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/*
 *  streams library
 *
 *  Copyright (C) 2011-2012 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 message 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() );
    }
}