/*******************************************************************************
 * Copyright (c) 2013, Daniel Murphy
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 * 	* Redistributions of source code must retain the above copyright notice,
 * 	  this list of conditions and the following disclaimer.
 * 	* Redistributions in binary form must reproduce the above copyright notice,
 * 	  this list of conditions and the following disclaimer in the documentation
 * 	  and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 ******************************************************************************/
package org.jbox2d.pooling.normal;

import org.jbox2d.pooling.IDynamicStack;

public abstract class MutableStack<E> implements IDynamicStack<E> {

  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);
}