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Added ringbufindex module
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Simon Duquennoy
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149
core/lib/ringbufindex.c
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149
core/lib/ringbufindex.c
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/*
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* Copyright (c) 2015, SICS Swedish ICT.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of the Contiki operating system.
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*
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*/
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/**
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* \file
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* ringbufindex library. Implements basic support for ring buffers
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* of any type, as opposed to the core/lib/ringbuf module which
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* is only for byte arrays. Simply returns index in the ringbuf
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* rather than actual elements. The ringbuf size must be power of two.
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* Like the original ringbuf, this module implements atomic put and get.
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* \author
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* Simon Duquennoy <simonduq@sics.se>
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* based on Contiki's core/lib/ringbuf library by Adam Dunkels
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*/
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#include <string.h>
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#include "lib/ringbufindex.h"
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/* Initialize a ring buffer. The size must be a power of two */
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void
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ringbufindex_init(struct ringbufindex *r, uint8_t size)
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{
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r->mask = size - 1;
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r->put_ptr = 0;
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r->get_ptr = 0;
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}
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/* Put one element to the ring buffer */
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int
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ringbufindex_put(struct ringbufindex *r)
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{
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/* Check if buffer is full. If it is full, return 0 to indicate that
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the element was not inserted.
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XXX: there is a potential risk for a race condition here, because
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the ->get_ptr field may be written concurrently by the
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ringbufindex_get() function. To avoid this, access to ->get_ptr must
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be atomic. We use an uint8_t type, which makes access atomic on
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most platforms, but C does not guarantee this.
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*/
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if(((r->put_ptr - r->get_ptr) & r->mask) == r->mask) {
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return 0;
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}
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r->put_ptr = (r->put_ptr + 1) & r->mask;
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return 1;
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}
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/* Check if there is space to put an element.
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* Return the index where the next element is to be added */
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int
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ringbufindex_peek_put(const struct ringbufindex *r)
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{
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/* Check if there are bytes in the buffer. If so, we return the
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first one. If there are no bytes left, we return -1.
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*/
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if(((r->put_ptr - r->get_ptr) & r->mask) == r->mask) {
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return -1;
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}
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return (r->put_ptr + 1) & r->mask;
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}
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/* Remove the first element and return its index */
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int
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ringbufindex_get(struct ringbufindex *r)
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{
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int get_ptr;
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/* Check if there are bytes in the buffer. If so, we return the
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first one and increase the pointer. If there are no bytes left, we
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return -1.
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XXX: there is a potential risk for a race condition here, because
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the ->put_ptr field may be written concurrently by the
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ringbufindex_put() function. To avoid this, access to ->get_ptr must
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be atomic. We use an uint8_t type, which makes access atomic on
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most platforms, but C does not guarantee this.
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*/
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if(((r->put_ptr - r->get_ptr) & r->mask) > 0) {
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get_ptr = r->get_ptr;
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r->get_ptr = (r->get_ptr + 1) & r->mask;
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return get_ptr;
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} else {
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return -1;
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}
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}
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/* Return the index of the first element
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* (which will be removed if calling ringbufindex_peek) */
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int
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ringbufindex_peek_get(const struct ringbufindex *r)
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{
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/* Check if there are bytes in the buffer. If so, we return the
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first one. If there are no bytes left, we return -1.
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*/
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if(((r->put_ptr - r->get_ptr) & r->mask) > 0) {
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return (r->get_ptr + 1) & r->mask;
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} else {
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return -1;
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}
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}
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/* Return the ring buffer size */
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int
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ringbufindex_size(const struct ringbufindex *r)
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{
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return r->mask + 1;
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}
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/* Return the number of elements currently in the ring buffer */
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int
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ringbufindex_elements(const struct ringbufindex *r)
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{
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return (r->put_ptr - r->get_ptr) & r->mask;
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}
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/* Is the ring buffer full? */
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int
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ringbufindex_full(const struct ringbufindex *r)
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{
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return ((r->put_ptr - r->get_ptr) & r->mask) == r->mask;
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}
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/* Is the ring buffer empty? */
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int
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ringbufindex_empty(const struct ringbufindex *r)
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{
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return ringbufindex_elements(r) == 0;
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}
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72
core/lib/ringbufindex.h
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72
core/lib/ringbufindex.h
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@ -0,0 +1,72 @@
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/*
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* Copyright (c) 2015, SICS Swedish ICT.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
|
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
|
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
|
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of the Contiki operating system.
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*
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*/
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/**
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* \file
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* Header file for the ringbufindex library
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* \author
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* Simon Duquennoy <simonduq@sics.se>
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*/
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#ifndef __RINGBUFINDEX_H__
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#define __RINGBUFINDEX_H__
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#include "contiki-conf.h"
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struct ringbufindex {
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uint8_t mask;
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/* These must be 8-bit quantities to avoid race conditions. */
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uint8_t put_ptr, get_ptr;
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};
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/* Initialize a ring buffer. The size must be a power of two */
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void ringbufindex_init(struct ringbufindex *r, uint8_t size);
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/* Put one element to the ring buffer */
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int ringbufindex_put(struct ringbufindex *r);
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/* Check if there is space to put an element.
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* Return the index where the next element is to be added */
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int ringbufindex_peek_put(const struct ringbufindex *r);
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/* Remove the first element and return its index */
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int ringbufindex_get(struct ringbufindex *r);
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/* Return the index of the first element
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* (which will be removed if calling ringbufindex_peek) */
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int ringbufindex_peek_get(const struct ringbufindex *r);
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/* Return the ring buffer size */
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int ringbufindex_size(const struct ringbufindex *r);
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/* Return the number of elements currently in the ring buffer */
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int ringbufindex_elements(const struct ringbufindex *r);
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/* Is the ring buffer full? */
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int ringbufindex_full(const struct ringbufindex *r);
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/* Is the ring buffer empty? */
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int ringbufindex_empty(const struct ringbufindex *r);
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#endif /* __RINGBUFINDEX_H__ */
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