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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.IOException;
import java.io.RandomAccessFile;
import java.nio.BufferUnderflowException;
import java.nio.ByteBuffer;

import com.hfg.exception.ProgrammingException;

//------------------------------------------------------------------------------
/**
 * Abstraction to normalize RandomAccessFiles and byte[].
 *
 * @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 ByteSource
{
   private ByteBuffer mByteBuffer;
   private RandomAccessFile mRandomAccessFile;


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

   //---------------------------------------------------------------------------
   public ByteSource(byte[] inBytes)
   {
      mByteBuffer = ByteBuffer.wrap(inBytes);
   }

   //---------------------------------------------------------------------------
   public ByteSource(ByteBuffer inByteBuffer)
   {
      mByteBuffer = inByteBuffer;
   }

   //---------------------------------------------------------------------------
   public ByteSource(RandomAccessFile inRandomAccessFile)
   {
      mRandomAccessFile = inRandomAccessFile;
   }


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

   //---------------------------------------------------------------------------
   public void seek(long inPosition)
         throws IOException
   {
      if (mByteBuffer != null)
      {
         mByteBuffer.position((int) inPosition);
      }
      else if (mRandomAccessFile != null)
      {
         mRandomAccessFile.seek(inPosition);
      }
      else
      {
         throw new ProgrammingException("Unsupported byte source!");
      }
   }

   //---------------------------------------------------------------------------
   public int read() throws IOException
   {
      int theByte;
      if (mByteBuffer != null)
      {
         theByte = mByteBuffer.get();
      }
      else if (mRandomAccessFile != null)
      {
         theByte = mRandomAccessFile.read();
      }
      else
      {
         throw new ProgrammingException("Unsupported byte source!");
      }

      return theByte;
   }

   //---------------------------------------------------------------------------
   public int read(byte inByteDest[], int inOffset, int inLength)
         throws IOException
   {
      int numBytesRead;
      if (mByteBuffer != null)
      {
         int remaining = mByteBuffer.remaining();
         try
         {
            mByteBuffer.get(inByteDest, inOffset, inLength);
            numBytesRead = inLength;
         }
         catch (BufferUnderflowException e)
         {
            numBytesRead = remaining;
         }
      }
      else if (mRandomAccessFile != null)
      {
         mRandomAccessFile.readFully(inByteDest, inOffset, inLength);
         numBytesRead = inLength;
      }
      else
      {
         throw new ProgrammingException("Unsupported byte source!");
      }

      return numBytesRead;
   }

   //---------------------------------------------------------------------------
   public int read(byte inByteDest[])
         throws IOException
   {
      return read(inByteDest, 0, inByteDest.length);
   }

   //---------------------------------------------------------------------------
   /**
    * Reads a signed 32-bit integer from this souce. This method reads 4
    * bytes from the source, starting at the current pointer.
    */
   public final int readInt()
         throws IOException
   {
      int theInt;
      if (mByteBuffer != null)
      {
         theInt = mByteBuffer.getInt();
      }
      else if (mRandomAccessFile != null)
      {
         theInt = mRandomAccessFile.readInt();
      }
      else
      {
         throw new ProgrammingException("Unsupported byte source!");
      }

      return theInt;
   }
}