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/*
 * FXGL - JavaFX Game Library. The MIT License (MIT).
 * Copyright (c) AlmasB ([email protected]).
 * See LICENSE for details.
 */
/**
 * Created at 12:52:04 AM Jan 20, 2011
 */
package com.almasb.fxgl.physics.box2d.pooling;

/**
 * @author Daniel Murphy
 */
public abstract class OrderedStack {

    private final Object[] pool;
    private int index;
    private final int size;
    private final Object[] container;

    public OrderedStack(int argStackSize, int argContainerSize) {
        size = argStackSize;
        pool = new Object[argStackSize];
        for (int i = 0; i < argStackSize; i++) {
            pool[i] = newInstance();
        }
        index = 0;
        container = new Object[argContainerSize];
    }

    @SuppressWarnings("unchecked")
    public final E pop() {
        assert index < size : "End of stack reached, there is probably a leak somewhere";
        return (E) pool[index++];
    }

    @SuppressWarnings("unchecked")
    public final E[] pop(int argNum) {
        assert index + argNum < size : "End of stack reached, there is probably a leak somewhere";
        assert argNum <= container.length : "Container array is too small";
        System.arraycopy(pool, index, container, 0, argNum);
        index += argNum;
        return (E[]) container;
    }

    public final void push(int argNum) {
        index -= argNum;
        assert index >= 0 : "Beginning of stack reached, push/pops are unmatched";
    }

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