Wrapping an InputStream into a ReadStream<Buffer> for vert.x

AsyncInputStream.java

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import io.vertx.core.*;
import io.vertx.core.buffer.Buffer;
import io.vertx.core.impl.Arguments;
import io.vertx.core.logging.Logger;
import io.vertx.core.logging.LoggerFactory;
import io.vertx.core.streams.ReadStream;
import io.vertx.core.streams.impl.InboundBuffer;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.util.Objects;

/**
 * @author stw, antimist
 */
public class AsyncInputStream implements ReadStream<Buffer> {

	public static final int DEFAULT_READ_BUFFER_SIZE = 8192;
	private static final Logger log = LoggerFactory.getLogger(AsyncInputStream.class);

	// Based on the inputStream with the real data
	private final ReadableByteChannel ch;
	private final Vertx vertx;
	private final Context context;

	private boolean closed;
	private boolean readInProgress;

	private Handler<Buffer> dataHandler;
	private Handler<Void> endHandler;
	private Handler<Throwable> exceptionHandler;
	private final InboundBuffer<Buffer> queue;

	private int readBufferSize = DEFAULT_READ_BUFFER_SIZE;
	private long readPos;

	/**
	 * Create a new Async InputStream that can we used with a Pump
	 *
	 * @param in
	 */
	public AsyncInputStream(Vertx vertx, Context context, InputStream in) {
		this.vertx = vertx;
		this.context = context;
		this.ch = Channels.newChannel(in);
		this.queue = new InboundBuffer<>(context, 0);
		queue.handler(buff -> {
			if (buff.length() > 0) {
				handleData(buff);
			} else {
				handleEnd();
			}
		});
		queue.drainHandler(v -> {
			doRead();
		});
	}

	public void close() {
		closeInternal(null);
	}

	public void close(Handler<AsyncResult<Void>> handler) {
		closeInternal(handler);
	}

	/*
	 * (non-Javadoc)
	 * @see io.vertx.core.streams.ReadStream#endHandler(io.vertx.core.Handler)
	 */
	@Override
	public synchronized AsyncInputStream endHandler(Handler<Void> endHandler) {
		check();
		this.endHandler = endHandler;
		return this;
	}

	/*
	 * (non-Javadoc)
	 * @see
	 * io.vertx.core.streams.ReadStream#exceptionHandler(io.vertx.core.Handler)
	 */
	@Override
	public synchronized AsyncInputStream exceptionHandler(Handler<Throwable> exceptionHandler) {
		check();
		this.exceptionHandler = exceptionHandler;
		return this;
	}

	/*
	 * (non-Javadoc)
	 * @see io.vertx.core.streams.ReadStream#handler(io.vertx.core.Handler)
	 */
	@Override
	public synchronized AsyncInputStream handler(Handler<Buffer> handler) {
		check();
		this.dataHandler = handler;
		if (this.dataHandler != null && !this.closed) {
			this.doRead();
		} else {
			queue.clear();
		}
		return this;
	}

	/*
	 * (non-Javadoc)
	 * @see io.vertx.core.streams.ReadStream#pause()
	 */
	@Override
	public synchronized AsyncInputStream pause() {
		check();
		queue.pause();
		return this;
	}

	/*
	 * (non-Javadoc)
	 * @see io.vertx.core.streams.ReadStream#resume()
	 */
	@Override
	public synchronized AsyncInputStream resume() {
		check();
		if (!closed) {
			queue.resume();
		}
		return this;
	}

	@Override
	public ReadStream<Buffer> fetch(long amount) {
		queue.fetch(amount);
		return this;
	}

	private void check() {
		if (this.closed) {
			throw new IllegalStateException("Inputstream is closed");
		}
	}

	private void checkContext() {
		if (!vertx.getOrCreateContext().equals(context)) {
			throw new IllegalStateException("AsyncInputStream must only be used in the context that created it, expected: " + this.context
				+ " actual " + vertx.getOrCreateContext());
		}
	}

	private synchronized void closeInternal(Handler<AsyncResult<Void>> handler) {
		check();
		closed = true;
		doClose(handler);
	}

	private void doClose(Handler<AsyncResult<Void>> handler) {

		try {
			ch.close();
			if (handler != null) {
				this.vertx.runOnContext(v -> handler.handle(Future.succeededFuture()));
			}
		} catch (IOException e) {
			if (handler != null) {
				this.vertx.runOnContext(v -> handler.handle(Future.failedFuture(e)));
			}
		}
	}

	public synchronized AsyncInputStream read(Buffer buffer, int offset, long position, int length,
	                                          Handler<AsyncResult<Buffer>> handler) {
		Objects.requireNonNull(buffer, "buffer");
		Objects.requireNonNull(handler, "handler");
		Arguments.require(offset >= 0, "offset must be >= 0");
		Arguments.require(position >= 0, "position must be >= 0");
		Arguments.require(length >= 0, "length must be >= 0");
		check();
		ByteBuffer bb = ByteBuffer.allocate(length);
		doRead(buffer, offset, bb, position, handler);
		return this;
	}

	private void doRead() {
		check();
		doRead(ByteBuffer.allocate(readBufferSize));
	}

	private synchronized void doRead(ByteBuffer bb) {
		if (!readInProgress) {
			readInProgress = true;
			Buffer buff = Buffer.buffer(readBufferSize);
			doRead(buff, 0, bb, readPos, ar -> {
				if (ar.succeeded()) {
					readInProgress = false;
					Buffer buffer = ar.result();
					readPos += buffer.length();
					// Empty buffer represents end of file
					if (queue.write(buffer) && buffer.length() > 0) {
						doRead(bb);
					}
				} else {
					handleException(ar.cause());
				}
			});
		}
	}

	private void doRead(Buffer writeBuff, int offset, ByteBuffer buff, long position, Handler<AsyncResult<Buffer>> handler) {

		// ReadableByteChannel doesn't have a completion handler, so we wrap it into
		// an executeBlocking and use the future there
		vertx.executeBlocking(future -> {
			try {
				Integer bytesRead = ch.read(buff);
				future.complete(bytesRead);
			} catch (Exception e) {
				log.error(e);
				future.fail(e);
			}

		}, res -> {

			if (res.failed()) {
				context.runOnContext((v) -> handler.handle(Future.failedFuture(res.cause())));
			} else {
				// Do the completed check
				Integer bytesRead = (Integer) res.result();
				if (bytesRead == -1) {
					//End of file
					context.runOnContext((v) -> {
						buff.flip();
						writeBuff.setBytes(offset, buff);
						buff.compact();
						handler.handle(Future.succeededFuture(writeBuff));
					});
				} else if (buff.hasRemaining()) {
					long pos = position;
					pos += bytesRead;
					// resubmit
					doRead(writeBuff, offset, buff, pos, handler);
				} else {
					// It's been fully written

					context.runOnContext((v) -> {
						buff.flip();
						writeBuff.setBytes(offset, buff);
						buff.compact();
						handler.handle(Future.succeededFuture(writeBuff));
					});
				}
			}
		});
	}

	private void handleData(Buffer buff) {
		Handler<Buffer> handler;
		synchronized (this) {
			handler = this.dataHandler;
		}
		if (handler != null) {
			checkContext();
			handler.handle(buff);
		}
	}

	private synchronized void handleEnd() {
		Handler<Void> endHandler;
		synchronized (this) {
			dataHandler = null;
			endHandler = this.endHandler;
		}
		if (endHandler != null) {
			checkContext();
			endHandler.handle(null);
		}
	}

	private void handleException(Throwable t) {
		if (exceptionHandler != null && t instanceof Exception) {
			exceptionHandler.handle(t);
		} else {
			log.error("Unhandled exception", t);

		}
	}

}

Well, I have updated this gist, and fixed a couple things on my fork here: https://gist.github.com/TheAntimist/af95e3ce63682e1d531b8a0b5a649fa5

Awesome @TheAntimist. Appreciate it

Updated based on @TheAntimist improvements

Sorry for spamming here but can you give some examples how can i use this class. In my case i want to send large String as stream in POST request.

Well, it depends on your use case. I used it to wrap a HTTP Body response from OkHttp Client and stream it asynchronously using this class.

Thanks a lot for example. In my case the read process is stack in first iteration. Looks like the runOnContext waiting for thread

Thank you, good implementation!. Is it possible to reuse this gist?, I did not find any license here or in the author's main GitHub page. BTW: I would be happy to modify the call to the method below, if you do not mind (is marked as deprecated in Vert.x 4.5.X): Vertx#executeBlocking(Handler<Promise<T>> blockingCodeHandler, Handler<AsyncResult<T>> resultHandler)

@rub24 License is on my main site https://wissel.net/ - added Apache header for convenience.
Happy to see your improvements

Thank you for adding the license and for your quick reply @Stwissel!