nes-proj/os/lib/list.c

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/*
* Copyright (c) 2004, 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.
*
* Author: Adam Dunkels <adam@sics.se>
*
*/
/**
* \file
* Linked list library implementation.
*
* \author Adam Dunkels <adam@sics.se>
*
*/
/**
* \addtogroup list
* @{
*/
#include "contiki.h"
#include "lib/list.h"
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#include <string.h>
/*---------------------------------------------------------------------------*/
struct list {
struct list *next;
};
/*---------------------------------------------------------------------------*/
/**
* Initialize a list.
*
* This function initalizes a list. The list will be empty after this
* function has been called.
*
* \param list The list to be initialized.
*/
void
list_init(list_t list)
{
*list = NULL;
}
/*---------------------------------------------------------------------------*/
/**
* Get a pointer to the first element of a list.
*
* This function returns a pointer to the first element of the
* list. The element will \b not be removed from the list.
*
* \param list The list.
* \return A pointer to the first element on the list.
*
* \sa list_tail()
*/
void *
list_head(list_t list)
{
return *list;
}
/*---------------------------------------------------------------------------*/
/**
* Duplicate a list.
*
* This function duplicates a list by copying the list reference, but
* not the elements.
*
* \note This function does \b not copy the elements of the list, but
* merely duplicates the pointer to the first element of the list.
*
* \param dest The destination list.
* \param src The source list.
*/
void
list_copy(list_t dest, list_t src)
{
*dest = *src;
}
/*---------------------------------------------------------------------------*/
/**
* Get the tail of a list.
*
* This function returns a pointer to the elements following the first
* element of a list. No elements are removed by this function.
*
* \param list The list
* \return A pointer to the element after the first element on the list.
*
* \sa list_head()
*/
void *
list_tail(list_t list)
{
struct list *l;
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if(*list == NULL) {
return NULL;
}
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for(l = *list; l->next != NULL; l = l->next);
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return l;
}
/*---------------------------------------------------------------------------*/
/**
* Add an item at the end of a list.
*
* This function adds an item to the end of the list.
*
* \param list The list.
* \param item A pointer to the item to be added.
*
* \sa list_push()
*
*/
void
list_add(list_t list, void *item)
{
struct list *l;
/* Make sure not to add the same element twice */
list_remove(list, item);
((struct list *)item)->next = NULL;
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l = list_tail(list);
if(l == NULL) {
*list = item;
} else {
l->next = item;
}
}
/*---------------------------------------------------------------------------*/
/**
* Add an item to the start of the list.
*/
void
list_push(list_t list, void *item)
{
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/* Make sure not to add the same element twice */
list_remove(list, item);
((struct list *)item)->next = *list;
*list = item;
}
/*---------------------------------------------------------------------------*/
/**
* Remove the last object on the list.
*
* This function removes the last object on the list and returns it.
*
* \param list The list
* \return The removed object
*
*/
void *
list_chop(list_t list)
{
struct list *l, *r;
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if(*list == NULL) {
return NULL;
}
if(((struct list *)*list)->next == NULL) {
l = *list;
*list = NULL;
return l;
}
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for(l = *list; l->next->next != NULL; l = l->next);
r = l->next;
l->next = NULL;
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return r;
}
/*---------------------------------------------------------------------------*/
/**
* Remove the first object on a list.
*
* This function removes the first object on the list and returns a
* pointer to it.
*
* \param list The list.
* \return Pointer to the removed element of list.
*/
/*---------------------------------------------------------------------------*/
void *
list_pop(list_t list)
{
struct list *l;
l = *list;
if(*list != NULL) {
*list = ((struct list *)*list)->next;
}
return l;
}
/*---------------------------------------------------------------------------*/
/**
* Remove a specific element from a list.
*
* This function removes a specified element from the list.
*
* \param list The list.
* \param item The item that is to be removed from the list.
*
*/
/*---------------------------------------------------------------------------*/
void
list_remove(list_t list, void *item)
{
struct list *l, *r;
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if(*list == NULL) {
return;
}
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r = NULL;
for(l = *list; l != NULL; l = l->next) {
if(l == item) {
if(r == NULL) {
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/* First on list */
*list = l->next;
} else {
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/* Not first on list */
r->next = l->next;
}
l->next = NULL;
return;
}
r = l;
}
}
/*---------------------------------------------------------------------------*/
/**
* Get the length of a list.
*
* This function counts the number of elements on a specified list.
*
* \param list The list.
* \return The length of the list.
*/
/*---------------------------------------------------------------------------*/
int
list_length(list_t list)
{
struct list *l;
int n = 0;
for(l = *list; l != NULL; l = l->next) {
++n;
}
return n;
}
/*---------------------------------------------------------------------------*/
/**
* \brief Insert an item after a specified item on the list
* \param list The list
* \param previtem The item after which the new item should be inserted
* \param newitem The new item that is to be inserted
* \author Adam Dunkels
*
* This function inserts an item right after a specified
* item on the list. This function is useful when using
* the list module to ordered lists.
*
* If previtem is NULL, the new item is placed at the
* start of the list.
*
*/
void
list_insert(list_t list, void *previtem, void *newitem)
{
if(previtem == NULL) {
list_push(list, newitem);
} else {
list_remove(list, newitem);
((struct list *)newitem)->next = ((struct list *)previtem)->next;
((struct list *)previtem)->next = newitem;
}
}
/*---------------------------------------------------------------------------*/
/**
* \brief Get the next item following this item
* \param item A list item
* \returns A next item on the list
*
* This function takes a list item and returns the next
* item on the list, or NULL if there are no more items on
* the list. This function is used when iterating through
* lists.
*/
void *
list_item_next(void *item)
{
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return item == NULL ? NULL : ((struct list *)item)->next;
}
/*---------------------------------------------------------------------------*/
/** @} */