1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 *
19 */
20 package org.apache.mina.util;
21
22 import java.io.Serializable;
23 import java.util.Arrays;
24
25 /**
26 * A unbounded stack with expiration.
27 *
28 * @author The Apache Directory Project (mina-dev@directory.apache.org)
29 * @version $Rev: 555855 $, $Date: 2007-07-13 12:19:00 +0900 (Fri, 13 Jul 2007) $
30 */
31 public class ExpiringStack implements Serializable {
32 private static final long serialVersionUID = 3546919169401434168L;
33
34 private static final int DEFAULT_CAPACITY = 4;
35
36 private Object[] items;
37
38 private long[] timestamps;
39
40 private int size = 0;
41
42 /**
43 * Construct a new, empty stack.
44 */
45 public ExpiringStack() {
46 items = new Object[DEFAULT_CAPACITY];
47 timestamps = new long[DEFAULT_CAPACITY];
48 }
49
50 /**
51 * Clears this stack.
52 */
53 public void clear() {
54 Arrays.fill(items, null);
55 size = 0;
56 }
57
58 /**
59 * Pops from this stack.
60 *
61 * @return <code>null</code>, if this stack is empty or the element is
62 * really <code>null</code>.
63 */
64 public Object pop() {
65 if (size == 0) {
66 return null;
67 }
68
69 int pos = size - 1;
70 Object ret = items[pos];
71 items[pos] = null;
72 size--;
73
74 return ret;
75 }
76
77 /**
78 * Push into this stack.
79 */
80 public void push(Object obj) {
81 if (size == items.length) {
82 // expand queue
83 final int oldLen = items.length;
84 Object[] tmpItems = new Object[oldLen * 2];
85 System.arraycopy(items, 0, tmpItems, 0, size);
86 long[] tmpTimestamps = new long[oldLen * 2];
87 System.arraycopy(timestamps, 0, tmpTimestamps, 0, size);
88 items = tmpItems;
89 timestamps = tmpTimestamps;
90 }
91
92 items[size] = obj;
93 timestamps[size] = System.currentTimeMillis();
94 size++;
95 }
96
97 public void remove(Object o) {
98 for (int i = size - 1; i >= 0; i--) {
99 if (items[i] == o) {
100 System.arraycopy(items, i + 1, items, i, size - i - 1);
101 System
102 .arraycopy(timestamps, i + 1, timestamps, i, size - i
103 - 1);
104 items[size - 1] = null;
105 size--;
106 break;
107 }
108 }
109 }
110
111 public void expireBefore(long time) {
112 int i;
113 for (i = 0; i < size; i++) {
114 if (timestamps[i] >= time) {
115 break;
116 }
117 }
118
119 if (i > 0) {
120 size -= i;
121 System.arraycopy(items, i, items, 0, size);
122 System.arraycopy(timestamps, i, timestamps, 0, size);
123 Arrays.fill(items, size, items.length, null);
124 }
125 }
126
127 /**
128 * Returns the first element of the stack.
129 *
130 * @return <code>null</code>, if the stack is empty, or the element is
131 * really <code>null</code>.
132 */
133 public Object first() {
134 if (size == 0) {
135 return null;
136 }
137
138 return items[size - 1];
139 }
140
141 public Object last() {
142 if (size == 0) {
143 return null;
144 }
145
146 return items[0];
147 }
148
149 /**
150 * Returns <code>true</code> if the stack is empty.
151 */
152 public boolean isEmpty() {
153 return (size == 0);
154 }
155
156 /**
157 * Returns the number of elements in the stack.
158 */
159 public int size() {
160 return size;
161 }
162 }
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