mirror of
https://gitlab.labs.nic.cz/labs/bird.git
synced 2024-05-11 16:54:54 +00:00
92 lines
2.7 KiB
C
92 lines
2.7 KiB
C
/*
|
|
* BIRD Library -- Safe Linked Lists
|
|
*
|
|
* (c) 1998 Martin Mares <mj@ucw.cz>
|
|
*
|
|
* Can be freely distributed and used under the terms of the GNU GPL.
|
|
*/
|
|
|
|
#ifndef _BIRD_SLISTS_H_
|
|
#define _BIRD_SLISTS_H_
|
|
|
|
/*
|
|
* These linked lists work in a way similar to standard lists defined
|
|
* in lib/lists.h, but in addition to all usual list functions they
|
|
* provide fast deletion/insertion/everything-safe asynchronous
|
|
* walking.
|
|
*
|
|
* Example:
|
|
* slist l;
|
|
* siterator i;
|
|
* snode *n;
|
|
*
|
|
* s_init(&i, &l); // Initialize iteration
|
|
* ...
|
|
* n = s_get(&i); // Some time later, fetch present
|
|
* // value of the iterator and unlink it
|
|
* // from the list.
|
|
* while (n->next) {
|
|
* ...
|
|
* if (decided_to_stop) {
|
|
* s_put(&i, n); // Store current position (maybe even
|
|
* // that we stay at list end)
|
|
* return; // and return
|
|
* }
|
|
* ...
|
|
* }
|
|
* // After finishing, don't link the iterator back
|
|
*/
|
|
|
|
typedef struct snode {
|
|
struct snode *next, *prev;
|
|
struct siterator *readers;
|
|
} snode;
|
|
|
|
typedef struct slist { /* In fact two overlayed snodes */
|
|
struct snode *head, *null, *tail;
|
|
struct siterator *tail_readers;
|
|
} slist;
|
|
|
|
typedef struct siterator {
|
|
/*
|
|
* Caution: Layout of this structure depends hard on layout of the
|
|
* snode. Our `next' must be at position of snode `readers'
|
|
* field, our `null' must be at position of `prev' and it must
|
|
* contain NULL in order to distinguish between siterator
|
|
* and snode (snodes with NULL `prev' field never carry
|
|
* iterators). You are not expected to understand this.
|
|
*/
|
|
struct siterator *prev, *null, *next;
|
|
/*
|
|
* For recently merged nodes this can be NULL, but then it's NULL
|
|
* for all successors as well. This is done to speed up iterator
|
|
* merging when there are lots of deletions.
|
|
*/
|
|
snode *node;
|
|
} siterator;
|
|
|
|
#define SNODE (snode *)
|
|
#define SHEAD(list) ((void *)((list).head))
|
|
#define STAIL(list) ((void *)((list).tail))
|
|
#define SNODE_NEXT(n) ((void *)((SNODE (n))->next))
|
|
#define SNODE_VALID(n) ((SNODE (n))->next)
|
|
|
|
#define WALK_SLIST(n,list) for(n=SHEAD(list); SNODE_VALID(n); n=SNODE_NEXT(n))
|
|
#define WALK_SLIST_DELSAFE(n,nxt,list) \
|
|
for(n=SHEAD(list); nxt=SNODE_NEXT(n); n=(void *) nxt)
|
|
#define EMPTY_SLIST(list) (!(list).head->next)
|
|
|
|
void s_add_tail(slist *, snode *);
|
|
void s_add_head(slist *, snode *);
|
|
void s_rem_node(snode *);
|
|
void s_add_tail_list(slist *, slist *);
|
|
void s_init_list(slist *);
|
|
void s_insert_node(snode *, snode *);
|
|
|
|
snode *s_get(siterator *);
|
|
void s_put(siterator *, snode *n);
|
|
static inline void s_init(siterator *i, slist *l) { s_put(i, SHEAD(*l)); }
|
|
static inline int s_is_used(siterator *i) { return (i->prev != NULL); }
|
|
|
|
#endif
|