MQTTStatus_t MQTT_GetConnectPacketSize()

in source/core_mqtt_serializer.c [1512:1608]
57 lines of code
11 McCabe index (conditional complexity)

MQTTStatus_t MQTT_GetConnectPacketSize( const MQTTConnectInfo_t * pConnectInfo,
                                        const MQTTPublishInfo_t * pWillInfo,
                                        size_t * pRemainingLength,
                                        size_t * pPacketSize )
{
    MQTTStatus_t status = MQTTSuccess;
    size_t remainingLength;

    /* The CONNECT packet will always include a 10-byte variable header. */
    size_t connectPacketSize = MQTT_PACKET_CONNECT_HEADER_SIZE;

    /* Validate arguments. */
    if( ( pConnectInfo == NULL ) || ( pRemainingLength == NULL ) ||
        ( pPacketSize == NULL ) )
    {
        LogError( ( "Argument cannot be NULL: pConnectInfo=%p, "
                    "pRemainingLength=%p, pPacketSize=%p.",
                    ( void * ) pConnectInfo,
                    ( void * ) pRemainingLength,
                    ( void * ) pPacketSize ) );
        status = MQTTBadParameter;
    }
    else if( ( pConnectInfo->clientIdentifierLength == 0U ) || ( pConnectInfo->pClientIdentifier == NULL ) )
    {
        LogError( ( "Mqtt_GetConnectPacketSize() client identifier must be set." ) );
        status = MQTTBadParameter;
    }
    else if( ( pWillInfo != NULL ) && ( pWillInfo->payloadLength > ( size_t ) UINT16_MAX ) )
    {
        /* The MQTTPublishInfo_t is reused for the will message. The payload
         * length for any other message could be larger than 65,535, but
         * the will message length is required to be represented in 2 bytes.
         * By bounding the payloadLength of the will message, the CONNECT
         * packet will never be larger than 327699 bytes. */
        LogError( ( "The Will Message length must not exceed %d. "
                    "pWillInfo->payloadLength=%lu.",
                    UINT16_MAX,
                    ( unsigned long ) pWillInfo->payloadLength ) );
        status = MQTTBadParameter;
    }
    else
    {
        /* Add the length of the client identifier. */
        connectPacketSize += pConnectInfo->clientIdentifierLength + sizeof( uint16_t );

        /* Add the lengths of the will message and topic name if provided. */
        if( pWillInfo != NULL )
        {
            connectPacketSize += pWillInfo->topicNameLength + sizeof( uint16_t ) +
                                 pWillInfo->payloadLength + sizeof( uint16_t );
        }

        /* Add the lengths of the user name and password if provided. */
        if( pConnectInfo->pUserName != NULL )
        {
            connectPacketSize += pConnectInfo->userNameLength + sizeof( uint16_t );
        }

        if( pConnectInfo->pPassword != NULL )
        {
            connectPacketSize += pConnectInfo->passwordLength + sizeof( uint16_t );
        }

        /* At this point, the "Remaining Length" field of the MQTT CONNECT packet has
         * been calculated. */
        remainingLength = connectPacketSize;

        /* Calculate the full size of the MQTT CONNECT packet by adding the size of
         * the "Remaining Length" field plus 1 byte for the "Packet Type" field. */
        connectPacketSize += 1U + remainingLengthEncodedSize( connectPacketSize );

        /* The connectPacketSize calculated from this function's parameters is
         * guaranteed to be less than the maximum MQTT CONNECT packet size, which
         * is 327700. If the maximum client identifier length, the maximum will
         * message topic length, the maximum will topic payload length, the
         * maximum username length, and the maximum password length are all present
         * in the MQTT CONNECT packet, the total size will be calculated to be
         * 327699:
         * (variable length header)10 +
         * (maximum client identifier length) 65535 + (encoded length) 2 +
         * (maximum will message topic name length) 65535 + (encoded length)2 +
         * (maximum will message payload length) 65535 + 2 +
         * (maximum username length) 65535 + (encoded length) 2 +
         * (maximum password length) 65535 + (encoded length) 2 +
         * (packet type field length) 1 +
         * (CONNECT packet encoded length) 3 = 327699 */

        *pRemainingLength = remainingLength;
        *pPacketSize = connectPacketSize;

        LogDebug( ( "CONNECT packet remaining length=%lu and packet size=%lu.",
                    ( unsigned long ) *pRemainingLength,
                    ( unsigned long ) *pPacketSize ) );
    }

    return status;
}