| gvSIG desktop 1

/* gvSIG. Desktop Geographic Information System.

 *

 * Copyright ? 2007-2012 gvSIG Association

 *

 * This program 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.

 *

 * This program 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; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,

 * MA  02110-1301, USA.

 *

 * For any additional information, do not hesitate to contact us

 * at info AT gvsig.com, or visit our website www.gvsig.com.

 */

package org.gvsig.installer.lib.impl.utils;

import java.io.BufferedReader;

import java.io.File;

import java.io.FileInputStream;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.net.URL;

import java.security.MessageDigest;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

/**

 * @author jldominguez

 *

 */

public class MD5BinaryFileUtils {

    private static final Logger LOG = LoggerFactory.getLogger(MD5BinaryFileUtils.class);

    /**

     * 

     * Gets the MD5 string of a md5 file which is associated with

     * the file provided.

     * 

     * @param remote_file the file that has a ".md5" file next to it

     * @return

     */

    public static String getMD5InRemoteFile(URL remote_file) {

        BufferedReader in = null;

        try {

            String _url = remote_file.toString() + ".md5";

            URL md5_url = new URL(_url);

            in = new BufferedReader(

            new InputStreamReader(md5_url.openStream()));

            String inputLine = in.readLine();

            int space = inputLine.indexOf(" "); 

            inputLine = inputLine.substring(0, space);

            return inputLine;

        } catch (Exception ex) {

            LOG.info("Error while reading MD5 file: " + ex.getMessage());

            return null;

        } finally {

            try {

                in.close();

            } catch (Exception ex) { }  

        }

    }

    public static byte[] createChecksum(File the_file) throws Exception {

        InputStream fis =  new FileInputStream(the_file);

        byte[] buffer = new byte[1024];

        MessageDigest complete = MessageDigest.getInstance("MD5");

        int numRead;

        do {

            numRead = fis.read(buffer);

            if (numRead > 0) {

                complete.update(buffer, 0, numRead);

            }

        } while (numRead != -1);

        fis.close();

        return complete.digest();

    }

    /**

     * In case this is too slow for you:

     * There are faster ways to convert

     * a byte array to a HEX string

     *  

     * @param the_file the input file

     * @return the given file's MD5 checksum as a hex string

     * @throws Exception

     */

    public static String getMD5Checksum(File the_file) throws Exception {

        byte[] b = createChecksum(the_file);

        String result = "";

        for (int i=0; i < b.length; i++) {

            result += Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring( 1 );

        }

        return result;

    }

}