/*
 * 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;

/**
 * Generic hash/message-digest algorithm.
 */
public abstract class MessageDigest {
	/**
	 * MessageDigest block update operation. Continues a message-digest
	 * operation, processing another message block, and updating the context.
	 */
	abstract public MessageDigest update(byte[] buffer, int offset, int len);

	/**
	 * MessageDigest block update operation. Continues a message-digest
	 * operation, processing another message block, and updating the context.
	 */
	public MessageDigest update(String str) {
		byte[] buf = str.getBytes();
		return update(buf, 0, buf.length);
	}

	/**
	 * MessageDigest block update operation. Continues a message-digest
	 * operation, processing another message block, and updating the context.
	 */
	public MessageDigest update(byte[] buffer) {
		return update(buffer, 0, buffer.length);
	}

	/**
	 * MessageDigest finalization. Ends a message-digest operation, writing the
	 * the message digest and zeroizing the context.
	 */
	abstract public byte[] doFinal();

	/** Gets the MessageDigest. The same as doFinal(). */
	public byte[] getDigest() {
		return doFinal();
	}

	/** Gets the Message Digest as string of hex values. */
	public String asHex() {
		return asHex(doFinal());
	}

	/** Transforms an array of bytes into a string of hex values. */
	public static String asHex(byte[] buf) {
		String str = new String();
		for (int i = 0; i < buf.length; i++) {
			str += Integer.toHexString((buf[i] >>> 4) & 0x0F);
			str += Integer.toHexString(buf[i] & 0x0F);
		}
		return str;
	}

}
