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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 downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.

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/*
 * #%L
 * SciJava Common shared library for SciJava software.
 * %%
 * Copyright (C) 2009 - 2017 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
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 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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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()]);
	}

}