gistfile1.cpp

            // first byte
            if (_mod_packets)
            {
                // need to rebuild packet type and window info

                if (!mode_blockflag)
                {
                    throw Parse_error_str("didn't load mode_blockflag");
                }

                // OUT: 1 bit packet type (0 == audio)
                Bit_uint<1> packet_type(0);
                os << packet_type;

                Bit_uintv * mode_number_p = 0;
                Bit_uintv * remainder_p = 0;

                {
                    // collect mode number from first byte

                    Bit_stream ss(_infile);

                    // IN/OUT: N bit mode number (max 6 bits)
                    mode_number_p = new Bit_uintv(mode_bits);
                    ss >> *mode_number_p;
                    os << *mode_number_p;

                    // IN: remaining bits of first (input) byte
                    remainder_p = new Bit_uintv(8-mode_bits);
                    ss >> *remainder_p;
                }

                if (mode_blockflag[*mode_number_p])
                {
                    // long window, peek at next frame

                    _infile.seekg(next_offset);
                    bool next_blockflag = false;
                    if (next_offset + packet_header_size <= _data_offset + _data_size)
                    {

                        // mod_packets always goes with 6-byte headers
                        Packet audio_packet(_infile, next_offset, _little_endian, _no_granule);
                        uint32_t next_packet_size = audio_packet.size();
                        if (next_packet_size > 0)
                        {
                            _infile.seekg(audio_packet.offset());

                            Bit_stream ss(_infile);
                            Bit_uintv next_mode_number(mode_bits);

                            ss >> next_mode_number;

                            next_blockflag = mode_blockflag[next_mode_number];
                        }
                    }

                    // OUT: previous window type bit
                    Bit_uint<1> prev_window_type(prev_blockflag);
                    os << prev_window_type;

                    // OUT: next window type bit
                    Bit_uint<1> next_window_type(next_blockflag);
                    os << next_window_type;

                    // fix seek for rest of stream
                    _infile.seekg(offset + 1);
                }

                prev_blockflag = mode_blockflag[*mode_number_p];
                delete mode_number_p;

                // OUT: remaining bits of first (input) byte
                os << *remainder_p;
                delete remainder_p;
            }