MD5InputStream.java Source Code

  • MD5 Documentation and Examples
  • MD5InputStream Javadoc
    /*
     * Copyright (C) 1996 Santeri Paavolainen, Helsinki Finland
     *
     * Copyright (C) 2002-2010 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 LICENSE.txt for details.
     *
     * The original work by Santeri Paavolainen can be found a
     * http://santtu.iki.fi/md5/
     */
    package com.Ostermiller.util;
    
    import java.io.*;
    
    /**
     * 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://santtu.iki.fi/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
    	 */
    	@Override public int read() throws IOException {
    		int c = in.read();
    		if (c == -1) {
    			return -1;
    		}
    		md5.update((byte)(c & 0xff));
    		return c;
    }
    
    	/**
    	 * Reads up to length 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
    	 */
    	@Override public int read(byte[] bytes, int offset, int length) throws IOException {
    		int	r;
    		if ((r = in.read(bytes, offset, length)) == -1) {
    			return r;
    		}
    		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();
    	}
    }