A ring buffer library. The ring buffer library is useful in device drivers, where bytes can be safely written to the buffer from an interrupt handler, and read from non-interrupt code.
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core/lib/ringbuf.c
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107
core/lib/ringbuf.c
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/*
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* Copyright (c) 2008, Swedish Institute of Computer Science.
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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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* $Id: ringbuf.c,v 1.1 2009/03/01 20:23:56 adamdunkels Exp $
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*/
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/**
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* \file
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* Ring buffer library implementation
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* \author
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* Adam Dunkels <adam@sics.se>
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*/
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#include "ringbuf.h"
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/*---------------------------------------------------------------------------*/
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void
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ringbuf_init(struct ringbuf *r, uint8_t *dataptr, uint8_t size)
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{
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r->data = dataptr;
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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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/*---------------------------------------------------------------------------*/
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int
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ringbuf_put(struct ringbuf *r, uint8_t c)
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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 into the buffer.
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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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ringbuf_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->data[r->put_ptr] = c;
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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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/*---------------------------------------------------------------------------*/
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int
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ringbuf_get(struct ringbuf *r)
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{
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uint8_t c;
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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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ringbuf_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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c = r->data[r->get_ptr];
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r->get_ptr = (r->get_ptr + 1) & r->mask;
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return c;
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} else {
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return -1;
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}
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}
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/*---------------------------------------------------------------------------*/
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int
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ringbuf_size(struct ringbuf *r)
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{
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return r->mask + 1;
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}
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/*---------------------------------------------------------------------------*/
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int
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ringbuf_elements(struct ringbuf *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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/*---------------------------------------------------------------------------*/
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132
core/lib/ringbuf.h
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132
core/lib/ringbuf.h
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/** \addtogroup lib
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* @{ */
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/**
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* \defgroup ringbuf Ring buffer library
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* @{
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*
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* The ring buffer library implements ring (circular) buffer where
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* bytes can be read and written independently. A ring buffer is
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* particularly useful in device drivers where data can come in
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* through interrupts.
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*
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*/
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/*
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* Copyright (c) 2008, Swedish Institute of Computer Science.
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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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* $Id: ringbuf.h,v 1.1 2009/03/01 20:23:56 adamdunkels Exp $
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*/
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/**
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* \file
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* Header file for the ring buffer library
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* \author
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* Adam Dunkels <adam@sics.se>
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*/
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#ifndef __RINGBUF_H__
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#define __RINGBUF_H__
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#include "contiki-conf.h"
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/**
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* \brief Structure that holds the state of a ring buffer.
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*
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* This structure holds the state of a ring buffer. The
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* actual buffer needs to be defined separately. This
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* struct is an opaque structure with no user-visible
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* elements.
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*
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*/
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struct ringbuf {
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uint8_t *data;
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uint8_t mask;
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/* XXX 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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/**
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* \brief Initialize a ring buffer
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* \param r A pointer to a struct ringbuf to hold the state of the ring buffer
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* \param a A pointer to an array to hold the data in the buffer
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* \param size_power_of_two The size of the ring buffer, which must be a power of two
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*
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* This function initiates a ring buffer. The data in the
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* buffer is stored in an external array, to which a
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* pointer must be supplied. The size of the ring buffer
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* must be a power of two and cannot be larger than 128
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* bytes.
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*
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*/
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void ringbuf_init(struct ringbuf *r, uint8_t *a,
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uint8_t size_power_of_two);
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/**
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* \brief Insert a byte into the ring buffer
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* \param r A pointer to a struct ringbuf to hold the state of the ring buffer
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* \param c The byte to be written to the buffer
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* \return Non-zero if there data could be written, or zero if the buffer was full.
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*
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* This function inserts a byte into the ring buffer. It
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* is safe to call this function from an interrupt
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* handler.
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*
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*/
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int ringbuf_put(struct ringbuf *r, uint8_t c);
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/**
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* \brief Get a byte from the ring buffer
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* \param r A pointer to a struct ringbuf to hold the state of the ring buffer
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* \return The data from the buffer, or -1 if the buffer was empty
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*
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* This function removes a byte from the ring buffer. It
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* is safe to call this function from an interrupt
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* handler.
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*
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*/
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int ringbuf_get(struct ringbuf *r);
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/**
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* \brief Get the size of a ring buffer
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* \param r A pointer to a struct ringbuf to hold the state of the ring buffer
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* \return The size of the buffer.
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*/
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int ringbuf_size(struct ringbuf *r);
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/**
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* \brief Get the number of elements currently in the ring buffer
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* \param r A pointer to a struct ringbuf to hold the state of the ring buffer
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* \return The number of elements in the buffer.
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*/
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int ringbuf_elements(struct ringbuf *r);
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#endif /* __RINGBUF_H__ */
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