https://github.com/spring-projects/spring-framework: Spring Core (Spring IO)
  • Juergen Hoeller 
/*
 * Copyright 2002-2018 the original author or authors.
 *
 * 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 org.springframework.core.io.buffer;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousFileChannel;
import java.nio.channels.Channel;
import java.nio.channels.Channels;
import java.nio.channels.CompletionHandler;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import java.nio.file.StandardOpenOption;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Consumer;

import org.reactivestreams.Publisher;
import org.reactivestreams.Subscription;
import reactor.core.publisher.BaseSubscriber;
import reactor.core.publisher.Flux;
import reactor.core.publisher.FluxSink;
import reactor.core.publisher.Mono;
import reactor.core.publisher.SynchronousSink;

import org.springframework.core.io.Resource;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;


Utility class for working with DataBuffers. 
Author:Arjen Poutsma, Brian Clozel
Since:5.0
/**
 * Utility class for working with {@link DataBuffer DataBuffers}.
 *
 * @author Arjen Poutsma
 * @author Brian Clozel
 * @since 5.0
 */
public abstract class DataBufferUtils {

	private static final Consumer<DataBuffer> RELEASE_CONSUMER = DataBufferUtils::release;


	//---------------------------------------------------------------------
	// Reading
	//---------------------------------------------------------------------

	
Obtain a InputStream from the given supplier, and read it into a Flux of DataBuffers. Closes the input stream when the flux is terminated. 
Params:
  • inputStreamSupplier – the supplier for the input stream to read from
  • dataBufferFactory – the factory to create data buffers with
  • bufferSize – the maximum size of the data buffers
Returns:a flux of data buffers read from the given channel
/**
	 * Obtain a {@link InputStream} from the given supplier, and read it into a {@code Flux}
	 * of {@code DataBuffer}s. Closes the input stream when the flux is terminated.
	 * @param inputStreamSupplier the supplier for the input stream to read from
	 * @param dataBufferFactory the factory to create data buffers with
	 * @param bufferSize the maximum size of the data buffers
	 * @return a flux of data buffers read from the given channel
	 */
	public static Flux<DataBuffer> readInputStream(
			Callable<InputStream> inputStreamSupplier, DataBufferFactory dataBufferFactory, int bufferSize) {

		Assert.notNull(inputStreamSupplier, "'inputStreamSupplier' must not be null");

		return readByteChannel(() -> Channels.newChannel(inputStreamSupplier.call()), dataBufferFactory, bufferSize);
	}

	
Obtain a ReadableByteChannel from the given supplier, and read it into a Flux of DataBuffers. Closes the channel when the flux is terminated. 
Params:
  • channelSupplier – the supplier for the channel to read from
  • dataBufferFactory – the factory to create data buffers with
  • bufferSize – the maximum size of the data buffers
Returns:a flux of data buffers read from the given channel
/**
	 * Obtain a {@link ReadableByteChannel} from the given supplier, and read it into a
	 * {@code Flux} of {@code DataBuffer}s. Closes the channel when the flux is terminated.
	 * @param channelSupplier the supplier for the channel to read from
	 * @param dataBufferFactory the factory to create data buffers with
	 * @param bufferSize the maximum size of the data buffers
	 * @return a flux of data buffers read from the given channel
	 */
	public static Flux<DataBuffer> readByteChannel(
			Callable<ReadableByteChannel> channelSupplier, DataBufferFactory dataBufferFactory, int bufferSize) {

		Assert.notNull(channelSupplier, "'channelSupplier' must not be null");
		Assert.notNull(dataBufferFactory, "'dataBufferFactory' must not be null");
		Assert.isTrue(bufferSize > 0, "'bufferSize' must be > 0");

		return Flux.using(channelSupplier,
				channel -> {
					ReadableByteChannelGenerator generator =
							new ReadableByteChannelGenerator(channel, dataBufferFactory,
									bufferSize);
					return Flux.generate(generator);
				},
				DataBufferUtils::closeChannel)
				.doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release);
	}

	
Obtain a AsynchronousFileChannel from the given supplier, and read it into a Flux of DataBuffers. Closes the channel when the flux is terminated. 
Params:
  • channelSupplier – the supplier for the channel to read from
  • dataBufferFactory – the factory to create data buffers with
  • bufferSize – the maximum size of the data buffers
Returns:a flux of data buffers read from the given channel
/**
	 * Obtain a {@code AsynchronousFileChannel} from the given supplier, and read it into a
	 * {@code Flux} of {@code DataBuffer}s. Closes the channel when the flux is terminated.
	 * @param channelSupplier the supplier for the channel to read from
	 * @param dataBufferFactory the factory to create data buffers with
	 * @param bufferSize the maximum size of the data buffers
	 * @return a flux of data buffers read from the given channel
	 */
	public static Flux<DataBuffer> readAsynchronousFileChannel(
			Callable<AsynchronousFileChannel> channelSupplier, DataBufferFactory dataBufferFactory, int bufferSize) {

		return readAsynchronousFileChannel(channelSupplier, 0, dataBufferFactory, bufferSize);
	}

	
Obtain a AsynchronousFileChannel from the given supplier, and read it into a Flux of DataBuffers, starting at the given position. Closes the channel when the flux is terminated. 
Params:
  • channelSupplier – the supplier for the channel to read from
  • position – the position to start reading from
  • dataBufferFactory – the factory to create data buffers with
  • bufferSize – the maximum size of the data buffers
Returns:a flux of data buffers read from the given channel
/**
	 * Obtain a {@code AsynchronousFileChannel} from the given supplier, and read it into a
	 * {@code Flux} of {@code DataBuffer}s, starting at the given position. Closes the
	 * channel when the flux is terminated.
	 * @param channelSupplier the supplier for the channel to read from
	 * @param position the position to start reading from
	 * @param dataBufferFactory the factory to create data buffers with
	 * @param bufferSize the maximum size of the data buffers
	 * @return a flux of data buffers read from the given channel
	 */
	public static Flux<DataBuffer> readAsynchronousFileChannel(Callable<AsynchronousFileChannel> channelSupplier,
			long position, DataBufferFactory dataBufferFactory, int bufferSize) {

		Assert.notNull(channelSupplier, "'channelSupplier' must not be null");
		Assert.notNull(dataBufferFactory, "'dataBufferFactory' must not be null");
		Assert.isTrue(position >= 0, "'position' must be >= 0");
		Assert.isTrue(bufferSize > 0, "'bufferSize' must be > 0");

		DataBuffer dataBuffer = dataBufferFactory.allocateBuffer(bufferSize);
		ByteBuffer byteBuffer = dataBuffer.asByteBuffer(0, bufferSize);

		Flux<DataBuffer> result = Flux.using(channelSupplier,
				channel -> Flux.create(sink -> {
					AsynchronousFileChannelReadCompletionHandler completionHandler =
							new AsynchronousFileChannelReadCompletionHandler(channel,
									sink, position, dataBufferFactory, bufferSize);
					channel.read(byteBuffer, position, dataBuffer, completionHandler);
					sink.onDispose(completionHandler::dispose);
				}),
				DataBufferUtils::closeChannel);

		return result.doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release);
	}

	
Read the given Resource into a Flux of DataBuffers. 
If the resource is a file, it is read into an AsynchronousFileChannel and turned to Flux via readAsynchronousFileChannel(Callable<AsynchronousFileChannel>, DataBufferFactory, int) or else fall back to readByteChannel(Callable<ReadableByteChannel>, DataBufferFactory, int). Closes the channel when the flux is terminated. 
Params:
  • resource – the resource to read from
  • dataBufferFactory – the factory to create data buffers with
  • bufferSize – the maximum size of the data buffers
Returns:a flux of data buffers read from the given channel
/**
	 * Read the given {@code Resource} into a {@code Flux} of {@code DataBuffer}s.
	 * <p>If the resource is a file, it is read into an
	 * {@code AsynchronousFileChannel} and turned to {@code Flux} via
	 * {@link #readAsynchronousFileChannel(Callable, DataBufferFactory, int)} or else
	 * fall back to {@link #readByteChannel(Callable, DataBufferFactory, int)}.
	 * Closes the channel when the flux is terminated.
	 * @param resource the resource to read from
	 * @param dataBufferFactory the factory to create data buffers with
	 * @param bufferSize the maximum size of the data buffers
	 * @return a flux of data buffers read from the given channel
	 */
	public static Flux<DataBuffer> read(
			Resource resource, DataBufferFactory dataBufferFactory, int bufferSize) {

		return read(resource, 0, dataBufferFactory, bufferSize);
	}

	
Read the given Resource into a Flux of DataBuffers starting at the given position. 
If the resource is a file, it is read into an AsynchronousFileChannel and turned to Flux via readAsynchronousFileChannel(Callable<AsynchronousFileChannel>, DataBufferFactory, int) or else fall back on readByteChannel(Callable<ReadableByteChannel>, DataBufferFactory, int). Closes the channel when the flux is terminated. 
Params:
  • resource – the resource to read from
  • position – the position to start reading from
  • dataBufferFactory – the factory to create data buffers with
  • bufferSize – the maximum size of the data buffers
Returns:a flux of data buffers read from the given channel
/**
	 * Read the given {@code Resource} into a {@code Flux} of {@code DataBuffer}s
	 * starting at the given position.
	 * <p>If the resource is a file, it is read into an
	 * {@code AsynchronousFileChannel} and turned to {@code Flux} via
	 * {@link #readAsynchronousFileChannel(Callable, DataBufferFactory, int)} or else
	 * fall back on {@link #readByteChannel(Callable, DataBufferFactory, int)}.
	 * Closes the channel when the flux is terminated.
	 * @param resource the resource to read from
	 * @param position the position to start reading from
	 * @param dataBufferFactory the factory to create data buffers with
	 * @param bufferSize the maximum size of the data buffers
	 * @return a flux of data buffers read from the given channel
	 */
	public static Flux<DataBuffer> read(
			Resource resource, long position, DataBufferFactory dataBufferFactory, int bufferSize) {

		try {
			if (resource.isFile()) {
				File file = resource.getFile();
				return readAsynchronousFileChannel(
						() -> AsynchronousFileChannel.open(file.toPath(), StandardOpenOption.READ),
						position, dataBufferFactory, bufferSize);
			}
		}
		catch (IOException ignore) {
			// fallback to resource.readableChannel(), below
		}

		Flux<DataBuffer> result = readByteChannel(resource::readableChannel, dataBufferFactory, bufferSize);
		return position == 0 ? result : skipUntilByteCount(result, position);
	}


	//---------------------------------------------------------------------
	// Writing
	//---------------------------------------------------------------------

	
Write the given stream of DataBuffers to the given OutputStream. Does not close the output stream when the flux is terminated, and does
not release the data buffers in the source. If releasing is required, then subscribe to the returned Flux with a releaseConsumer(). 
Note that the writing process does not start until the returned Flux is subscribed to. 
Params:
  • source – the stream of data buffers to be written
  • outputStream – the output stream to write to
Returns:a flux containing the same buffers as in source, that starts the writing process when subscribed to, and that publishes any writing errors and the completion signal
/**
	 * Write the given stream of {@link DataBuffer DataBuffers} to the given {@code OutputStream}. Does
	 * <strong>not</strong> close the output stream when the flux is terminated, and does
	 * <strong>not</strong> {@linkplain #release(DataBuffer) release} the data buffers in the
	 * source. If releasing is required, then subscribe to the returned {@code Flux} with a
	 * {@link #releaseConsumer()}.
	 * <p>Note that the writing process does not start until the returned {@code Flux} is subscribed to.
	 * @param source the stream of data buffers to be written
	 * @param outputStream the output stream to write to
	 * @return a flux containing the same buffers as in {@code source}, that starts the writing
	 * process when subscribed to, and that publishes any writing errors and the completion signal
	 */
	public static Flux<DataBuffer> write(Publisher<DataBuffer> source, OutputStream outputStream) {
		Assert.notNull(source, "'source' must not be null");
		Assert.notNull(outputStream, "'outputStream' must not be null");

		WritableByteChannel channel = Channels.newChannel(outputStream);
		return write(source, channel);
	}

	
Write the given stream of DataBuffers to the given WritableByteChannel. Does not close the channel when the flux is terminated, and does
not release the data buffers in the source. If releasing is required, then subscribe to the returned Flux with a releaseConsumer(). 
Note that the writing process does not start until the returned Flux is subscribed to. 
Params:
  • source – the stream of data buffers to be written
  • channel – the channel to write to
Returns:a flux containing the same buffers as in source, that starts the writing process when subscribed to, and that publishes any writing errors and the completion signal
/**
	 * Write the given stream of {@link DataBuffer DataBuffers} to the given {@code WritableByteChannel}. Does
	 * <strong>not</strong> close the channel when the flux is terminated, and does
	 * <strong>not</strong> {@linkplain #release(DataBuffer) release} the data buffers in the
	 * source. If releasing is required, then subscribe to the returned {@code Flux} with a
	 * {@link #releaseConsumer()}.
	 * <p>Note that the writing process does not start until the returned {@code Flux} is subscribed to.
	 * @param source the stream of data buffers to be written
	 * @param channel the channel to write to
	 * @return a flux containing the same buffers as in {@code source}, that starts the writing
	 * process when subscribed to, and that publishes any writing errors and the completion signal
	 */
	public static Flux<DataBuffer> write(Publisher<DataBuffer> source, WritableByteChannel channel) {
		Assert.notNull(source, "'source' must not be null");
		Assert.notNull(channel, "'channel' must not be null");

		Flux<DataBuffer> flux = Flux.from(source);
		return Flux.create(sink -> {
			WritableByteChannelSubscriber subscriber =
					new WritableByteChannelSubscriber(sink, channel);
			sink.onDispose(subscriber);
			flux.subscribe(subscriber);
		});
	}

	
Write the given stream of DataBuffers to the given AsynchronousFileChannel. Does not close the channel when the flux is terminated, and does
not release the data buffers in the source. If releasing is required, then subscribe to the returned Flux with a releaseConsumer(). 
Note that the writing process does not start until the returned Flux is subscribed to. 
Params:
  • source – the stream of data buffers to be written
  • channel – the channel to write to
Returns:a flux containing the same buffers as in source, that starts the writing process when subscribed to, and that publishes any writing errors and the completion signal
Since:5.0.10
/**
	 * Write the given stream of {@link DataBuffer DataBuffers} to the given {@code AsynchronousFileChannel}.
	 * Does <strong>not</strong> close the channel when the flux is terminated, and does
	 * <strong>not</strong> {@linkplain #release(DataBuffer) release} the data buffers in the
	 * source. If releasing is required, then subscribe to the returned {@code Flux} with a
	 * {@link #releaseConsumer()}.
	 * <p>Note that the writing process does not start until the returned {@code Flux} is subscribed to.
	 * @param source the stream of data buffers to be written
	 * @param channel the channel to write to
	 * @return a flux containing the same buffers as in {@code source}, that starts the writing
	 * process when subscribed to, and that publishes any writing errors and the completion signal
	 * @since 5.0.10
	 */
	public static Flux<DataBuffer> write(Publisher<DataBuffer> source, AsynchronousFileChannel channel) {
		return write(source, channel, 0);
	}

	
Write the given stream of DataBuffers to the given AsynchronousFileChannel. Does not close the channel when the flux is terminated, and does
not release the data buffers in the source. If releasing is required, then subscribe to the returned Flux with a releaseConsumer(). 
Note that the writing process does not start until the returned Flux is subscribed to. 
Params:
  • source – the stream of data buffers to be written
  • channel – the channel to write to
  • position – the file position at which the write is to begin; must be non-negative
Returns:a flux containing the same buffers as in source, that starts the writing process when subscribed to, and that publishes any writing errors and the completion signal
/**
	 * Write the given stream of {@link DataBuffer DataBuffers} to the given {@code AsynchronousFileChannel}.
	 * Does <strong>not</strong> close the channel when the flux is terminated, and does
	 * <strong>not</strong> {@linkplain #release(DataBuffer) release} the data buffers in the
	 * source. If releasing is required, then subscribe to the returned {@code Flux} with a
	 * {@link #releaseConsumer()}.
	 * <p>Note that the writing process does not start until the returned {@code Flux} is subscribed to.
	 * @param source the stream of data buffers to be written
	 * @param channel the channel to write to
	 * @param position the file position at which the write is to begin; must be non-negative
	 * @return a flux containing the same buffers as in {@code source}, that starts the writing
	 * process when subscribed to, and that publishes any writing errors and the completion signal
	 */
	public static Flux<DataBuffer> write(
			Publisher<DataBuffer> source, AsynchronousFileChannel channel, long position) {

		Assert.notNull(source, "'source' must not be null");
		Assert.notNull(channel, "'channel' must not be null");
		Assert.isTrue(position >= 0, "'position' must be >= 0");

		Flux<DataBuffer> flux = Flux.from(source);
		return Flux.create(sink -> {
			AsynchronousFileChannelWriteCompletionHandler completionHandler =
					new AsynchronousFileChannelWriteCompletionHandler(sink, channel, position);
			sink.onDispose(completionHandler);
			flux.subscribe(completionHandler);
		});
	}

	static void closeChannel(@Nullable Channel channel) {
		if (channel != null && channel.isOpen()) {
			try {
				channel.close();
			}
			catch (IOException ignored) {
			}
		}
	}


	//---------------------------------------------------------------------
	// Various
	//---------------------------------------------------------------------

	
Relay buffers from the given Publisher until the total byte count reaches the given maximum byte count, or until the publisher is complete. 
Params:
  • publisher – the publisher to filter
  • maxByteCount – the maximum byte count
Returns:a flux whose maximum byte count is maxByteCount
/**
	 * Relay buffers from the given {@link Publisher} until the total
	 * {@linkplain DataBuffer#readableByteCount() byte count} reaches
	 * the given maximum byte count, or until the publisher is complete.
	 * @param publisher the publisher to filter
	 * @param maxByteCount the maximum byte count
	 * @return a flux whose maximum byte count is {@code maxByteCount}
	 */
	public static Flux<DataBuffer> takeUntilByteCount(Publisher<DataBuffer> publisher, long maxByteCount) {
		Assert.notNull(publisher, "Publisher must not be null");
		Assert.isTrue(maxByteCount >= 0, "'maxByteCount' must be a positive number");

		return Flux.defer(() -> {
			AtomicLong countDown = new AtomicLong(maxByteCount);
			return Flux.from(publisher)
					.map(buffer -> {
						long remainder = countDown.addAndGet(-buffer.readableByteCount());
						if (remainder < 0) {
							int length = buffer.readableByteCount() + (int) remainder;
							return buffer.slice(0, length);
						}
						else {
							return buffer;
						}
					})
					.takeUntil(buffer -> countDown.get() <= 0);
		}); // no doOnDiscard necessary, as this method does not drop buffers
	}

	
Skip buffers from the given Publisher until the total byte count reaches the given maximum byte count, or until the publisher is complete. 
Params:
  • publisher – the publisher to filter
  • maxByteCount – the maximum byte count
Returns:a flux with the remaining part of the given publisher
/**
	 * Skip buffers from the given {@link Publisher} until the total
	 * {@linkplain DataBuffer#readableByteCount() byte count} reaches
	 * the given maximum byte count, or until the publisher is complete.
	 * @param publisher the publisher to filter
	 * @param maxByteCount the maximum byte count
	 * @return a flux with the remaining part of the given publisher
	 */
	public static Flux<DataBuffer> skipUntilByteCount(Publisher<DataBuffer> publisher, long maxByteCount) {
		Assert.notNull(publisher, "Publisher must not be null");
		Assert.isTrue(maxByteCount >= 0, "'maxByteCount' must be a positive number");

		return Flux.defer(() -> {
			AtomicLong countDown = new AtomicLong(maxByteCount);
			return Flux.from(publisher)
					.skipUntil(buffer -> {
						long remainder = countDown.addAndGet(-buffer.readableByteCount());
						return remainder < 0;
					})
					.map(buffer -> {
						long remainder = countDown.get();
						if (remainder < 0) {
							countDown.set(0);
							int start = buffer.readableByteCount() + (int)remainder;
							int length = (int) -remainder;
							return buffer.slice(start, length);
						}
						else {
							return buffer;
						}
					});
		}).doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release);
	}

	
Retain the given data buffer, it it is a PooledDataBuffer. 
Params:
  • dataBuffer – the data buffer to retain
Returns:the retained buffer
/**
	 * Retain the given data buffer, it it is a {@link PooledDataBuffer}.
	 * @param dataBuffer the data buffer to retain
	 * @return the retained buffer
	 */
	@SuppressWarnings("unchecked")
	public static <T extends DataBuffer> T retain(T dataBuffer) {
		if (dataBuffer instanceof PooledDataBuffer) {
			return (T) ((PooledDataBuffer) dataBuffer).retain();
		}
		else {
			return dataBuffer;
		}
	}

	
Release the given data buffer, if it is a PooledDataBuffer and has been allocated. 
Params:
  • dataBuffer – the data buffer to release
Returns:true if the buffer was released; false otherwise.
/**
	 * Release the given data buffer, if it is a {@link PooledDataBuffer} and
	 * has been {@linkplain PooledDataBuffer#isAllocated() allocated}.
	 * @param dataBuffer the data buffer to release
	 * @return {@code true} if the buffer was released; {@code false} otherwise.
	 */
	public static boolean release(@Nullable DataBuffer dataBuffer) {
		if (dataBuffer instanceof PooledDataBuffer) {
			PooledDataBuffer pooledDataBuffer = (PooledDataBuffer) dataBuffer;
			if (pooledDataBuffer.isAllocated()) {
				return pooledDataBuffer.release();
			}
		}
		return false;
	}

	
Return a consumer that calls release(DataBuffer) on all passed data buffers. 
/**
	 * Return a consumer that calls {@link #release(DataBuffer)} on all
	 * passed data buffers.
	 */
	public static Consumer<DataBuffer> releaseConsumer() {
		return RELEASE_CONSUMER;
	}

	
Return a new DataBuffer composed from joining together the given dataBuffers elements. Depending on the DataBuffer type, the returned buffer may be a single buffer containing all data of the provided buffers, or it may be a zero-copy, composite with references to the given buffers. 
If dataBuffers produces an error or if there is a cancel signal, then all accumulated buffers will be released. 
Note that the given data buffers do not have to be
released. They will be released as part of the returned composite.

Params:
  • dataBuffers – the data buffers that are to be composed
Returns:a buffer that is composed from the dataBuffers argument
Since:5.0.3
/**
	 * Return a new {@code DataBuffer} composed from joining together the given
	 * {@code dataBuffers} elements. Depending on the {@link DataBuffer} type,
	 * the returned buffer may be a single buffer containing all data of the
	 * provided buffers, or it may be a zero-copy, composite with references to
	 * the given buffers.
	 * <p>If {@code dataBuffers} produces an error or if there is a cancel
	 * signal, then all accumulated buffers will be
	 * {@linkplain #release(DataBuffer) released}.
	 * <p>Note that the given data buffers do <strong>not</strong> have to be
	 * released. They will be released as part of the returned composite.
	 * @param dataBuffers the data buffers that are to be composed
	 * @return a buffer that is composed from the {@code dataBuffers} argument
	 * @since 5.0.3
	 */
	public static Mono<DataBuffer> join(Publisher<DataBuffer> dataBuffers) {
		Assert.notNull(dataBuffers, "'dataBuffers' must not be null");

		return Flux.from(dataBuffers)
				.collectList()
				.filter(list -> !list.isEmpty())
				.map(list -> list.get(0).factory().join(list))
				.doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release);

	}


	private static class ReadableByteChannelGenerator implements Consumer<SynchronousSink<DataBuffer>> {

		private final ReadableByteChannel channel;

		private final DataBufferFactory dataBufferFactory;

		private final int bufferSize;

		public ReadableByteChannelGenerator(
				ReadableByteChannel channel, DataBufferFactory dataBufferFactory, int bufferSize) {

			this.channel = channel;
			this.dataBufferFactory = dataBufferFactory;
			this.bufferSize = bufferSize;
		}

		@Override
		public void accept(SynchronousSink<DataBuffer> sink) {
			boolean release = true;
			DataBuffer dataBuffer = this.dataBufferFactory.allocateBuffer(this.bufferSize);
			try {
				int read;
				ByteBuffer byteBuffer = dataBuffer.asByteBuffer(0, dataBuffer.capacity());
				if ((read = this.channel.read(byteBuffer)) >= 0) {
					dataBuffer.writePosition(read);
					release = false;
					sink.next(dataBuffer);
				}
				else {
					sink.complete();
				}
			}
			catch (IOException ex) {
				sink.error(ex);
			}
			finally {
				if (release) {
					release(dataBuffer);
				}
			}
		}
	}


	private static class AsynchronousFileChannelReadCompletionHandler
			implements CompletionHandler<Integer, DataBuffer> {

		private final AsynchronousFileChannel channel;

		private final FluxSink<DataBuffer> sink;

		private final DataBufferFactory dataBufferFactory;

		private final int bufferSize;

		private final AtomicLong position;

		private final AtomicBoolean disposed = new AtomicBoolean();

		public AsynchronousFileChannelReadCompletionHandler(AsynchronousFileChannel channel,
				FluxSink<DataBuffer> sink, long position, DataBufferFactory dataBufferFactory, int bufferSize) {

			this.channel = channel;
			this.sink = sink;
			this.position = new AtomicLong(position);
			this.dataBufferFactory = dataBufferFactory;
			this.bufferSize = bufferSize;
		}

		@Override
		public void completed(Integer read, DataBuffer dataBuffer) {
			if (read != -1) {
				long pos = this.position.addAndGet(read);
				dataBuffer.writePosition(read);
				this.sink.next(dataBuffer);
				if (!this.disposed.get()) {
					DataBuffer newDataBuffer = this.dataBufferFactory.allocateBuffer(this.bufferSize);
					ByteBuffer newByteBuffer = newDataBuffer.asByteBuffer(0, this.bufferSize);
					this.channel.read(newByteBuffer, pos, newDataBuffer, this);
				}
			}
			else {
				release(dataBuffer);
				this.sink.complete();
			}
		}

		@Override
		public void failed(Throwable exc, DataBuffer dataBuffer) {
			release(dataBuffer);
			this.sink.error(exc);
		}

		public void dispose() {
			this.disposed.set(true);
		}
	}


	private static class WritableByteChannelSubscriber extends BaseSubscriber<DataBuffer> {

		private final FluxSink<DataBuffer> sink;

		private final WritableByteChannel channel;

		public WritableByteChannelSubscriber(FluxSink<DataBuffer> sink, WritableByteChannel channel) {
			this.sink = sink;
			this.channel = channel;
		}

		@Override
		protected void hookOnSubscribe(Subscription subscription) {
			request(1);
		}

		@Override
		protected void hookOnNext(DataBuffer dataBuffer) {
			try {
				ByteBuffer byteBuffer = dataBuffer.asByteBuffer();
				while (byteBuffer.hasRemaining()) {
					this.channel.write(byteBuffer);
				}
				this.sink.next(dataBuffer);
				request(1);
			}
			catch (IOException ex) {
				this.sink.next(dataBuffer);
				this.sink.error(ex);
			}
		}

		@Override
		protected void hookOnError(Throwable throwable) {
			this.sink.error(throwable);
		}

		@Override
		protected void hookOnComplete() {
			this.sink.complete();
		}
	}


	private static class AsynchronousFileChannelWriteCompletionHandler extends BaseSubscriber<DataBuffer>
			implements CompletionHandler<Integer, ByteBuffer> {

		private final FluxSink<DataBuffer> sink;

		private final AsynchronousFileChannel channel;

		private final AtomicBoolean completed = new AtomicBoolean();

		private final AtomicReference<Throwable> error = new AtomicReference<>();

		private final AtomicLong position;

		private final AtomicReference<DataBuffer> dataBuffer = new AtomicReference<>();

		public AsynchronousFileChannelWriteCompletionHandler(
				FluxSink<DataBuffer> sink, AsynchronousFileChannel channel, long position) {

			this.sink = sink;
			this.channel = channel;
			this.position = new AtomicLong(position);
		}

		@Override
		protected void hookOnSubscribe(Subscription subscription) {
			request(1);
		}

		@Override
		protected void hookOnNext(DataBuffer value) {
			if (!this.dataBuffer.compareAndSet(null, value)) {
				throw new IllegalStateException();
			}
			ByteBuffer byteBuffer = value.asByteBuffer();
			this.channel.write(byteBuffer, this.position.get(), byteBuffer, this);
		}

		@Override
		protected void hookOnError(Throwable throwable) {
			this.error.set(throwable);

			if (this.dataBuffer.get() == null) {
				this.sink.error(throwable);
			}
		}

		@Override
		protected void hookOnComplete() {
			this.completed.set(true);

			if (this.dataBuffer.get() == null) {
				this.sink.complete();
			}
		}

		@Override
		public void completed(Integer written, ByteBuffer byteBuffer) {
			long pos = this.position.addAndGet(written);
			if (byteBuffer.hasRemaining()) {
				this.channel.write(byteBuffer, pos, byteBuffer, this);
				return;
			}
			sinkDataBuffer();

			Throwable throwable = this.error.get();
			if (throwable != null) {
				this.sink.error(throwable);
			}
			else if (this.completed.get()) {
				this.sink.complete();
			}
			else {
				request(1);
			}
		}

		@Override
		public void failed(Throwable exc, ByteBuffer byteBuffer) {
			sinkDataBuffer();
			this.sink.error(exc);
		}

		private void sinkDataBuffer() {
			DataBuffer dataBuffer = this.dataBuffer.get();
			Assert.state(dataBuffer != null, "DataBuffer should not be null");
			this.sink.next(dataBuffer);
			this.dataBuffer.set(null);
		}
	}

}