root/webserver/example/freeRTOS/Demo/Common/Minimal/AltPollQ.c

/*
        FreeRTOS V5.4.1 - Copyright (C) 2009 Real Time Engineers Ltd.

        This file is part of the FreeRTOS distribution.

        FreeRTOS is free software; you can redistribute it and/or modify it     under 
        the terms of the GNU General Public License (version 2) as published by the 
        Free Software Foundation and modified by the FreeRTOS exception.
        **NOTE** The exception to the GPL is included to allow you to distribute a
        combined work that includes FreeRTOS without being obliged to provide the 
        source code for proprietary components outside of the FreeRTOS kernel.  
        Alternative commercial license and support terms are also available upon 
        request.  See the licensing section of http://www.FreeRTOS.org for full 
        license details.

        FreeRTOS is distributed in the hope that it will be useful,     but WITHOUT
        ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
        FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
        more details.

        You should have received a copy of the GNU General Public License along
        with FreeRTOS; if not, write to the Free Software Foundation, Inc., 59
        Temple Place, Suite 330, Boston, MA  02111-1307  USA.


        ***************************************************************************
        *                                                                         *
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        * See http://www.FreeRTOS.org/Documentation for details                   *
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        ***************************************************************************

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        Please ensure to read the configuration and relevant port sections of the
        online documentation.

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*/

/*
 * This is a version of PollQ.c that uses the alternative (Alt) API.
 * 
 * Creates two tasks that communicate over a single queue.  One task acts as a
 * producer, the other a consumer.
 *
 * The producer loops for three iteration, posting an incrementing number onto the
 * queue each cycle.  It then delays for a fixed period before doing exactly the
 * same again.
 *
 * The consumer loops emptying the queue.  Each item removed from the queue is
 * checked to ensure it contains the expected value.  When the queue is empty it
 * blocks for a fixed period, then does the same again.
 *
 * All queue access is performed without blocking.  The consumer completely empties
 * the queue each time it runs so the producer should never find the queue full.
 *
 * An error is flagged if the consumer obtains an unexpected value or the producer
 * find the queue is full.
 */

/*
Changes from V2.0.0

        + Delay periods are now specified using variables and constants of
          portTickType rather than unsigned portLONG.
*/

#include <stdlib.h>

/* Scheduler include files. */
#include "FreeRTOS.h"
#include "task.h"
#include "queue.h"

/* Demo program include files. */
#include "AltPollQ.h"

#define pollqSTACK_SIZE                 configMINIMAL_STACK_SIZE
#define pollqQUEUE_SIZE                 ( 10 )
#define pollqPRODUCER_DELAY             ( ( portTickType ) 200 / portTICK_RATE_MS )
#define pollqCONSUMER_DELAY             ( pollqPRODUCER_DELAY - ( portTickType ) ( 20 / portTICK_RATE_MS ) )
#define pollqNO_DELAY                   ( ( portTickType ) 0 )
#define pollqVALUES_TO_PRODUCE  ( ( signed portBASE_TYPE ) 3 )
#define pollqINITIAL_VALUE              ( ( signed portBASE_TYPE ) 0 )

/* The task that posts the incrementing number onto the queue. */
static portTASK_FUNCTION_PROTO( vPolledQueueProducer, pvParameters );

/* The task that empties the queue. */
static portTASK_FUNCTION_PROTO( vPolledQueueConsumer, pvParameters );

/* Variables that are used to check that the tasks are still running with no
errors. */
static volatile signed portBASE_TYPE xPollingConsumerCount = pollqINITIAL_VALUE, xPollingProducerCount = pollqINITIAL_VALUE;

/*-----------------------------------------------------------*/

void vStartAltPolledQueueTasks( unsigned portBASE_TYPE uxPriority )
{
static xQueueHandle xPolledQueue;

        /* Create the queue used by the producer and consumer. */
        xPolledQueue = xQueueCreate( pollqQUEUE_SIZE, ( unsigned portBASE_TYPE ) sizeof( unsigned portSHORT ) );

        /* vQueueAddToRegistry() adds the queue to the queue registry, if one is
        in use.  The queue registry is provided as a means for kernel aware 
        debuggers to locate queues and has no purpose if a kernel aware debugger
        is not being used.  The call to vQueueAddToRegistry() will be removed
        by the pre-processor if configQUEUE_REGISTRY_SIZE is not defined or is 
        defined to be less than 1. */
        vQueueAddToRegistry( xPolledQueue, ( signed portCHAR * ) "AltPollQueue" );


        /* Spawn the producer and consumer. */
        xTaskCreate( vPolledQueueConsumer, ( signed portCHAR * ) "QConsNB", pollqSTACK_SIZE, ( void * ) &xPolledQueue, uxPriority, ( xTaskHandle * ) NULL );
        xTaskCreate( vPolledQueueProducer, ( signed portCHAR * ) "QProdNB", pollqSTACK_SIZE, ( void * ) &xPolledQueue, uxPriority, ( xTaskHandle * ) NULL );
}
/*-----------------------------------------------------------*/

static portTASK_FUNCTION( vPolledQueueProducer, pvParameters )
{
unsigned portSHORT usValue = ( unsigned portSHORT ) 0;
signed portBASE_TYPE xError = pdFALSE, xLoop;

        #ifdef USE_STDIO
        void vPrintDisplayMessage( const portCHAR * const * ppcMessageToSend );
        
                const portCHAR * const pcTaskStartMsg = "Alt polling queue producer task started.\r\n";

                /* Queue a message for printing to say the task has started. */
                vPrintDisplayMessage( &pcTaskStartMsg );
        #endif

        for( ;; )
        {               
                for( xLoop = 0; xLoop < pollqVALUES_TO_PRODUCE; xLoop++ )
                {
                        /* Send an incrementing number on the queue without blocking. */
                        if( xQueueAltSendToBack( *( ( xQueueHandle * ) pvParameters ), ( void * ) &usValue, pollqNO_DELAY ) != pdPASS )
                        {
                                /* We should never find the queue full so if we get here there
                                has been an error. */
                                xError = pdTRUE;
                        }
                        else
                        {
                                if( xError == pdFALSE )
                                {
                                        /* If an error has ever been recorded we stop incrementing the
                                        check variable. */
                                        portENTER_CRITICAL();
                                                xPollingProducerCount++;
                                        portEXIT_CRITICAL();
                                }

                                /* Update the value we are going to post next time around. */
                                usValue++;
                        }
                }

                /* Wait before we start posting again to ensure the consumer runs and
                empties the queue. */
                vTaskDelay( pollqPRODUCER_DELAY );
        }
}  /*lint !e818 Function prototype must conform to API. */
/*-----------------------------------------------------------*/

static portTASK_FUNCTION( vPolledQueueConsumer, pvParameters )
{
unsigned portSHORT usData, usExpectedValue = ( unsigned portSHORT ) 0;
signed portBASE_TYPE xError = pdFALSE;

        #ifdef USE_STDIO
        void vPrintDisplayMessage( const portCHAR * const * ppcMessageToSend );
        
                const portCHAR * const pcTaskStartMsg = "Alt blocking queue consumer task started.\r\n";

                /* Queue a message for printing to say the task has started. */
                vPrintDisplayMessage( &pcTaskStartMsg );
        #endif

        for( ;; )
        {               
                /* Loop until the queue is empty. */
                while( uxQueueMessagesWaiting( *( ( xQueueHandle * ) pvParameters ) ) )
                {
                        if( xQueueAltReceive( *( ( xQueueHandle * ) pvParameters ), &usData, pollqNO_DELAY ) == pdPASS )
                        {
                                if( usData != usExpectedValue )
                                {
                                        /* This is not what we expected to receive so an error has
                                        occurred. */
                                        xError = pdTRUE;

                                        /* Catch-up to the value we received so our next expected
                                        value should again be correct. */
                                        usExpectedValue = usData;
                                }
                                else
                                {
                                        if( xError == pdFALSE )
                                        {
                                                /* Only increment the check variable if no errors have
                                                occurred. */
                                                portENTER_CRITICAL();
                                                        xPollingConsumerCount++;
                                                portEXIT_CRITICAL();
                                        }
                                }

                                /* Next time round we would expect the number to be one higher. */
                                usExpectedValue++;
                        }
                }

                /* Now the queue is empty we block, allowing the producer to place more
                items in the queue. */
                vTaskDelay( pollqCONSUMER_DELAY );
        }
} /*lint !e818 Function prototype must conform to API. */
/*-----------------------------------------------------------*/

/* This is called to check that all the created tasks are still running with no errors. */
portBASE_TYPE xAreAltPollingQueuesStillRunning( void )
{
portBASE_TYPE xReturn;

        /* Check both the consumer and producer poll count to check they have both
        been changed since out last trip round.  We do not need a critical section
        around the check variables as this is called from a higher priority than
        the other tasks that access the same variables. */
        if( ( xPollingConsumerCount == pollqINITIAL_VALUE ) ||
                ( xPollingProducerCount == pollqINITIAL_VALUE )
          )
        {
                xReturn = pdFALSE;
        }
        else
        {
                xReturn = pdTRUE;
        }

        /* Set the check variables back down so we know if they have been
        incremented the next time around. */
        xPollingConsumerCount = pollqINITIAL_VALUE;
        xPollingProducerCount = pollqINITIAL_VALUE;

        return xReturn;
}