2.x: first step switching to the reduced-allocation architecture (#4030)

Author: akarnokd

src/main/java/io/reactivex/Completable.java

@@ -37,7 +37,7 @@
  * 
  * The class follows a similar event pattern as Reactive-Streams: onSubscribe (onError|onComplete)?
  */
-public class Completable {
+public abstract class Completable {
     /**
      * Callback used for building deferred computations that takes a CompletableSubscriber.
      */
@@ -386,7 +386,7 @@ public static Completable create(CompletableOnSubscribe onSubscribe) {
         try {
             // TODO plugin wrapping onSubscribe
 
-            return new Completable(onSubscribe);
+            return new CompletableWrapper(onSubscribe);
         } catch (NullPointerException ex) {
             throw ex;
         } catch (Throwable ex) {
@@ -986,18 +986,6 @@ public void dispose() {
         });
     }
 
-    /** The actual subscription action. */
-    private final CompletableOnSubscribe onSubscribe;
-    
-    /**
-     * Constructs a Completable instance with the given onSubscribe callback.
-     * @param onSubscribe the callback that will receive CompletableSubscribers when they subscribe,
-     * not null (not verified)
-     */
-    protected Completable(CompletableOnSubscribe onSubscribe) {
-        this.onSubscribe = onSubscribe;
-    }
-    
     /**
      * Returns a Completable that emits the a terminated event of either this Completable
      * or the other Completable whichever fires first.
@@ -1929,14 +1917,16 @@ public final void subscribe(CompletableSubscriber s) {
         try {
             // TODO plugin wrapping the subscriber
 
-            onSubscribe.accept(s);
+            subscribeActual(s);
         } catch (NullPointerException ex) {
             throw ex;
         } catch (Throwable ex) {
             RxJavaPlugins.onError(ex);
             throw toNpe(ex);
         }
     }
+    
+    protected abstract void subscribeActual(CompletableSubscriber s);
 
     /**
      * Subscribes to this Completable and calls back either the onError or onComplete functions.

src/main/java/io/reactivex/Flowable.java

@@ -32,7 +32,7 @@
 import io.reactivex.schedulers.*;
 import io.reactivex.subscribers.*;
 
-public class Flowable<T> implements Publisher<T> {
+public abstract class Flowable<T> implements Publisher<T> {
     /**
      * Interface to map/wrap a downstream subscriber to an upstream subscriber.
      *
@@ -385,7 +385,7 @@ public static <T> Flowable<T> concatArray(Publisher<? extends T>... sources) {
     public static <T> Flowable<T> create(Publisher<T> onSubscribe) {
         Objects.requireNonNull(onSubscribe, "onSubscribe is null");
         onSubscribe = RxJavaPlugins.onCreate(onSubscribe);
-        return new Flowable<T>(onSubscribe);
+        return fromPublisher(onSubscribe);
     }
 
     @BackpressureSupport(BackpressureKind.PASS_THROUGH)
@@ -497,12 +497,7 @@ public static <T> Flowable<T> fromPublisher(final Publisher<? extends T> publish
         }
         Objects.requireNonNull(publisher, "publisher is null");
 
-        return create(new Publisher<T>() {
-            @Override
-            public void subscribe(Subscriber<? super T> s) {
-                publisher.subscribe(s);
-            }
-        });
+        return new FlowableWrapper<T>(publisher);
     }
 
     @BackpressureSupport(BackpressureKind.FULL)
@@ -1160,12 +1155,6 @@ public static <T, R> Flowable<R> zipIterable(Function<? super Object[], ? extend
         return create(new PublisherZip<T, R>(null, sources, zipper, bufferSize, delayError));
     }
 
-    final Publisher<T> onSubscribe;
-    
-    protected Flowable(Publisher<T> onSubscribe) {
-        this.onSubscribe = onSubscribe;
-    }
-    
     @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
     @SchedulerSupport(SchedulerKind.NONE)
     public final Flowable<Boolean> all(Predicate<? super T> predicate) {
@@ -2162,7 +2151,7 @@ public final Flowable<T> last(T defaultValue) {
     public final <R> Flowable<R> lift(Operator<? extends R, ? super T> lifter) {
         Objects.requireNonNull(lifter, "lifter is null");
         // using onSubscribe so the fusing has access to the underlying raw Publisher
-        return create(new PublisherLift<R, T>(onSubscribe, lifter));
+        return create(new PublisherLift<R, T>(this, lifter));
     }
 
     @BackpressureSupport(BackpressureKind.PASS_THROUGH)
@@ -2939,18 +2928,14 @@ public final Disposable subscribe(Consumer<? super T> onNext, Consumer<? super T
     @Override
     public final void subscribe(Subscriber<? super T> s) {
         Objects.requireNonNull(s, "s is null");
-        subscribeActual(s);
-    }
-    
-    private void subscribeActual(Subscriber<? super T> s) {
         try {
             s = RxJavaPlugins.onSubscribe(s);
 
             if (s == null) {
                 throw new NullPointerException("Plugin returned null Subscriber");
             }
 
-            onSubscribe.subscribe(s);
+            subscribeActual(s);
         } catch (NullPointerException e) {
             throw e;
         } catch (Throwable e) {
@@ -2965,6 +2950,8 @@ private void subscribeActual(Subscriber<? super T> s) {
         }
     }
 
+    protected abstract void subscribeActual(Subscriber<? super T> s);
+    
     @BackpressureSupport(BackpressureKind.PASS_THROUGH)
     @SchedulerSupport(SchedulerKind.CUSTOM)
     public final Flowable<T> subscribeOn(Scheduler scheduler) {

src/main/java/io/reactivex/Observable.java

@@ -38,7 +38,7 @@
  * Observable for delivering a sequence of values without backpressure. 
  * @param <T>
  */
-public class Observable<T> {
+public abstract class Observable<T> {
 
     public interface NbpOnSubscribe<T> extends Consumer<Observer<? super T>> {
 
@@ -358,7 +358,7 @@ public static <T> Observable<T> concatArray(Observable<? extends T>... sources)
     public static <T> Observable<T> create(NbpOnSubscribe<T> onSubscribe) {
         Objects.requireNonNull(onSubscribe, "onSubscribe is null");
         // TODO plugin wrapper
-        return new Observable<T>(onSubscribe);
+        return new ObservableWrapper<T>(onSubscribe);
     }
 
     @SchedulerSupport(SchedulerKind.NONE)
@@ -1089,12 +1089,6 @@ public static <T, R> Observable<R> zipIterable(Function<? super Object[], ? exte
     }
 
 
-    protected final NbpOnSubscribe<T> onSubscribe;
-
-    protected Observable(NbpOnSubscribe<T> onSubscribe) {
-        this.onSubscribe = onSubscribe;
-    }
-
     @SchedulerSupport(SchedulerKind.NONE)
     public final Observable<Boolean> all(Predicate<? super T> predicate) {
         Objects.requireNonNull(predicate, "predicate is null");
@@ -2634,10 +2628,15 @@ public final Disposable subscribe(Consumer<? super T> onNext, Consumer<? super T
         return ls;
     }
 
-    public final void subscribe(Observer<? super T> subscriber) {
-        Objects.requireNonNull(subscriber, "subscriber is null");
-        onSubscribe.accept(subscriber);
+    public final void subscribe(Observer<? super T> observer) {
+        Objects.requireNonNull(observer, "observer is null");
+        
+        // TODO plugin wrappings
+        
+        subscribeActual(observer);
     }
+    
+    protected abstract void subscribeActual(Observer<? super T> observer);
 
     @SchedulerSupport(SchedulerKind.CUSTOM)
     public final Observable<T> subscribeOn(Scheduler scheduler) {

src/main/java/io/reactivex/Single.java

@@ -36,7 +36,7 @@
  * 
  * @param <T> the value type
  */
-public class Single<T> {
+public abstract class Single<T> {
 
     public interface SingleOnSubscribe<T> extends Consumer<SingleSubscriber<? super T>> {
 
@@ -356,7 +356,7 @@ public static <T> Flowable<T> concat(
     public static <T> Single<T> create(SingleOnSubscribe<T> onSubscribe) {
         Objects.requireNonNull(onSubscribe, "onSubscribe is null");
         // TODO plugin wrapper
-        return new Single<T>(onSubscribe);
+        return new SingleWrapper<T>(onSubscribe);
     }
 
     public static <T> Single<T> defer(final Supplier<? extends Single<? extends T>> singleSupplier) {
@@ -1003,12 +1003,6 @@ public static <T, R> Single<R> zipArray(Function<? super Object[], ? extends R>
         return Flowable.zipArray(zipper, false, 1, sourcePublishers).toSingle();
     }
 
-    protected final SingleOnSubscribe<T> onSubscribe;
-
-    protected Single(SingleOnSubscribe<T> onSubscribe) {
-        this.onSubscribe = onSubscribe;
-    }
-
     @SuppressWarnings("unchecked")
     public final Single<T> ambWith(Single<? extends T> other) {
         Objects.requireNonNull(other, "other is null");
@@ -1374,7 +1368,7 @@ public void accept(SingleSubscriber<? super R> s) {
                         throw new NullPointerException("The onLift returned a null subscriber");
                     }
                     // TODO plugin wrapper
-                    onSubscribe.accept(sr);
+                    subscribe(sr);
                 } catch (NullPointerException ex) {
                     throw ex;
                 } catch (Throwable ex) {
@@ -1690,9 +1684,11 @@ public void onSuccess(T value) {
     public final void subscribe(SingleSubscriber<? super T> subscriber) {
         Objects.requireNonNull(subscriber, "subscriber is null");
         // TODO plugin wrapper
-        onSubscribe.accept(subscriber);
+        subscribeActual(subscriber);
     }
 
+    protected abstract void subscribeActual(SingleSubscriber<? super T> subscriber);
+    
     public final void subscribe(Subscriber<? super T> s) {
         toFlowable().subscribe(s);
     }

src/main/java/io/reactivex/flowables/ConnectableFlowable.java

@@ -36,10 +36,6 @@
  */
 public abstract class ConnectableFlowable<T> extends Flowable<T> {
 
-    protected ConnectableFlowable(Publisher<T> onSubscribe) {
-        super(onSubscribe);
-    }
-    
     /**
      * Instructs the {@code ConnectableObservable} to begin emitting the items from its underlying
      * {@link Flowable} to its {@link Subscriber}s.

src/main/java/io/reactivex/flowables/GroupedFlowable.java

@@ -12,14 +12,11 @@
  */
 package io.reactivex.flowables;
 
-import org.reactivestreams.Publisher;
-
 import io.reactivex.Flowable;
 
-public class GroupedFlowable<K, T> extends Flowable<T> {
+public abstract class GroupedFlowable<K, T> extends Flowable<T> {
     final K key;
-    protected GroupedFlowable(Publisher<T> onSubscribe, K key) {
-        super(onSubscribe);
+    protected GroupedFlowable(K key) {
         this.key = key;
     }
 

src/main/java/io/reactivex/internal/operators/completable/CompletableWrapper.java

@@ -0,0 +1,17 @@
+package io.reactivex.internal.operators.completable;
+
+import io.reactivex.Completable;
+
+public final class CompletableWrapper extends Completable {
+
+    final CompletableOnSubscribe onSubscribe;
+
+    public CompletableWrapper(CompletableOnSubscribe onSubscribe) {
+        this.onSubscribe = onSubscribe;
+    }
+    
+    @Override
+    protected void subscribeActual(CompletableSubscriber s) {
+        onSubscribe.accept(s);
+    }
+}

src/main/java/io/reactivex/internal/operators/flowable/CachedObservable.java

@@ -33,6 +33,7 @@ public final class CachedObservable<T> extends Flowable<T> {
     /** The cache and replay state. */
     private CacheState<T> state;
 
+    private final AtomicBoolean once;
     /**
      * Creates a cached Observable with a default capacity hint of 16.
      * @param <T> the value type
@@ -55,21 +56,35 @@ public static <T> CachedObservable<T> from(Flowable<? extends T> source, int cap
             throw new IllegalArgumentException("capacityHint > 0 required");
         }
         CacheState<T> state = new CacheState<T>(source, capacityHint);
-        CachedSubscribe<T> onSubscribe = new CachedSubscribe<T>(state);
-        return new CachedObservable<T>(onSubscribe, state);
+        return new CachedObservable<T>(state);
     }
 
     /**
      * Private constructor because state needs to be shared between the Observable body and
      * the onSubscribe function.
-     * @param onSubscribe
      * @param state
      */
-    private CachedObservable(Publisher<T> onSubscribe, CacheState<T> state) {
-        super(onSubscribe);
+    private CachedObservable(CacheState<T> state) {
         this.state = state;
+        this.once = new AtomicBoolean();
     }
 
+    @Override
+    protected void subscribeActual(Subscriber<? super T> t) {
+        // we can connect first because we replay everything anyway
+        ReplaySubscription<T> rp = new ReplaySubscription<T>(t, state);
+        state.addProducer(rp);
+        
+        t.onSubscribe(rp);
+
+        // we ensure a single connection here to save an instance field of AtomicBoolean in state.
+        if (!once.get() && once.compareAndSet(false, true)) {
+            state.connect();
+        }
+        
+        // no need to call rp.replay() here because the very first request will trigger it anyway
+    }
+    
     /**
      * Check if this cached observable is connected to its source.
      * @return true if already connected
@@ -222,35 +237,6 @@ void dispatch() {
         }
     }
 
-    /**
-     * Manages the subscription of child subscribers by setting up a replay producer and
-     * performs auto-connection of the very first subscription.
-     * @param <T> the value type emitted
-     */
-    static final class CachedSubscribe<T> extends AtomicBoolean implements Publisher<T> {
-        /** */
-        private static final long serialVersionUID = -2817751667698696782L;
-        final CacheState<T> state;
-        public CachedSubscribe(CacheState<T> state) {
-            this.state = state;
-        }
-        @Override
-        public void subscribe(Subscriber<? super T> t) {
-            // we can connect first because we replay everything anyway
-            ReplaySubscription<T> rp = new ReplaySubscription<T>(t, state);
-            state.addProducer(rp);
-            
-            t.onSubscribe(rp);
-
-            // we ensure a single connection here to save an instance field of AtomicBoolean in state.
-            if (!get() && compareAndSet(false, true)) {
-                state.connect();
-            }
-            
-            // no need to call rp.replay() here because the very first request will trigger it anyway
-        }
-    }
-    
     /**
      * Keeps track of the current request amount and the replay position for a child Subscriber.
      *

src/main/java/io/reactivex/internal/operators/flowable/FlowableWrapper.java

@@ -0,0 +1,18 @@
+package io.reactivex.internal.operators.flowable;
+
+import org.reactivestreams.*;
+
+import io.reactivex.Flowable;
+
+public final class FlowableWrapper<T> extends Flowable<T> {
+    final Publisher<? extends T> publisher;
+
+    public FlowableWrapper(Publisher<? extends T> publisher) {
+        this.publisher = publisher;
+    }
+    
+    @Override
+    protected void subscribeActual(Subscriber<? super T> s) {
+        publisher.subscribe(s);
+    }
+}