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This library provides efficient implementations for various collection data structures (esp. linked lists and priority queues), which have very insufficient implementation in the Java Collections Foundations that makes it hard or even impossible to exploit their efficiencies.

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/* Copyright (C) 2013-2023 TU Dortmund
 * This file is part of AutomataLib, http://www.automatalib.net/.
 *
 * 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 net.automatalib.common.smartcollection;

import java.lang.reflect.Array;
import java.util.Arrays;

/**
 * Class that provides a resizable array storage of a certain type.
 *
 * @param 
 *         element class.
 */
public final class ResizingArrayStorage implements CapacityManagement {

    /**
     * The default initial capacity of the array storage.
     */
    public static final int DEFAULT_INITIAL_CAPACITY = 10;

    public T[] array;
    private int nextCapacityHint;

    /**
     * Constructor. Creates an array storage with a default initial capacity of {@link
     * ResizingArrayStorage#DEFAULT_INITIAL_CAPACITY}.
     *
     * @param arrayClazz
     *         the class of the storage array.
     */
    public ResizingArrayStorage(Class arrayClazz) {
        this(arrayClazz, DEFAULT_INITIAL_CAPACITY);
    }

    /**
     * Constructor. Creates an array with the specified initial capacity.
     *
     * @param arrayClazz
     *         the class of the storage array.
     * @param initialCapacity
     *         the initial capacity.
     */
    @SuppressWarnings("unchecked")
    public ResizingArrayStorage(Class arrayClazz, int initialCapacity) {
        this.array = (T[]) Array.newInstance(arrayClazz, Math.max(0, initialCapacity));
    }

    /**
     * Copy-constructor which (shallowly) clones the storage of the other {@link ResizingArrayStorage}.
     *
     * @param other
     *         the other storage whose data should be (shallowly) cloned
     */
    public ResizingArrayStorage(ResizingArrayStorage other) {
        this.array = other.array.clone();
        this.nextCapacityHint = other.nextCapacityHint;
    }

    @Override
    public boolean ensureCapacity(int minCapacity) {
        if (minCapacity <= array.length) {
            return false;
        }

        final int newCapacity = ArrayUtil.computeNewCapacity(array.length, minCapacity, nextCapacityHint);

        array = Arrays.copyOf(array, newCapacity);
        nextCapacityHint = 0;
        return true;
    }

    @Override
    public boolean ensureAdditionalCapacity(int additionalCapacity) {
        return ensureCapacity(array.length + additionalCapacity);
    }

    @Override
    public void hintNextCapacity(int nextCapacityHint) {
        this.nextCapacityHint = nextCapacityHint;
    }

    /**
     * Shrinks the storage to the specified maximum capacity.
     * 
     * If the current capacity is less or equal to the specified capacity, nothing happens.
     *
     * @param maxCapacity
     *         the maximal number of elements the storage array has to provide room for.
     *
     * @return true iff the storage array had to be resized, false otherwise.
     */
    public boolean shrink(int maxCapacity) {
        if (maxCapacity >= array.length) {
            return false;
        }

        array = Arrays.copyOf(array, maxCapacity);
        return true;
    }

    /**
     * Sets all the elements in the array to the specified value.
     *
     * @param value
     *         the value.
     */
    public void setAll(T value) {
        Arrays.fill(array, value);
    }

    public void swap(ResizingArrayStorage other) {
        final Class myType = array.getClass().getComponentType();
        final Class otherType = other.array.getClass().getComponentType();
        if (myType != otherType) {
            throw new IllegalArgumentException(
                    "Cannot swap array storages of different array classes (" + myType + " vs. " + otherType + ")");
        }
        T[] arrayTmp = array;
        int hintTmp = nextCapacityHint;
        array = other.array;
        nextCapacityHint = other.nextCapacityHint;
        other.array = arrayTmp;
        other.nextCapacityHint = hintTmp;
    }
}