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EasyStream is a small set of utilities for dealing with streams (InputStreams and OutputStreams). The aim is to ease the use of pipes when they're required. Main features are: * "Convert" an OutputStream to an InputStream. * Count the number of bytes read or wrote to a given stream. * While reading the data from an InputStream copy it to a supplied OutputStream. * Read the content of an InputStream multiple times or seek to a definite position

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package com.gc.iotools.stream.is;

/*
 * Copyright (c) 2008, 2015 Gabriele Contini. This source code is released
 * under the BSD License.
 */

import java.io.InputStream;
import java.io.OutputStream;
import java.util.concurrent.ExecutorService;

import org.apache.commons.io.IOUtils;

import com.gc.iotools.stream.base.ExecutionModel;
import com.gc.iotools.stream.base.ExecutorServiceFactory;

/**
 * 
 * This class tries to read the InputStream passed as a parameter
 * in a memory buffer, thus improving the reading performances.
 * 
 * 
 * This can speed up reading when the time spent in reading from the stream is
 * same order as the time spent in elaborating the stream, because it decouples
 * the reading process and the elaboration in two different threads putting them
 * in parallel.
 * 
 * 
 * Sample Usage:
 * 
 * 
 * InputStream source = ... some slow InputStream.
 * InputStream fastIs = new ReadAheadInputStream(source);
 * //use here fastIs instead of the source InputStream
 * ...
 * fastIs.close();
 * 
 * 
 * 
 * @author dvd.smnt
 * @since 1.2.6
 * @version $Id: ReadAheadInputStream.java 527 2014-02-24 19:29:50Z
 *           $
 */
public class ReadAheadInputStream extends InputStreamFromOutputStream {
	private final InputStream source;

	/**
	 * 

	 * Constructor for ReadAheadInputStream.
	 * 
	 * 
	 * @param source
	 *            a {@link java.io.InputStream} object.
	 */
	public ReadAheadInputStream(final InputStream source) {
		this(source, -1);
	}

	/**
	 * 
	 * Constructor for ReadAheadInputStream.
	 * 
	 * 
	 * @param source
	 *            a {@link java.io.InputStream} object.
	 * @param bufferSize
	 *            a int.
	 */
	public ReadAheadInputStream(final InputStream source, final int bufferSize) {
		this(source, bufferSize, ExecutionModel.THREAD_PER_INSTANCE);
	}

	/**
	 * 
	 * Constructor for ReadAheadInputStream.
	 * 
	 * 
	 * @param source
	 *            a {@link java.io.InputStream} object.
	 * @param bufferSize
	 *            a int.
	 * @param executionModel
	 *            a {@link com.gc.iotools.stream.base.ExecutionModel} object.
	 */
	public ReadAheadInputStream(final InputStream source, final int bufferSize,
			final ExecutionModel executionModel) {
		this(source, bufferSize, ExecutorServiceFactory
				.getExecutor(executionModel));
	}

	/**
	 * 
	 * Constructor for ReadAheadInputStream.
	 * 
	 * 
	 * @param source
	 *            a {@link java.io.InputStream} object.
	 * @param bufferSize
	 *            a int.
	 * @param executorService
	 *            a {@link java.util.concurrent.ExecutorService} object.
	 */
	public ReadAheadInputStream(final InputStream source, final int bufferSize,
			final ExecutorService executorService) {
		// 256K buffer by default
		super(false, executorService, (bufferSize > 0 ? bufferSize
				: (65536 * 4)));
		this.source = source;
	}

	/** {@inheritDoc} */
	@Override
	protected Void produce(final OutputStream sink) throws Exception {
		IOUtils.copy(this.source, sink);
		this.source.close();
		return null;
	}

}