mru.h

   1 #ifndef MRU_H
   2 #define MRU_H
   3
   4 /**
   5  * A simple most-recently-used cache, backed by a doubly-linked list.
   6  *
   7  * Usage is roughly:
   8  *
   9  *   // Create a list.  Zero-initialization is required.
  10  *   static struct mru cache;
  11  *   mru_append(&cache, item);
  12  *   ...
  13  *
  14  *   // Iterate in MRU order.
  15  *   struct mru_entry *p;
  16  *   for (p = cache.head; p; p = p->next) {
  17  *      if (matches(p->item))
  18  *              break;
  19  *   }
  20  *
  21  *   // Mark an item as used, moving it to the front of the list.
  22  *   mru_mark(&cache, p);
  23  *
  24  *   // Reset the list to empty, cleaning up all resources.
  25  *   mru_clear(&cache);
  26  *
  27  * Note that you SHOULD NOT call mru_mark() and then continue traversing the
  28  * list; it reorders the marked item to the front of the list, and therefore
  29  * you will begin traversing the whole list again.
  30  */
  31
  32 struct mru_entry {
  33         void *item;
  34         struct mru_entry *prev, *next;
  35 };
  36
  37 struct mru {
  38         struct mru_entry *head, *tail;
  39 };
  40
  41 void mru_append(struct mru *mru, void *item);
  42 void mru_mark(struct mru *mru, struct mru_entry *entry);
  43 void mru_clear(struct mru *mru);
  44
  45 #endif /* MRU_H */