package org.codehaus.plexus.digest;

 /*

  * Copyright 2001-2006 The Codehaus.

  *

  * Licensed 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 java.io.IOException;

 import java.io.InputStream;

 import java.security.MessageDigest;

 import java.security.NoSuchAlgorithmException;

 /**

  * Gradually create a digest for a stream.

  *

  * @author <a href="mailto:brett@apache.org">Brett Porter</a>

  */

 public abstract class AbstractStreamingDigester

     implements StreamingDigester

 {

     protected final MessageDigest md;

     private static final int BUFFER_SIZE = 32768;

     protected AbstractStreamingDigester( String algorithm )

     {

         try

         {

             md = MessageDigest.getInstance( algorithm );

         }

         catch ( NoSuchAlgorithmException e )

         {

             throw new IllegalStateException( "Unable to initialize digest algorithm " + algorithm + " : "

                 + e.getMessage() );

         }

     }

     public String getAlgorithm()

     {

         return md.getAlgorithm();

     }

     public String calc()

         throws DigesterException

     {

         return calc( this.md );

     }

     public void reset()

         throws DigesterException

     {

         md.reset();

     }

     public void update( InputStream is )

         throws DigesterException

     {

         update( is, md );

     }

     protected static String calc( MessageDigest md )

     {

         return Hex.encode( md.digest() );

     }

     protected static void update( InputStream is, MessageDigest digest )

         throws DigesterException

     {

         try

         {

             byte[] buffer = new byte[BUFFER_SIZE];

             int size = is.read( buffer, 0, BUFFER_SIZE );

             while ( size >= 0 )

             {

                 digest.update( buffer, 0, size );

                 size = is.read( buffer, 0, BUFFER_SIZE );

             }

         }

         catch ( IOException e )

         {

             throw new DigesterException( "Unable to update " + digest.getAlgorithm() + " hash: " + e.getMessage(), e );

         }

     }

 }