diff options
Diffstat (limited to 'decoder.h')
| -rw-r--r-- | decoder.h | 97 |
1 files changed, 55 insertions, 42 deletions
@@ -40,7 +40,7 @@ public: bool finished() const throw() { return at_stream_end && pos >= stream_pos; } - uint8_t read_byte() + uint8_t get_byte() { if( pos >= stream_pos && !read_block() ) return 0; return buffer[pos++]; @@ -62,59 +62,68 @@ public: code( 0 ), range( 0xFFFFFFFF ), ibuf( buf ) - { for( int i = 0; i < 5; ++i ) code = (code << 8) | read_byte(); } + { for( int i = 0; i < 5; ++i ) code = (code << 8) | get_byte(); } - uint8_t read_byte() const + 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.read_byte(); + return ibuf.get_byte(); } - long long member_position() const throw() { return member_pos; } - bool finished() const throw() { return ibuf.finished(); } + 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) | read_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; + if( range <= 0x00FFFFFF ) + { range <<= 8; code = (code << 8) | get_byte(); } 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) | read_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); } @@ -122,27 +131,31 @@ 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; } }; @@ -215,32 +228,32 @@ class LZ_decoder uint8_t get_byte( const int distance ) const throw() { - int newpos = pos - distance - 1; - if( newpos < 0 ) newpos += buffer_size; - return buffer[newpos]; + int i = pos - distance - 1; + if( i < 0 ) i += buffer_size; + return buffer[i]; } void put_byte( const uint8_t b ) { - crc32.update( crc_, b ); buffer[pos] = b; if( ++pos >= buffer_size ) flush_data(); } - bool copy_block( const int distance, int len ) + void copy_block( const int distance, int len ) { - if( distance < 0 || distance >= buffer_size || - len <= 0 || len > max_match_len ) return false; - int newpos = pos - distance - 1; - if( newpos < 0 ) newpos += buffer_size; - for( ; len > 0 ; --len ) + int i = pos - distance - 1; + if( i < 0 ) i += buffer_size; + if( len < buffer_size - std::max( pos, i ) && len <= distance ) + { + std::memcpy( buffer + pos, buffer + i, len ); + pos += len; + } + else for( ; len > 0 ; --len ) { - crc32.update( crc_, buffer[newpos] ); - buffer[pos] = buffer[newpos]; + buffer[pos] = buffer[i]; if( ++pos >= buffer_size ) flush_data(); - if( ++newpos >= buffer_size ) newpos = 0; + if( ++i >= buffer_size ) i = 0; } - return true; } void flush_data(); |