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

HMCLAPI/src/main/java/rx/operators/OperationTakeWhile.java

@@ -0,0 +1,131 @@
+/**
+ * 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.operators;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+import rx.Observable;
+import rx.Observer;
+import rx.Subscription;
+import rx.util.AtomicObservableSubscription;
+import rx.util.AtomicObserver;
+import rx.util.functions.Func1;
+import rx.util.functions.Func2;
+
+/**
+ * Returns values from an observable sequence as long as a specified condition is true, and then skips the remaining values.
+ */
+public final class OperationTakeWhile {
+
+    /**
+     * Returns a specified number of contiguous values from the start of an observable sequence.
+     * 
+     * @param items
+     * @param predicate
+     *            a function to test each source element for a condition
+     * @return
+     */
+    public static <T> Func1<Observer<T>, Subscription> takeWhile(final Observable<T> items, final Func1<T, Boolean> predicate) {
+        return takeWhileWithIndex(items, OperationTakeWhile.<T> skipIndex(predicate));
+    }
+
+    /**
+     * Returns values from an observable sequence as long as a specified condition is true, and then skips the remaining values.
+     * 
+     * @param items
+     * @param predicate
+     *            a function to test each element for a condition; the second parameter of the function represents the index of the source element; otherwise, false.
+     * @return
+     */
+    public static <T> Func1<Observer<T>, Subscription> takeWhileWithIndex(final Observable<T> items, final Func2<T, Integer, Boolean> predicate) {
+        // wrap in a Func so that if a chain is built up, then asynchronously subscribed to twice we will have 2 instances of Take<T> rather than 1 handing both, which is not thread-safe.
+        return new TakeWhile<T>(items, predicate)::call;
+    }
+
+    private static <T> Func2<T, Integer, Boolean> skipIndex(final Func1<T, Boolean> underlying) {
+        return (T input, Integer index) -> underlying.call(input);
+    }
+
+    /**
+     * This class is NOT thread-safe if invoked and referenced multiple times. In other words, don't subscribe to it multiple times from different threads.
+     * <p>
+     * It IS thread-safe from within it while receiving onNext events from multiple threads.
+     * <p>
+     * This should all be fine as long as it's kept as a private class and a new instance created from static factory method above.
+     * <p>
+     * Note how the takeWhileWithIndex() factory method above protects us from a single instance being exposed with the Observable wrapper handling the subscribe flow.
+     * 
+     * @param <T>
+     */
+    private static class TakeWhile<T> implements Func1<Observer<T>, Subscription> {
+        private final AtomicInteger counter = new AtomicInteger();
+        private final Observable<T> items;
+        private final Func2<T, Integer, Boolean> predicate;
+        private final AtomicObservableSubscription subscription = new AtomicObservableSubscription();
+
+        private TakeWhile(Observable<T> items, Func2<T, Integer, Boolean> predicate) {
+            this.items = items;
+            this.predicate = predicate;
+        }
+
+        @Override
+        public Subscription call(Observer<T> observer) {
+            return subscription.wrap(items.subscribe(new ItemObserver(observer)));
+        }
+
+        private class ItemObserver implements Observer<T> {
+            private final Observer<T> observer;
+
+            public ItemObserver(Observer<T> observer) {
+                // Using AtomicObserver because the unsubscribe, onCompleted, onError and error handling behavior
+                // needs "isFinished" logic to not send duplicated events
+                // The 'testTakeWhile1' and 'testTakeWhile2' tests fail without this.
+                this.observer = new AtomicObserver<>(subscription, observer);
+            }
+
+            @Override
+            public void onCompleted() {
+                observer.onCompleted();
+            }
+
+            @Override
+            public void onError(Exception e) {
+                observer.onError(e);
+            }
+
+            @Override
+            public void onNext(T args) {
+                Boolean isSelected;
+                try {
+                    isSelected = predicate.call(args, counter.getAndIncrement());
+                } catch (Exception e) {
+                    observer.onError(e);
+                    return;
+                }
+                if (isSelected) {
+                    observer.onNext(args);
+                } else {
+                    observer.onCompleted();
+                    // this will work if the sequence is asynchronous, it will have no effect on a synchronous observable
+                    subscription.unsubscribe();
+                }
+            }
+
+        }
+
+    }
+
+}