158 lines
4.6 KiB
C
158 lines
4.6 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 circular-singly-linked-list
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* @{
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*
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* \file
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* Implementation of circular singly linked lists
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*/
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/*---------------------------------------------------------------------------*/
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#include "contiki.h"
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#include "lib/circular-list.h"
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#include <stdint.h>
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#include <stdbool.h>
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#include <string.h>
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/*---------------------------------------------------------------------------*/
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struct cl {
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struct cl *next;
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};
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/*---------------------------------------------------------------------------*/
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void
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circular_list_init(circular_list_t cl)
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{
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*cl = NULL;
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}
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/*---------------------------------------------------------------------------*/
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void *
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circular_list_head(circular_list_t cl)
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{
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return *cl;
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}
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/*---------------------------------------------------------------------------*/
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void *
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circular_list_tail(circular_list_t cl)
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{
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struct cl *this;
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if(*cl == NULL) {
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return NULL;
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}
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for(this = *cl; this->next != *cl; this = this->next);
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return this;
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}
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/*---------------------------------------------------------------------------*/
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void
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circular_list_remove(circular_list_t cl, void *element)
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{
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struct cl *this, *previous;
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if(*cl == NULL) {
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return;
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}
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/*
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* We start traversing from the second element.
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* The head will be visited last. We always update the list's head after
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* removal, just in case we have just removed the head.
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*/
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previous = *cl;
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this = previous->next;
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do {
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if(this == element) {
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previous->next = this->next;
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*cl = this->next == this ? NULL : previous;
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return;
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}
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previous = this;
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this = this->next;
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} while(this != ((struct cl *)*cl)->next);
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}
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/*---------------------------------------------------------------------------*/
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void
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circular_list_add(circular_list_t cl, void *element)
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{
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struct cl *head;
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if(element == NULL) {
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return;
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}
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/* Don't add twice */
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circular_list_remove(cl, element);
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head = *cl;
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if(head == NULL) {
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/* If the list was empty, we update the new element to point to itself */
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((struct cl *)element)->next = element;
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} else {
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/* If the list exists, we add the new element between the current head and
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* the previously second element. */
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((struct cl *)element)->next = head->next;
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head->next = element;
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}
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/* In all cases, the new element becomes the list's new head */
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*cl = element;
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}
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/*---------------------------------------------------------------------------*/
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unsigned long
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circular_list_length(circular_list_t cl)
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{
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unsigned long len = 1;
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struct cl *this;
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if(circular_list_is_empty(cl)) {
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return 0;
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}
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for(this = *cl; this->next != *cl; this = this->next) {
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len++;
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}
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return len;
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}
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/*---------------------------------------------------------------------------*/
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bool
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circular_list_is_empty(circular_list_t cl)
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{
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return *cl == NULL ? true : false;
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}
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/*---------------------------------------------------------------------------*/
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/** @} */
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