fast_encoder.h

/* Lzip - LZMA lossless data compressor
   Copyright (C) 2008-2024 Antonio Diaz Diaz.

   This program 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.

   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 General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

class FLZ_encoder : public LZ_encoder_base
  {
  unsigned key4;			// key made from latest 4 bytes

  void reset_key4()
    {
    key4 = 0;
    for( int i = 0; i < 3 && i < available_bytes(); ++i )
      key4 = ( key4 << 4 ) ^ buffer[i];
    }

  int longest_match_len( int * const distance );

  void update_and_move( int n )
    {
    while( --n >= 0 )
      {
      if( available_bytes() >= 4 )
        {
        key4 = ( ( key4 << 4 ) ^ buffer[pos+3] ) & key4_mask;
        pos_array[cyclic_pos] = prev_positions[key4];
        prev_positions[key4] = pos + 1;
        }
      move_pos();
      }
    }

  enum { before_size = 0,
         dict_size = 65536,
         // bytes to keep in buffer after pos
         after_size = max_match_len,
         dict_factor = 16,
         num_prev_positions23 = 0,
         pos_array_factor = 1 };

public:
  FLZ_encoder( const int ifd, const int outfd )
    :
    LZ_encoder_base( before_size, dict_size, after_size, dict_factor,
                     num_prev_positions23, pos_array_factor, ifd, outfd )
    {}

  bool encode_member( const unsigned long long member_size );
  };