144 lines
4.9 KiB
C
144 lines
4.9 KiB
C
/*
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* Copyright (c) 2017, George Oikonomou - http://www.spd.gr
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* Copyright (c) 2017, James Pope
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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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*
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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 copyright holder nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* 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,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*---------------------------------------------------------------------------*/
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/**
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* \addtogroup data
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* @{
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*
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* \defgroup queue Queue library
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*
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* This library provides functions for the creation and manipulation of
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* queues. The library is implemented as a wrapper around the list library.
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*
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* A queue is declared using the QUEUE macro. Queue elements must be
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* allocated by the calling code and must be of a C struct datatype. In this
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* struct, the first field must be a pointer called \e next. This field will
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* be used by the library to maintain the queue. Application code must not
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* modify this field directly.
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* @{
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*/
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/*---------------------------------------------------------------------------*/
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#ifndef QUEUE_H_
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#define QUEUE_H_
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/*---------------------------------------------------------------------------*/
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#include "contiki.h"
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#include "lib/list.h"
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#include <stdbool.h>
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/*---------------------------------------------------------------------------*/
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/**
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* \brief The queue data type
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*/
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typedef list_t queue_t;
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Define a queue.
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*
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* This macro defines a queue.
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*
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* The datatype for elements must be a C struct. The struct's first member must
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* be a pointer called \e next. This is used internally by the library to
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* maintain data structure integrity and must not be modified directly by
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* application code.
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*
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* \param name The name of the queue.
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*/
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#define QUEUE(name) LIST(name)
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/*---------------------------------------------------------------------------*/
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struct queue {
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struct queue *next;
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};
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Initialise a queue
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* \param queue The queue
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*/
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static inline void
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queue_init(queue_t queue)
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{
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list_init(queue);
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Adds an element to the tail of the queue
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* \param queue The queue
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* \param element A pointer to the element to be added
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*/
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static inline void
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queue_enqueue(queue_t queue, void *element)
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{
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list_add(queue, element);
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Removes the element at the front of the queue
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* \param queue The queue
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* \return A pointer to the element removed
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*
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* If this function returns NULL if the queue was empty (queue underflow)
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*/
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static inline void *
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queue_dequeue(queue_t queue)
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{
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return list_pop(queue);
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Returns the front element of the queue, without removing it
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* \param queue The queue
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* \return A pointer to the element at the front of the queue
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*/
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static inline void *
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queue_peek(queue_t queue)
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{
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return list_head(queue);
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}
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/*---------------------------------------------------------------------------*/
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/**
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* \brief Check if a queue is empty
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* \param queue The queue
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* \retval true The queue is empty
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* \retval false The queue has at least one element
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*/
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static inline bool
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queue_is_empty(queue_t queue)
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{
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return *queue == NULL ? true : false;
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}
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/*---------------------------------------------------------------------------*/
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#endif /* QUEUE_H_ */
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/*---------------------------------------------------------------------------*/
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/**
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* @}
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* @}
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*/
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