package gnu.crypto.hash;
// ----------------------------------------------------------------------------
// $Id: BaseHash.java,v 1.10 2005/10/06 04:24:14 rsdio Exp $
//
// Copyright (C) 2001, 2002, Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto 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, or (at your option)
// any later version.
//
// GNU Crypto 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 this program; see the file COPYING. If not, write to the
//
// Free Software Foundation Inc.,
// 51 Franklin Street, Fifth Floor,
// Boston, MA 02110-1301
// USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library. Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
//
// As a special exception, the copyright holders of this library give
// you permission to link this library with independent modules to
// produce an executable, regardless of the license terms of these
// independent modules, and to copy and distribute the resulting
// executable under terms of your choice, provided that you also meet,
// for each linked independent module, the terms and conditions of the
// license of that module. An independent module is a module which is
// not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the
// library, but you are not obligated to do so. If you do not wish to
// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------
/**
* <p>A base abstract class to facilitate hash implementations.</p>
*
* @version $Revision: 1.10 $
*/
public abstract class BaseHash implements IMessageDigest {
// Constants and variables
// -------------------------------------------------------------------------
/** The canonical name prefix of the hash. */
protected String name;
/** The hash (output) size in bytes. */
protected int hashSize;
/** The hash (inner) block size in bytes. */
protected int blockSize;
/** Number of bytes processed so far. */
protected long count;
/** Temporary input buffer. */
protected byte[] buffer;
// Constructor(s)
// -------------------------------------------------------------------------
/**
* <p>Trivial constructor for use by concrete subclasses.</p>
*
* @param name the canonical name prefix of this instance.
* @param hashSize the block size of the output in bytes.
* @param blockSize the block size of the internal transform.
*/
protected BaseHash(String name, int hashSize, int blockSize) {
super();
this.name = name;
this.hashSize = hashSize;
this.blockSize = blockSize;
this.buffer = new byte[blockSize];
resetContext();
}
// Class methods
// -------------------------------------------------------------------------
// Instance methods
// -------------------------------------------------------------------------
// IMessageDigest interface implementation ---------------------------------
public String name() {
return name;
}
public int hashSize() {
return hashSize;
}
public int blockSize() {
return blockSize;
}
public void update(byte b) {
// compute number of bytes still unhashed; ie. present in buffer
int i = (int)(count % blockSize);
count++;
buffer[i] = b;
if (i == (blockSize - 1)) {
transform(buffer, 0);
}
}
public void update(byte[] b) {
update(b, 0, b.length);
}
public void update(byte[] b, int offset, int len) {
int n = (int)(count % blockSize);
count += len;
int partLen = blockSize - n;
int i = 0;
if (len >= partLen) {
System.arraycopy(b, offset, buffer, n, partLen);
transform(buffer, 0);
for (i = partLen; i + blockSize - 1 < len; i+= blockSize) {
transform(b, offset + i);
}
n = 0;
}
if (i < len) {
System.arraycopy(b, offset + i, buffer, n, len - i);
}
}
public byte[] digest() {
byte[] tail = padBuffer(); // pad remaining bytes in buffer
update(tail, 0, tail.length); // last transform of a message
byte[] result = getResult(); // make a result out of context
reset(); // reset this instance for future re-use
return result;
}
public void reset() { // reset this instance for future re-use
count = 0L;
for (int i = 0; i < blockSize; ) {
buffer[i++] = 0;
}
resetContext();
}
// methods to be implemented by concrete subclasses ------------------------
public abstract Object clone();
public abstract boolean selfTest();
/**
* <p>Returns the byte array to use as padding before completing a hash
* operation.</p>
*
* @return the bytes to pad the remaining bytes in the buffer before
* completing a hash operation.
*/
protected abstract byte[] padBuffer();
/**
* <p>Constructs the result from the contents of the current context.</p>
*
* @return the output of the completed hash operation.
*/
protected abstract byte[] getResult();
/** Resets the instance for future re-use. */
protected abstract void resetContext();
/**
* <p>The block digest transformation per se.</p>
*
* @param in the <i>blockSize</i> long block, as an array of bytes to digest.
* @param offset the index where the data to digest is located within the
* input buffer.
*/
protected abstract void transform(byte[] in, int offset);
}