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Diffstat (limited to '')
| -rw-r--r-- | decoder.h | 344 |
1 files changed, 344 insertions, 0 deletions
diff --git a/decoder.h b/decoder.h new file mode 100644 index 0000000..29fdef6 --- /dev/null +++ b/decoder.h @@ -0,0 +1,344 @@ +/* Lzip - LZMA lossless data compressor + Copyright (C) 2008-2022 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 Range_decoder + { + enum { buffer_size = 16384 }; + unsigned long long partial_member_pos; + uint8_t * const buffer; // input buffer + int pos; // current pos in buffer + int stream_pos; // when reached, a new block must be read + uint32_t code; + uint32_t range; + const int infd; // input file descriptor + bool at_stream_end; + + bool read_block(); + + Range_decoder( const Range_decoder & ); // declared as private + void operator=( const Range_decoder & ); // declared as private + +public: + explicit Range_decoder( const int ifd ) + : + partial_member_pos( 0 ), + buffer( new uint8_t[buffer_size] ), + pos( 0 ), + stream_pos( 0 ), + code( 0 ), + range( 0xFFFFFFFFU ), + infd( ifd ), + at_stream_end( false ) + {} + + ~Range_decoder() { delete[] buffer; } + + bool finished() { return pos >= stream_pos && !read_block(); } + + unsigned long long member_position() const + { return partial_member_pos + pos; } + + void reset_member_position() + { partial_member_pos = 0; partial_member_pos -= pos; } + + uint8_t get_byte() + { + // 0xFF avoids decoder error if member is truncated at EOS marker + if( finished() ) return 0xFF; + return buffer[pos++]; + } + + int read_data( uint8_t * const outbuf, const int size ) + { + int sz = 0; + while( sz < size && !finished() ) + { + const int rd = std::min( size - sz, stream_pos - pos ); + std::memcpy( outbuf + sz, buffer + pos, rd ); + pos += rd; + sz += rd; + } + return sz; + } + + void load() + { + code = 0; + for( int i = 0; i < 5; ++i ) code = ( code << 8 ) | get_byte(); + range = 0xFFFFFFFFU; + code &= range; // make sure that first byte is discarded + } + + void normalize() + { + if( range <= 0x00FFFFFFU ) + { range <<= 8; code = ( code << 8 ) | get_byte(); } + } + + unsigned decode( const int num_bits ) + { + unsigned symbol = 0; + for( int i = num_bits; i > 0; --i ) + { + normalize(); + range >>= 1; +// symbol <<= 1; +// if( code >= range ) { code -= range; symbol |= 1; } + const bool bit = ( code >= range ); + symbol <<= 1; symbol += bit; + code -= range & ( 0U - bit ); + } + return symbol; + } + + bool decode_bit( Bit_model & bm ) + { + normalize(); + const uint32_t bound = ( range >> bit_model_total_bits ) * bm.probability; + if( code < bound ) + { + range = bound; + bm.probability += + ( bit_model_total - bm.probability ) >> bit_model_move_bits; + return 0; + } + else + { + code -= bound; + range -= bound; + bm.probability -= bm.probability >> bit_model_move_bits; + return 1; + } + } + + void decode_symbol_bit( Bit_model & bm, unsigned & symbol ) + { + normalize(); + symbol <<= 1; + const uint32_t bound = ( range >> bit_model_total_bits ) * bm.probability; + if( code < bound ) + { + range = bound; + bm.probability += + ( bit_model_total - bm.probability ) >> bit_model_move_bits; + } + else + { + code -= bound; + range -= bound; + bm.probability -= bm.probability >> bit_model_move_bits; + symbol |= 1; + } + } + + void decode_symbol_bit_reversed( Bit_model & bm, unsigned & model, + unsigned & symbol, const int i ) + { + normalize(); + model <<= 1; + const uint32_t bound = ( range >> bit_model_total_bits ) * bm.probability; + if( code < bound ) + { + range = bound; + bm.probability += + ( bit_model_total - bm.probability ) >> bit_model_move_bits; + } + else + { + code -= bound; + range -= bound; + bm.probability -= bm.probability >> bit_model_move_bits; + model |= 1; + symbol |= 1 << i; + } + } + + unsigned decode_tree6( Bit_model bm[] ) + { + unsigned symbol = 1; + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + return symbol & 0x3F; + } + + unsigned decode_tree8( Bit_model bm[] ) + { + unsigned symbol = 1; + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + return symbol & 0xFF; + } + + unsigned decode_tree_reversed( Bit_model bm[], const int num_bits ) + { + unsigned model = 1; + unsigned symbol = 0; + for( int i = 0; i < num_bits; ++i ) + decode_symbol_bit_reversed( bm[model], model, symbol, i ); + return symbol; + } + + unsigned decode_tree_reversed4( Bit_model bm[] ) + { + unsigned model = 1; + unsigned symbol = 0; + decode_symbol_bit_reversed( bm[model], model, symbol, 0 ); + decode_symbol_bit_reversed( bm[model], model, symbol, 1 ); + decode_symbol_bit_reversed( bm[model], model, symbol, 2 ); + decode_symbol_bit_reversed( bm[model], model, symbol, 3 ); + return symbol; + } + + unsigned decode_matched( Bit_model bm[], unsigned match_byte ) + { + Bit_model * const bm1 = bm + 0x100; + unsigned symbol = 1; + while( symbol < 0x100 ) + { + const unsigned match_bit = ( match_byte <<= 1 ) & 0x100; + const bool bit = decode_bit( bm1[symbol+match_bit] ); + symbol <<= 1; symbol |= bit; + if( match_bit >> 8 != bit ) + { + while( symbol < 0x100 ) decode_symbol_bit( bm[symbol], symbol ); + break; + } + } + return symbol & 0xFF; + } + + unsigned decode_len( Len_model & lm, const int pos_state ) + { + Bit_model * bm; + unsigned mask, offset, symbol = 1; + + if( decode_bit( lm.choice1 ) == 0 ) + { bm = lm.bm_low[pos_state]; mask = 7; offset = 0; goto len3; } + if( decode_bit( lm.choice2 ) == 0 ) + { bm = lm.bm_mid[pos_state]; mask = 7; offset = len_low_symbols; goto len3; } + bm = lm.bm_high; mask = 0xFF; offset = len_low_symbols + len_mid_symbols; + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); +len3: + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + decode_symbol_bit( bm[symbol], symbol ); + return ( symbol & mask ) + min_match_len + offset; + } + }; + + +class LZ_decoder + { + unsigned long long partial_data_pos; + Range_decoder & rdec; + const unsigned dictionary_size; + uint8_t * const buffer; // output buffer + unsigned pos; // current pos in buffer + unsigned stream_pos; // first byte not yet written to file + uint32_t crc_; + const int outfd; // output file descriptor + bool pos_wrapped; + + void flush_data(); + bool verify_trailer( const Pretty_print & pp ) const; + + uint8_t peek_prev() const + { return buffer[((pos > 0) ? pos : dictionary_size)-1]; } + + uint8_t peek( const unsigned distance ) const + { + const unsigned i = ( ( pos > distance ) ? 0 : dictionary_size ) + + pos - distance - 1; + return buffer[i]; + } + + void put_byte( const uint8_t b ) + { + buffer[pos] = b; + if( ++pos >= dictionary_size ) flush_data(); + } + + void copy_block( const unsigned distance, unsigned len ) + { + unsigned lpos = pos, i = lpos - distance - 1; + bool fast, fast2; + if( lpos > distance ) + { + fast = ( len < dictionary_size - lpos ); + fast2 = ( fast && len <= lpos - i ); + } + else + { + i += dictionary_size; + fast = ( len < dictionary_size - i ); // (i == pos) may happen + fast2 = ( fast && len <= i - lpos ); + } + if( fast ) // no wrap + { + pos += len; + if( fast2 ) // no wrap, no overlap + std::memcpy( buffer + lpos, buffer + i, len ); + else + for( ; len > 0; --len ) buffer[lpos++] = buffer[i++]; + } + else for( ; len > 0; --len ) + { + buffer[pos] = buffer[i]; + if( ++pos >= dictionary_size ) flush_data(); + if( ++i >= dictionary_size ) i = 0; + } + } + + LZ_decoder( const LZ_decoder & ); // declared as private + void operator=( const LZ_decoder & ); // declared as private + +public: + LZ_decoder( Range_decoder & rde, const unsigned dict_size, const int ofd ) + : + partial_data_pos( 0 ), + rdec( rde ), + dictionary_size( dict_size ), + buffer( new uint8_t[dictionary_size] ), + pos( 0 ), + stream_pos( 0 ), + crc_( 0xFFFFFFFFU ), + outfd( ofd ), + pos_wrapped( false ) + // prev_byte of first byte; also for peek( 0 ) on corrupt file + { buffer[dictionary_size-1] = 0; } + + ~LZ_decoder() { delete[] buffer; } + + unsigned crc() const { return crc_ ^ 0xFFFFFFFFU; } + unsigned long long data_position() const { return partial_data_pos + pos; } + + int decode_member( const Pretty_print & pp ); + }; |