//C-  -*- C++ -*-

//C- -------------------------------------------------------------------

//C- DjVuLibre-3.5

//C- Copyright (c) 2002  Leon Bottou and Yann Le Cun.

//C- Copyright (c) 2001  AT&T

//C-

//C- This software is subject to, and may be distributed under, the

//C- GNU General Public License, either Version 2 of the license,

//C- or (at your option) any later version. The license should have

//C- accompanied the software or you may obtain a copy of the license

//C- from the Free Software Foundation at http://www.fsf.org .

//C-

//C- This program is distributed in the hope that it will be useful,

//C- but WITHOUT ANY WARRANTY; without even the implied warranty of

//C- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

//C- GNU General Public License for more details.

//C- 

//C- DjVuLibre-3.5 is derived from the DjVu(r) Reference Library from

//C- Lizardtech Software.  Lizardtech Software has authorized us to

//C- replace the original DjVu(r) Reference Library notice by the following

//C- text (see doc/lizard2002.djvu and doc/lizardtech2007.djvu):

//C-

//C-  ------------------------------------------------------------------

//C- | DjVu (r) Reference Library (v. 3.5)

//C- | Copyright (c) 1999-2001 LizardTech, Inc. All Rights Reserved.

//C- | The DjVu Reference Library is protected by U.S. Pat. No.

//C- | 6,058,214 and patents pending.

//C- |

//C- | This software is subject to, and may be distributed under, the

//C- | GNU General Public License, either Version 2 of the license,

//C- | or (at your option) any later version. The license should have

//C- | accompanied the software or you may obtain a copy of the license

//C- | from the Free Software Foundation at http://www.fsf.org .

//C- |

//C- | The computer code originally released by LizardTech under this

//C- | license and unmodified by other parties is deemed "the LIZARDTECH

//C- | ORIGINAL CODE."  Subject to any third party intellectual property

//C- | claims, LizardTech grants recipient a worldwide, royalty-free, 

//C- | non-exclusive license to make, use, sell, or otherwise dispose of 

//C- | the LIZARDTECH ORIGINAL CODE or of programs derived from the 

//C- | LIZARDTECH ORIGINAL CODE in compliance with the terms of the GNU 

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//C- |

//C- | The LIZARDTECH ORIGINAL CODE is provided "AS IS" WITHOUT WARRANTY

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//C- +------------------------------------------------------------------

#ifndef _BSBYTESTREAM_H

#define _BSBYTESTREAM_H

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#if NEED_GNUG_PRAGMAS

# pragma interface

#endif

/** @name BSByteStream.h

    Files #"BSByteStream.h"# and #"BSByteStream.cpp"# implement a very compact

    general purpose compressor based on the Burrows-Wheeler transform.  The

    utility program \Ref{bzz} provides a front-end for this class. Although

    this compression model is not currently used in DjVu files, it may be used

    in the future for encoding textual data chunks.

    {\bf Algorithms} --- The Burrows-Wheeler transform (also named Block-Sorting)

    is performed using a combination of the Karp-Miller-Rosenberg and the

    Bentley-Sedgewick algorithms. This is comparable to (Sadakane, DCC 98)

    with a slightly more flexible ranking scheme. Symbols are then ordered

    according to a running estimate of their occurrence frequencies.  The

    symbol ranks are then coded using a simple fixed tree and the

    \Ref{ZPCodec} binary adaptive coder.

    {\bf Performances} --- The basic algorithm is mostly similar to those

    implemented in well known compressors like #bzip# or #bzip2#

    (\URL{http://www.muraroa.demon.co.uk}).  The adaptive binary coder however

    generates small differences. The adaptation noise may cost up to 5\% in

    file size, but this penalty is usually offset by the benefits of

    adaptation.  This is good when processing large and highly structured

    files like spreadsheet files.  Compression and decompression speed is

    about twice slower than #bzip2# but the sorting algorithms is more

    robust. Unlike #bzip2# (as of August 1998), this code can compress half a

    megabyte of "abababab...." in bounded time.

    Here are some comparative results (in bits per character) obtained on the

    Canterbury Corpus (\URL{http://corpus.canterbury.ac.nz}) as of August

    1998. The BSByteStream performance on the single spreadsheet file #Excl#

    moves #bzz#'s weighted average ahead of much more sophisticated methods,

    like Suzanne Bunton's #fsmxBest# system

    \URL{http://corpus.canterbury.ac.nz/methodinfo/fsmx.html}.  This result

    will not last very long.

    {\footnotesize

    \begin{tabular}{lccccccccccccc}

      & text & fax & Csrc & Excl & SPRC & tech 

      & poem & html & lisp & man & play & Weighted & Average \\

      compress 

      & 3.27 & 0.97 & 3.56 & 2.41 & 4.21 & 3.06 

      & 3.38 & 3.68 & 3.90 & 4.43 & 3.51 

      & 2.55 & 3.31 \\

      gzip -9

      & 2.85 & 0.82 & 2.24 & 1.63 & 2.67 & 2.71 

      & 3.23 & 2.59 & 2.65 & 3.31 & 3.12 

      & 2.08 & 2.53 \\  

      bzip2 -9

      & 2.27 & 0.78 & 2.18 & 1.01 & 2.70 & 2.02 

      & 2.42 & 2.48 & 2.79 & 3.33 & 2.53 

      & 1.54 & 2.23 \\

      ppmd

      & 2.31 & 0.99 & 2.11 & 1.08 & 2.68 & 2.19 

      & 2.48 & 2.38 & 2.43 & 3.00 & 2.53 

      & 1.65 & 2.20 \\

      fsmx

      & {\bf 2.10} & 0.79 & {\bf 1.89} & 1.48 & {\bf 2.52} & {\bf 1.84} 

      & {\bf 2.21} & {\bf 2.24} & {\bf 2.29} & {\bf 2.91} & {\bf 2.35} 

      & 1.63 & {\bf 2.06} \\

      {\bf bzz}

      & 2.25 & {\bf 0.76} & 2.13 & {\bf 0.78} & 2.67 & 2.00

      & 2.40 & 2.52 & 2.60 & 3.19 & 2.52 

      & {\bf 1.44} & 2.16

    \end{tabular}

    }

    Note that the DjVu people have several entries in this table.  Program

    #compress# was written some time ago by Joe Orost

    (\URL{http://www.research.att.com/info/orost}). The #ppmc# method, (a

    precursor of #ppmd#) was created by Paul Howard

    (\URL{http://www.research.att.com/info/pgh}). The #bzz# program is just

    below your eyes.

    @author

    L\'eon Bottou <leonb@research.att.com> -- Initial implementation\\

    Andrei Erofeev <eaf@geocities.com> -- Improved Block Sorting algorithm.

    @memo

    Simple Burrows-Wheeler general purpose compressor.

*/

//@{

#include "ByteStream.h"

#include "GException.h"

#include "ZPCodec.h"

#ifdef HAVE_NAMESPACES

namespace DJVU {

# ifdef NOT_DEFINED // Just to fool emacs c++ mode

}

#endif

#endif

/** Performs bzz compression/decompression.

    Class #BSByteStream# defines a \Ref{ByteStream} which transparently

    performs the BZZ compression/decompression. The constructor of class

    \Ref{BSByteStream} takes another \Ref{ByteStream} as argument.  Any data

    written to the BSByteStream is compressed and written to this second

    ByteStream. Any data read from the BSByteStream is internally generated by

    decompressing data read from the second ByteStream.

    Program \Ref{bzz} demonstrates how to use this class.  All the hard work

    is achieved by a simple ByteStream to ByteStream copy, as shown below.

    \begin{verbatim}

      GP<ByteStream> in=ByteStream::create(infile,"rb");

      GP<ByteStream> out=ByteStream::create(outfile,"wb");

      if (encoding) {

          BSByteStream bsb(out, blocksize);

          bsb.copy(*in);

      } else {

          BSByteStream bsb(in);

          out->copy(bsb);

      }

    \end{verbatim}

    Due to the block oriented nature of the Burrows-Wheeler transform, there

    is a very significant latency between the data input and the data output.

    You can use function #flush# to force data output at the expense of

    compression efficiency.

    You should never directly access a ByteStream object connected to a valid

    BSByteStream object. The ByteStream object can be accessed again after the

    destruction of the BSByteStream object.  Note that the encoder always

    flushes its internal buffers and writes a few final code bytes when the

    BSByteStream object is destroyed.  Note also that the decoder often reads

    a few bytes beyond the last code byte written by the encoder.  This lag

    means that you must reposition the ByteStream after the destruction of the

    BSByteStream object and before re-using the ByteStream object (see

    \Ref{IFFByteStream}.)

*/

class DJVUAPI BSByteStream : public ByteStream

{

public:

// Limits on block sizes

  enum { MINBLOCK=10, MAXBLOCK=4096 };

// Sorting tresholds

  enum { FREQMAX=4, CTXIDS=3 };

  class Decode;

  class Encode;

protected:

  BSByteStream(GP<ByteStream> bs);

public:

  /** Creates a BSByteStream.

      The BSByteStream will be used for decompressing data.

      \begin{description}

      \item[Decompression]

      The BSByteStream is created and the decompressor initializes.  Chunks of

      data will be read from ByteStream #bs# and decompressed into an internal

      buffer. Function #read# can be used to access the decompressed data.

      \end{description} */

  static GP<ByteStream> create(GP<ByteStream> bs);

  /** Constructs a BSByteStream.

      The BSByteStream will be used for compressing data.

      \begin{description}

      \item[Compression]

      Set #blocksize# to a positive number smaller than 4096 to 

      initialize the compressor.  Data written to the BSByteStream will be

      accumulated into an internal buffer.  The buffered data will be

      compressed and written to ByteStream #bs# whenever the buffer sizes

      reaches the maximum value specified by argument #blocksize# (in

      kilobytes).  Using a larger block size usually increases the compression

      ratio at the expense of computation time.  There is no need however to

      specify a block size larger than the total number of bytes to compress.

      Setting #blocksize# to #1024# is a good starting point.  A minimal block

      size of 10 is silently enforced.

      \end{description} */

  static GP<ByteStream> create(GP<ByteStream> bs, const int blocksize);

  // ByteStream Interface

  ~BSByteStream();

  virtual long tell(void) const;

  virtual void flush(void) = 0;

protected:

  // Data

  long            offset;

  int             bptr;

  unsigned int    blocksize;

  int             size;

  ByteStream *bs;

  GP<ByteStream> gbs;

  unsigned char  *data;

  GPBuffer<unsigned char> gdata;

  // Coder

  GP<ZPCodec> gzp;

  BitContext ctx[300];

private:  

  // Cancel C++ default stuff

  BSByteStream(const BSByteStream &);

  BSByteStream & operator=(const BSByteStream &);

  BSByteStream(ByteStream *);

  BSByteStream(ByteStream *, int);

};

//@}

#ifdef HAVE_NAMESPACES

}

# ifndef NOT_USING_DJVU_NAMESPACE

using namespace DJVU;

# endif

#endif

#endif