1/*
2 * Copyright (c) 2003, 2006, 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
26package com.sun.jmx.remote.internal;
27
28import java.util.AbstractList;
29import java.util.Iterator;
30
31public class ArrayQueue<T> extends AbstractList<T> {
32    public ArrayQueue(int capacity) {
33        this.capacity = capacity + 1;
34        this.queue = newArray(capacity + 1);
35        this.head = 0;
36        this.tail = 0;
37    }
38
39    public void resize(int newcapacity) {
40        int size = size();
41        if (newcapacity < size)
42            throw new IndexOutOfBoundsException("Resizing would lose data");
43        newcapacity++;
44        if (newcapacity == this.capacity)
45            return;
46        T[] newqueue = newArray(newcapacity);
47        for (int i = 0; i < size; i++)
48            newqueue[i] = get(i);
49        this.capacity = newcapacity;
50        this.queue = newqueue;
51        this.head = 0;
52        this.tail = size;
53    }
54
55    @SuppressWarnings("unchecked")
56    private T[] newArray(int size) {
57        return (T[]) new Object[size];
58    }
59
60    public boolean add(T o) {
61        queue[tail] = o;
62        int newtail = (tail + 1) % capacity;
63        if (newtail == head)
64            throw new IndexOutOfBoundsException("Queue full");
65        tail = newtail;
66        return true; // we did add something
67    }
68
69    public T remove(int i) {
70        if (i != 0)
71            throw new IllegalArgumentException("Can only remove head of queue");
72        if (head == tail)
73            throw new IndexOutOfBoundsException("Queue empty");
74        T removed = queue[head];
75        queue[head] = null;
76        head = (head + 1) % capacity;
77        return removed;
78    }
79
80    public T get(int i) {
81        int size = size();
82        if (i < 0 || i >= size) {
83            final String msg = "Index " + i + ", queue size " + size;
84            throw new IndexOutOfBoundsException(msg);
85        }
86        int index = (head + i) % capacity;
87        return queue[index];
88    }
89
90    public int size() {
91        // Can't use % here because it's not mod: -3 % 2 is -1, not +1.
92        int diff = tail - head;
93        if (diff < 0)
94            diff += capacity;
95        return diff;
96    }
97
98    private int capacity;
99    private T[] queue;
100    private int head;
101    private int tail;
102}
103