function lfds711_queue_bss_query

Source Files

└───liblfds711
    ├───inc
    │   └───liblfds711
    │           lfds711_queue_bounded_singleproducer_singleconsumer.h
    └───src
        └───lfds711_queue_bounded_singleproducer_singleconsumer
                lfds711_queue_bounded_singleproducer_singleconsumer_query.c

Enums

enum lfds711_queue_bss_query
{
  LFDS711_QUEUE_BSS_QUERY_GET_POTENTIALLY_INACCURATE_COUNT,
  LFDS711_QUEUE_BSS_QUERY_VALIDATE
};

Opaque Structures

struct lfds711_queue_bss_state;

Prototype

void lfds711_queue_bss_query( struct lfds711_queue_bss_state *qbsss,
                              enum lfds711_queue_bss_query query_type,
                              void *query_input,
                              void *query_output );

Parameters

struct lfds711_queue_bss_state *qbsss

A pointer to an initialized struct lfds711_queue_bss_state.

enum lfds711_queue_bss_query query_type

A single value from enum lfds711_queue_bss_query, which indicates which query to perform.

void *query_input

A pointer to input data for the query, where the data varies by query;

LFDS711_QUEUE_BSS_QUERY_GET_POTENTIALLY_INACCURATE_COUNT

query_input is NULL.

LFDS711_QUEUE_BSS_QUERY_VALIDATE

query_input can be NULL, or or can be a pointer to a struct lfds711_misc_validation_info, which specifies an expected min/max count, in which case validation also counts the number of elements and check they fall within the specified range.

void *query_output

A pointer to output store for the query, where the output varies by query;

LFDS711_QUEUE_BSS_QUERY_GET_POTENTIALLY_INACCURATE_COUNT

Points to a lfds711_pal_uint_t, which is set to the number of elements in the queue.

LFDS711_QUEUE_BSS_QUERY_VALIDATE

Points to an enum lfds711_misc_validity, which is set to indicate the result of the validation operation.

Notes

All SINGLETHREADED queries can only be safely performed if no enqueue or dequeue operations occur while the operation runs. If enqueue or dequeue operations do occur during the execution of a SINGLETHREADED query, it is theoretically possible for the query to enter an infinite loop. Do not do this.

The LFDS711_QUEUE_BSS_QUERY_GET_POTENTIALLY_INACCURATE_COUNT query is not guaranteed to be accurate. Where enqueue and dequeue operations are not guaranteed to be visible by the time the function calls return, similarly, it may be that a count will during its operation not see an element which has been enqueued, or see that an element has been dequeued. In general however it should be bang on; it's just it's not guaranteed.

See Also

• Queue (bounded, single producer, single consumer)