nes-proj/os/lib/circular-list.c
2017-12-13 16:38:50 +00:00

158 lines
4.6 KiB
C

/*
* Copyright (c) 2017, George Oikonomou - http://www.spd.gr
* Copyright (c) 2017, James Pope
* 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 copyright holder 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 COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDER 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.
*/
/*---------------------------------------------------------------------------*/
/**
* \addtogroup circular-singly-linked-list
* @{
*
* \file
* Implementation of circular singly linked lists
*/
/*---------------------------------------------------------------------------*/
#include "contiki.h"
#include "lib/circular-list.h"
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
/*---------------------------------------------------------------------------*/
struct cl {
struct cl *next;
};
/*---------------------------------------------------------------------------*/
void
circular_list_init(circular_list_t cl)
{
*cl = NULL;
}
/*---------------------------------------------------------------------------*/
void *
circular_list_head(circular_list_t cl)
{
return *cl;
}
/*---------------------------------------------------------------------------*/
void *
circular_list_tail(circular_list_t cl)
{
struct cl *this;
if(*cl == NULL) {
return NULL;
}
for(this = *cl; this->next != *cl; this = this->next);
return this;
}
/*---------------------------------------------------------------------------*/
void
circular_list_remove(circular_list_t cl, void *element)
{
struct cl *this, *previous;
if(*cl == NULL) {
return;
}
/*
* We start traversing from the second element.
* The head will be visited last. We always update the list's head after
* removal, just in case we have just removed the head.
*/
previous = *cl;
this = previous->next;
do {
if(this == element) {
previous->next = this->next;
*cl = this->next == this ? NULL : previous;
return;
}
previous = this;
this = this->next;
} while(this != ((struct cl *)*cl)->next);
}
/*---------------------------------------------------------------------------*/
void
circular_list_add(circular_list_t cl, void *element)
{
struct cl *head;
if(element == NULL) {
return;
}
/* Don't add twice */
circular_list_remove(cl, element);
head = *cl;
if(head == NULL) {
/* If the list was empty, we update the new element to point to itself */
((struct cl *)element)->next = element;
} else {
/* If the list exists, we add the new element between the current head and
* the previously second element. */
((struct cl *)element)->next = head->next;
head->next = element;
}
/* In all cases, the new element becomes the list's new head */
*cl = element;
}
/*---------------------------------------------------------------------------*/
unsigned long
circular_list_length(circular_list_t cl)
{
unsigned long len = 1;
struct cl *this;
if(circular_list_is_empty(cl)) {
return 0;
}
for(this = *cl; this->next != *cl; this = this->next) {
len++;
}
return len;
}
/*---------------------------------------------------------------------------*/
bool
circular_list_is_empty(circular_list_t cl)
{
return *cl == NULL ? true : false;
}
/*---------------------------------------------------------------------------*/
/** @} */