MD5InputStream.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.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;

/**
 * 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 read from 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 MD5OutputStream
 * 
 * @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 MD5InputStream extends FilterInputStream
{

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

	/**
	 * Creates a MD5InputStream
	 * 
	 * @param in
	 *            the underlying input stream
	 */
	public MD5InputStream(InputStream in)
	{
		super(in);
		md5 = new MD5();
	}

	/**
	 * Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.
	 * <p>
	 * This method simply performs in.read() and returns the result.
	 * 
	 * @return the next byte of data, or -1 if the end of the stream is reached.
	 * @throws IOException
	 *             if an I/O error occurs.
	 * 
	 * @since ostermillerutils 1.00.00
	 */
	public int read() throws IOException
	{
		int c = in.read();
		if (c == -1)
		{
			return -1;
		}
		else
		{
			md5.update((byte) (c & 0xff));
			return c;
		}
	}

	/**
	 * Reads up to len bytes of data from this input stream into an array of bytes. This method blocks until some input is available.
	 * 
	 * @param bytes
	 *            the buffer into which the data is read.
	 * @param offset
	 *            the start offset of the data.
	 * @param length
	 *            the maximum number of bytes read.
	 * @throws IOException
	 *             if an I/O error occurs.
	 * 
	 * @since ostermillerutils 1.00.00
	 */
	public int read(byte[] bytes, int offset, int length) throws IOException
	{
		int r;
		if ((r = in.read(bytes, offset, length)) == -1)
		{
			return r;
		}
		else
		{
			md5.update(bytes, offset, r);
			return r;
		}
	}

	/**
	 * Returns array of bytes representing hash of the stream so far.
	 * 
	 * @return Array of 16 bytes, the hash of all read 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();
	}
}