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com.hfg xml, html, svg, and bioinformatics utility library
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package com.hfg.util.io;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;


//------------------------------------------------------------------------------
/**
 An InputStream variant for calculating the MD5 checksum for the bytes that pass through.
 
 @author J. Alex Taylor, hairyfatguy.com
 
 */
//------------------------------------------------------------------------------
// com.hfg XML/HTML Coding Library
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
// J. Alex Taylor, President, Founder, CEO, COO, CFO, OOPS hairyfatguy.com
// [email protected]
//------------------------------------------------------------------------------

public class MD5InputStream extends FilterInputStream
{
   private MessageDigest mChecksum;

   //##########################################################################
   // CONSTRUCTORS
   //##########################################################################

   //--------------------------------------------------------------------------
   /**
    An InputStream that measures the number of bytes that pass through.
    */
   public MD5InputStream(InputStream in)
   {
      super(in);

      try
      {
         mChecksum = MessageDigest.getInstance("MD5");
      }
      catch (NoSuchAlgorithmException e)
      {
         throw new RuntimeException(e);
      }
   }


   //##########################################################################
   // PUBLIC METHODS
   //##########################################################################

   //--------------------------------------------------------------------------
   @Override
   public int read()
         throws IOException
   {
      int theByte = super.read();
      if (theByte > 0)
      {
         mChecksum.update((byte) theByte);
      }

      return theByte;
   }

   //--------------------------------------------------------------------------
   @Override
   public int read(byte[] inBytes, int inOffset, int inLength)
         throws IOException
   {
      int numBytesRead = super.read(inBytes, inOffset, inLength);
      if (numBytesRead > 0)
      {
         mChecksum.update(inBytes, inOffset, numBytesRead);
      }

      return numBytesRead;
   }

   //--------------------------------------------------------------------------
   public void reset()
   {
      mChecksum.reset();
   }

   //--------------------------------------------------------------------------
   public byte[] getChecksum()
   {
      return mChecksum.digest();
   }
}