package org.apache.archiva.checksum;
   
   /*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you under the Apache License, Version 2.0 (the
    * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License is distributed on an
   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
   * KIND, either express or implied.  See the License for the
   * specific language governing permissions and limitations
   * under the License.
   */
  
  import org.apache.commons.io.IOUtils;
  import org.apache.commons.io.output.NullOutputStream;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.security.DigestInputStream;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  import java.util.List;
  
  /**
   * Checksum - simple checksum hashing routines.
   */
  public class Checksum
  {
      private static final int BUFFER_SIZE = 32768;
  
      public static void update( List<Checksum> checksums, InputStream stream )
          throws IOException
      {
          byte[] buffer = new byte[BUFFER_SIZE];
          int size = stream.read( buffer, 0, BUFFER_SIZE );
          while ( size >= 0 )
          {
              for ( Checksum checksum : checksums )
              {
                  checksum.update( buffer, 0, size );
              }
              size = stream.read( buffer, 0, BUFFER_SIZE );
          }
      }
  
      private final MessageDigest md;
  
      private ChecksumAlgorithm checksumAlgorithm;
  
      public Checksum( ChecksumAlgorithm checksumAlgorithm )
      {
          this.checksumAlgorithm = checksumAlgorithm;
          try
          {
              md = MessageDigest.getInstance( checksumAlgorithm.getAlgorithm() );
          }
          catch ( NoSuchAlgorithmException e )
          {
              // Not really possible, but here none-the-less
              throw new IllegalStateException(
                  "Unable to initialize MessageDigest algorithm " + checksumAlgorithm.getAlgorithm() + " : "
                      + e.getMessage(), e );
          }
      }
  
      public String getChecksum()
      {
          return Hex.encode( md.digest() );
      }
  
      public ChecksumAlgorithm getAlgorithm()
      {
          return this.checksumAlgorithm;
      }
  
      public void reset()
      {
          md.reset();
      }
  
      public Checksum update( byte[] buffer, int offset, int size )
      {
          md.update( buffer, 0, size );
          return this;
      }
  
      public Checksum update( InputStream stream )
          throws IOException
      {
          try (DigestInputStream dig = new DigestInputStream( stream, md ))
          {
             IOUtils.copy( dig, new NullOutputStream() );
         }
         return this;
     }
 }