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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by both ImageJ and SCIFIO.

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/*
 * #%L
 * SciJava Common shared library for SciJava software.
 * %%
 * Copyright (C) 2009 - 2016 Board of Regents of the University of
 * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
 * Institute of Molecular Cell Biology and Genetics.
 * %%
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 * 
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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package org.scijava.console;

import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;

/**
 * A {@code MultiOutputStream} is a collection of constituent
 * {@link OutputStream} objects, to which all output is forwarded.
 * 
 * Thanks to Ian F. Darwin for his implementation of a similar concept.
 * 
 *
 * @author Curtis Rueden
 */
public class MultiOutputStream extends OutputStream {

	private final ArrayList streams;

	private OutputStream[] cachedStreams;

	/**
	 * Forwards output to a list of output streams.
	 *
	 * @param os Output streams which will receive this stream's output.
	 */
	public MultiOutputStream(final OutputStream... os) {
		streams = new ArrayList(os.length);
		for (int i = 0; i < os.length; i++) {
			streams.add(os[i]);
		}
		cacheStreams();
	}

	// -- MultiOutputStream methods --

	/** Adds an output stream to those receiving this stream's output. */
	public void addOutputStream(final OutputStream os) {
		synchronized (streams) {
			streams.add(os);
			cacheStreams();
		}
	}

	/** Removes an output stream from those receiving this stream's output. */
	public void removeOutputStream(final OutputStream os) {
		synchronized (streams) {
			streams.remove(os);
			cacheStreams();
		}
	}

	// -- OutputStream methods --

	@Override
	public void write(final int b) throws IOException {
		final OutputStream[] toWrite = cachedStreams;
		for (final OutputStream stream : toWrite)
			stream.write(b);
	}

	@Override
	public void write(final byte[] buf, final int off, final int len)
		throws IOException
	{
		final OutputStream[] toWrite = cachedStreams;
		for (final OutputStream stream : toWrite)
			stream.write(buf, off, len);
	}

	// -- Closeable methods --

	@Override
	public void close() throws IOException {
		final OutputStream[] toClose = cachedStreams;
		for (final OutputStream stream : toClose)
			stream.close();
	}

	// -- Flushable methods --

	@Override
	public void flush() throws IOException {
		final OutputStream[] toFlush = cachedStreams;
		for (final OutputStream stream : toFlush)
			stream.flush();
	}

	// -- Helper methods --

	private void cacheStreams() {
		cachedStreams = streams.toArray(new OutputStream[streams.size()]);
	}

}