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Added ringbufindex module

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Simon Duquennoy 2015-09-21 18:21:55 +02:00
parent 5d1feac63e
commit 2112dff217
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149
core/lib/ringbufindex.c Normal file
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/*
* Copyright (c) 2015, SICS Swedish ICT.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
*/
/**
* \file
* ringbufindex library. Implements basic support for ring buffers
* of any type, as opposed to the core/lib/ringbuf module which
* is only for byte arrays. Simply returns index in the ringbuf
* rather than actual elements. The ringbuf size must be power of two.
* Like the original ringbuf, this module implements atomic put and get.
* \author
* Simon Duquennoy <simonduq@sics.se>
* based on Contiki's core/lib/ringbuf library by Adam Dunkels
*/
#include <string.h>
#include "lib/ringbufindex.h"
/* Initialize a ring buffer. The size must be a power of two */
void
ringbufindex_init(struct ringbufindex *r, uint8_t size)
{
r->mask = size - 1;
r->put_ptr = 0;
r->get_ptr = 0;
}
/* Put one element to the ring buffer */
int
ringbufindex_put(struct ringbufindex *r)
{
/* Check if buffer is full. If it is full, return 0 to indicate that
the element was not inserted.
XXX: there is a potential risk for a race condition here, because
the ->get_ptr field may be written concurrently by the
ringbufindex_get() function. To avoid this, access to ->get_ptr must
be atomic. We use an uint8_t type, which makes access atomic on
most platforms, but C does not guarantee this.
*/
if(((r->put_ptr - r->get_ptr) & r->mask) == r->mask) {
return 0;
}
r->put_ptr = (r->put_ptr + 1) & r->mask;
return 1;
}
/* Check if there is space to put an element.
* Return the index where the next element is to be added */
int
ringbufindex_peek_put(const struct ringbufindex *r)
{
/* Check if there are bytes in the buffer. If so, we return the
first one. If there are no bytes left, we return -1.
*/
if(((r->put_ptr - r->get_ptr) & r->mask) == r->mask) {
return -1;
}
return (r->put_ptr + 1) & r->mask;
}
/* Remove the first element and return its index */
int
ringbufindex_get(struct ringbufindex *r)
{
int get_ptr;
/* Check if there are bytes in the buffer. If so, we return the
first one and increase the pointer. If there are no bytes left, we
return -1.
XXX: there is a potential risk for a race condition here, because
the ->put_ptr field may be written concurrently by the
ringbufindex_put() function. To avoid this, access to ->get_ptr must
be atomic. We use an uint8_t type, which makes access atomic on
most platforms, but C does not guarantee this.
*/
if(((r->put_ptr - r->get_ptr) & r->mask) > 0) {
get_ptr = r->get_ptr;
r->get_ptr = (r->get_ptr + 1) & r->mask;
return get_ptr;
} else {
return -1;
}
}
/* Return the index of the first element
* (which will be removed if calling ringbufindex_peek) */
int
ringbufindex_peek_get(const struct ringbufindex *r)
{
/* Check if there are bytes in the buffer. If so, we return the
first one. If there are no bytes left, we return -1.
*/
if(((r->put_ptr - r->get_ptr) & r->mask) > 0) {
return (r->get_ptr + 1) & r->mask;
} else {
return -1;
}
}
/* Return the ring buffer size */
int
ringbufindex_size(const struct ringbufindex *r)
{
return r->mask + 1;
}
/* Return the number of elements currently in the ring buffer */
int
ringbufindex_elements(const struct ringbufindex *r)
{
return (r->put_ptr - r->get_ptr) & r->mask;
}
/* Is the ring buffer full? */
int
ringbufindex_full(const struct ringbufindex *r)
{
return ((r->put_ptr - r->get_ptr) & r->mask) == r->mask;
}
/* Is the ring buffer empty? */
int
ringbufindex_empty(const struct ringbufindex *r)
{
return ringbufindex_elements(r) == 0;
}

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/*
* Copyright (c) 2015, SICS Swedish ICT.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* This file is part of the Contiki operating system.
*
*/
/**
* \file
* Header file for the ringbufindex library
* \author
* Simon Duquennoy <simonduq@sics.se>
*/
#ifndef __RINGBUFINDEX_H__
#define __RINGBUFINDEX_H__
#include "contiki-conf.h"
struct ringbufindex {
uint8_t mask;
/* These must be 8-bit quantities to avoid race conditions. */
uint8_t put_ptr, get_ptr;
};
/* Initialize a ring buffer. The size must be a power of two */
void ringbufindex_init(struct ringbufindex *r, uint8_t size);
/* Put one element to the ring buffer */
int ringbufindex_put(struct ringbufindex *r);
/* Check if there is space to put an element.
* Return the index where the next element is to be added */
int ringbufindex_peek_put(const struct ringbufindex *r);
/* Remove the first element and return its index */
int ringbufindex_get(struct ringbufindex *r);
/* Return the index of the first element
* (which will be removed if calling ringbufindex_peek) */
int ringbufindex_peek_get(const struct ringbufindex *r);
/* Return the ring buffer size */
int ringbufindex_size(const struct ringbufindex *r);
/* Return the number of elements currently in the ring buffer */
int ringbufindex_elements(const struct ringbufindex *r);
/* Is the ring buffer full? */
int ringbufindex_full(const struct ringbufindex *r);
/* Is the ring buffer empty? */
int ringbufindex_empty(const struct ringbufindex *r);
#endif /* __RINGBUFINDEX_H__ */