1 /*
   2  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package jdk.nashorn.internal;
  27 
  28 /**
  29  * Small helper class for fast int deques
  30  */
  31 public class IntDeque {
  32     private int[] deque = new int[16];
  33     private int nextFree = 0;
  34 
  35     /**
  36      * Push an int value
  37      * @param value value
  38      */
  39     public void push(final int value) {
  40         if (nextFree == deque.length) {
  41             final int[] newDeque = new int[nextFree * 2];
  42             System.arraycopy(deque, 0, newDeque, 0, nextFree);
  43             deque = newDeque;
  44         }
  45         deque[nextFree++] = value;
  46     }
  47 
  48     /**
  49      * Pop an int value
  50      * @return value
  51      */
  52     public int pop() {
  53         return deque[--nextFree];
  54     }
  55 
  56     /**
  57      * Peek
  58      * @return top value
  59      */
  60     public int peek() {
  61         return deque[nextFree - 1];
  62     }
  63 
  64     /**
  65      * Get the value of the top element and increment it.
  66      * @return top value
  67      */
  68     public int getAndIncrement() {
  69         return deque[nextFree - 1]++;
  70     }
  71 
  72     /**
  73      * Decrement the value of the top element and return it.
  74      * @return decremented top value
  75      */
  76     public int decrementAndGet() {
  77         return --deque[nextFree - 1];
  78     }
  79 
  80     /**
  81      * Check if deque is empty
  82      * @return true if empty
  83      */
  84     public boolean isEmpty() {
  85         return nextFree == 0;
  86     }
  87 }