BUF_RING_PEEK - reference manual online


September 27, 2012
BUF_RING(9)                       BSD 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, ā€” multi- producer, {single, 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 freeā€ ing 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.
RETURN VALUES The buf_ring_enqueue() function return ENOBUFS if there are no available slots in the buf_ring.
HISTORY These functions were introduced in FreeBSD 8.0.
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