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/*******************************************************************************
 * Copyright (c) 2013, Daniel Murphy
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without modification,
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 * 	  and/or other materials provided with the distribution.
 * 
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package org.jbox2d.pooling.normal;

import org.jbox2d.pooling.IDynamicStack;

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);
}