Return null on getSubscription() when previously unsubscribed to match

initial contract

Author: jloisel

rxjava-core/src/main/java/rx/subscriptions/SerialSubscription.java

@@ -1,66 +1,62 @@
-/**
- * Copyright 2013 Netflix, Inc.
- * 
- * 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 rx.subscriptions;
-
-import static rx.subscriptions.Subscriptions.empty;
-
-import java.util.concurrent.atomic.AtomicReference;
-
-import rx.Subscription;
-
-/**
- * Represents a subscription whose underlying subscription can be swapped for another subscription
- * which causes the previous underlying subscription to be unsubscribed.
- * 
- * @see <a href="http://msdn.microsoft.com/en-us/library/system.reactive.disposables.serialdisposable(v=vs.103).aspx">Rx.Net equivalent SerialDisposable</a>
- */
-public class SerialSubscription implements Subscription {
-    private final AtomicReference<Subscription> reference = new AtomicReference<Subscription>(empty());
-    private volatile Subscription unsubscribe;
-    
-    private static final Subscription UNSUBSCRIBED = new Subscription() {
-        @Override
-        public void unsubscribe() {
-        }
-    };
-
-    @Override
-    public void unsubscribe() {
-        setSubscription(UNSUBSCRIBED);
-    }
-
-    public void setSubscription(final Subscription subscription) {
-        do {
-            final Subscription current = reference.get();
-            if (current == UNSUBSCRIBED) {
-                subscription.unsubscribe();
-                break;
-            }
-            if (reference.compareAndSet(current, subscription)) {
-                current.unsubscribe();
-                if(subscription == UNSUBSCRIBED) {
-                	unsubscribe = current;
-                }
-                break;
-            }
-        } while (true);
-    }
-    
-    public Subscription getSubscription() {
-    	Subscription subscription = reference.get();
-		return subscription == UNSUBSCRIBED ? unsubscribe : subscription;
-    }
-}
+/**
+ * Copyright 2013 Netflix, Inc.
+ * 
+ * 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 rx.subscriptions;
+
+import static rx.subscriptions.Subscriptions.empty;
+
+import java.util.concurrent.atomic.AtomicReference;
+
+import rx.Subscription;
+
+/**
+ * Represents a subscription whose underlying subscription can be swapped for another subscription
+ * which causes the previous underlying subscription to be unsubscribed.
+ * 
+ * @see <a href="http://msdn.microsoft.com/en-us/library/system.reactive.disposables.serialdisposable(v=vs.103).aspx">Rx.Net equivalent SerialDisposable</a>
+ */
+public class SerialSubscription implements Subscription {
+    private final AtomicReference<Subscription> reference = new AtomicReference<Subscription>(empty());
+    
+    private static final Subscription UNSUBSCRIBED = new Subscription() {
+        @Override
+        public void unsubscribe() {
+        }
+    };
+
+    @Override
+    public void unsubscribe() {
+        setSubscription(UNSUBSCRIBED);
+    }
+
+    public void setSubscription(final Subscription subscription) {
+        do {
+            final Subscription current = reference.get();
+            if (current == UNSUBSCRIBED) {
+                subscription.unsubscribe();
+                break;
+            }
+            if (reference.compareAndSet(current, subscription)) {
+                current.unsubscribe();
+                break;
+            }
+        } while (true);
+    }
+    
+    public Subscription getSubscription() {
+        final Subscription subscription = reference.get();
+        return subscription == UNSUBSCRIBED ? null : subscription;
+    }
+}