Creating FreeRTOS+Nabto Applications
Part 2: Worked Examples

/*
 * Parameters:
 * pxRequest     A pointer to a structure that contains details of the query, 
 *               including the query's unique ID.
 * pxReadBuffer  A buffer that contains the request parameters. Do not read from 
 *               the buffer directly. Access functions are provided.
 * pxWriteBuffer A buffer into which response parameters are written. Do not 
 *               write to the buffer directly. Access functions are provided.
 */
application_event_result_t application_event( application_request_t* pxRequest,
                                              buffer_read_t* pxReadBuffer,
                                              buffer_write_t* pxWriteBuffer );
						

/* Define a text constant for query ID #1. */
#define sysQUERY_TICK_VALUE	 1

/* The standard function prototype as shown in list 1. */
application_event_result_t application_event( application_request_t* pxRequest,
                                              buffer_read_t* pxReadBuffer,
                                              buffer_write_t* pxWriteBuffer )
{
application_event_result_t xReturn;

    /*
     * The bullet points directly above this code listing provide an explanation of
     * the following code.
     */
    switch( request->query_id )
    {
        case sysQUERY_TICK_VALUE:

            /* Write the response parameter to pxWriteBuffer. */
            if( buffer_write_uint32( pxWriteBuffer, xTaskGetTickCount() ) == pdFAIL )
            {
                /* The response parameter would not fit in the write buffer. */
                xReturn = AER_REQ_RSP_TOO_LARGE;
            }
            else
            {
                /* The write buffer contains the value of the response parameter. */
                xReturn = AER_REQ_RESPONSE_READY;
            }
            break;
    }

    return xReturn;
}
						

/* Define a text constant for query ID #2. */
#define sysQUERY_NET_STAT  2

/* The standard function prototype as shown in list 1. */
application_event_result_t application_event( application_request_t* pxRequest,
                                              buffer_read_t* pxReadBuffer,
                                              buffer_write_t* pxWriteBuffer )
{
application_event_result_t xReturn;
unsigned long ulRequestParameter, ulStatValue;

    /*
     * The bullet points directly above this code listing provide an explanation
     * of the following code.
     */
    switch( request->query_id )
    {
        case sysQUERY_NET_STAT:

            /* Read the request parameter from pxReadBuffer. */
            if( buffer_read_uint32( pxReadBuffer, &ulRequestParameter ) == pdFAIL )
            {
                /* There are two few bytes remaining in pxReadBuffer to complete the
                read request. */
                xReturn = AER_REQ_TOO_SMALL;
            }
            else
            {
                ulStatValue = prvGetNetworkStatistic( ulRequestParameter );

                /* Write the response parameter to pxWriteBuffer. */
                if( buffer_write_uint32( pxWriteBuffer, ulStatValue ) == pdFAIL )
                {
                    /* The response parameter would not fit in the write buffer. */
                    xReturn = AER_REQ_RSP_TOO_LARGE;
                }
                else
                {
                    /* The write buffer contains the value of the response parameter. */
                    xReturn = AER_REQ_RESPONSE_READY;
                }
            }
    }

    return xReturn;
}
						

/* Define a text constant for query ID #3. */
#define sysQUERY_COMMAND_STRING  3

/* Dimensions local buffers to be large enough to hold one line of input/output. */
#define sysMAX_LINE_LENGTH  128

/* The standard function prototype as shown in list 1. */
application_event_result_t application_event( application_request_t* pxRequest,
                                              buffer_read_t* pxReadBuffer,
                                              buffer_write_t* pxWriteBuffer )
{
application_event_result_t xReturn;
buffer_t xRawBuffer;
static uint8_t ucLocalBuffer[ sysMAX_LINE_LENGTH ];

    /*
     * The bullet points directly above this code listing provide an explanation
     * of the following code.
     */
    switch( request->query_id )
    {
        case sysQUERY_COMMAND_STRING:
            /* The locally declared raw buffer is used to point to the locally
            declared ucLocalBuffer array. */
            xRawBuffer.data = ucLocalBuffer;
            xRawBuffer.size = sizeof( ucLocalBuffer );

            /* Read raw data from pxReadBuffer into the buffer pointed to by
            pxReadBuffer (pxReadBuffer is pointing to ucLocalBuffer). */
            if( buffer_read_raw( pxReadBuffer, &xRawBuffer ) != pdFALSE )
            {
                /* ucLocalBuffer now holds the command string.  Ensure it is
                terminated. */
                ucLocalBuffer[ xRawBuffer.size ] = 0x00;

                /* Execute the command.  xRawBuffer is now set to point to the
                output generated when the command was executed. */
                xRawBuffer.data = prvProcessCommandString( ucLocalBuffer );

                /* Update the length of data in the raw buffer to reflect the
                length of the string it now contains. */
                xRawBuffer.size = strlen( xRawBuffer.data );

                /* Write the raw buffer to the output buffer. */
                if( buffer_write_raw( pxWriteBuffer, &xRawBuffer ) == pdFALSE )
                {
                    xReturn = AER_REQ_RSP_TOO_LARGE;
                }
                else
                {
                    xReturn = AER_REQ_RESPONSE_READY;
                }
            }
            else
            {
                xReturn = AER_REQ_TOO_SMALL;
            }
            break;
    }

    return xReturn;
}