root/webserver/example/freeRTOSexample/EnergyMeters/Common/Minimal/QPeek.c

/*
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        ***************************************************************************
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*/


/* 
 * Tests the behaviour when data is peeked from a queue when there are
 * multiple tasks blocked on the queue.
 */


#include <stdlib.h>

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

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

#define qpeekQUEUE_LENGTH               ( 5 )
#define qpeekNO_BLOCK                   ( 0 )
#define qpeekSHORT_DELAY                ( 10 )

#define qpeekLOW_PRIORITY                       ( tskIDLE_PRIORITY + 0 )
#define qpeekMEDIUM_PRIORITY            ( tskIDLE_PRIORITY + 1 )
#define qpeekHIGH_PRIORITY                      ( tskIDLE_PRIORITY + 2 )
#define qpeekHIGHEST_PRIORITY           ( tskIDLE_PRIORITY + 3 )

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

/*
 * The following three tasks are used to demonstrate the peeking behaviour.
 * Each task is given a different priority to demonstrate the order in which
 * tasks are woken as data is peeked from a queue.
 */
static void prvLowPriorityPeekTask( void *pvParameters );
static void prvMediumPriorityPeekTask( void *pvParameters );
static void prvHighPriorityPeekTask( void *pvParameters );
static void prvHighestPriorityPeekTask( void *pvParameters );

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

/* Flag that will be latched to pdTRUE should any unexpected behaviour be
detected in any of the tasks. */
static volatile portBASE_TYPE xErrorDetected = pdFALSE;

/* Counter that is incremented on each cycle of a test.  This is used to
detect a stalled task - a test that is no longer running. */
static volatile unsigned portLONG ulLoopCounter = 0;

/* Handles to the test tasks. */
xTaskHandle xMediumPriorityTask, xHighPriorityTask, xHighestPriorityTask;
/*-----------------------------------------------------------*/

void vStartQueuePeekTasks( void )
{
xQueueHandle xQueue;

        /* Create the queue that we are going to use for the test/demo. */
        xQueue = xQueueCreate( qpeekQUEUE_LENGTH, sizeof( unsigned portLONG ) );

        /* 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( xQueue, ( signed portCHAR * ) "QPeek_Test_Queue" );

        /* Create the demo tasks and pass it the queue just created.  We are
        passing the queue handle by value so it does not matter that it is declared
        on the stack here. */
        xTaskCreate( prvLowPriorityPeekTask, ( signed portCHAR * )"PeekL", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekLOW_PRIORITY, NULL );
        xTaskCreate( prvMediumPriorityPeekTask, ( signed portCHAR * )"PeekM", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekMEDIUM_PRIORITY, &xMediumPriorityTask );
        xTaskCreate( prvHighPriorityPeekTask, ( signed portCHAR * )"PeekH1", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekHIGH_PRIORITY, &xHighPriorityTask );
        xTaskCreate( prvHighestPriorityPeekTask, ( signed portCHAR * )"PeekH2", configMINIMAL_STACK_SIZE, ( void * ) xQueue, qpeekHIGHEST_PRIORITY, &xHighestPriorityTask );
}
/*-----------------------------------------------------------*/

static void prvHighestPriorityPeekTask( void *pvParameters )
{
xQueueHandle xQueue = ( xQueueHandle ) pvParameters;
unsigned portLONG ulValue;

        #ifdef USE_STDIO
        {
                void vPrintDisplayMessage( const portCHAR * const * ppcMessageToSend );
        
                const portCHAR * const pcTaskStartMsg = "Queue peek test started.\r\n";

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

        for( ;; )
        {
                /* Try peeking from the queue.  The queue should be empty so we will
                block, allowing the high priority task to execute. */
                if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
                {
                        /* We expected to have received something by the time we unblock. */
                        xErrorDetected = pdTRUE;
                }

                /* When we reach here the high and medium priority tasks should still
                be blocked on the queue.  We unblocked because the low priority task
                wrote a value to the queue, which we should have peeked.  Peeking the
                data (rather than receiving it) will leave the data on the queue, so
                the high priority task should then have also been unblocked, but not
                yet executed. */
                if( ulValue != 0x11223344 )
                {
                        /* We did not receive the expected value. */
                        xErrorDetected = pdTRUE;
                }

                if( uxQueueMessagesWaiting( xQueue ) != 1 )
                {
                        /* The message should have been left on the queue. */
                        xErrorDetected = pdTRUE;
                }

                /* Now we are going to actually receive the data, so when the high
                priority task runs it will find the queue empty and return to the
                blocked state. */
                ulValue = 0;
                if( xQueueReceive( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
                {
                        /* We expected to receive the value. */
                        xErrorDetected = pdTRUE;
                }

                if( ulValue != 0x11223344 )
                {
                        /* We did not receive the expected value - which should have been
                        the same value as was peeked. */
                        xErrorDetected = pdTRUE;
                }

                /* Now we will block again as the queue is once more empty.  The low 
                priority task can then execute again. */
                if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
                {
                        /* We expected to have received something by the time we unblock. */
                        xErrorDetected = pdTRUE;
                }

                /* When we get here the low priority task should have again written to the
                queue. */
                if( ulValue != 0x01234567 )
                {
                        /* We did not receive the expected value. */
                        xErrorDetected = pdTRUE;
                }

                if( uxQueueMessagesWaiting( xQueue ) != 1 )
                {
                        /* The message should have been left on the queue. */
                        xErrorDetected = pdTRUE;
                }

                /* We only peeked the data, so suspending ourselves now should enable
                the high priority task to also peek the data.  The high priority task
                will have been unblocked when we peeked the data as we left the data
                in the queue. */
                vTaskSuspend( NULL );



                /* This time we are going to do the same as the above test, but the
                high priority task is going to receive the data, rather than peek it.
                This means that the medium priority task should never peek the value. */
                if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
                {
                        xErrorDetected = pdTRUE;
                }

                if( ulValue != 0xaabbaabb )
                {
                        xErrorDetected = pdTRUE;
                }

                vTaskSuspend( NULL );           
        }
}
/*-----------------------------------------------------------*/

static void prvHighPriorityPeekTask( void *pvParameters )
{
xQueueHandle xQueue = ( xQueueHandle ) pvParameters;
unsigned portLONG ulValue;

        for( ;; )
        {
                /* Try peeking from the queue.  The queue should be empty so we will
                block, allowing the medium priority task to execute.  Both the high
                and highest priority tasks will then be blocked on the queue. */
                if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
                {
                        /* We expected to have received something by the time we unblock. */
                        xErrorDetected = pdTRUE;
                }

                /* When we get here the highest priority task should have peeked the data
                (unblocking this task) then suspended (allowing this task to also peek
                the data). */
                if( ulValue != 0x01234567 )
                {
                        /* We did not receive the expected value. */
                        xErrorDetected = pdTRUE;
                }

                if( uxQueueMessagesWaiting( xQueue ) != 1 )
                {
                        /* The message should have been left on the queue. */
                        xErrorDetected = pdTRUE;
                }

                /* We only peeked the data, so suspending ourselves now should enable
                the medium priority task to also peek the data.  The medium priority task
                will have been unblocked when we peeked the data as we left the data
                in the queue. */
                vTaskSuspend( NULL );


                /* This time we are going actually receive the value, so the medium
                priority task will never peek the data - we removed it from the queue. */
                if( xQueueReceive( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
                {
                        xErrorDetected = pdTRUE;
                }

                if( ulValue != 0xaabbaabb )
                {
                        xErrorDetected = pdTRUE;
                }

                vTaskSuspend( NULL );                           
        }
}
/*-----------------------------------------------------------*/

static void prvMediumPriorityPeekTask( void *pvParameters )
{
xQueueHandle xQueue = ( xQueueHandle ) pvParameters;
unsigned portLONG ulValue;

        for( ;; )
        {
                /* Try peeking from the queue.  The queue should be empty so we will
                block, allowing the low priority task to execute.  The highest, high
                and medium priority tasks will then all be blocked on the queue. */
                if( xQueuePeek( xQueue, &ulValue, portMAX_DELAY ) != pdPASS )
                {
                        /* We expected to have received something by the time we unblock. */
                        xErrorDetected = pdTRUE;
                }

                /* When we get here the high priority task should have peeked the data
                (unblocking this task) then suspended (allowing this task to also peek
                the data). */
                if( ulValue != 0x01234567 )
                {
                        /* We did not receive the expected value. */
                        xErrorDetected = pdTRUE;
                }

                if( uxQueueMessagesWaiting( xQueue ) != 1 )
                {
                        /* The message should have been left on the queue. */
                        xErrorDetected = pdTRUE;
                }

                /* Just so we know the test is still running. */
                ulLoopCounter++;

                /* Now we can suspend ourselves so the low priority task can execute
                again. */
                vTaskSuspend( NULL );
        }
}
/*-----------------------------------------------------------*/

static void prvLowPriorityPeekTask( void *pvParameters )
{
xQueueHandle xQueue = ( xQueueHandle ) pvParameters;
unsigned portLONG ulValue;

        for( ;; )
        {
                /* Write some data to the queue.  This should unblock the highest 
                priority task that is waiting to peek data from the queue. */
                ulValue = 0x11223344;
                if( xQueueSendToBack( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
                {
                        /* We were expecting the queue to be empty so we should not of
                        had a problem writing to the queue. */
                        xErrorDetected = pdTRUE;
                }

                /* By the time we get here the data should have been removed from
                the queue. */
                if( uxQueueMessagesWaiting( xQueue ) != 0 )
                {
                        xErrorDetected = pdTRUE;
                }

                /* Write another value to the queue, again waking the highest priority
                task that is blocked on the queue. */
                ulValue = 0x01234567;
                if( xQueueSendToBack( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
                {
                        /* We were expecting the queue to be empty so we should not of
                        had a problem writing to the queue. */
                        xErrorDetected = pdTRUE;
                }

                /* All the other tasks should now have successfully peeked the data.
                The data is still in the queue so we should be able to receive it. */
                ulValue = 0;
                if( xQueueReceive( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
                {
                        /* We expected to receive the data. */
                        xErrorDetected = pdTRUE;
                }

                if( ulValue != 0x01234567 )
                {
                        /* We did not receive the expected value. */
                }
                
                /* Lets just delay a while as this is an intensive test as we don't
                want to starve other tests of processing time. */
                vTaskDelay( qpeekSHORT_DELAY );

                /* Unsuspend the other tasks so we can repeat the test - this time
                however not all the other tasks will peek the data as the high
                priority task is actually going to remove it from the queue.  Send
                to front is used just to be different.  As the queue is empty it
                makes no difference to the result. */
                vTaskResume( xMediumPriorityTask );
                vTaskResume( xHighPriorityTask );
                vTaskResume( xHighestPriorityTask );

                ulValue = 0xaabbaabb;
                if( xQueueSendToFront( xQueue, &ulValue, qpeekNO_BLOCK ) != pdPASS )
                {
                        /* We were expecting the queue to be empty so we should not of
                        had a problem writing to the queue. */
                        xErrorDetected = pdTRUE;
                }

                /* This time we should find that the queue is empty.  The high priority
                task actually removed the data rather than just peeking it. */
                if( xQueuePeek( xQueue, &ulValue, qpeekNO_BLOCK ) != errQUEUE_EMPTY )
                {
                        /* We expected to receive the data. */
                        xErrorDetected = pdTRUE;
                }

                /* Unsuspend the highest and high priority tasks so we can go back
                and repeat the whole thing.  The medium priority task should not be
                suspended as it was not able to peek the data in this last case. */
                vTaskResume( xHighPriorityTask );
                vTaskResume( xHighestPriorityTask );            

                /* Lets just delay a while as this is an intensive test as we don't
                want to starve other tests of processing time. */
                vTaskDelay( qpeekSHORT_DELAY );
        }
}
/*-----------------------------------------------------------*/

/* This is called to check that all the created tasks are still running. */
portBASE_TYPE xAreQueuePeekTasksStillRunning( void )
{
static unsigned portLONG ulLastLoopCounter = 0;

        /* If the demo task is still running then we expect the loopcounter to
        have incremented since this function was last called. */
        if( ulLastLoopCounter == ulLoopCounter )
        {
                xErrorDetected = pdTRUE;
        }

        ulLastLoopCounter = ulLoopCounter;

        /* Errors detected in the task itself will have latched xErrorDetected
        to true. */

        return !xErrorDetected;
}