public static double PackDouble()

in src/Elastic.Apm/Libraries/Newtonsoft.Json/Utilities/ConvertUtils.cs [871:1022]
116 lines of code
26 McCabe index (conditional complexity)

            public static double PackDouble(bool negative, ulong val, int scale)
            {
                // handle zero value
                if (val == 0)
                {
                    return negative ? -0.0 : 0.0;
                }

                // normalize the mantissa
                int exp = 64;

                if ((val & 0xFFFFFFFF00000000) == 0)
                {
                    val <<= 32;
                    exp -= 32;
                }
                if ((val & 0xFFFF000000000000) == 0)
                {
                    val <<= 16;
                    exp -= 16;
                }
                if ((val & 0xFF00000000000000) == 0)
                {
                    val <<= 8;
                    exp -= 8;
                }
                if ((val & 0xF000000000000000) == 0)
                {
                    val <<= 4;
                    exp -= 4;
                }
                if ((val & 0xC000000000000000) == 0)
                {
                    val <<= 2;
                    exp -= 2;
                }
                if ((val & 0x8000000000000000) == 0)
                {
                    val <<= 1;
                    exp -= 1;
                }

                if (scale < 0)
                {
                    scale = -scale;

                    // check scale bounds
                    if (scale >= 22 * 16)
                    {
                        // underflow
                        return negative ? -0.0 : 0.0;
                    }

                    // perform scaling
                    int index = scale & 15;
                    if (index != 0)
                    {
                        exp -= MultExp64Power10[index - 1] - 1;
                        val = Mul64Lossy(val, MultVal64Power10Inv[index - 1], ref exp);
                    }

                    index = scale >> 4;
                    if (index != 0)
                    {
                        exp -= MultExp64Power10By16[index - 1] - 1;
                        val = Mul64Lossy(val, MultVal64Power10By16Inv[index - 1], ref exp);
                    }
                }
                else
                {
                    // check scale bounds
                    if (scale >= 22 * 16)
                    {
                        // overflow
                        return negative ? double.NegativeInfinity : double.PositiveInfinity;
                    }

                    // perform scaling
                    int index = scale & 15;
                    if (index != 0)
                    {
                        exp += MultExp64Power10[index - 1];
                        val = Mul64Lossy(val, MultVal64Power10[index - 1], ref exp);
                    }

                    index = scale >> 4;
                    if (index != 0)
                    {
                        exp += MultExp64Power10By16[index - 1];
                        val = Mul64Lossy(val, MultVal64Power10By16[index - 1], ref exp);
                    }
                }

                // round & scale down

                if ((val & (1 << 10)) != 0)
                {
                    // IEEE round to even
                    ulong tmp = val + ((1UL << 10) - 1 + ((val >> 11) & 1));
                    if (tmp < val)
                    {
                        // overflow
                        tmp = (tmp >> 1) | 0x8000000000000000;
                        exp++;
                    }
                    val = tmp;
                }

                // return the exponent to a biased state

                exp += 0x3FE;

                // handle overflow, underflow, "Epsilon - 1/2 Epsilon", denormalized, and the normal case

                if (exp <= 0)
                {
                    if (exp == -52 && (val >= 0x8000000000000058))
                    {
                        // round X where {Epsilon > X >= 2.470328229206232730000000E-324} up to Epsilon (instead of down to zero)
                        val = 0x0000000000000001;
                    }
                    else if (exp <= -52)
                    {
                        // underflow
                        val = 0;
                    }
                    else
                    {
                        // denormalized value
                        val >>= (-exp + 12);
                    }
                }
                else if (exp >= 0x7FF)
                {
                    // overflow
                    val = 0x7FF0000000000000;
                }
                else
                {
                    // normal positive exponent case
                    val = ((ulong)exp << 52) | ((val >> 11) & 0x000FFFFFFFFFFFFF);
                }

                // apply sign

                if (negative)
                {
                    val |= 0x8000000000000000;
                }

                return BitConverter.Int64BitsToDouble((long)val);
            }