QPID-56

Also resolves a race condition where an messages could be sent out of order.
Modification of the Java ConcurrentLinkedQueue to provide a constant time size() method



git-svn-id: https://svn.apache.org/repos/asf/incubator/qpid/trunk/qpid@469424 13f79535-47bb-0310-9956-ffa450edef68

2 files changed, 90 insertions, 0 deletions

diff --git a/java/common/src/org/apache/qpid/util/ConcurrentLinkedQueueAtomicSize.java b/java/common/src/org/apache/qpid/util/ConcurrentLinkedQueueAtomicSize.java
new file mode 100644
index 0000000000..82a2ca0551
--- /dev/null
+++ b/java/common/src/org/apache/qpid/util/ConcurrentLinkedQueueAtomicSize.java
@@ -0,0 +1,55 @@
+/*
+ *
+ * Copyright (c) 2006 The Apache Software Foundation
+ *
+ * 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.
+ *
+ */
+package org.apache.qpid.util;
+
+import java.util.concurrent.ConcurrentLinkedQueue;
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class ConcurrentLinkedQueueAtomicSize<E> extends ConcurrentLinkedQueue<E>
+{
+    AtomicInteger _size = new AtomicInteger(0);
+
+    public int size()
+    {
+        return _size.get();
+    }
+
+    public boolean offer(E o)
+    {
+
+        if (super.offer(o))
+        {
+            _size.incrementAndGet();
+            return true;
+        }
+
+        return false;
+    }
+
+    public E poll()
+    {
+        E e = super.poll();
+
+        if (e != null)
+        {
+            _size.decrementAndGet();
+        }
+
+        return e;
+    }
+}
diff --git a/java/common/src/org/apache/qpid/util/ConcurrentLinkedQueueNoSize.java b/java/common/src/org/apache/qpid/util/ConcurrentLinkedQueueNoSize.java
new file mode 100644
index 0000000000..95cc225187
--- /dev/null
+++ b/java/common/src/org/apache/qpid/util/ConcurrentLinkedQueueNoSize.java
@@ -0,0 +1,35 @@
+/*
+ *
+ * Copyright (c) 2006 The Apache Software Foundation
+ *
+ * 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.
+ *
+ */
+package org.apache.qpid.util;
+
+import java.util.concurrent.ConcurrentLinkedQueue;
+
+public class ConcurrentLinkedQueueNoSize<E> extends ConcurrentLinkedQueue<E>
+{
+    public int size()
+    {
+        if (isEmpty())
+        {
+            return 0;
+        }
+        else
+        {
+            return 1;
+        }
+    }        
+}