1.\" Copyright (c) 2009 Bitgravity Inc 2.\" Written by: Kip Macy <kmacy@FreeBSD.org> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.Dd September 27, 2012 27.Dt BUF_RING 9 28.Os 29.Sh NAME 30.Nm buf_ring , 31.Nm buf_ring_alloc , 32.Nm buf_ring_free , 33.Nm buf_ring_enqueue , 34.Nm buf_ring_dequeue_mc , 35.Nm buf_ring_dequeue_sc , 36.Nm buf_ring_count , 37.Nm buf_ring_empty , 38.Nm buf_ring_full , 39.Nm buf_ring_peek 40.Nd multi-producer, {single, multi}-consumer lock-less ring buffer 41.Sh SYNOPSIS 42.In sys/param.h 43.In sys/buf_ring.h 44.Ft struct buf_ring * 45.Fn buf_ring_alloc "int count" "struct malloc_type *type" "int flags" "struct mtx *sc_lock" 46.Ft void 47.Fn buf_ring_free "struct buf_ring *br" "struct malloc_type *type" 48.Ft int 49.Fn buf_ring_enqueue "struct buf_ring *br" "void *buf" 50.Ft void * 51.Fn buf_ring_dequeue_mc "struct buf_ring *br" 52.Ft void * 53.Fn buf_ring_dequeue_sc "struct buf_ring *br" 54.Ft int 55.Fn buf_ring_count "struct buf_ring *br" 56.Ft int 57.Fn buf_ring_empty "struct buf_ring *br" 58.Ft int 59.Fn buf_ring_full "struct buf_ring *br" 60.Ft void * 61.Fn buf_ring_peek "struct buf_ring *br" 62.Sh DESCRIPTION 63The 64.Nm 65functions provide a lock-less multi-producer and lock-less multi-consumer as 66well as single-consumer ring buffer. 67.Pp 68The 69.Fn buf_ring_alloc 70function is used to allocate a buf_ring ring buffer with 71.Fa count 72slots using malloc_type 73.Fa type 74and memory flags 75.Fa flags . 76The single consumer interface is protected by 77.Fa sc_lock . 78.Pp 79The 80.Fn buf_ring_free 81function is used to free a buf_ring. 82The user is responsible for freeing any enqueued items. 83.Pp 84The 85.Fn buf_ring_enqueue 86function is used to enqueue a buffer to a buf_ring. 87.Pp 88The 89.Fn buf_ring_dequeue_mc 90function is a multi-consumer safe way of dequeueing elements from a buf_ring. 91.Pp 92The 93.Fn buf_ring_dequeue_sc 94function is a single-consumer interface to dequeue elements - requiring 95the user to serialize accesses with a lock. 96.Pp 97The 98.Fn buf_ring_count 99function returns the number of elements in a buf_ring. 100.Pp 101The 102.Fn buf_ring_empty 103function returns 104.Dv TRUE 105if the buf_ring is empty, 106.Dv FALSE 107otherwise. 108.Pp 109The 110.Fn buf_ring_full 111function returns 112.Dv TRUE 113if no more items can be enqueued, 114.Dv FALSE 115otherwise. 116.Pp 117The 118.Fn buf_ring_peek 119function returns a pointer to the last element in the buf_ring if the 120buf_ring is not empty, 121.Dv NULL 122otherwise. 123.Sh RETURN VALUES 124The 125.Fn buf_ring_enqueue 126function return 127.Er ENOBUFS 128if there are no available slots in the buf_ring. 129.Sh HISTORY 130These functions were introduced in 131.Fx 8.0 . 132