uint16_t MqttConnection::Subscribe()

in source/mqtt/MqttClient.cpp [468:519]
43 lines of code
6 McCabe index (conditional complexity)

            uint16_t MqttConnection::Subscribe(
                const char *topicFilter,
                QOS qos,
                OnMessageReceivedHandler &&onMessage,
                OnSubAckHandler &&onSubAck) noexcept
            {
                auto pubCallbackData = Crt::New<PubCallbackData>(m_owningClient->allocator);

                if (!pubCallbackData)
                {
                    return 0;
                }

                pubCallbackData->connection = this;
                pubCallbackData->onMessageReceived = std::move(onMessage);
                pubCallbackData->allocator = m_owningClient->allocator;

                auto subAckCallbackData = Crt::New<SubAckCallbackData>(m_owningClient->allocator);

                if (!subAckCallbackData)
                {
                    Crt::Delete(pubCallbackData, m_owningClient->allocator);
                    return 0;
                }

                subAckCallbackData->connection = this;
                subAckCallbackData->allocator = m_owningClient->allocator;
                subAckCallbackData->onSubAck = std::move(onSubAck);
                subAckCallbackData->topic = nullptr;
                subAckCallbackData->allocator = m_owningClient->allocator;

                ByteBuf topicFilterBuf = aws_byte_buf_from_c_str(topicFilter);
                ByteCursor topicFilterCur = aws_byte_cursor_from_buf(&topicFilterBuf);

                uint16_t packetId = aws_mqtt_client_connection_subscribe(
                    m_underlyingConnection,
                    &topicFilterCur,
                    qos,
                    s_onPublish,
                    pubCallbackData,
                    s_cleanUpOnPublishData,
                    s_onSubAck,
                    subAckCallbackData);

                if (!packetId)
                {
                    Crt::Delete(pubCallbackData, pubCallbackData->allocator);
                    Crt::Delete(subAckCallbackData, subAckCallbackData->allocator);
                }

                return packetId;
            }