list.h

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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 manipulation routines.
 * \author Adam Dunkels <adam@sics.se>
 *
 */
 
/** \addtogroup data
    @{ */
/**
 * \defgroup list Linked list library
 *
 * The linked list library provides a set of functions for
 * manipulating linked lists.
 *
 * A linked list is made up of elements where the first element \b
 * must be a pointer. This pointer is used by the linked list library
 * to form lists of the elements.
 *
 * Lists are declared with the LIST() macro. The declaration specifies
 * the name of the list that later is used with all list functions.
 *
 * Lists can be manipulated by inserting or removing elements from
 * either sides of the list (list_push(), list_add(), list_pop(),
 * list_chop()). A specified element can also be removed from inside a
 * list with list_remove(). The head and tail of a list can be
 * extracted using list_head() and list_tail(), respectively.
 *
 * This library is not safe to be used within an interrupt context.
 * @{
 */
 
#ifndef LIST_H_
#define LIST_H_
 
#include <stdbool.h>
#include <stddef.h>
 
#define LIST_CONCAT2(s1, s2) s1##s2
#define LIST_CONCAT(s1, s2) LIST_CONCAT2(s1, s2)
 
/**
 * Declare a linked list.
 *
 * This macro declares a linked list with the specified \c type. The
 * type \b must be a structure (\c struct) with its first element
 * being a pointer. This pointer is used by the linked list library to
 * form the linked lists.
 *
 * The list variable is declared as static to make it easy to use in a
 * single C module without unnecessarily exporting the name to other
 * modules.
 *
 * \param name The name of the list.
 */
#define LIST(name) \
         static void *LIST_CONCAT(name,_list) = NULL; \
         static list_t name = (list_t)&LIST_CONCAT(name,_list)
 
/**
 * Declare a linked list inside a structure declaraction.
 *
 * This macro declares a linked list with the specified \c type. The
 * type \b must be a structure (\c struct) with its first element
 * being a pointer. This pointer is used by the linked list library to
 * form the linked lists.
 *
 * Internally, the list is defined as two items: the list itself and a
 * pointer to the list. The pointer has the name of the parameter to
 * the macro and the name of the list is a concatenation of the name
 * and the suffix "_list". The pointer must point to the list for the
 * list to work. Thus the list must be initialized before using.
 *
 * The list is initialized with the LIST_STRUCT_INIT() macro.
 *
 * \param name The name of the list.
 */
#define LIST_STRUCT(name) \
         void *LIST_CONCAT(name,_list); \
         list_t name
 
/**
 * Initialize a linked list that is part of a structure.
 *
 * This macro sets up the internal pointers in a list that has been
 * defined as part of a struct. This macro must be called before using
 * the list.
 *
 * \param struct_ptr A pointer to the struct
 * \param name The name of the list.
 */
#define LIST_STRUCT_INIT(struct_ptr, name)                              \
    do {                                                                \
       (struct_ptr)->name = &((struct_ptr)->LIST_CONCAT(name,_list));   \
       (struct_ptr)->LIST_CONCAT(name,_list) = NULL;                    \
       list_init((struct_ptr)->name);                                   \
    } while(0)
 
/**
 * The linked list type.
 */
typedef void ** list_t;
 
/**
 * The non-modifiable linked list type.
 */
typedef void *const *const_list_t;
 
/**
 * 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.
 */
static inline 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()
 */
static inline void *
list_head(const_list_t list)
{
  return *list;
}
 
/**
 * 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(const_list_t list);
 
/**
 * 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);
 
/**
 * Add an item to the start of the list.
 */
void   list_push(list_t list, void *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);
 
/**
 * 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);
 
/**
 * 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, const void *item);
 
/**
 * 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(const_list_t 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.
 */
static inline void
list_copy(list_t dest, const_list_t src)
{
  *dest = *src;
}
 
/**
 * \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);
 
/**
 * \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.
 */
static inline void *
list_item_next(const void *item)
{
  struct list {
    struct list *next;
  };
  return item == NULL ? NULL : ((struct list *)item)->next;
}
 
/**
 * \brief      Check if the list contains an item
 * \param list The list that is checked
 * \param item An item to look for in the list
 * \returns    0 if the list does not contains the item, and 1 otherwise
 *
 *             This function searches for an item in the list and returns
 *         0 if the list does not contain the item, and 1 if the item
 *         is present in the list.
 */
bool list_contains(const_list_t list, const void *item);
 
#endif /* LIST_H_ */
 
/** @} */
/** @} */