.length) {
            System.arraycopy(array, index, array, index + 1, currentSize - index);
            array[index] = element;
            return array;
        }

        int[] newArray = ArrayUtils.newUnpaddedIntArray(growSize(currentSize));
        System.arraycopy(array, 0, newArray, 0, index);
        newArray[index] = element;
        System.arraycopy(array, index, newArray, index + 1, array.length - index);
        return newArray;
    }

    
Primitive long version of insert(Object[], int, int, Object). 
/**
     * Primitive long version of {@link #insert(Object[], int, int, Object)}.
     */
    public static long[] insert(long[] array, int currentSize, int index, long element) {
        assert currentSize <= array.length;

        if (currentSize + 1 <= array.length) {
            System.arraycopy(array, index, array, index + 1, currentSize - index);
            array[index] = element;
            return array;
        }

        long[] newArray = ArrayUtils.newUnpaddedLongArray(growSize(currentSize));
        System.arraycopy(array, 0, newArray, 0, index);
        newArray[index] = element;
        System.arraycopy(array, index, newArray, index + 1, array.length - index);
        return newArray;
    }

    
Primitive boolean version of insert(Object[], int, int, Object). 
/**
     * Primitive boolean version of {@link #insert(Object[], int, int, Object)}.
     */
    public static boolean[] insert(boolean[] array, int currentSize, int index, boolean element) {
        assert currentSize <= array.length;

        if (currentSize + 1 <= array.length) {
            System.arraycopy(array, index, array, index + 1, currentSize - index);
            array[index] = element;
            return array;
        }

        boolean[] newArray = ArrayUtils.newUnpaddedBooleanArray(growSize(currentSize));
        System.arraycopy(array, 0, newArray, 0, index);
        newArray[index] = element;
        System.arraycopy(array, index, newArray, index + 1, array.length - index);
        return newArray;
    }

    
Given the current size of an array, returns an ideal size to which the array should grow.
This is typically double the given size, but should not be relied upon to do so in the
future.

/**
     * Given the current size of an array, returns an ideal size to which the array should grow.
     * This is typically double the given size, but should not be relied upon to do so in the
     * future.
     */
    public static int growSize(int currentSize) {
        return currentSize <= 4 ? 8 : currentSize * 2;
    }

    // Uninstantiable
    private GrowingArrayUtils() {}
}