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-rw-r--r--decoder.h110
1 files changed, 75 insertions, 35 deletions
diff --git a/decoder.h b/decoder.h
index 785f310..6484898 100644
--- a/decoder.h
+++ b/decoder.h
@@ -25,10 +25,9 @@
Public License.
*/
-const int min_available_bytes = 8 + sizeof( File_trailer );
-
class Input_buffer : public Circular_buffer
{
+ enum { min_available_bytes = 8 + sizeof( File_trailer ) };
bool at_stream_end_;
public:
@@ -42,6 +41,12 @@ public:
bool finished() const throw() { return at_stream_end_ && !used_bytes(); }
void purge() throw() { at_stream_end_ = true; Circular_buffer::reset(); }
+ bool enough_available_bytes() const throw()
+ {
+ return ( used_bytes() > 0 &&
+ ( at_stream_end_ || used_bytes() >= min_available_bytes ) );
+ }
+
int write_data( uint8_t * const in_buffer, const int in_size ) throw()
{
if( at_stream_end_ || in_size <= 0 ) return 0;
@@ -55,6 +60,7 @@ class Range_decoder
mutable long long member_pos;
uint32_t code;
uint32_t range;
+ bool reload_pending;
Input_buffer & ibuf;
public:
@@ -63,62 +69,86 @@ public:
member_pos( header_size ),
code( 0 ),
range( 0xFFFFFFFF ),
+ reload_pending( false ),
ibuf( buf )
{ for( int i = 0; i < 5; ++i ) code = (code << 8) | get_byte(); }
+ bool at_stream_end() const throw() { return ibuf.at_stream_end(); }
+ int available_bytes() const throw() { return ibuf.used_bytes(); }
+ bool enough_available_bytes() const throw()
+ { return ibuf.enough_available_bytes(); }
+ bool finished() const throw() { return ibuf.finished(); }
+ long long member_position() const throw() { return member_pos; }
+
uint8_t get_byte() const
{
++member_pos;
return ibuf.get_byte();
}
- bool at_stream_end() const throw() { return ibuf.at_stream_end(); }
- int available_bytes() const throw() { return ibuf.used_bytes(); }
- bool finished() const throw() { return ibuf.finished(); }
- long long member_position() const throw() { return member_pos; }
+ bool try_reload( const bool force = false ) throw()
+ {
+ if( force ) reload_pending = true;
+ if( reload_pending && available_bytes() >= 5 )
+ {
+ code = 0;
+ range = 0xFFFFFFFF;
+ reload_pending = false;
+ for( int i = 0; i < 5; ++i ) code = (code << 8) | get_byte();
+ }
+ return !reload_pending;
+ }
+
+ void normalize()
+ {
+ if( range <= 0x00FFFFFF )
+ { range <<= 8; code = (code << 8) | get_byte(); }
+ }
int decode( const int num_bits )
{
int symbol = 0;
- for( int i = num_bits - 1; i >= 0; --i )
+ for( int i = num_bits; i > 0; --i )
{
- range >>= 1;
symbol <<= 1;
- if( code >= range )
- { code -= range; symbol |= 1; }
if( range <= 0x00FFFFFF )
- { range <<= 8; code = (code << 8) | get_byte(); }
+ {
+ range <<= 7; code = (code << 8) | get_byte();
+ if( code >= range ) { code -= range; symbol |= 1; }
+ }
+ else
+ {
+ range >>= 1;
+ if( code >= range ) { code -= range; symbol |= 1; }
+ }
}
return symbol;
}
int decode_bit( Bit_model & bm )
{
- int symbol;
+ 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;
- symbol = 0;
+ return 0;
}
else
{
range -= bound;
code -= bound;
bm.probability -= bm.probability >> bit_model_move_bits;
- symbol = 1;
+ return 1;
}
- if( range <= 0x00FFFFFF )
- { range <<= 8; code = (code << 8) | get_byte(); }
- return symbol;
}
int decode_tree( Bit_model bm[], const int num_bits )
{
int model = 1;
for( int i = num_bits; i > 0; --i )
- model = ( model << 1 ) | decode_bit( bm[model-1] );
+ model = ( model << 1 ) | decode_bit( bm[model] );
return model - (1 << num_bits);
}
@@ -126,27 +156,31 @@ public:
{
int model = 1;
int symbol = 0;
- for( int i = 1; i < (1 << num_bits); i <<= 1 )
+ for( int i = 0; i < num_bits; ++i )
{
- const int bit = decode_bit( bm[model-1] );
- model = ( model << 1 ) | bit;
- if( bit ) symbol |= i;
+ const int bit = decode_bit( bm[model] );
+ model <<= 1;
+ if( bit ) { model |= 1; symbol |= (1 << i); }
}
return symbol;
}
int decode_matched( Bit_model bm[], const int match_byte )
{
+ Bit_model *bm1 = bm + 0x100;
int symbol = 1;
- for( int i = 7; i >= 0; --i )
+ for( int i = 1; i <= 8; ++i )
{
- const int match_bit = ( match_byte >> i ) & 1;
- const int bit = decode_bit( bm[(match_bit<<8)+symbol+0xFF] );
+ const int match_bit = ( match_byte << i ) & 0x100;
+ const int bit = decode_bit( bm1[match_bit+symbol] );
symbol = ( symbol << 1 ) | bit;
- if( match_bit != bit ) break;
+ if( ( match_bit && !bit ) || ( !match_bit && bit ) )
+ {
+ while( ++i <= 8 )
+ symbol = ( symbol << 1 ) | decode_bit( bm[symbol] );
+ break;
+ }
}
- while( symbol < 0x100 )
- symbol = ( symbol << 1 ) | decode_bit( bm[symbol-1] );
return symbol & 0xFF;
}
};
@@ -193,6 +227,7 @@ public:
class LZ_decoder : public Circular_buffer
{
+ enum { min_free_bytes = max_match_len };
long long partial_data_pos;
const int format_version;
const int dictionary_size;
@@ -220,7 +255,6 @@ class LZ_decoder : public Circular_buffer
Len_decoder rep_match_len_decoder;
Literal_decoder literal_decoder;
-// using Circular_buffer::get_byte;
uint8_t get_byte( const int distance ) const throw()
{
int i = put - distance - 1;
@@ -235,20 +269,23 @@ class LZ_decoder : public Circular_buffer
if( ++put >= buffer_size ) { partial_data_pos += put; put = 0; }
}
- bool copy_block( const int distance, int len )
+ void copy_block( const int distance, int len )
{
- if( distance < 0 || distance >= dictionary_size ||
- len <= 0 || len > max_match_len ) return false;
int i = put - distance - 1;
if( i < 0 ) i += buffer_size;
- for( ; len > 0 ; --len )
+ if( len < buffer_size - std::max( put, i ) && len <= distance )
+ {
+ crc32.update( crc_, buffer + i, len );
+ std::memcpy( buffer + put, buffer + i, len );
+ put += len;
+ }
+ else for( ; len > 0 ; --len )
{
crc32.update( crc_, buffer[i] );
buffer[put] = buffer[i];
if( ++put >= buffer_size ) { partial_data_pos += put; put = 0; }
if( ++i >= buffer_size ) i = 0;
}
- return true;
}
bool verify_trailer();
@@ -256,7 +293,7 @@ class LZ_decoder : public Circular_buffer
public:
LZ_decoder( const File_header & header, Input_buffer & ibuf )
:
- Circular_buffer( std::max( 65536, header.dictionary_size() ) + max_match_len ),
+ Circular_buffer( std::max( 65536, header.dictionary_size() ) + min_free_bytes ),
partial_data_pos( 0 ),
format_version( header.version ),
dictionary_size( header.dictionary_size() ),
@@ -270,6 +307,9 @@ public:
range_decoder( sizeof header, ibuf ),
literal_decoder() {}
+ bool enough_free_bytes() const throw()
+ { return free_bytes() >= min_free_bytes; }
+
uint32_t crc() const throw() { return crc_ ^ 0xFFFFFFFF; }
int decode_member();
bool member_finished() const throw()