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/*
 * CompressedInputStream.java
 * 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
 * 
 * Linking this library statically or dynamically with other modules is
 * making a combined work based on this library.  Thus, the terms and
 * conditions of the GNU General Public License cover the whole
 * combination.
 *
 * As a special exception, the copyright holders of this library give you
 * permission to link this library with independent modules to produce an
 * executable, regardless of the license terms of these independent
 * modules, and to copy and distribute the resulting executable under
 * terms of your choice, provided that you also meet, for each linked
 * independent module, the terms and conditions of the license of that
 * module.  An independent module is a module which is not derived from
 * or based on this library.  If you modify this library, you may extend
 * this exception to your version of the library, but you are not
 * obliged to do so.  If you do not wish to do so, delete this
 * exception statement from your version.
 */

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 Chris Burdess
 */
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);
  }

}