1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
/*******************************************************************************
* Copyright (c) 1997, 2008 by ProSyst Software GmbH
* http://www.prosyst.com
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* ProSyst Software GmbH - initial API and implementation
*******************************************************************************/
package org.eclipse.equinox.internal.util.event;
/**
* @author Pavlin Dobrev
* @version 1.0
*/
public class Queue {
protected Object[] queue;
protected int first, last = -1;
protected int initial, count;
protected int increment;
protected int decrement;
public Queue(int size) {
queue = new Object[initial = size];
increment = initial / 2;
decrement = increment + (increment / 2);
}
public void put(Object element) {
if (count == queue.length)
resize(true);
queue[++last == queue.length ? last = 0 : last] = element;
count++;
}
public void unget(Object element) {
if (count == queue.length)
resize(true);
queue[--first == -1 ? first = queue.length - 1 : first] = element;
count++;
}
public Object get() {
if (count == 0)
return null;
if (queue.length > initial && queue.length - count > decrement)
resize(false);
Object element = queue[first];
queue[first++] = null;
if (first == queue.length)
first = 0;
count--;
return element;
}
public void clear() {
if (queue.length > initial) {
queue = new Object[initial];
count = 0;
} else
for (; count > 0; count--) {
queue[first++] = null;
if (first == queue.length)
first = 0;
}
first = 0;
last = -1;
}
public int size() {
return count;
}
protected void resize(boolean up) {
Object[] tmp = new Object[queue.length + (up ? increment : -increment)];
if (first <= last)
System.arraycopy(queue, first, tmp, 0, count);
else {
int count1 = queue.length - first;
if (count1 > 0)
System.arraycopy(queue, first, tmp, 0, count1);
if (count > count1)
System.arraycopy(queue, 0, tmp, count1, count - count1);
}
queue = tmp;
first = 0;
last = count - 1;
increment = queue.length / 2;
decrement = increment + (increment / 2);
}
}
|
