MD5OutputStream.java

/*
 * Implements MD5 functionality on a stream.
 * 
 * written Santeri Paavolainen, Helsinki Finland 1996 (c) Santeri Paavolainen, Helsinki Finland 1996 modifications Copyright (C) 2002 Stephen Ostermiller
 * http://ostermiller.org/contact.pl?regarding=Java+Utilities
 * 
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 * 
 * See COPYING.TXT for details.
 * 
 * The original work by Santeri Paavolainen can be found a http://www.helsinki.fi/~sjpaavol/programs/md5/
 */

package org.caudexorigo.cryto;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * Implements MD5 functionality on a stream. More information about this class is available from <a target="_top" href= "http://ostermiller.org/utils/MD5.html">ostermiller.org </a>.
 * <p>
 * This class produces a 128-bit "fingerprint" or "message digest" for all data written to this stream. It is conjectured that it is computationally infeasible to produce two messages having the same message digest, or to produce any message having a given pre-specified target message digest. The MD5 algorithm is intended for digital signature applications, where a large file must be "compressed" in a secure manner before being encrypted with a private (secret) key under a public-key cryptosystem such as RSA.
 * <p>
 * For more information see RFC1321.
 * 
 * @see MD5
 * @see MD5InputStream
 * 
 * @author Santeri Paavolainen http://www.helsinki.fi/~sjpaavol/programs/md5/
 * @author Stephen Ostermiller http://ostermiller.org/contact.pl?regarding=Java+Utilities
 * @since ostermillerutils 1.00.00
 */
public class MD5OutputStream extends FilterOutputStream
{

	/**
	 * MD5 context
	 */
	private MD5 md5;

	/**
	 * Creates MD5OutputStream
	 * 
	 * @param out
	 *            The output stream
	 * 
	 * @since ostermillerutils 1.00.00
	 */
	public MD5OutputStream(OutputStream out)
	{
		super(out);
		md5 = new MD5();
	}

	/**
	 * Writes the specified byte to this output stream.
	 * 
	 * @param b
	 *            the byte.
	 * @throws IOException
	 *             if an I/O error occurs.
	 * 
	 * @since ostermillerutils 1.00.00
	 */
	public void write(int b) throws IOException
	{
		out.write(b);
		md5.update((byte) (b & 0xff));
	}

	/**
	 * Writes len bytes from the specified byte array starting a offset off to this output stream.
	 * 
	 * @param b
	 *            the data.
	 * @param off
	 *            the start offset in the data.
	 * @param len
	 *            the number of bytes to write.
	 * @throws IOException
	 *             if an I/O error occurs.
	 * 
	 * @since ostermillerutils 1.00.00
	 */
	public void write(byte b[], int off, int len) throws IOException
	{
		out.write(b, off, len);
		md5.update(b, off, len);
	}

	/**
	 * Returns array of bytes representing hash of the stream so far.
	 * 
	 * @return Array of 16 bytes, the hash of all written bytes.
	 * 
	 * @since ostermillerutils 1.00.00
	 */
	public byte[] getHash()
	{
		return md5.getHash();
	}

	/**
	 * Get a 32-character hex representation representing hash of the stream so far.
	 * 
	 * @return A string containing the hash of all written bytes.
	 * 
	 * @since ostermillerutils 1.00.00
	 */
	public String getHashString()
	{
		return md5.getHashString();
	}
}