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.\" $FreeBSD$ 27.\" 28.Dd September 27, 2012 29.Dt BUF_RING 9 30.Os 31.Sh NAME 32.Nm buf_ring , 33.Nm buf_ring_alloc , 34.Nm buf_ring_free , 35.Nm buf_ring_enqueue , 36.Nm buf_ring_dequeue_mc , 37.Nm buf_ring_dequeue_sc , 38.Nm buf_ring_count , 39.Nm buf_ring_empty , 40.Nm buf_ring_full , 41.Nm buf_ring_peek 42.Nd multi-producer, {single, multi}-consumer lock-less ring buffer 43.Sh SYNOPSIS 44.In sys/param.h 45.In sys/buf_ring.h 46.Ft struct buf_ring * 47.Fn buf_ring_alloc "int count" "struct malloc_type *type" "int flags" "struct mtx *sc_lock" 48.Ft void 49.Fn buf_ring_free "struct buf_ring *br" "struct malloc_type *type" 50.Ft int 51.Fn buf_ring_enqueue "struct buf_ring *br" "void *buf" 52.Ft void * 53.Fn buf_ring_dequeue_mc "struct buf_ring *br" 54.Ft void * 55.Fn buf_ring_dequeue_sc "struct buf_ring *br" 56.Ft int 57.Fn buf_ring_count "struct buf_ring *br" 58.Ft int 59.Fn buf_ring_empty "struct buf_ring *br" 60.Ft int 61.Fn buf_ring_full "struct buf_ring *br" 62.Ft void * 63.Fn buf_ring_peek "struct buf_ring *br" 64.Sh DESCRIPTION 65The 66.Nm 67functions provide a lock-less multi-producer and lock-less multi-consumer as 68well as single-consumer ring buffer. 69.Pp 70The 71.Fn buf_ring_alloc 72function is used to allocate a buf_ring ring buffer with 73.Fa count 74slots using malloc_type 75.Fa type 76and memory flags 77.Fa flags . 78The single consumer interface is protected by 79.Fa sc_lock . 80.Pp 81The 82.Fn buf_ring_free 83function is used to free a buf_ring. 84The user is responsible for freeing any enqueued items. 85.Pp 86The 87.Fn buf_ring_enqueue 88function is used to enqueue a buffer to a buf_ring. 89.Pp 90The 91.Fn buf_ring_dequeue_mc 92function is a multi-consumer safe way of dequeueing elements from a buf_ring. 93.Pp 94The 95.Fn buf_ring_dequeue_sc 96function is a single-consumer interface to dequeue elements - requiring 97the user to serialize accesses with a lock. 98.Pp 99The 100.Fn buf_ring_count 101function returns the number of elements in a buf_ring. 102.Pp 103The 104.Fn buf_ring_empty 105function returns 106.Dv TRUE 107if the buf_ring is empty, 108.Dv FALSE 109otherwise. 110.Pp 111The 112.Fn buf_ring_full 113function returns 114.Dv TRUE 115if no more items can be enqueued, 116.Dv FALSE 117otherwise. 118.Pp 119The 120.Fn buf_ring_peek 121function returns a pointer to the last element in the buf_ring if the 122buf_ring is not empty, 123.Dv NULL 124otherwise. 125.Sh RETURN VALUES 126The 127.Fn buf_ring_enqueue 128function return 129.Er ENOBUFS 130if there are no available slots in the buf_ring. 131.Sh HISTORY 132These functions were introduced in 133.Fx 8.0 . 134