diff options
Diffstat (limited to '')
| -rw-r--r-- | decoder.h | 110 |
1 files changed, 75 insertions, 35 deletions
@@ -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() |