public bool ReadHeader()

in src/CSVReader/ETLStackBrowse/ZL/gzipdecoder.cs [35:261]
189 lines of code
62 McCabe index (conditional complexity)

        public bool ReadHeader(InputBuffer input)
        {

            while (true)
            {
                int bits;
                switch (gzipHeaderSubstate)
                {
                    case GzipHeaderState.ReadingID1:
                        bits = input.GetBits(8);
                        if (bits < 0)
                        {
                            return false;
                        }

                        if (bits != GZipConstants.ID1)
                        {
                            throw new InvalidDataException("CorruptedGZipHeader");
                        }
                        gzipHeaderSubstate = GzipHeaderState.ReadingID2;
                        goto case GzipHeaderState.ReadingID2;

                    case GzipHeaderState.ReadingID2:
                        bits = input.GetBits(8);
                        if (bits < 0)
                        {
                            return false;
                        }

                        if (bits != GZipConstants.ID2)
                        {
                            throw new InvalidDataException("CorruptedGZipHeader");
                        }

                        gzipHeaderSubstate = GzipHeaderState.ReadingCM;
                        goto case GzipHeaderState.ReadingCM;

                    case GzipHeaderState.ReadingCM:
                        bits = input.GetBits(8);
                        if (bits < 0)
                        {
                            return false;
                        }

                        if (bits != GZipConstants.Deflate)
                        {         // compression mode must be 8 (deflate)
                            throw new InvalidDataException("UnknownCompressionMode");
                        }

                        gzipHeaderSubstate = GzipHeaderState.ReadingFLG; ;
                        goto case GzipHeaderState.ReadingFLG;

                    case GzipHeaderState.ReadingFLG:
                        bits = input.GetBits(8);
                        if (bits < 0)
                        {
                            return false;
                        }

                        gzip_header_flag = bits;
                        gzipHeaderSubstate = GzipHeaderState.ReadingMMTime;
                        loopCounter = 0; // 4 MMTIME bytes
                        goto case GzipHeaderState.ReadingMMTime;

                    case GzipHeaderState.ReadingMMTime:
                        bits = 0;
                        while (loopCounter < 4)
                        {
                            bits = input.GetBits(8);
                            if (bits < 0)
                            {
                                return false;
                            }

                            loopCounter++;
                        }

                        gzipHeaderSubstate = GzipHeaderState.ReadingXFL;
                        loopCounter = 0;
                        goto case GzipHeaderState.ReadingXFL;

                    case GzipHeaderState.ReadingXFL:      // ignore XFL
                        bits = input.GetBits(8);
                        if (bits < 0)
                        {
                            return false;
                        }

                        gzipHeaderSubstate = GzipHeaderState.ReadingOS;
                        goto case GzipHeaderState.ReadingOS;

                    case GzipHeaderState.ReadingOS:      // ignore OS
                        bits = input.GetBits(8);
                        if (bits < 0)
                        {
                            return false;
                        }

                        gzipHeaderSubstate = GzipHeaderState.ReadingXLen1;
                        goto case GzipHeaderState.ReadingXLen1;

                    case GzipHeaderState.ReadingXLen1:
                        if ((gzip_header_flag & (int)GZipOptionalHeaderFlags.ExtraFieldsFlag) == 0)
                        {
                            goto case GzipHeaderState.ReadingFileName;
                        }

                        bits = input.GetBits(8);
                        if (bits < 0)
                        {
                            return false;
                        }

                        gzip_header_xlen = bits;
                        gzipHeaderSubstate = GzipHeaderState.ReadingXLen2;
                        goto case GzipHeaderState.ReadingXLen2;

                    case GzipHeaderState.ReadingXLen2:
                        bits = input.GetBits(8);
                        if (bits < 0)
                        {
                            return false;
                        }

                        gzip_header_xlen |= (bits << 8);
                        gzipHeaderSubstate = GzipHeaderState.ReadingXLenData;
                        loopCounter = 0; // 0 bytes of XLEN data read so far
                        goto case GzipHeaderState.ReadingXLenData;

                    case GzipHeaderState.ReadingXLenData:
                        bits = 0;
                        while (loopCounter < gzip_header_xlen)
                        {
                            bits = input.GetBits(8);
                            if (bits < 0)
                            {
                                return false;
                            }

                            loopCounter++;
                        }
                        gzipHeaderSubstate = GzipHeaderState.ReadingFileName;
                        loopCounter = 0;
                        goto case GzipHeaderState.ReadingFileName;

                    case GzipHeaderState.ReadingFileName:
                        if ((gzip_header_flag & (int)GZipOptionalHeaderFlags.FileNameFlag) == 0)
                        {
                            gzipHeaderSubstate = GzipHeaderState.ReadingComment;
                            goto case GzipHeaderState.ReadingComment;
                        }

                        do
                        {
                            bits = input.GetBits(8);
                            if (bits < 0)
                            {
                                return false;
                            }

                            if (bits == 0)
                            {   // see '\0' in the file name string
                                break;
                            }
                        } while (true);

                        gzipHeaderSubstate = GzipHeaderState.ReadingComment;
                        goto case GzipHeaderState.ReadingComment;

                    case GzipHeaderState.ReadingComment:
                        if ((gzip_header_flag & (int)GZipOptionalHeaderFlags.CommentFlag) == 0)
                        {
                            gzipHeaderSubstate = GzipHeaderState.ReadingCRC16Part1;
                            goto case GzipHeaderState.ReadingCRC16Part1;
                        }

                        do
                        {
                            bits = input.GetBits(8);
                            if (bits < 0)
                            {
                                return false;
                            }

                            if (bits == 0)
                            {   // see '\0' in the file name string
                                break;
                            }
                        } while (true);

                        gzipHeaderSubstate = GzipHeaderState.ReadingCRC16Part1;
                        goto case GzipHeaderState.ReadingCRC16Part1;

                    case GzipHeaderState.ReadingCRC16Part1:
                        if ((gzip_header_flag & (int)GZipOptionalHeaderFlags.CRCFlag) == 0)
                        {
                            gzipHeaderSubstate = GzipHeaderState.Done;
                            goto case GzipHeaderState.Done;
                        }

                        bits = input.GetBits(8);     // ignore crc
                        if (bits < 0)
                        {
                            return false;
                        }

                        gzipHeaderSubstate = GzipHeaderState.ReadingCRC16Part2;
                        goto case GzipHeaderState.ReadingCRC16Part2;

                    case GzipHeaderState.ReadingCRC16Part2:
                        bits = input.GetBits(8);     // ignore crc
                        if (bits < 0)
                        {
                            return false;
                        }

                        gzipHeaderSubstate = GzipHeaderState.Done;
                        goto case GzipHeaderState.Done;

                    case GzipHeaderState.Done:
                        return true;
                    default:
                        Debug.Assert(false, "We should not reach unknown state!");
                        throw new InvalidDataException("UnknownState");
                }
            }
        }