ReaderInputStream.java

package org.openedit.util;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;

/**
 * Adapts a <code>Reader</code> as an <code>InputStream</code>. Adapted
 * from <CODE>StringInputStream</CODE>.
 * 
 */
public class ReaderInputStream extends InputStream
{
	/** Source Reader */
	private Reader in;
	private String encoding = System.getProperty("file.encoding");
	private byte[] slack;
	private int begin;

	/**
	 * Construct a <CODE>ReaderInputStream</CODE> for the specified <CODE>Reader</CODE>.
	 * 
	 * @param reader
	 *            <CODE>Reader</CODE>. Must not be <code>null</code>.
	 */
	public ReaderInputStream(Reader reader)
	{
		in = reader;
	}

	/**
	 * Construct a <CODE>ReaderInputStream</CODE> for the specified <CODE>Reader</CODE>,
	 * with the specified encoding.
	 * 
	 * @param reader
	 *            non-null <CODE>Reader</CODE>.
	 * @param encoding
	 *            non-null <CODE>String</CODE> encoding.
	 */
	public ReaderInputStream(Reader reader, String encoding)
	{
		this(reader);
		if (encoding == null)
		{
			throw new IllegalArgumentException("encoding must not be null");
		}
		else
		{
			this.encoding = encoding;
		}
	}

	/**
	 * Reads from the <CODE>Reader</CODE>, returning the same value.
	 * 
	 * @return the value of the next character in the <CODE>Reader</CODE>.
	 * 
	 * @exception IOException
	 *                if the original <code>Reader</code> fails to be read
	 */
	public synchronized int read() throws IOException
	{
		if (in == null)
		{
			throw new IOException("Stream Closed");
		}

		byte result;
		if (slack != null && begin < slack.length)
		{
			result = slack[begin];
			if (++begin == slack.length)
			{
				slack = null;
			}
		}
		else
		{
			byte[] buf = new byte[1];
			if (read(buf, 0, 1) <= 0)
			{
				result = -1;
			}
			result = buf[0];
		}

		if (result < -1)
		{
			result += 256;
		}

		return result;
	}

	/**
	 * Reads from the <code>Reader</code> into a byte array
	 * 
	 * @param b
	 *            the byte array to read into
	 * @param off
	 *            the offset in the byte array
	 * @param len
	 *            the length in the byte array to fill
	 * @return the actual number read into the byte array, -1 at the end of the
	 *         stream
	 * @exception IOException
	 *                if an error occurs
	 */
	public synchronized int read(byte[] b, int off, int len) throws IOException
	{
		if (in == null)
		{
			throw new IOException("Stream Closed");
		}

		while (slack == null)
		{
			char[] buf = new char[len]; // might read too much
			int n = in.read(buf);
			if (n == -1)
			{
				return -1;
			}
			if (n > 0)
			{
				slack = new String(buf, 0, n).getBytes(encoding);
				begin = 0;
			}
		}

		if (len > slack.length - begin)
		{
			len = slack.length - begin;
		}

		System.arraycopy(slack, begin, b, off, len);

		if ((begin += len) >= slack.length)
		{
			slack = null;
		}

		return len;
	}

	/**
	 * Marks the read limit of the StringReader.
	 * 
	 * @param limit
	 *            the maximum limit of bytes that can be read before the mark
	 *            position becomes invalid
	 */
	public synchronized void mark(final int limit)
	{
		try
		{
			in.mark(limit);
		}
		catch (IOException ioe)
		{
			throw new RuntimeException(ioe.getMessage());
		}
	}

	/**
	 * @return the current number of bytes ready for reading
	 * @exception IOException
	 *                if an error occurs
	 */
	public synchronized int available() throws IOException
	{
		if (in == null)
		{
			throw new IOException("Stream Closed");
		}
		if (slack != null)
		{
			return slack.length - begin;
		}
		if (in.ready())
		{
			return 1;
		}
		else
		{
			return 0;
		}
	}

	/**
	 * @return false - mark is not supported
	 */
	public boolean markSupported()
	{
		return false; // would be imprecise
	}

	/**
	 * Resets the StringReader.
	 * 
	 * @exception IOException
	 *                if the StringReader fails to be reset
	 */
	public synchronized void reset() throws IOException
	{
		if (in == null)
		{
			throw new IOException("Stream Closed");
		}
		slack = null;
		in.reset();
	}

	/**
	 * Closes the Stringreader.
	 * 
	 * @exception IOException
	 *                if the original StringReader fails to be closed
	 */
	public synchronized void close() throws IOException
	{
		if (in != null)
		{
			in.close();
			slack = null;
			in = null;
		}
	}
}