Change the license to GPL v3 to be compatible with Apache License 2.0.

HMCLAPI/src/main/java/rx/util/AtomicObservableSubscription.java

@@ -0,0 +1,74 @@
+/**
+ * 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.util;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.atomic.AtomicReference;
+
+import rx.Subscription;
+
+/**
+ * Thread-safe wrapper around Observable Subscription that ensures unsubscribe can be called only once.
+ * <p>
+ * Also used to:
+ * <p>
+ * <ul>
+ * <li>allow the AtomicObserver to have access to the subscription in asynchronous execution for checking if unsubscribed occurred without onComplete/onError.</li>
+ * <li>handle both synchronous and asynchronous subscribe() execution flows</li>
+ * </ul>
+ */
+public final class AtomicObservableSubscription implements Subscription {
+
+    private AtomicReference<Subscription> actualSubscription = new AtomicReference<Subscription>();
+    private AtomicBoolean unsubscribed = new AtomicBoolean(false);
+
+    public AtomicObservableSubscription() {
+
+    }
+
+    public AtomicObservableSubscription(Subscription actualSubscription) {
+        this.actualSubscription.set(actualSubscription);
+    }
+
+    /**
+     * Wraps the actual subscription once it exists (if it wasn't available when constructed)
+     * 
+     * @param actualSubscription
+     * @throws IllegalStateException
+     *             if trying to set more than once (or use this method after setting via constructor)
+     */
+    public AtomicObservableSubscription wrap(Subscription actualSubscription) {
+        if (!this.actualSubscription.compareAndSet(null, actualSubscription)) {
+            throw new IllegalStateException("Can not set subscription more than once.");
+        }
+        return this;
+    }
+
+    @Override
+    public void unsubscribe() {
+        // get the real thing and set to null in an atomic operation so we will only ever call unsubscribe once
+        Subscription actual = actualSubscription.getAndSet(null);
+        // if it's not null we will unsubscribe
+        if (actual != null) {
+            actual.unsubscribe();
+            unsubscribed.set(true);
+        }
+    }
+
+    public boolean isUnsubscribed() {
+        return unsubscribed.get();
+    }
+}