#ifndef __LIST_H
#define __LIST_H
/* This code is taken from the Pintos education OS.
* For copyright information, see www.pintos-os.org */
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/* 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;
…other members…
Then a list of `struct foo’ can be be declared and initialized
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
#include
#include
/* 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 */
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