summaryrefslogtreecommitdiffstats
path: root/decoder.h
diff options
context:
space:
mode:
Diffstat (limited to 'decoder.h')
-rw-r--r--decoder.h90
1 files changed, 59 insertions, 31 deletions
diff --git a/decoder.h b/decoder.h
index b0e9f16..01d875e 100644
--- a/decoder.h
+++ b/decoder.h
@@ -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] );