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     buf_ring, buf_ring_alloc, buf_ring_free, buf_ring_enqueue, buf_ring_dequeue_mc,
     buf_ring_dequeue_sc, buf_ring_count, buf_ring_empty, buf_ring_full, buf_ring_peek, — multi-
     producer, {single, multi}-consumer lock-less ring buffer


     #include <sys/param.h>
     #include <sys/buf_ring.h>

     struct buf_ring *
     buf_ring_alloc(int count, struct malloc_type *type, int flags, struct mtx *sc_lock);

     buf_ring_free(struct buf_ring *br, struct malloc_type *type);

     buf_ring_enqueue(struct buf_ring *br, void *buf);

     void *
     buf_ring_dequeue_mc(struct buf_ring *br);

     void *
     buf_ring_dequeue_sc(struct buf_ring *br);

     buf_ring_count(struct buf_ring *br);

     buf_ring_empty(struct buf_ring *br);

     buf_ring_full(struct buf_ring *br);

     void *
     buf_ring_peek(struct buf_ring *br);


     The buf_ring functions provide a lock-less multi-producer and lock-less multi-consumer as
     well as single-consumer ring buffer.

     The buf_ring_alloc() function is used to allocate a buf_ring ring buffer with count slots
     using malloc_type type and memory flags flags.  The single consumer interface is protected
     by sc_lock.

     The buf_ring_free() function is used to free a buf_ring.  The user is responsible for
     freeing any enqueued items.

     The buf_ring_enqueue() function is used to enqueue a buffer to a buf_ring.

     The buf_ring_dequeue_mc() function is a multi-consumer safe way of dequeueing elements from
     a buf_ring.

     The buf_ring_dequeue_sc() function is a single-consumer interface to dequeue elements -
     requiring the user to serialize accesses with a lock.

     The buf_ring_count() function returns the number of elements in a buf_ring.

     The buf_ring_empty() function returns TRUE if the buf_ring is empty, FALSE otherwise.

     The buf_ring_full() function returns TRUE if no more items can be enqueued, FALSE otherwise.

     The buf_ring_peek() function returns a pointer to the last element in the buf_ring if the
     buf_ring is not empty, NULL otherwise.


     The buf_ring_enqueue() function return ENOBUFS if there are no available slots in the


     These functions were introduced in FreeBSD 8.0.