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package com.hfg.util.io;

import java.io.FilterReader;
import java.io.IOException;
import java.io.Reader;

//------------------------------------------------------------------------------
/**
 FilterReader that only allows letters through.
 
  @author J. Alex Taylor, hairyfatguy.com
 
 */
//------------------------------------------------------------------------------
// com.hfg 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 LettersOnlyReader extends FilterReader
{
   private char[]  mBuffer = new char[8196];
   private int     mBufferLimit;
   private int     mBufferIndex;
   private boolean mEndOfStreamReached;

   //---------------------------------------------------------------------------
   public LettersOnlyReader(Reader inReader)
   {
      super(inReader);
   }

   //---------------------------------------------------------------------------
   public int read()
         throws IOException
   {
      int returnChar;

      do
      {
         returnChar = innerRead();
      }
      while (returnChar >= 0
             && ! Character.isLetter(returnChar));

      return returnChar;
   }

   //---------------------------------------------------------------------------
   public int read(char[] inBuffer, int inOffset, int inMaxReadLength)
         throws IOException
   {
      int theChar;
      int numCharsRead = 0;
      do
      {
         theChar = read();
         if (theChar > 0)
         {
            inBuffer[inOffset++] = (char) theChar;
            numCharsRead++;
         }
      }
      while (theChar >= 0
             && numCharsRead < inMaxReadLength);

      return (theChar < 0 && 0 == numCharsRead ? -1 : numCharsRead);
   }

   //---------------------------------------------------------------------------
   protected int innerRead()
      throws IOException
   {
      if (mBufferIndex >= mBufferLimit)
      {
         fillBuffer();
      }

      return (mEndOfStreamReached ? -1 : mBuffer[mBufferIndex++]);
   }

   //---------------------------------------------------------------------------
   private void fillBuffer()
      throws IOException
   {
      mBufferLimit = super.in.read(mBuffer, 0, mBuffer.length);

      if (-1 == mBufferLimit)
      {
         mEndOfStreamReached = true;
      }

      // Reset the index
      mBufferIndex = 0;
   }
}