/*
 * $Id: CompressedInputStream.java,v 1.4 2004/06/08 19:05:27 dog Exp $
 * Copyright (C) 2003 The Free Software Foundation
 * 
 * This file is part of GNU inetlib, a library.
 * 
 * GNU inetlib is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * GNU inetlib 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 General Public License for more details.
 * 
 * You should have received a copy of the GNU 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
 * 
 * As a special exception, if you link this library with other files to
 * produce an executable, this library does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * This exception does not however invalidate any other reasons why the
 * executable file might be covered by the GNU General Public License.
 */

package gnu.inet.ftp;

import java.io.InputStream;
import java.io.IOException;
import java.net.ProtocolException;

/**
 * A DTP input stream that implements the FTP compressed transfer mode.
 *
 * @author <a href='mailto:dog@gnu.org'>Chris Burdess</a>
 * @version $Revision: 1.4 $ $Date: 2004/06/08 19:05:27 $
 */
class CompressedInputStream extends DTPInputStream
{

  static final int EOF = 64;

  static final int RAW = 0x00;
  static final int COMPRESSED = 0x80;
  static final int FILLER = 0xc0;

  int descriptor;
  int max = -1;
  int count = -1;

  int state = RAW;              // RAW | STATE | FILLER
  int rep;                      // the compressed byte
  int n = 0;                    // the number of compressed or raw bytes

  CompressedInputStream (DTP dtp, InputStream in)
    {
      super (dtp, in);
    }

  public int read () throws IOException
    {
      if (transferComplete)
        {
          return -1;
        }
      if (count == -1)
        {
          readHeader ();
        }
      if (max < 1)
        {
          close ();
          return -1;
        }
      if (n > 0 && (state == COMPRESSED || state == FILLER))
        {
          n--;
          return rep;
        }
      int c = in.read ();
      if (c == -1)
        {
          close ();
        }
      count++;
      if (count >= max)
        {
          count = -1;
          if (descriptor == EOF)
            {
              close ();
            }
        }
      if (c == -1)
        {
          return c;
        }
      while (n == 0)              // read code header
        {
          state = (c & 0xc0);
          n = (c & 0x3f);
          c = in.read ();
          if (c == -1)
            {
              return -1;
            }
        }
      switch (state)
        {
        case RAW:
          break;
        case COMPRESSED:
        case FILLER:
          rep = c;
          break;
        default:
          throw new ProtocolException ("Illegal state: " + state);
        }
      n--;
      return c;
    }

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

  public int read (byte[] buf, int off, int len) throws IOException
    {
      if (transferComplete)
        {
          return -1;
        }
      if (count == -1)
        {
          readHeader ();
        }
      if (max < 1)
        {
          close ();
          return -1;
        }
      // TODO improve performance
      for (int i = off; i < len; i++)
        {
          int c = read ();
          if (c == -1)
            {
              close ();
              return i;
            }
          buf[i] = (byte) c;
        }
      return len;
      /*
         int l = in.read (buf, off, len);
         if (l==-1)
         {
         close ();
         }
         count += l;
         if (count>=max)
         {
         count = -1;
         if (descriptor==EOF)
         {
         close ();
         }
         }
         return l;
       */
    }

  /**
   * Reads the block header.
   */
  void readHeader () throws IOException
    {
      descriptor = in.read ();
      int max_hi = in.read ();
      int max_lo = in.read ();
      max = (max_hi << 8) | max_lo;
      count = 0;
    }

  /**
   * Reads the code header.
   */
  void readCodeHeader () throws IOException
    {
      int code = in.read ();
      state = (code & 0xc0);
      n = (code & 0x3f);
    }

}
