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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.InputStream;
import java.io.IOException;


//------------------------------------------------------------------------------
/**
 An InputStream variant for reading up to a specified marker.
 
   @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 InputStreamSegment extends FilterInputStream
{
   //##########################################################################
   // PRIVATE FIELDS
   //##########################################################################

   private byte[]  mSegmentEndMarker;
   private byte[]  mBuffer;
   private int     mBufferPtr;
   private int     mBufferLimit;
   private int     mBufferReadLimit;
   private boolean mEndOfSegmentReached = false;


   private static int sDefaultBufferSize = 4 * 1024;

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

   //--------------------------------------------------------------------------
   public InputStreamSegment(InputStream inStream, byte[] inSegmentEndMarker)
   {
      super(inStream);

      if (0 == inSegmentEndMarker.length)
      {
         throw new RuntimeException("No segment end marker was specifed!");
      }

      mSegmentEndMarker = inSegmentEndMarker;
      mBuffer = new byte[(inSegmentEndMarker.length * 2 > sDefaultBufferSize ? inSegmentEndMarker.length * 2 : sDefaultBufferSize)];
   }

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

   //--------------------------------------------------------------------------
   public InputStreamSegment setBufferSize(int inValue)
   {
      if (inValue < mSegmentEndMarker.length)
      {
         throw new RuntimeException("The buffer size cannot be smaller than the size of the segment end marker!");
      }

      mBuffer = new byte[inValue];

      return this;
   }

   //--------------------------------------------------------------------------
   public int read()
         throws IOException
   {
      if (mBufferPtr >= mBufferReadLimit)
      {
         if (!mEndOfSegmentReached)
         {
           fillBuffer();
         }
         else
         {
            return -1;
         }
      }

      return (mBufferPtr < mBufferReadLimit ? (int) mBuffer[mBufferPtr++] & 0xff : -1);
   }

   //--------------------------------------------------------------------------
   public int read(byte[] buffer, int offset, int length)
         throws IOException
   {
      int index = offset;
      int theChar = 0;
      while (index - offset < length
             && (theChar = read()) != -1)
      {
         buffer[index++] = (byte) theChar;
      }

      int bytesRead = index - offset;
      if (0 == bytesRead
          && -1 == theChar)
      {
         bytesRead = -1;
      }

      return bytesRead;
   }


   //##########################################################################
   // PRIVATE METHODS
   //##########################################################################

   //--------------------------------------------------------------------------
   private void fillBuffer()
         throws IOException
   {
      int markerIndex = mBufferLimit - mBufferReadLimit;

      // Move leftover content to the beginning of the buffer
      if (mBufferPtr > 0)
      {
         System.arraycopy(mBuffer, mBufferReadLimit, mBuffer, 0, mBufferLimit - mBufferReadLimit);
         mBufferPtr = 0;
         mBufferLimit = mBufferLimit - mBufferReadLimit;
         mBufferReadLimit = 0;
      }

      while (mBufferLimit < mBuffer.length)
      {
         int nextChar = in.read();
         if (-1 == nextChar)
         {
            throw new IOException("End of stream reached without detecting the segment end marker '" + new String(mSegmentEndMarker) + "'!");
         }

         mBuffer[mBufferLimit++] = (byte) nextChar;
         if (nextChar == mSegmentEndMarker[markerIndex])
         {
            if (markerIndex == mSegmentEndMarker.length - 1)
            {
               // Found the segment end marker.
               mEndOfSegmentReached = true;
               break;
            }

            markerIndex++;
         }
         else
         {
            if (nextChar == mSegmentEndMarker[0])
            {
               mBufferReadLimit += markerIndex;
               markerIndex = 1;
            }
            else
            {
               mBufferReadLimit += (markerIndex + 1);
               markerIndex = 0;
            }
         }
      }
   }
}