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.

core/lib/ringbuf.h

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+/** \addtogroup lib
+ * @{ */
+
+/**
+ * \defgroup ringbuf Ring buffer library
+ * @{
+ *
+ * The ring buffer library implements ring (circular) buffer where
+ * bytes can be read and written independently. A ring buffer is
+ * particularly useful in device drivers where data can come in
+ * through interrupts.
+ *
+ */
+/*
+ * Copyright (c) 2008, Swedish Institute of Computer Science.
+ * 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.
+ *
+ * $Id: ringbuf.h,v 1.1 2009/03/01 20:23:56 adamdunkels Exp $
+ */
+
+/**
+ * \file
+ *         Header file for the ring buffer library
+ * \author
+ *         Adam Dunkels <adam@sics.se>
+ */
+
+#ifndef __RINGBUF_H__
+#define __RINGBUF_H__
+
+#include "contiki-conf.h"
+
+/**
+ * \brief      Structure that holds the state of a ring buffer.
+ *
+ *             This structure holds the state of a ring buffer. The
+ *             actual buffer needs to be defined separately. This
+ *             struct is an opaque structure with no user-visible
+ *             elements.
+ *
+ */
+struct ringbuf {
+  uint8_t *data;
+  uint8_t mask;
+  
+  /* XXX these must be 8-bit quantities to avoid race conditions. */
+  uint8_t put_ptr, get_ptr;
+};
+
+/**
+ * \brief      Initialize a ring buffer
+ * \param r    A pointer to a struct ringbuf to hold the state of the ring buffer
+ * \param a    A pointer to an array to hold the data in the buffer
+ * \param size_power_of_two The size of the ring buffer, which must be a power of two
+ *
+ *             This function initiates a ring buffer. The data in the
+ *             buffer is stored in an external array, to which a
+ *             pointer must be supplied. The size of the ring buffer
+ *             must be a power of two and cannot be larger than 128
+ *             bytes.
+ *
+ */
+void    ringbuf_init(struct ringbuf *r, uint8_t *a,
+		     uint8_t size_power_of_two);
+
+/**
+ * \brief      Insert a byte into the ring buffer
+ * \param r    A pointer to a struct ringbuf to hold the state of the ring buffer
+ * \param c    The byte to be written to the buffer
+ * \return     Non-zero if there data could be written, or zero if the buffer was full.
+ *
+ *             This function inserts a byte into the ring buffer. It
+ *             is safe to call this function from an interrupt
+ *             handler.
+ *
+ */
+int     ringbuf_put(struct ringbuf *r, uint8_t c);
+
+
+/**
+ * \brief      Get a byte from the ring buffer
+ * \param r    A pointer to a struct ringbuf to hold the state of the ring buffer
+ * \return     The data from the buffer, or -1 if the buffer was empty
+ *
+ *             This function removes a byte from the ring buffer. It
+ *             is safe to call this function from an interrupt
+ *             handler.
+ *
+ */
+int     ringbuf_get(struct ringbuf *r);
+
+/**
+ * \brief      Get the size of a ring buffer
+ * \param r    A pointer to a struct ringbuf to hold the state of the ring buffer
+ * \return     The size of the buffer.
+ */
+int     ringbuf_size(struct ringbuf *r);
+
+/**
+ * \brief      Get the number of elements currently in the ring buffer
+ * \param r    A pointer to a struct ringbuf to hold the state of the ring buffer
+ * \return     The number of elements in the buffer.
+ */
+int     ringbuf_elements(struct ringbuf *r);
+
+#endif /* __RINGBUF_H__ */