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BUF_RING(9)		   Kernel Developer's Manual		   BUF_RING(9)

NAME
       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, {sin-
       gle, multi}-consumer lock-less ring buffer

SYNOPSIS
       #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);

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

       int
       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);

       int
       buf_ring_count(struct buf_ring *br);

       int
       buf_ring_empty(struct buf_ring *br);

       int
       buf_ring_full(struct buf_ring *br);

       void *
       buf_ring_peek(struct buf_ring *br);

DESCRIPTION
       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 de-
       queueing	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  en-
       queued, 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.

RETURN VALUES
       The buf_ring_enqueue() function return ENOBUFS if there are  no	avail-
       able slots in the buf_ring.

HISTORY
       These functions were introduced in FreeBSD 8.0.

FreeBSD	14.3		      September	27, 2012		   BUF_RING(9)

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