/*
* Copyright (C) 2005 Luca Veltri - University of Parma - Italy
*
* This file is part of MjSip (http://www.mjsip.org)
*
* MjSip 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.
*
* MjSip 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.
*
* You should have received a copy of the GNU General Public License
* along with MjSip; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Author(s):
* Luca Veltri (luca.veltri@unipr.it)
*/
package org.zoolu.tools;
/** Simple and fast hash/message-digest algorithm.
*/
public class SimpleDigest extends MessageDigest
{
// ************************* Attributes *************************
/** The digest */
byte[] message_digest;
/** Whether is finalized. */
boolean is_done;
/** Index within the message_digest. */
int index;
/** Add term */
byte add_term;
// *********************** Public methods ***********************
/** Constructor */
public SimpleDigest(int size)
{ init(size);
}
/** Constructor */
public SimpleDigest(int size, byte[] buffer)
{ init(size);
update(buffer);
}
/** Constructor */
public SimpleDigest(int size, byte[] buffer, int offset, int len)
{ init(size);
update(buffer,offset,len);
}
/** Constructor */
public SimpleDigest(int size, String str)
{ init(size);
update(str);
}
/** Inits the SimpleDigest */
private void init(int size)
{ is_done=false;
message_digest=new byte[size];
for (int i=0; i<size; i++) message_digest[i]=(byte)(i);
index=0;
add_term=0;
}
/** MessageDigest block update operation.
* Continues a message-digest operation,
* processing another message block, and updating the context. */
public MessageDigest update(byte[] buffer, int offset, int len)
{
if (is_done) return this;
//else
for (int i=0; i<len; i++)
{ if (index==message_digest.length) index=0;
add_term+=buffer[offset+i];
message_digest[index]=(byte)(message_digest[index]^add_term);
index++;
}
return this;
}
/** MessageDigest finalization. Ends a message-digest operation, writing the
* the message digest and zeroizing the context. */
public byte[] doFinal()
{
if (is_done) return message_digest;
//else
int k=message_digest.length-index;
while (index<message_digest.length)
{ message_digest[index]=(byte)(message_digest[index]^(k));
index++;
k++;
}
for (int i=0; i<message_digest.length; i++) message_digest[i]=(byte)(message_digest[i]^add_term);
return message_digest;
}
/** Calculates the SimpleDigest. */
public static byte[] digest(int size, byte[] buffer, int offset, int len)
{ MessageDigest md=new SimpleDigest(size,buffer,offset,len);
return md.doFinal();
}
/** Calculates the SimpleDigest. */
public static byte[] digest(int size, byte[] buffer)
{ return digest(size,buffer,0,buffer.length);
}
/** Calculates the SimpleDigest. */
public static byte[] digest(int size, String str)
{ MessageDigest md=new SimpleDigest(size,str);
return md.doFinal();
}
}