Function xQueuePeekFromISR

queue.c:1930–1982

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

BaseType_t xQueuePeekFromISR( QueueHandle_t xQueue,
                              void * const pvBuffer )
{
    BaseType_t xReturn;
    UBaseType_t uxSavedInterruptStatus;
    int8_t * pcOriginalReadPosition;
    Queue_t * const pxQueue = xQueue;

    configASSERT( pxQueue );
    configASSERT( !( ( pvBuffer == NULL ) && ( pxQueue->uxItemSize != ( UBaseType_t ) 0U ) ) );
    configASSERT( pxQueue->uxItemSize != 0 ); /* Can't peek a semaphore. */

    /* RTOS ports that support interrupt nesting have the concept of a maximum
     * system call (or maximum API call) interrupt priority.  Interrupts that are
     * above the maximum system call priority are kept permanently enabled, even
     * when the RTOS kernel is in a critical section, but cannot make any calls to
     * FreeRTOS API functions.  If configASSERT() is defined in FreeRTOSConfig.h
     * then portASSERT_IF_INTERRUPT_PRIORITY_INVALID() will result in an assertion
     * failure if a FreeRTOS API function is called from an interrupt that has been
     * assigned a priority above the configured maximum system call priority.
     * Only FreeRTOS functions that end in FromISR can be called from interrupts
     * that have been assigned a priority at or (logically) below the maximum
     * system call interrupt priority.  FreeRTOS maintains a separate interrupt
     * safe API to ensure interrupt entry is as fast and as simple as possible.
     * More information (albeit Cortex-M specific) is provided on the following
     * link: https://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html */
    portASSERT_IF_INTERRUPT_PRIORITY_INVALID();

    uxSavedInterruptStatus = portSET_INTERRUPT_MASK_FROM_ISR();
    {
        /* Cannot block in an ISR, so check there is data available. */
        if( pxQueue->uxMessagesWaiting > ( UBaseType_t ) 0 )
        {
            traceQUEUE_PEEK_FROM_ISR( pxQueue );

            /* Remember the read position so it can be reset as nothing is
             * actually being removed from the queue. */
            pcOriginalReadPosition = pxQueue->u.xQueue.pcReadFrom;
            prvCopyDataFromQueue( pxQueue, pvBuffer );
            pxQueue->u.xQueue.pcReadFrom = pcOriginalReadPosition;

            xReturn = pdPASS;
        }
        else
        {
            xReturn = pdFAIL;
            traceQUEUE_PEEK_FROM_ISR_FAILED( pxQueue );
        }
    }
    portCLEAR_INTERRUPT_MASK_FROM_ISR( uxSavedInterruptStatus );

    return xReturn;
}
/*-----------------------------------------------------------*/

UBaseType_t uxQueueMessagesWaiting( const QueueHandle_t xQueue )