com.Ostermiller.util.MD5InputStream Maven / Gradle / Ivy
/*
* 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 com.Ostermiller.util;
import java.io.*;
/**
* Implements MD5 functionality on a stream.
* More information about this class is available from ostermiller.org.
*
* 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.
*
* 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.
*
* 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();
}
}