public static bool CheckTopicFilterMatch()

in iothub/device/src/Transport/Mqtt/MqttIotHubAdapter.cs [1319:1374]
52 lines of code
14 McCabe index (conditional complexity)

        public static bool CheckTopicFilterMatch(string topicName, string topicFilter)
        {
            int topicFilterIndex = 0;
            int topicNameIndex = 0;
            while (topicNameIndex < topicName.Length && topicFilterIndex < topicFilter.Length)
            {
                int wildcardIndex = topicFilter.IndexOfAny(s_wildcardChars, topicFilterIndex);
                if (wildcardIndex == -1)
                {
                    int matchLength = Math.Max(topicFilter.Length - topicFilterIndex, topicName.Length - topicNameIndex);
                    return string.Compare(topicFilter, topicFilterIndex, topicName, topicNameIndex, matchLength, StringComparison.Ordinal) == 0;
                }
                else
                {
                    if (topicFilter[wildcardIndex] == MultiSegmentWildcardChar)
                    {
                        if (wildcardIndex == 0) // special case -- any topic name would match
                        {
                            return true;
                        }
                        else
                        {
                            int matchLength = wildcardIndex - topicFilterIndex - 1;
                            if (string.Compare(topicFilter, topicFilterIndex, topicName, topicNameIndex, matchLength, StringComparison.Ordinal) == 0
                                && (topicName.Length == topicNameIndex + matchLength || (topicName.Length > topicNameIndex + matchLength && topicName[topicNameIndex + matchLength] == SegmentSeparatorChar)))
                            {
                                // paths match up till wildcard and either it is parent topic in hierarchy (one level above # specified) or any child topic under a matching parent topic
                                return true;
                            }
                            else
                            {
                                return false;
                            }
                        }
                    }
                    else
                    {
                        // single segment wildcard
                        int matchLength = wildcardIndex - topicFilterIndex;
                        if (matchLength > 0 && string.Compare(topicFilter, topicFilterIndex, topicName, topicNameIndex, matchLength, StringComparison.Ordinal) != 0)
                        {
                            return false;
                        }
                        topicNameIndex = topicName.IndexOf(SegmentSeparatorChar, topicNameIndex + matchLength);
                        topicFilterIndex = wildcardIndex + 1;
                        if (topicNameIndex == -1)
                        {
                            // there's no more segments following matched one
                            return topicFilterIndex == topicFilter.Length;
                        }
                    }
                }
            }

            return topicFilterIndex == topicFilter.Length && topicNameIndex == topicName.Length;
        }