package liquibase.util;

 import liquibase.exception.UnexpectedLiquibaseException;

 import liquibase.logging.LogFactory;

 import java.io.InputStream;

 import java.security.DigestInputStream;

 import java.security.MessageDigest;

 /**

  * Generates md5-sums based on a string.

  */

 public class MD5Util {

     /**

      * Used to build output as Hex

      */

     private static final char[] DIGITS_LOWER = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',

             'e', 'f' };

     public static String computeMD5(String input) {

         if (input == null) {

             return null;

         }

         MessageDigest digest;

         try {

             digest = MessageDigest.getInstance("MD5");

             digest.update(input.getBytes("UTF-8"));

         } catch (Exception e) {

             throw new UnexpectedLiquibaseException(e);

         }

         byte[] digestBytes = digest.digest();

         String returnString = new String(encodeHex(digestBytes));

         LogFactory.getLogger().debug("Computed checksum for " + input + " as " + returnString);

         return returnString;

     }

     public static String computeMD5(InputStream stream) {

         MessageDigest digest;

         try {

             digest = MessageDigest.getInstance("MD5");

             DigestInputStream digestStream = new DigestInputStream(stream, digest);

             while (digestStream.read() != -1) {

                 ; // digest is updating

             }

         } catch (Exception e) {

             throw new RuntimeException(e);

         }

         byte[] digestBytes = digest.digest();

         String returnString = new String(encodeHex(digestBytes));

         LogFactory.getLogger().debug("Computed checksum for " + returnString + " as " + returnString);

         return returnString;

     }

     /**

      * Converts an array of bytes into an array of characters representing the hexadecimal values of each byte in order.

      * The returned array will be double the length of the passed array, as it takes two characters to represent any

      * given byte.

      * 

      * @param data

      *            a byte[] to convert to Hex characters

      * @return A char[] containing hexadecimal characters

      */

     private static char[] encodeHex(byte[] data) {

         int l = data.length;

         char[] out = new char[l << 1];

         // two characters form the hex value.

         for (int i = 0, j = 0; i < l; i++) {

             out[j++] = DIGITS_LOWER[(0xF0 & data[i]) >>> 4];

             out[j++] = DIGITS_LOWER[0x0F & data[i]];

         }

         return out;

     }

 }