Update project structure to org.onap

[dmaap/datarouter.git] / datarouter-node / src / main / java / org / onap / dmaap / datarouter / node / TaskList.java

diff --git a/datarouter-node/src/main/java/org/onap/dmaap/datarouter/node/TaskList.java b/datarouter-node/src/main/java/org/onap/dmaap/datarouter/node/TaskList.java
new file mode 100644 (file)
index 0000000..c8d58e6
--- /dev/null
+++ b/datarouter-node/src/main/java/org/onap/dmaap/datarouter/node/TaskList.java
@@ -0,0 +1,113 @@
+/*******************************************************************************\r
+ * ============LICENSE_START==================================================\r
+ * * org.onap.dmaap\r
+ * * ===========================================================================\r
+ * * Copyright © 2017 AT&T Intellectual Property. All rights reserved.\r
+ * * ===========================================================================\r
+ * * Licensed under the Apache License, Version 2.0 (the "License");\r
+ * * you may not use this file except in compliance with the License.\r
+ * * You may obtain a copy of the License at\r
+ * * \r
+ *  *      http://www.apache.org/licenses/LICENSE-2.0\r
+ * * \r
+ *  * Unless required by applicable law or agreed to in writing, software\r
+ * * distributed under the License is distributed on an "AS IS" BASIS,\r
+ * * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\r
+ * * See the License for the specific language governing permissions and\r
+ * * limitations under the License.\r
+ * * ============LICENSE_END====================================================\r
+ * *\r
+ * * ECOMP is a trademark and service mark of AT&T Intellectual Property.\r
+ * *\r
+ ******************************************************************************/\r
+\r
+\r
+package org.onap.dmaap.datarouter.node;\r
+\r
+import java.util.*;\r
+\r
+/**\r
+ *     Manage a list of tasks to be executed when an event occurs.\r
+ *     This makes the following guarantees:\r
+ *     <ul>\r
+ *     <li>Tasks can be safely added and removed in the middle of a run.</li>\r
+ *     <li>No task will be returned more than once during a run.</li>\r
+ *     <li>No task will be returned when it is not, at that moment, in the list of tasks.</li>\r
+ *     <li>At the moment when next() returns null, all tasks on the list have been returned during the run.</li>\r
+ *     <li>Initially and once next() returns null during a run, next() will continue to return null until startRun() is called.\r
+ *     </ul>\r
+ */\r
+public class TaskList  {\r
+       private Iterator<Runnable>      runlist;\r
+       private HashSet<Runnable>       tasks = new HashSet<Runnable>();\r
+       private HashSet<Runnable>       togo;\r
+       private HashSet<Runnable>       sofar;\r
+       private HashSet<Runnable>       added;\r
+       private HashSet<Runnable>       removed;\r
+       /**\r
+        *      Construct a new TaskList\r
+        */\r
+       public TaskList() {\r
+       }\r
+       /**\r
+        *      Start executing the sequence of tasks.\r
+        */\r
+       public synchronized void        startRun() {\r
+               sofar = new HashSet<Runnable>();\r
+               added = new HashSet<Runnable>();\r
+               removed = new HashSet<Runnable>();\r
+               togo = new HashSet<Runnable>(tasks);\r
+               runlist = togo.iterator();\r
+       }\r
+       /**\r
+        *      Get the next task to execute\r
+        */\r
+       public synchronized Runnable    next() {\r
+               while (runlist != null) {\r
+                       if (runlist.hasNext()) {\r
+                               Runnable task = runlist.next();\r
+                               if (removed.contains(task)) {\r
+                                       continue;\r
+                               }\r
+                               if (sofar.contains(task)) {\r
+                                       continue;\r
+                               }\r
+                               sofar.add(task);\r
+                               return(task);\r
+                       }\r
+                       if (added.size() != 0) {\r
+                               togo = added;\r
+                               added = new HashSet<Runnable>();\r
+                               removed.clear();\r
+                               runlist = togo.iterator();\r
+                               continue;\r
+                       }\r
+                       togo = null;\r
+                       added = null;\r
+                       removed = null;\r
+                       sofar = null;\r
+                       runlist = null;\r
+               }\r
+               return(null);\r
+       }\r
+       /**\r
+        *      Add a task to the list of tasks to run whenever the event occurs.\r
+        */\r
+       public synchronized void addTask(Runnable task) {\r
+               if (runlist != null) {\r
+                       added.add(task);\r
+                       removed.remove(task);\r
+               }\r
+               tasks.add(task);\r
+       }\r
+       /**\r
+        *      Remove a task from the list of tasks to run whenever the event occurs.\r
+        */\r
+       public synchronized void removeTask(Runnable task) {\r
+               if (runlist != null) {\r
+                       removed.add(task);\r
+                       added.remove(task);\r
+               }\r
+               tasks.remove(task);\r
+       }\r
+}\r