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/*
 * FXGL - JavaFX Game Library. The MIT License (MIT).
 * Copyright (c) AlmasB ([email protected]).
 * See LICENSE for details.
 */
package com.almasb.fxgl.physics.box2d.pooling;

public abstract class MutableStack implements IDynamicStack {

    private E[] stack;
    private int index;
    private int size;

    public MutableStack(int argInitSize) {
        index = 0;
        stack = null;
        index = 0;
        extendStack(argInitSize);
    }

    private void extendStack(int argSize) {
        E[] newStack = newArray(argSize);
        if (stack != null) {
            System.arraycopy(stack, 0, newStack, 0, size);
        }
        for (int i = 0; i < newStack.length; i++) {
            newStack[i] = newInstance();
        }
        stack = newStack;
        size = newStack.length;
    }

    public final E pop() {
        if (index >= size) {
            extendStack(size * 2);
        }
        return stack[index++];
    }

    public final void push(E argObject) {
        assert (index > 0);
        stack[--index] = argObject;
    }

    /** Creates a new instance of the object contained by this stack. */
    protected abstract E newInstance();

    protected abstract E[] newArray(int size);
}