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/*
 *  streams library
 *
 *  Copyright (C) 2011-2014 by Christian Bockermann, Hendrik Blom
 * 
 *  streams is a library, API and runtime environment for processing high
 *  volume data streams. It is composed of three submodules "stream-api",
 *  "stream-core" and "stream-runtime".
 *
 *  The streams library (and its submodules) is free software: you can 
 *  redistribute it and/or modify it under the terms of the 
 *  GNU Affero General Public License as published by the Free Software 
 *  Foundation, either version 3 of the License, or (at your option) any 
 *  later version.
 *
 *  The stream.ai library (and its submodules) 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 Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/.
 */
package stream.util;

import java.io.ByteArrayOutputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * 
 * This is a small helper-class that wraps around the java md5 message-digest
 * and computes the md5 hex-string of a given input string. It is basically just
 * a wrapper and uses the MessageDigest class of the Java runtime library.
 * 
 * @author Christian Bockermann <[email protected]>
 * 
 */
public class MD5 {

	/**
	 * Create a hex string of the MD5 sum of the given data (byte[] array).
	 * 
	 * @param array
	 *            The data to compute the hash from.
	 * @return The hex string of the MD5 hash.
	 */
	private static String hex(byte[] array) {
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < array.length; ++i) {
			sb.append(Integer.toHexString((array[i] & 0xFF) | 0x100)
					.toLowerCase().substring(1, 3));
		}
		return sb.toString();
	}

	/**
	 * This method will simply return the computed MD5 sum of the given input
	 * string. The sum is returned in hex notation.
	 * 
	 * This is just a convenience method. Calls this method are delegated to
	 * md5( byte[] data).
	 * 
	 * 
	 * @param message
	 *            The message to create the digest from.
	 * @return The hex string of the message digest.
	 */
	public static String md5(String message) {
		return md5(message.getBytes());
	}

	/**
	 * This method will simply return the computed MD5 sum of the given input
	 * data. The sum is returned in hex notation.
	 * 
	 * @param data
	 *            The message to create the digest from.
	 * @return The hex string of the message digest.
	 */
	public static String md5(byte[] data) {
		try {
			MessageDigest md = MessageDigest.getInstance("MD5");
			return hex(md.digest(data));
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
			return null;
		}
	}

	public static String md5(Serializable object) {
		try {
			ByteArrayOutputStream out = new ByteArrayOutputStream();
			ObjectOutputStream oos = new ObjectOutputStream(out);
			oos.writeObject(object);
			oos.flush();
			oos.close();
			return md5(out.toByteArray());
		} catch (Exception e) {
			e.printStackTrace();
		}
		return md5(object.toString().getBytes());
	}
}