1 files changed, 45 insertions, 0 deletions
diff --git a/mru.h b/mru.h
new file mode 100644
index 0000000000..42e4aeaa10
--- /dev/null
+++ b/mru.h
@@ -0,0 +1,45 @@
+#ifndef MRU_H
+#define MRU_H
+
+/**
+ * A simple most-recently-used cache, backed by a doubly-linked list.
+ *
+ * Usage is roughly:
+ *
+ *   // Create a list.  Zero-initialization is required.
+ *   static struct mru cache;
+ *   mru_append(&cache, item);
+ *   ...
+ *
+ *   // Iterate in MRU order.
+ *   struct mru_entry *p;
+ *   for (p = cache.head; p; p = p->next) {
+ *	if (matches(p->item))
+ *		break;
+ *   }
+ *
+ *   // Mark an item as used, moving it to the front of the list.
+ *   mru_mark(&cache, p);
+ *
+ *   // Reset the list to empty, cleaning up all resources.
+ *   mru_clear(&cache);
+ *
+ * Note that you SHOULD NOT call mru_mark() and then continue traversing the
+ * list; it reorders the marked item to the front of the list, and therefore
+ * you will begin traversing the whole list again.
+ */
+
+struct mru_entry {
+	void *item;
+	struct mru_entry *prev, *next;
+};
+
+struct mru {
+	struct mru_entry *head, *tail;
+};
+
+void mru_append(struct mru *mru, void *item);
+void mru_mark(struct mru *mru, struct mru_entry *entry);
+void mru_clear(struct mru *mru);
+
+#endif /* MRU_H */