/*
 * $Id: CompressedOutputStream.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.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * A DTP output 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 CompressedOutputStream extends DTPOutputStream
{

  static final byte RECORD = -128;      // 0x80
  static final byte EOF = 64;   // 0x40

  CompressedOutputStream (DTP dtp, OutputStream out)
    {
      super (dtp, out);
    }

  /**
   * Just one byte cannot be compressed.
   * It takes 5 bytes to transmit - hardly very compressed!
   */
  public void write (int c) throws IOException
    {
      if (transferComplete)
        {
          return;
        }
      byte[] buf = new byte[]
        {
          RECORD,                   /* record descriptor */
          0x00, 0x01,             /* one byte */
          0x01,                   /* one uncompressed byte */
          (byte) c                /* the byte */
        };
      out.write (buf, 0, 5);
    }

  public void write (byte[] b) throws IOException
    {
      write (b, 0, b.length);
    }

  /**
   * The larger len is, the better.
   */
  public void write (byte[] b, int off, int len) throws IOException
    {
      if (transferComplete)
        {
          return;
        }
      byte[] buf = compress (b, off, len);
      len = buf.length;
      buf[0] = RECORD;            /* record descriptor */
      buf[1] = (byte) ((len & 0x00ff) >> 8);      /* high byte of bytecount */
      buf[2] = (byte) (len & 0xff00);     /* low byte of bytecount */
      out.write (buf, 0, len);
    }

  /**
   * Returns the compressed form of the given byte array.
   * The first 3 bytes are left free for header information.
   */
  byte[] compress (byte[] b, int off, int len)
    {
      byte[] buf = new byte[len];
      byte last = 0;
      int pos = 0, raw_count = 0, rep_count = 1;
      for (int i = off; i < len; i++)
        {
          byte c = b[i];
          if (i > off && c == last) // compress
            {
              if (raw_count > 0)      // flush raw bytes to buf
                {
                  // need to add raw_count+1 bytes
                  if (pos + (raw_count + 1) > buf.length)
                    {
                      buf = realloc (buf, len);
                    }
                  pos = flush_raw (buf, pos, b, (i - raw_count) - 1,
                                   raw_count);
                  raw_count = 0;
                }
              rep_count++;            // keep looking for same byte
            }
          else
            {
              if (rep_count > 1)      // flush compressed bytes to buf
                {
                  // need to add 2 bytes
                  if (pos + 2 > buf.length)
                    {
                      buf = realloc (buf, len);
                    }
                  pos = flush_compressed (buf, pos, rep_count, last);
                  rep_count = 1;
                }
              raw_count++;            // keep looking for raw bytes
            }
          if (rep_count == 127)     // flush compressed bytes
            {
              // need to add 2 bytes
              if (pos + 2 > buf.length)
                {
                  buf = realloc (buf, len);
                }
              pos = flush_compressed (buf, pos, rep_count, last);
              rep_count = 1;
            }
          if (raw_count == 127)     // flush raw bytes
            {
              // need to add raw_count+1 bytes
              if (pos + (raw_count + 1) > buf.length)
                {
                  buf = realloc (buf, len);
                }
              pos = flush_raw (buf, pos, b, (i - raw_count), raw_count);
              raw_count = 0;
            }
          last = c;
        }
      if (rep_count > 1)          // flush compressed bytes
        {
          // need to add 2 bytes
          if (pos + 2 > buf.length)
            {
              buf = realloc (buf, len);
            }
          pos = flush_compressed (buf, pos, rep_count, last);
          rep_count = 1;
        }
      if (raw_count > 0)          // flush raw bytes
        {
          // need to add raw_count+1 bytes
          if (pos + (raw_count + 1) > buf.length)
            {
              buf = realloc (buf, len);
            }
          pos = flush_raw (buf, pos, b, (len - raw_count), raw_count);
          raw_count = 0;
        }
      byte[] ret = new byte[pos + 3];
      System.arraycopy (buf, 0, ret, 3, pos);
      return ret;
    }

  int flush_compressed (byte[] buf, int pos, int count, byte c)
    {
      buf[pos++] = (byte) (0x80 | count);
      buf[pos++] = c;
      return pos;
    }

  int flush_raw (byte[] buf, int pos, byte[] src, int off, int len)
    {
      buf[pos++] = (byte) len;
      System.arraycopy (src, off, buf, pos, len);
      return pos + len;
    }

  byte[] realloc (byte[] buf, int len)
    {
      byte[] ret = new byte[buf.length + len];
      System.arraycopy (buf, 0, ret, 0, buf.length);
      return ret;
    }

  public void close () throws IOException
    {
      byte[] buf = new byte[]
        {
          EOF,                      /* eof descriptor */
          0x00, 0x00              /* no bytes */
        };
      out.write (buf, 0, 3);
      out.close ();
    }

}
