blob: a77277f29f354cc49e0cc963fc8d2af58f915c07 (
plain)
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
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
|
/*******************************************************************************
* ============LICENSE_START==================================================
* * org.onap.dmaap
* * ===========================================================================
* * Copyright © 2017 AT&T Intellectual Property. All rights reserved.
* * ===========================================================================
* * Licensed under the Apache License, Version 2.0 (the "License");
* * you may not use this file except in compliance with the License.
* * You may obtain a copy of the License at
* *
* * http://www.apache.org/licenses/LICENSE-2.0
* *
* * Unless required by applicable law or agreed to in writing, software
* * distributed under the License is distributed on an "AS IS" BASIS,
* * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* * See the License for the specific language governing permissions and
* * limitations under the License.
* * ============LICENSE_END====================================================
* *
* * ECOMP is a trademark and service mark of AT&T Intellectual Property.
* *
******************************************************************************/
package org.onap.dmaap.datarouter.node;
import java.util.HashSet;
import java.util.Iterator;
/**
* Manage a list of tasks to be executed when an event occurs. This makes the following guarantees:
* <ul>
* <li>Tasks can be safely added and removed in the middle of a run.</li>
* <li>No task will be returned more than once during a run.</li>
* <li>No task will be returned when it is not, at that moment, in the list of tasks.</li>
* <li>At the moment when next() returns null, all tasks on the list have been returned during the run.</li>
* <li>Initially and once next() returns null during a run, next() will continue to return null until startRun() is
* called.
* </ul>
*/
class TaskList {
private Iterator<Runnable> runlist;
private HashSet<Runnable> tasks = new HashSet<>();
private HashSet<Runnable> togo;
private HashSet<Runnable> sofar;
private HashSet<Runnable> added;
private HashSet<Runnable> removed;
/**
* Start executing the sequence of tasks.
*/
synchronized void startRun() {
sofar = new HashSet<>();
added = new HashSet<>();
removed = new HashSet<>();
togo = new HashSet<>(tasks);
runlist = togo.iterator();
}
/**
* Get the next task to execute.
*/
synchronized Runnable next() {
while (runlist != null) {
if (runlist.hasNext()) {
Runnable task = runlist.next();
if (addTaskToSoFar(task)) {
return task;
}
}
if (!added.isEmpty()) {
togo = added;
added = new HashSet<>();
removed.clear();
runlist = togo.iterator();
continue;
}
togo = null;
added = null;
removed = null;
sofar = null;
runlist = null;
}
return (null);
}
/**
* Add a task to the list of tasks to run whenever the event occurs.
*/
synchronized void addTask(Runnable task) {
if (runlist != null) {
added.add(task);
removed.remove(task);
}
tasks.add(task);
}
/**
* Remove a task from the list of tasks to run whenever the event occurs.
*/
synchronized void removeTask(Runnable task) {
if (runlist != null) {
removed.add(task);
added.remove(task);
}
tasks.remove(task);
}
private boolean addTaskToSoFar(Runnable task) {
if (removed.contains(task)) {
return false;
}
if (sofar.contains(task)) {
return false;
}
sofar.add(task);
return true;
}
}
|
