lzlib/fast_encoder.c

/*  Lzlib - Compression library for the lzip format
    Copyright (C) 2009-2015 Antonio Diaz Diaz.

    This library 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 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.  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, see <http://www.gnu.org/licenses/>.

    As a special exception, you may use this file as part of a free
    software library without restriction.  Specifically, if other files
    instantiate templates or use macros or inline functions from this
    file, or you compile this file and link it with other files to
    produce an executable, this file 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.
*/

int FLZe_longest_match_len( struct FLZ_encoder * const fe, int * const distance )
  {
  enum { len_limit = 16 };
  const uint8_t * const data = Mb_ptr_to_current_pos( &fe->eb.mb );
  int32_t * ptr0 = fe->eb.mb.pos_array + fe->eb.mb.cyclic_pos;
  int32_t * newptr;
  const int pos1 = fe->eb.mb.pos + 1;
  int maxlen = 0;
  int count, delta, newpos;
  if( len_limit > Mb_available_bytes( &fe->eb.mb ) ) { *ptr0 = 0; return 0; }

  fe->key4 = ( ( fe->key4 << 4 ) ^ data[3] ) & fe->eb.mb.key4_mask;
  newpos = fe->eb.mb.prev_positions[fe->key4];
  fe->eb.mb.prev_positions[fe->key4] = pos1;


  for( count = 4; ; )
    {
    if( --count < 0 || newpos <= 0 ) { *ptr0 = 0; break; }
    delta = pos1 - newpos;
    if( delta > fe->eb.mb.dictionary_size ) { *ptr0 = 0; break; }
    newptr = fe->eb.mb.pos_array +
      ( fe->eb.mb.cyclic_pos - delta +
        ( ( fe->eb.mb.cyclic_pos >= delta ) ? 0 : fe->eb.mb.dictionary_size + 1 ) );

    if( data[maxlen-delta] == data[maxlen] )
      {
      int len = 0;
      while( len < len_limit && data[len-delta] == data[len] ) ++len;
      if( maxlen < len ) { maxlen = len; *distance = delta - 1; }
      }

    if( maxlen < len_limit )
      {
      *ptr0 = newpos;
      ptr0 = newptr;
      newpos = *ptr0;
      }
    else
      {
      *ptr0 = *newptr;
      maxlen += Mb_true_match_len( &fe->eb.mb, maxlen, *distance + 1,
                                   max_match_len - maxlen );
      break;
      }
    }
  return maxlen;
  }


bool FLZe_encode_member( struct FLZ_encoder * const fe )
  {
  int rep = 0, i;
  State * const state = &fe->eb.state;

  if( fe->eb.member_finished ) return true;
  if( Re_member_position( &fe->eb.renc ) >= fe->eb.member_size_limit )
    {
    if( LZeb_full_flush( &fe->eb ) ) fe->eb.member_finished = true;
    return true;
    }

  if( Mb_data_position( &fe->eb.mb ) == 0 &&
      !Mb_data_finished( &fe->eb.mb ) )		/* encode first byte */
    {
    const uint8_t prev_byte = 0;
    uint8_t cur_byte;
    if( !Mb_enough_available_bytes( &fe->eb.mb ) ||
        !Re_enough_free_bytes( &fe->eb.renc ) ) return true;
    cur_byte = Mb_peek( &fe->eb.mb, 0 );
    Re_encode_bit( &fe->eb.renc, &fe->eb.bm_match[*state][0], 0 );
    LZeb_encode_literal( &fe->eb, prev_byte, cur_byte );
    CRC32_update_byte( &fe->eb.crc, cur_byte );
    FLZe_reset_key4( fe );
    if( !FLZe_update_and_move( fe, 1 ) ) return false;
    }

  while( !Mb_data_finished( &fe->eb.mb ) &&
         Re_member_position( &fe->eb.renc ) < fe->eb.member_size_limit )
    {
    int match_distance;
    int main_len, pos_state, len;
    if( !Mb_enough_available_bytes( &fe->eb.mb ) ||
        !Re_enough_free_bytes( &fe->eb.renc ) ) return true;
    main_len = FLZe_longest_match_len( fe, &match_distance );
    pos_state = Mb_data_position( &fe->eb.mb ) & pos_state_mask;
    len = 0;

    for( i = 0; i < num_rep_distances; ++i )
      {
      const int tlen = Mb_true_match_len( &fe->eb.mb, 0,
                                          fe->eb.reps[i] + 1, max_match_len );
      if( tlen > len ) { len = tlen; rep = i; }
      }
    if( len > min_match_len && len + 3 > main_len )
      {
      CRC32_update_buf( &fe->eb.crc, Mb_ptr_to_current_pos( &fe->eb.mb ), len );
      Re_encode_bit( &fe->eb.renc, &fe->eb.bm_match[*state][pos_state], 1 );
      Re_encode_bit( &fe->eb.renc, &fe->eb.bm_rep[*state], 1 );
      Re_encode_bit( &fe->eb.renc, &fe->eb.bm_rep0[*state], rep != 0 );
      if( rep == 0 )
        Re_encode_bit( &fe->eb.renc, &fe->eb.bm_len[*state][pos_state], 1 );
      else
        {
        int distance;
        Re_encode_bit( &fe->eb.renc, &fe->eb.bm_rep1[*state], rep > 1 );
        if( rep > 1 )
          Re_encode_bit( &fe->eb.renc, &fe->eb.bm_rep2[*state], rep > 2 );
        distance = fe->eb.reps[rep];
        for( i = rep; i > 0; --i ) fe->eb.reps[i] = fe->eb.reps[i-1];
        fe->eb.reps[0] = distance;
        }
      *state = St_set_rep( *state );
      Re_encode_len( &fe->eb.renc, &fe->eb.rep_len_model, len, pos_state );
      if( !Mb_move_pos( &fe->eb.mb ) ) return false;
      if( !FLZe_update_and_move( fe, len - 1 ) ) return false;
      continue;
      }

    if( main_len > min_match_len )
      {
      CRC32_update_buf( &fe->eb.crc, Mb_ptr_to_current_pos( &fe->eb.mb ), main_len );
      Re_encode_bit( &fe->eb.renc, &fe->eb.bm_match[*state][pos_state], 1 );
      Re_encode_bit( &fe->eb.renc, &fe->eb.bm_rep[*state], 0 );
      *state = St_set_match( *state );
      for( i = num_rep_distances - 1; i > 0; --i ) fe->eb.reps[i] = fe->eb.reps[i-1];
      fe->eb.reps[0] = match_distance;
      LZeb_encode_pair( &fe->eb, match_distance, main_len, pos_state );
      if( !Mb_move_pos( &fe->eb.mb ) ) return false;
      if( !FLZe_update_and_move( fe, main_len - 1 ) ) return false;
      continue;
      }

    {
    const uint8_t prev_byte = Mb_peek( &fe->eb.mb, 1 );
    const uint8_t cur_byte = Mb_peek( &fe->eb.mb, 0 );
    const uint8_t match_byte = Mb_peek( &fe->eb.mb, fe->eb.reps[0] + 1 );
    if( !Mb_move_pos( &fe->eb.mb ) ) return false;
    CRC32_update_byte( &fe->eb.crc, cur_byte );

    if( match_byte == cur_byte )
      {
      const int short_rep_price = price1( fe->eb.bm_match[*state][pos_state] ) +
                                  price1( fe->eb.bm_rep[*state] ) +
                                  price0( fe->eb.bm_rep0[*state] ) +
                                  price0( fe->eb.bm_len[*state][pos_state] );
      int price = price0( fe->eb.bm_match[*state][pos_state] );
      if( St_is_char( *state ) )
        price += LZeb_price_literal( &fe->eb, prev_byte, cur_byte );
      else
        price += LZeb_price_matched( &fe->eb, prev_byte, cur_byte, match_byte );
      if( short_rep_price < price )
        {
        Re_encode_bit( &fe->eb.renc, &fe->eb.bm_match[*state][pos_state], 1 );
        Re_encode_bit( &fe->eb.renc, &fe->eb.bm_rep[*state], 1 );
        Re_encode_bit( &fe->eb.renc, &fe->eb.bm_rep0[*state], 0 );
        Re_encode_bit( &fe->eb.renc, &fe->eb.bm_len[*state][pos_state], 0 );
        *state = St_set_short_rep( *state );
        continue;
        }
      }

    /* literal byte */
    Re_encode_bit( &fe->eb.renc, &fe->eb.bm_match[*state][pos_state], 0 );
    if( St_is_char( *state ) )
      LZeb_encode_literal( &fe->eb, prev_byte, cur_byte );
    else
      LZeb_encode_matched( &fe->eb, prev_byte, cur_byte, match_byte );
    *state = St_set_char( *state );
    }
    }

  if( LZeb_full_flush( &fe->eb ) ) fe->eb.member_finished = true;
  return true;
  }