[MINOR] imported mini-clist.h (circular lists) from librt. It might be wise to merge this with list.h and use sort of common structures.

include/mini-clist.h

@@ -0,0 +1,92 @@
+/*
+ * list.h : list manipulation macros and structures.
+ * (C) 2002-2006 - Willy Tarreau - willy@ant-computing.com
+ *
+ */
+
+#ifndef __MINI_CLIST_H__
+#define __MINI_CLIST_H__
+
+/* these are circular or bidirectionnal lists only. Each list pointer points to
+ * another list pointer in a structure, and not the structure itself. The
+ * pointer to the next element MUST be the first one so that the list is easily
+ * cast as a single linked list or pointer.
+ */
+struct list {
+    struct list *n;	/* next */
+    struct list *p;	/* prev */
+};
+
+#define LIST_INIT(l) ((l)->n = (l)->p = (l))
+
+/* dual linked lists :
+ * Start = (struct list *) pointer to the next elem's prev list entry
+ * For each element :
+ *   - prev = pointer to previous element's next (or start). Cannot be NULL
+ *   - next = pointer to next element's prev. NULL = end.
+ *
+ */
+
+/****** circular lists ********/
+
+/* adds an element at the beginning of a list ; returns the element */
+#define LIST_ADD(lh, el) ({ (el)->n = (lh)->n; (el)->n->p = (lh)->n = (el); (el)->p = (lh); (el); })
+
+/* adds an element at the end of a list ; returns the element */
+#define LIST_ADDQ(lh, el) ({ (el)->p = (lh)->p; (el)->p->n = (lh)->p = (el); (el)->n = (lh); (el); })
+
+/* removes an element from a list and returns it */
+#define LIST_DEL(el) ({ typeof(el) __ret = (el); (el)->n->p = (el)->p; (el)->p->n = (el)->n; (__ret); })
+
+/* returns a pointer of type <pt> to a structure containing a list head called
+ * <el> at address <lh>. Note that <lh> can be the result of a function or macro
+ * since it's used only once.
+ * Example: LIST_ELEM(cur_node->args.next, struct node *, args)
+ */
+#define LIST_ELEM(lh, pt, el) ((pt)(((void *)(lh)) - ((void *)&((pt)NULL)->el)))
+
+/* checks if the list head <lh> is empty or not */
+#define LIST_ISEMPTY(lh) ((lh)->n == (lh))
+
+/* returns a pointer of type <pt> to a structure following the element
+ * which contains list head <lh>, which is known as element <el> in
+ * struct pt.
+ * Example: LIST_NEXT(args, struct node *, list)
+ */
+#define LIST_NEXT(lh, pt, el) (LIST_ELEM((lh)->n, pt, el))
+
+
+/* returns a pointer of type <pt> to a structure preceeding the element
+ * which contains list head <lh>, which is known as element <el> in
+ * struct pt.
+ */
+#define LIST_PREV(lh, pt, el) (LIST_ELEM((lh)->p, pt, el))
+
+/*
+ * iterates through a list of items of type "<struct_type>" which are
+ * linked via a "struct list" member named <struct_member>. The head of the
+ * list is stored at a location designed by <list_head>, which should be a
+ * "struct list *". A variable <end_item> of type "<struct_type>" will
+ * be used as temporary end of list pointer. It can be derived from <list_head>
+ * since this one is only used before.
+ * Example: FOREACH_ITEM(cur_node, &node->args, node, struct node *, neigh) { ... };
+ */
+#define FOREACH_ITEM(iterator, list_head, end_item, struct_type, struct_member) \
+	iterator = end_item = LIST_ELEM(list_head, struct_type, struct_member); \
+	while (((iterator) = LIST_ELEM((iterator)->struct_member.n, 		\
+			     struct_type, struct_member)) != (end_item))
+
+/*
+ * idem except that this one is safe against deletion, but it needs a backup
+ * pointer of the element after the iterator.
+ * Example: FOREACH_ITEM_SAFE(cur_node, backup, &node->args, node, struct node *, neigh) { ... };
+ */
+#define FOREACH_ITEM_SAFE(iterator, backup, list_head, end_item, struct_type, struct_member) \
+	end_item = LIST_ELEM(list_head, struct_type, struct_member); \
+	iterator = LIST_ELEM((end_item)->struct_member.n, struct_type, struct_member); \
+	if ((iterator) != (end_item)) \
+		backup = LIST_ELEM((iterator)->struct_member.n, struct_type, struct_member); \
+	for ( ; (iterator) != (end_item); (iterator) = (backup),   \
+		backup = LIST_ELEM((iterator)->struct_member.n, struct_type, struct_member))
+
+#endif /* __MINI_CLIST_H__ */