BaseType_t xQueueReceive()

in queue.c [1378:1518]

• 102 lines of code
• 14 McCabe index (conditional complexity)

BaseType_t xQueueReceive( QueueHandle_t xQueue,
                          void * const pvBuffer,
                          TickType_t xTicksToWait )
{
    BaseType_t xEntryTimeSet = pdFALSE;
    TimeOut_t xTimeOut;
    Queue_t * const pxQueue = xQueue;

    /* Check the pointer is not NULL. */
    configASSERT( ( pxQueue ) );

    /* The buffer into which data is received can only be NULL if the data size
     * is zero (so no data is copied into the buffer). */
    configASSERT( !( ( ( pvBuffer ) == NULL ) && ( ( pxQueue )->uxItemSize != ( UBaseType_t ) 0U ) ) );

    /* Cannot block if the scheduler is suspended. */
    #if ( ( INCLUDE_xTaskGetSchedulerState == 1 ) || ( configUSE_TIMERS == 1 ) )
    {
        configASSERT( !( ( xTaskGetSchedulerState() == taskSCHEDULER_SUSPENDED ) && ( xTicksToWait != 0 ) ) );
    }
    #endif

    /*lint -save -e904  This function relaxes the coding standard somewhat to
     * allow return statements within the function itself.  This is done in the
     * interest of execution time efficiency. */
    for( ; ; )
    {
        taskENTER_CRITICAL();
        {
            const UBaseType_t uxMessagesWaiting = pxQueue->uxMessagesWaiting;

            /* Is there data in the queue now?  To be running the calling task
             * must be the highest priority task wanting to access the queue. */
            if( uxMessagesWaiting > ( UBaseType_t ) 0 )
            {
                /* Data available, remove one item. */
                prvCopyDataFromQueue( pxQueue, pvBuffer );
                traceQUEUE_RECEIVE( pxQueue );
                pxQueue->uxMessagesWaiting = uxMessagesWaiting - ( UBaseType_t ) 1;

                /* There is now space in the queue, were any tasks waiting to
                 * post to the queue?  If so, unblock the highest priority waiting
                 * task. */
                if( listLIST_IS_EMPTY( &( pxQueue->xTasksWaitingToSend ) ) == pdFALSE )
                {
                    if( xTaskRemoveFromEventList( &( pxQueue->xTasksWaitingToSend ) ) != pdFALSE )
                    {
                        queueYIELD_IF_USING_PREEMPTION();
                    }
                    else
                    {
                        mtCOVERAGE_TEST_MARKER();
                    }
                }
                else
                {
                    mtCOVERAGE_TEST_MARKER();
                }

                taskEXIT_CRITICAL();
                return pdPASS;
            }
            else
            {
                if( xTicksToWait == ( TickType_t ) 0 )
                {
                    /* The queue was empty and no block time is specified (or
                     * the block time has expired) so leave now. */
                    taskEXIT_CRITICAL();
                    traceQUEUE_RECEIVE_FAILED( pxQueue );
                    return errQUEUE_EMPTY;
                }
                else if( xEntryTimeSet == pdFALSE )
                {
                    /* The queue was empty and a block time was specified so
                     * configure the timeout structure. */
                    vTaskInternalSetTimeOutState( &xTimeOut );
                    xEntryTimeSet = pdTRUE;
                }
                else
                {
                    /* Entry time was already set. */
                    mtCOVERAGE_TEST_MARKER();
                }
            }
        }
        taskEXIT_CRITICAL();

        /* Interrupts and other tasks can send to and receive from the queue
         * now the critical section has been exited. */

        vTaskSuspendAll();
        prvLockQueue( pxQueue );

        /* Update the timeout state to see if it has expired yet. */
        if( xTaskCheckForTimeOut( &xTimeOut, &xTicksToWait ) == pdFALSE )
        {
            /* The timeout has not expired.  If the queue is still empty place
             * the task on the list of tasks waiting to receive from the queue. */
            if( prvIsQueueEmpty( pxQueue ) != pdFALSE )
            {
                traceBLOCKING_ON_QUEUE_RECEIVE( pxQueue );
                vTaskPlaceOnEventList( &( pxQueue->xTasksWaitingToReceive ), xTicksToWait );
                prvUnlockQueue( pxQueue );

                if( xTaskResumeAll() == pdFALSE )
                {
                    portYIELD_WITHIN_API();
                }
                else
                {
                    mtCOVERAGE_TEST_MARKER();
                }
            }
            else
            {
                /* The queue contains data again.  Loop back to try and read the
                 * data. */
                prvUnlockQueue( pxQueue );
                ( void ) xTaskResumeAll();
            }
        }
        else
        {
            /* Timed out.  If there is no data in the queue exit, otherwise loop
             * back and attempt to read the data. */
            prvUnlockQueue( pxQueue );
            ( void ) xTaskResumeAll();

            if( prvIsQueueEmpty( pxQueue ) != pdFALSE )
            {
                traceQUEUE_RECEIVE_FAILED( pxQueue );
                return errQUEUE_EMPTY;
            }
            else
            {
                mtCOVERAGE_TEST_MARKER();
            }
        }
    } /*lint -restore */
}