/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.flink.runtime.io.network;

import org.apache.flink.runtime.io.network.partition.ResultPartitionID;
import org.apache.flink.runtime.io.network.partition.ResultPartitionProvider;
import org.apache.flink.runtime.io.network.partition.consumer.InputChannel.BufferAndAvailability;
import org.apache.flink.runtime.io.network.partition.consumer.InputChannelID;

import java.io.IOException;

/**
 * Simple wrapper for the partition readerQueue iterator, which increments a
 * sequence number for each returned buffer and remembers the receiver ID.
 */
public interface NetworkSequenceViewReader {

	void requestSubpartitionView(
		ResultPartitionProvider partitionProvider,
		ResultPartitionID resultPartitionId,
		int subPartitionIndex) throws IOException;

	BufferAndAvailability getNextBuffer() throws IOException;

	/**
	 * The credits from consumer are added in incremental way.
	 *
	 * @param creditDeltas The credit deltas
	 */
	void addCredit(int creditDeltas);

	/**
	 * Resumes data consumption after an exactly once checkpoint.
	 */
	void resumeConsumption();

	/**
	 * Checks whether this reader is available or not.
	 *
	 * @return True if the reader is available.
	 */
	boolean isAvailable();

	boolean isRegisteredAsAvailable();

	/**
	 * Updates the value to indicate whether the reader is enqueued in the pipeline or not.
	 *
	 * @param isRegisteredAvailable True if this reader is already enqueued in the pipeline.
	 */
	void setRegisteredAsAvailable(boolean isRegisteredAvailable);

	boolean isReleased();

	void releaseAllResources() throws IOException;

	Throwable getFailureCause();

	InputChannelID getReceiverId();

	int getSequenceNumber();
}

@@ -1173,16 +1173,51 @@
 nelID;%0A%0A
+import javax.annotation.Nullable;%0A%0A
 import j
@@ -1604,16 +1604,27 @@
 ption;%0A%0A
+%09@Nullable%0A
 %09BufferA

Annotate NetworkSequenceViewReader#getNextBuffer as Nullable.