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Diffstat (limited to 'decoder.c')
| -rw-r--r-- | decoder.c | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/decoder.c b/decoder.c new file mode 100644 index 0000000..6544ec6 --- /dev/null +++ b/decoder.c @@ -0,0 +1,145 @@ +/* Lzlib - Compression library for the lzip format + Copyright (C) 2009-2024 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. +*/ + +static int LZd_try_check_trailer( struct LZ_decoder * const d ) + { + Lzip_trailer trailer; + if( Rd_available_bytes( d->rdec ) < Lt_size ) + { if( !d->rdec->at_stream_end ) return 0; else return 2; } + d->check_trailer_pending = false; + d->member_finished = true; + + if( Rd_read_data( d->rdec, trailer, Lt_size ) == Lt_size && + Lt_get_data_crc( trailer ) == LZd_crc( d ) && + Lt_get_data_size( trailer ) == LZd_data_position( d ) && + Lt_get_member_size( trailer ) == d->rdec->member_position ) return 0; + return 3; + } + + +/* Return value: 0 = OK, 1 = decoder error, 2 = unexpected EOF, + 3 = trailer error, 4 = unknown marker found, + 5 = library error. */ +static int LZd_decode_member( struct LZ_decoder * const d ) + { + struct Range_decoder * const rdec = d->rdec; + State * const state = &d->state; + /* unsigned old_mpos = rdec->member_position; */ + + if( d->member_finished ) return 0; + if( !Rd_try_reload( rdec ) ) + { if( !rdec->at_stream_end ) return 0; else return 2; } + if( d->check_trailer_pending ) return LZd_try_check_trailer( d ); + + while( !Rd_finished( rdec ) ) + { + /* const unsigned mpos = rdec->member_position; + if( mpos - old_mpos > rd_min_available_bytes ) return 5; + old_mpos = mpos; */ + if( !Rd_enough_available_bytes( rdec ) ) /* check unexpected EOF */ + { if( !rdec->at_stream_end ) return 0; + if( Cb_empty( &rdec->cb ) ) break; } /* decode until EOF */ + if( !LZd_enough_free_bytes( d ) ) return 0; + const int pos_state = LZd_data_position( d ) & pos_state_mask; + if( Rd_decode_bit( rdec, &d->bm_match[*state][pos_state] ) == 0 ) /* 1st bit */ + { + /* literal byte */ + Bit_model * const bm = d->bm_literal[get_lit_state(LZd_peek_prev( d ))]; + if( ( *state = St_set_char( *state ) ) < 4 ) + LZd_put_byte( d, Rd_decode_tree8( rdec, bm ) ); + else + LZd_put_byte( d, Rd_decode_matched( rdec, bm, LZd_peek( d, d->rep0 ) ) ); + continue; + } + /* match or repeated match */ + int len; + if( Rd_decode_bit( rdec, &d->bm_rep[*state] ) != 0 ) /* 2nd bit */ + { + if( Rd_decode_bit( rdec, &d->bm_rep0[*state] ) == 0 ) /* 3rd bit */ + { + if( Rd_decode_bit( rdec, &d->bm_len[*state][pos_state] ) == 0 ) /* 4th bit */ + { *state = St_set_short_rep( *state ); + LZd_put_byte( d, LZd_peek( d, d->rep0 ) ); continue; } + } + else + { + unsigned distance; + if( Rd_decode_bit( rdec, &d->bm_rep1[*state] ) == 0 ) /* 4th bit */ + distance = d->rep1; + else + { + if( Rd_decode_bit( rdec, &d->bm_rep2[*state] ) == 0 ) /* 5th bit */ + distance = d->rep2; + else + { distance = d->rep3; d->rep3 = d->rep2; } + d->rep2 = d->rep1; + } + d->rep1 = d->rep0; + d->rep0 = distance; + } + *state = St_set_rep( *state ); + len = Rd_decode_len( rdec, &d->rep_len_model, pos_state ); + } + else /* match */ + { + len = Rd_decode_len( rdec, &d->match_len_model, pos_state ); + unsigned distance = Rd_decode_tree6( rdec, d->bm_dis_slot[get_len_state(len)] ); + if( distance >= start_dis_model ) + { + const unsigned dis_slot = distance; + const int direct_bits = ( dis_slot >> 1 ) - 1; + distance = ( 2 | ( dis_slot & 1 ) ) << direct_bits; + if( dis_slot < end_dis_model ) + distance += Rd_decode_tree_reversed( rdec, + d->bm_dis + ( distance - dis_slot ), direct_bits ); + else + { + distance += + Rd_decode( rdec, direct_bits - dis_align_bits ) << dis_align_bits; + distance += Rd_decode_tree_reversed4( rdec, d->bm_align ); + if( distance == 0xFFFFFFFFU ) /* marker found */ + { + Rd_normalize( rdec ); + /* const unsigned mpos = rdec->member_position; + if( mpos - old_mpos > rd_min_available_bytes ) return 5; + old_mpos = mpos; */ + if( len == min_match_len ) /* End Of Stream marker */ + { + d->check_trailer_pending = true; + return LZd_try_check_trailer( d ); + } + if( len == min_match_len + 1 ) /* Sync Flush marker */ + { + rdec->reload_pending = true; + if( Rd_try_reload( rdec ) ) continue; + if( !rdec->at_stream_end ) return 0; else break; + } + return 4; + } + } + } + d->rep3 = d->rep2; d->rep2 = d->rep1; d->rep1 = d->rep0; d->rep0 = distance; + *state = St_set_match( *state ); + if( d->rep0 >= d->dictionary_size || + ( d->rep0 >= d->cb.put && !d->pos_wrapped ) ) return 1; + } + LZd_copy_block( d, d->rep0, len ); + } + return 2; + } |