diff options
Diffstat (limited to 'decoder.h')
| -rw-r--r-- | decoder.h | 90 |
1 files changed, 59 insertions, 31 deletions
@@ -1,18 +1,18 @@ -/* Lziprecover - Data recovery tool for the lzip format - Copyright (C) 2009-2019 Antonio Diaz Diaz. +/* Lziprecover - Data recovery tool for the lzip format + Copyright (C) 2009-2021 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 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. + 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/>. + 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 @@ -49,7 +49,9 @@ public: unsigned get_code() const { return code; } bool finished() { return pos >= stream_pos && !read_block(); } - unsigned long long member_position() const { return partial_member_pos + pos; } + + unsigned long long member_position() const + { return partial_member_pos + pos; } void reset_member_position() { partial_member_pos = 0; partial_member_pos -= pos; } @@ -74,10 +76,40 @@ public: return sz; } + /* if ignore_errors, stop reading before the first wrong byte, so that + unreading the header is not required to sync to next member */ + int read_header_carefully( Lzip_header & header, const bool ignore_errors ) + { + int sz = 0; + while( sz < Lzip_header::size && !finished() ) + { + header.data[sz] = buffer[pos]; + if( ignore_errors && + ( ( sz < 4 && header.data[sz] != lzip_magic[sz] ) || + ( sz == 4 && !header.verify_version() ) || + ( sz == 5 && !isvalid_ds( header.dictionary_size() ) ) ) ) break; + ++pos; ++sz; + } + return sz; + } + + bool find_header( Lzip_header & header ) + { + while( !finished() ) + { + if( buffer[pos] != lzip_magic[0] ) { ++pos; continue; } + reset_member_position(); + Lzip_header h; + if( read_header_carefully( h, true ) == Lzip_header::size ) + { header = h; return true; } + } + return false; + } + void load() { code = 0; - for( int i = 0; i < 5; ++i ) code = (code << 8) | get_byte(); + for( int i = 0; i < 5; ++i ) code = ( code << 8 ) | get_byte(); range = 0xFFFFFFFFU; code &= range; // make sure that first byte is discarded } @@ -85,7 +117,7 @@ public: void normalize() { if( range <= 0x00FFFFFFU ) - { range <<= 8; code = (code << 8) | get_byte(); } + { range <<= 8; code = ( code << 8 ) | get_byte(); } } unsigned decode( const int num_bits ) @@ -98,7 +130,7 @@ public: // symbol <<= 1; // if( code >= range ) { code -= range; symbol |= 1; } const bool bit = ( code >= range ); - symbol = ( symbol << 1 ) + bit; + symbol <<= 1; symbol += bit; code -= range & ( 0U - bit ); } return symbol; @@ -111,7 +143,8 @@ public: if( code < bound ) { range = bound; - bm.probability += (bit_model_total - bm.probability) >> bit_model_move_bits; + bm.probability += + ( bit_model_total - bm.probability ) >> bit_model_move_bits; return 0; } else @@ -125,8 +158,7 @@ public: unsigned decode_tree3( Bit_model bm[] ) { - unsigned symbol = 1; - symbol = ( symbol << 1 ) | decode_bit( bm[symbol] ); + unsigned symbol = 2 | decode_bit( bm[1] ); symbol = ( symbol << 1 ) | decode_bit( bm[symbol] ); symbol = ( symbol << 1 ) | decode_bit( bm[symbol] ); return symbol & 7; @@ -134,8 +166,7 @@ public: unsigned decode_tree6( Bit_model bm[] ) { - unsigned symbol = 1; - symbol = ( symbol << 1 ) | decode_bit( bm[symbol] ); + unsigned symbol = 2 | decode_bit( bm[1] ); symbol = ( symbol << 1 ) | decode_bit( bm[symbol] ); symbol = ( symbol << 1 ) | decode_bit( bm[symbol] ); symbol = ( symbol << 1 ) | decode_bit( bm[symbol] ); @@ -159,7 +190,7 @@ public: for( int i = 0; i < num_bits; ++i ) { const unsigned bit = decode_bit( bm[model] ); - model = ( model << 1 ) + bit; + model <<= 1; model += bit; symbol |= ( bit << i ); } return symbol; @@ -168,12 +199,9 @@ public: unsigned decode_tree_reversed4( Bit_model bm[] ) { unsigned symbol = decode_bit( bm[1] ); - unsigned model = 2 + symbol; - unsigned bit = decode_bit( bm[model] ); - model = ( model << 1 ) + bit; symbol |= ( bit << 1 ); - bit = decode_bit( bm[model] ); - model = ( model << 1 ) + bit; symbol |= ( bit << 2 ); - symbol |= ( decode_bit( bm[model] ) << 3 ); + symbol += decode_bit( bm[2+symbol] ) << 1; + symbol += decode_bit( bm[4+symbol] ) << 2; + symbol += decode_bit( bm[8+symbol] ) << 3; return symbol; } @@ -184,9 +212,9 @@ public: while( symbol < 0x100 ) { const unsigned match_bit = ( match_byte <<= 1 ) & 0x100; - const unsigned bit = decode_bit( bm1[match_bit+symbol] ); - symbol = ( symbol << 1 ) | bit; - if( match_bit != bit << 8 ) + const bool bit = decode_bit( bm1[symbol+match_bit] ); + symbol <<= 1; symbol |= bit; + if( match_bit >> 8 != bit ) { while( symbol < 0x100 ) symbol = ( symbol << 1 ) | decode_bit( bm[symbol] ); |