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#ifndef __LIST_H

#define __LIST_H

/* This code is taken from the Pintos education OS.

 * For copyright information, see www.pintos-os.org */

/* Doubly linked list.

   This implementation of a doubly linked list does not require

   use of dynamically allocated memory.  Instead, each structure

   that is a potential list element must embed a struct list_elem

   member.  All of the list functions operate on these `struct

   list_elem's.  The list_entry macro allows conversion from a

   struct list_elem back to a structure object that contains it.

   For example, suppose there is a needed for a list of `struct

   foo'.  `struct foo' should contain a `struct list_elem'

   member, like so:

      struct foo

        {

          struct list_elem elem;

          int bar;

          ...other members...

        };

   Then a list of `struct foo' can be be declared and initialized

   like so:

      struct list foo_list;

      list_init (&foo_list);

   Iteration is a typical situation where it is necessary to

   convert from a struct list_elem back to its enclosing

   structure.  Here's an example using foo_list:

      struct list_elem *e;

      for (e = list_begin (&foo_list); e != list_end (&foo_list);

           e = list_next (e))

        {

          struct foo *f = list_entry (e, struct foo, elem);

          ...do something with f...

        }

   You can find real examples of list usage throughout the

   source; for example, malloc.c, palloc.c, and thread.c in the

   threads directory all use lists.

   The interface for this list is inspired by the list<> template

   in the C++ STL.  If you're familiar with list<>, you should

   find this easy to use.  However, it should be emphasized that

   these lists do *no* type checking and can't do much other

   correctness checking.  If you screw up, it will bite you.

   Glossary of list terms:

     - "front": The first element in a list.  Undefined in an

       empty list.  Returned by list_front().

     - "back": The last element in a list.  Undefined in an empty

       list.  Returned by list_back().

     - "tail": The element figuratively just after the last

       element of a list.  Well defined even in an empty list.

       Returned by list_end().  Used as the end sentinel for an

       iteration from front to back.

     - "beginning": In a non-empty list, the front.  In an empty

       list, the tail.  Returned by list_begin().  Used as the

       starting point for an iteration from front to back.

     - "head": The element figuratively just before the first

       element of a list.  Well defined even in an empty list.

       Returned by list_rend().  Used as the end sentinel for an

       iteration from back to front.

     - "reverse beginning": In a non-empty list, the back.  In an

       empty list, the head.  Returned by list_rbegin().  Used as

       the starting point for an iteration from back to front.

     - "interior element": An element that is not the head or

       tail, that is, a real list element.  An empty list does

       not have any interior elements.

*/

#include <stdbool.h>

#include <stddef.h>

#include <stdint.h>

/* List element. */

struct list_elem 

  {

    struct list_elem *prev;     /* Previous list element. */

    struct list_elem *next;     /* Next list element. */

  };

/* List. */

struct list 

  {

    struct list_elem head;      /* List head. */

    struct list_elem tail;      /* List tail. */

  };

/* Converts pointer to list element LIST_ELEM into a pointer to

   the structure that LIST_ELEM is embedded inside.  Supply the

   name of the outer structure STRUCT and the member name MEMBER

   of the list element.  See the big comment at the top of the

   file for an example. */

#define list_entry(LIST_ELEM, STRUCT, MEMBER)           \

        ((STRUCT *) ((uint8_t *) &(LIST_ELEM)->next     \

                     - offsetof (STRUCT, MEMBER.next)))

void list_init (struct list *);

/* List traversal. */

struct list_elem *list_begin (struct list *);

struct list_elem *list_next (struct list_elem *);

struct list_elem *list_end (struct list *);

struct list_elem *list_rbegin (struct list *);

struct list_elem *list_prev (struct list_elem *);

struct list_elem *list_rend (struct list *);

struct list_elem *list_head (struct list *);

struct list_elem *list_tail (struct list *);

/* List insertion. */

void list_insert (struct list_elem *, struct list_elem *);

void list_splice (struct list_elem *before,

                  struct list_elem *first, struct list_elem *last);

void list_push_front (struct list *, struct list_elem *);

void list_push_back (struct list *, struct list_elem *);

/* List removal. */

struct list_elem *list_remove (struct list_elem *);

struct list_elem *list_pop_front (struct list *);

struct list_elem *list_pop_back (struct list *);

/* List elements. */

struct list_elem *list_front (struct list *);

struct list_elem *list_back (struct list *);

/* List properties. */

size_t list_size (struct list *);

bool list_empty (struct list *);

/* Miscellaneous. */

void list_reverse (struct list *);

/* Compares the value of two list elements A and B, given

   auxiliary data AUX.  Returns true if A is less than B, or

   false if A is greater than or equal to B. */

typedef bool list_less_func (const struct list_elem *a,

                             const struct list_elem *b,

                             void *aux);

/* Operations on lists with ordered elements. */

void list_sort (struct list *,

                list_less_func *, void *aux);

void list_insert_ordered (struct list *, struct list_elem *,

                          list_less_func *, void *aux);

void list_unique (struct list *, struct list *duplicates,

                  list_less_func *, void *aux);

/* Max and min. */

struct list_elem *list_max (struct list *, list_less_func *, void *aux);

struct list_elem *list_min (struct list *, list_less_func *, void *aux);

#endif /* list.h */