package org.owasp.dependencycheck.utils;

 import java.io.File;

 import java.io.FileInputStream;

 import java.io.IOException;

 import java.io.InputStream;

 import java.security.MessageDigest;

 import java.security.NoSuchAlgorithmException;

 import java.util.logging.Level;

 import java.util.logging.Logger;

 /**

  * Includes methods to generate the MD5 and SHA1 checksum.

  *

  * This code was copied from Real's How To. It has been slightly modified.

  *

  * Written and compiled by Réal Gagnon ©1998-2012

  *

  * @author Real's How To: http://www.rgagnon.com/javadetails/java-0416.html

  *

  */

 public class Checksum {

     /**

      * <p>Creates the cryptographic checksum of a given file using the specified

      * algorithm.</p> <p>This algorithm was copied and heavily modified from

      * Real's How To: http://www.rgagnon.com/javadetails/java-0416.html</p>

      *

      * @param algorithm the algorithm to use to calculate the checksum

      * @param file the file to calculate the checksum for

      * @return the checksum

      * @throws IOException when the file does not exist

      * @throws NoSuchAlgorithmException when an algorithm is specified that does

      * not exist

      */

     public static byte[] getChecksum(String algorithm, File file) throws NoSuchAlgorithmException, IOException {

         InputStream fis = null;

         byte[] buffer = new byte[1024];

         MessageDigest complete = MessageDigest.getInstance(algorithm);

         int numRead;

         try {

             fis = new FileInputStream(file);

             do {

                 numRead = fis.read(buffer);

                 if (numRead > 0) {

                     complete.update(buffer, 0, numRead);

                 }

             } while (numRead != -1);

         } finally {

             if (fis != null) {

                 try {

                     fis.close();

                 } catch (IOException ex) {

                     Logger.getLogger(Checksum.class.getName()).log(Level.FINEST, "Error closing file '" + file.getName() + "'.", ex);

                 }

             }

         }

         return complete.digest();

     }

     /**

      * Calculates the MD5 checksum of a specified file.

      *

      * @param file the file to generate the MD5 checksum

      * @return the hex representation of the MD5 hash

      * @throws IOException when the file passed in does not exist

      * @throws NoSuchAlgorithmException when the MD5 algorithm is not available

      */

     public static String getMD5Checksum(File file) throws IOException, NoSuchAlgorithmException {

         byte[] b = getChecksum("MD5", file);

         return getHex(b);

     }

     /**

      * Calculates the SHA1 checksum of a specified file.

      *

      * @param file the file to generate the MD5 checksum

      * @return the hex representation of the SHA1 hash

      * @throws IOException when the file passed in does not exist

      * @throws NoSuchAlgorithmException when the SHA1 algorithm is not available

      */

     public static String getSHA1Checksum(File file) throws IOException, NoSuchAlgorithmException {

         byte[] b = getChecksum("SHA1", file);

         return getHex(b);

     }

     private static final String HEXES = "0123456789ABCDEF";

     /**

      * <p>Converts a byte array into a hex string.</p>

      *

      * <p>This method was copied from <a

      * href="http://www.rgagnon.com/javadetails/java-0596.html">http://www.rgagnon.com/javadetails/java-0596.html</a></p>

      *

      * @param raw a byte array

      * @return the hex representation of the byte array

      */

     public static String getHex(byte[] raw) {

         if (raw == null) {

             return null;

         }

         final StringBuilder hex = new StringBuilder(2 * raw.length);

         for (final byte b : raw) {

             hex.append(HEXES.charAt((b & 0xF0) >> 4)).append(HEXES.charAt((b & 0x0F)));

         }

         return hex.toString();

     }

 }