lzlib/fast_encoder.h

/* Lzlib - Compression library for the lzip format
   Copyright (C) 2009-2025 Antonio Diaz Diaz.

   This library is free software. Redistribution and use in source and
   binary forms, with or without modification, are permitted provided
   that the following conditions are met:

   1. Redistributions of source code must retain the above copyright
   notice, this list of conditions, and the following disclaimer.

   2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions, and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

   This library 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.
*/

typedef struct FLZ_encoder
  {
  LZ_encoder_base eb;
  unsigned key4;			/* key made from latest 4 bytes */
  } FLZ_encoder;

static inline void FLZe_reset_key4( FLZ_encoder * const fe )
  {
  int i;
  fe->key4 = 0;
  for( i = 0; i < 3 && i < Mb_available_bytes( &fe->eb.mb ); ++i )
    fe->key4 = ( fe->key4 << 4 ) ^ fe->eb.mb.buffer[i];
  }

static inline bool FLZe_update_and_move( FLZ_encoder * const fe, int n )
  {
  Matchfinder_base * const mb = &fe->eb.mb;
  while( --n >= 0 )
    {
    if( Mb_available_bytes( mb ) >= 4 )
      {
      fe->key4 = ( ( fe->key4 << 4 ) ^ mb->buffer[mb->pos+3] ) & mb->key4_mask;
      mb->pos_array[mb->cyclic_pos] = mb->prev_positions[fe->key4];
      mb->prev_positions[fe->key4] = mb->pos + 1;
      }
    else mb->pos_array[mb->cyclic_pos] = 0;
    if( !Mb_move_pos( mb ) ) return false;
    }
  return true;
  }

static inline bool FLZe_init( FLZ_encoder * const fe,
                              const unsigned long long member_size )
  {
  enum { before_size = 0,
         dict_size = 65536,
         /* bytes to keep in buffer after pos */
         after_size = max_match_len,
         dict_factor = 16,
         min_free_bytes = max_marker_size,
         num_prev_positions23 = 0,
         pos_array_factor = 1 };

  return LZeb_init( &fe->eb, before_size, dict_size, after_size, dict_factor,
                    num_prev_positions23, pos_array_factor, min_free_bytes,
                    member_size );
  }

static inline void FLZe_reset( FLZ_encoder * const fe,
                               const unsigned long long member_size )
  { LZeb_reset( &fe->eb, member_size ); }