lib/lists.h

   1 /*
   2  *      BIRD Library -- Linked Lists
   3  *
   4  *      (c) 1998 Martin Mares <mj@ucw.cz>
   5  *
   6  *      Can be freely distributed and used under the terms of the GNU GPL.
   7  */
   8
   9 #ifndef _BIRD_LISTS_H_
  10 #define _BIRD_LISTS_H_
  11
  12 /*
  13  * I admit the list structure is very tricky and also somewhat awkward,
  14  * but it's both efficient and easy to manipulate once one understands the
  15  * basic trick: The list head always contains two synthetic nodes which are
  16  * always present in the list: the head and the tail. But as the `next'
  17  * entry of the tail and the `prev' entry of the head are both NULL, the
  18  * nodes can overlap each other:
  19  *
  20  *     head    head_node.next
  21  *     null    head_node.prev  tail_node.next
  22  *     tail                    tail_node.prev
  23  */
  24
  25 typedef struct node {
  26   struct node *next, *prev;
  27 } node;
  28
  29 typedef struct list {                   /* In fact two overlayed nodes */
  30   struct node *head, *null, *tail;
  31 } list;
  32
  33 #define NODE (node *)
  34 #define HEAD(list) ((void *)((list).head))
  35 #define TAIL(list) ((void *)((list).tail))
  36 #define NODE_NEXT(n) ((void *)((NODE (n))->next))
  37 #define NODE_VALID(n) ((NODE (n))->next)
  38 #define WALK_LIST(n,list) for(n=HEAD(list); NODE_VALID(n); n=NODE_NEXT(n))
  39 #define WALK_LIST_DELSAFE(n,nxt,list) \
  40      for(n=HEAD(list); nxt=NODE_NEXT(n); n=(void *) nxt)
  41 /* WALK_LIST_FIRST supposes that called code removes each processed node */
  42 #define WALK_LIST_FIRST(n,list) \
  43      while(n=HEAD(list), (NODE (n))->next)
  44 #define WALK_LIST_BACKWARDS(n,list) for(n=TAIL(list);(NODE (n))->prev; \
  45                                 n=(void *)((NODE (n))->prev))
  46 #define WALK_LIST_BACKWARDS_DELSAFE(n,prv,list) \
  47      for(n=TAIL(list); prv=(void *)((NODE (n))->prev); n=(void *) prv)
  48
  49 #define EMPTY_LIST(list) (!(list).head->next)
  50
  51 void add_tail(list *, node *);
  52 void add_head(list *, node *);
  53 void rem_node(node *);
  54 void rem2_node(node *);
  55 void add_tail_list(list *, list *);
  56 void init_list(list *);
  57 void insert_node(node *, node *);
  58
  59 #ifndef _BIRD_LISTS_C_
  60 #define LIST_INLINE extern inline
  61 #include "lib/lists.c"
  62 #undef LIST_INLINE
  63 #else
  64 #define LIST_INLINE
  65 #endif
  66
  67 #endif