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huffman.cpp

/***************************************************************************
 *   Copyright (C) 2008 by Valerio Pilo                                    *
 *   valerio@kmess.org                                                     *
 *                                                                         *
 *   This program 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 program 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 Lesser General Public      *
 *   License along with this program; if not, write to the                 *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/

#include "huffman.h"

#include "isfqt-internal.h"

#include <math.h>


#define HUFFMAN_BASES_NUM   8
#define HUFFMAN_BASE_SIZE  11


using namespace Isf::Compress;


/// Bit amounts.
const int bitAmounts_[HUFFMAN_BASES_NUM][HUFFMAN_BASE_SIZE] =
{
    {0, 1, 2,  4,  6,  8, 12, 16, 24, 32, -1},
    {0, 1, 1,  2,  4,  8, 12, 16, 24, 32, -1},
    {0, 1, 1,  1,  2,  4,  8, 14, 22, 32, -1},
    {0, 2, 2,  3,  5,  8, 12, 16, 24, 32, -1},
    {0, 3, 4,  5,  8, 12, 16, 24, 32, -1, -1},
    {0, 4, 6,  8, 12, 16, 24, 32, -1, -1, -1},
    {0, 6, 8, 12, 16, 24, 32, -1, -1, -1, -1},
    {0, 7, 8, 12, 16, 24, 32, -1, -1, -1, -1},
};


/// Huffman codec value bases.
const int huffmanBases_[HUFFMAN_BASES_NUM][HUFFMAN_BASE_SIZE] =
{
    {0, 1,  2,   4,   12,    44,     172,    2220,   34988, 8423596, -1},
    {0, 1,  2,   3,    5,    13,     141,    2189,   34957, 8423565, -1},
    {0, 1,  2,   3,    4,     6,      14,     142,    8334, 2105486, -1},
    {0, 1,  3,   5,    9,    25,     153,    2201,   34969, 8423577, -1},
    {0, 1,  5,  13,   29,   157,    2205,   34973, 8423581,      -1, -1},
    {0, 1,  9,  41,  169,  2217,   34985, 8423593,      -1,      -1, -1},
    {0, 1, 33, 161, 2209, 34977, 8423585,      -1,      -1,      -1, -1},
    {0, 1, 65, 193, 2241, 35009, 8423617,      -1,      -1,      -1, -1},
};



/**
 * Get the most appropriate index for the given data.
 *
 * @param data Data to analyze
 * @return index value
 */
quint8 HuffmanAlgorithm::index( const QList<qint64>& data )
{
  quint8 index = 0;

  // TODO: Find out what the Huffman index algorithm is
  Q_UNUSED( data )
  index = 2;

  return index;
}



/**
 * Compress data with the Huffman algorithm.
 *
 * @param encodedData Byte array where to store the compressed data
 * @param index Index to use for compression
 * @param source List of values to compress
 * @return bool
 */
bool HuffmanAlgorithm::deflate( QByteArray& encodedData, quint8 index, const QList<qint64>& source )
{
  DataSource output( encodedData );
  output.skipToNextByte();

  foreach( quint64 value, source )
  {
    if( ! deflateValue( &output, index, value ) )
    {
#ifdef ISFQT_DEBUG
      qDebug() << "Deflating failure for value:" << value;
#endif
      return false;
    }
  }

  // Flush any leftover bit to the byte array
  output.flush();

  encodedData = output.data();
  return true;
}



/**
 * Compress a single value with the Huffman algorithm.
 *
 * @param output Data source where to store the compressed value
 * @param index Index to use for compression
 * @param value Value to compress
 * @return bool
 */
bool HuffmanAlgorithm::deflateValue( DataSource* output, quint8 index, qint64 value )
{
  qint64 temp = value;
  quint8 requiredBits = 0;
  QBitArray valueBits;

  // Fill in a bitAmounts local vector
  QVector<int> bitAmounts;
  for( int i = 0; i < HUFFMAN_BASE_SIZE; ++i )
  {
    if( bitAmounts_[ index ][ i ] == -1 )
    {
      break;
    }

    bitAmounts.append( bitAmounts_[ index ][ i ] );
  }

  // Find the number of bits needed to store this value
  while( temp )
  {
    temp /= 2;
    ++requiredBits;
  }

  while( ! bitAmounts.count( requiredBits ) )
  {
    ++requiredBits;
  }

  qint64 offset = ( value < 0 ) ? -value : +value;

  quint8 prefixLength;
  for( prefixLength = 1;
        ( prefixLength < HUFFMAN_BASE_SIZE ) && ( offset >= huffmanBases_[ index ][ prefixLength ] ); prefixLength++ )
  {
    // Empty loop on purpose
  }


  // Write prefixLength 1s to the stream, then a 0
  QBitArray bits( prefixLength );
  bits.fill( true );
  bits.clearBit( bits.size() - 1 );

  // Write the number using the minimum possible number of bits
  qint32 size = bitAmounts_[ index ][ prefixLength - 1 ];
  qint64 mask = ( 1 << ( size - 1 ) ) - 1;

  valueBits.resize( size );
  offset = ( offset - huffmanBases_[ index ][ prefixLength - 1 ] ) & mask;
  offset <<= 1;
  offset |= ( value < 0 ) ? 1 : 0;

  // Copy the resulting offset
  for( qint64 i = 0; i < size; ++i )
  {
    valueBits.setBit( i, offset & ( 1 << ( size - i - 1 ) ) );
  }

  // Add the bits to the data source
  output->append( bits );
  output->append( valueBits );

  return true;
}



/**
 * Decompress data with the Huffman algorithm.
 *
 * @param source Data source where to read the compressed bytes
 * @param length Number of items to read
 * @param index Index to use for compression
 * @param decodedData List where to place decompressed values
 * @return bool
 */
bool HuffmanAlgorithm::inflate( DataSource* source, quint64 length, quint8 index, QList<qint64>& decodedData )
{
  QVector<int> huffmanBases;
  QVector<int> bitAmounts( HUFFMAN_BASE_SIZE );

  // Initialize the bit amounts vector
  memcpy( bitAmounts.data(), bitAmounts_[ index ], sizeof(int)*HUFFMAN_BASE_SIZE );

  int base = 1;
  huffmanBases.append( 0 );

  // Fill up the huffman bases vector
  for( quint8 i = 0; i < bitAmounts.size(); ++i )
  {
    int value = bitAmounts[ i ];

    // The bit amounts sequence ends in -1
    if( value == -1 )
    {
      bitAmounts.resize( i );
      break;
    }

    if( value == 0 )
    {
      continue;
    }

    huffmanBases.append( base );
    base += pow( 2, value - 1 );
  }


  quint32 count = 0;
  qint64 value = 0;
  bool bit;

  while( (uint)decodedData.length() < length )
  {
    bit = source->getBit();

    if( bit )
    {
      count++;
      continue;
    }

    if( count == 0 )
    {
      value = 0;
    }
    else if( count < (uint)bitAmounts.size() )
    {
      quint64 offset = source->getBits( bitAmounts[ count ] );
      bool sign = offset & 0x1;
      offset /= 2;
      value = huffmanBases[ count ] + offset;
      value *= ( sign ? -1 : +1 );
    }
    else if( count == (uint)bitAmounts.size() )
    {
      // TODO: Implement 64-bit data decompression :)
#ifdef ISFQT_DEBUG
      qDebug() << "Unsupported 64-bit value found!";
#endif
      value = 0;
    }
    else
    {
#ifdef ISFQT_DEBUG
      qDebug() << "Decompression error!";
#endif
      value = 0;
    }

    decodedData.append( value );
    count = 0;
  }

  return true;
}



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