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Updated Jul 2025

Queue Management

Modules

Detailed Description

uxQueueMessagesWaiting

queue.h

1UBaseType_t uxQueueMessagesWaiting( QueueHandle_t xQueue );

Return the number of messages stored in a queue.

Parameters:

  • xQueue

    A handle to the queue being queried.

Returns:

  • The number of messages available in the queue.

uxQueueMessagesWaitingFromISR

queue.h

1UBaseType_t uxQueueMessagesWaiting( QueueHandle_t xQueue );

A version of

uxQueueMessagesWaiting()
that can be called from an ISR. Return the number of messages stored in a queue.

Parameters:

  • xQueue

    A handle to the queue being queried.

Returns:

  • The number of messages available in the queue.

uxQueueSpacesAvailable

queue.h

1UBaseType_t uxQueueSpacesAvailable( QueueHandle_t xQueue );

Return the number of free spaces in a queue.

Parameters:

  • xQueue

    A handle to the queue being queried.

Returns:

  • The number of free spaces available in the queue.

vQueueDelete

queue.h

1void vQueueDelete( QueueHandle_t xQueue );

Delete a queue - freeing all the memory allocated for storing of items placed on the queue.

Parameters:

  • xQueue

    A handle to the queue to be deleted.


xQueueReset

queue.h

1BaseType_t xQueueReset( QueueHandle_t xQueue );

Resets a queue to its original empty state.

Parameters:

  • xQueue

    The handle of the queue being reset.

Returns:

  • Since FreeRTOS V7.2.0
    xQueueReset()
    always returns pdPASS.

xQueueIsQueueEmptyFromISR

queue.h

1BaseType_t xQueueIsQueueEmptyFromISR( const QueueHandle_t pxQueue );

Queries a queue to determine if the queue is empty. This function should only be used in an ISR.

Parameters:

  • xQueue

    The handle of the queue being queried

Returns:

  • pdFALSE if the queue is not empty, or
  • pdTRUE if the queue is empty.

xQueueIsQueueFullFromISR

queue.h

1BaseType_t xQueueIsQueueFullFromISR( const QueueHandle_t pxQueue );

Queries a queue to determine if the queue is full. This function should only be used in an ISR.

Parameters:

  • xQueue

    The handle of the queue being queried.

Returns:

  • pdFALSE if the queue is not full, or
  • pdTRUE if the queue is full.