code: /*
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * 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 io.reactivex.rxjava3.internal.operators.observable;
  
  import java.util.*;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import io.reactivex.rxjava3.core.ObservableSource;
  import io.reactivex.rxjava3.core.Observer;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.Supplier;
  import io.reactivex.rxjava3.internal.disposables.*;
  import io.reactivex.rxjava3.internal.util.ExceptionHelper;
  
  public final class ObservableBuffer<T, U extends Collection<? super T>> extends AbstractObservableWithUpstream<T, U> {
      final int count;
      final int skip;
      final Supplier<U> bufferSupplier;
  
      public ObservableBuffer(ObservableSource<T> source, int count, int skip, Supplier<U> bufferSupplier) {
          super(source);
          this.count = count;
          this.skip = skip;
          this.bufferSupplier = bufferSupplier;
      }
  
      @Override
      protected void subscribeActual(Observer<? super U> t) {
          if (skip == count) {
              BufferExactObserver<T, U> bes = new BufferExactObserver<>(t, count, bufferSupplier);
              if (bes.createBuffer()) {
                  source.subscribe(bes);
              }
          } else {
              source.subscribe(new BufferSkipObserver<>(t, count, skip, bufferSupplier));
          }
      }
  
      static final class BufferExactObserver<T, U extends Collection<? super T>> implements Observer<T>, Disposable {
          final Observer<? super U> downstream;
          final int count;
          final Supplier<U> bufferSupplier;
          U buffer;
  
          int size;
  
          Disposable upstream;
  
          BufferExactObserver(Observer<? super U> actual, int count, Supplier<U> bufferSupplier) {
              this.downstream = actual;
              this.count = count;
              this.bufferSupplier = bufferSupplier;
          }
  
          boolean createBuffer() {
              U b;
              try {
                  b = Objects.requireNonNull(bufferSupplier.get(), "Empty buffer supplied");
              } catch (Throwable t) {
                  Exceptions.throwIfFatal(t);
                  buffer = null;
                  if (upstream == null) {
                      EmptyDisposable.error(t, downstream);
                  } else {
                      upstream.dispose();
                      downstream.onError(t);
                  }
                  return false;
              }
  
              buffer = b;
  
              return true;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void dispose() {
              upstream.dispose();
          }
  
          @Override
          public boolean isDisposed() {
              return upstream.isDisposed();
          }
  
          @Override
          public void onNext(T t) {
              U b = buffer;
              if (b != null) {
                  b.add(t);
  
                  if (++size >= count) {
                      downstream.onNext(b);
  
                      size = 0;
                      createBuffer();
                  }
              }
          }
  
          @Override
          public void onError(Throwable t) {
              buffer = null;
              downstream.onError(t);
          }
  
          @Override
          public void onComplete() {
              U b = buffer;
              if (b != null) {
                  buffer = null;
                  if (!b.isEmpty()) {
                      downstream.onNext(b);
                  }
                  downstream.onComplete();
              }
          }
      }
  
      static final class BufferSkipObserver<T, U extends Collection<? super T>>
      extends AtomicBoolean implements Observer<T>, Disposable {
  
          private static final long serialVersionUID = -8223395059921494546L;
          final Observer<? super U> downstream;
          final int count;
          final int skip;
          final Supplier<U> bufferSupplier;
  
          Disposable upstream;
  
          final ArrayDeque<U> buffers;
  
          long index;
  
          BufferSkipObserver(Observer<? super U> actual, int count, int skip, Supplier<U> bufferSupplier) {
              this.downstream = actual;
              this.count = count;
              this.skip = skip;
              this.bufferSupplier = bufferSupplier;
              this.buffers = new ArrayDeque<>();
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void dispose() {
              upstream.dispose();
          }
  
          @Override
          public boolean isDisposed() {
              return upstream.isDisposed();
          }
  
          @Override
          public void onNext(T t) {
              if (index++ % skip == 0) {
                  U b;
  
                  try {
                      b = ExceptionHelper.nullCheck(bufferSupplier.get(), "The bufferSupplier returned a null Collection.");
                  } catch (Throwable e) {
                      Exceptions.throwIfFatal(e);
                      buffers.clear();
                      upstream.dispose();
                      downstream.onError(e);
                      return;
                  }
  
                  buffers.offer(b);
              }
  
              Iterator<U> it = buffers.iterator();
              while (it.hasNext()) {
                  U b = it.next();
                  b.add(t);
                  if (count <= b.size()) {
                      it.remove();
  
                      downstream.onNext(b);
                  }
              }
          }
  
          @Override
          public void onError(Throwable t) {
              buffers.clear();
              downstream.onError(t);
          }
  
          @Override
          public void onComplete() {
              while (!buffers.isEmpty()) {
                  downstream.onNext(buffers.poll());
              }
              downstream.onComplete();
          }
      }
  }
  