lib: typesafe *_member()

This provides a "is this item on this list" check, which may or may not
be faster than using *_find() for the same purpose.  (If the container
has no faster way of doing it, it falls back to using *_find().)

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

1 files changed, 38 insertions, 0 deletions

diff --git a/lib/typesafe.c b/lib/typesafe.c
index 76705fad0d..f886c5bdf6 100644
--- a/lib/typesafe.c
+++ b/lib/typesafe.c
@@ -29,6 +29,44 @@ DEFINE_MTYPE_STATIC(LIB, TYPEDHASH_BUCKET, "Typed-hash bucket");
 DEFINE_MTYPE_STATIC(LIB, SKIPLIST_OFLOW, "Skiplist overflow");
 DEFINE_MTYPE_STATIC(LIB, HEAP_ARRAY, "Typed-heap array");
 
+bool typesafe_list_member(const struct slist_head *head,
+			  const struct slist_item *item)
+{
+	struct slist_item *fromhead = head->first;
+	struct slist_item **fromnext = (struct slist_item **)&item->next;
+
+	while (fromhead) {
+		if (fromhead == item || fromnext == head->last_next)
+			return true;
+
+		fromhead = fromhead->next;
+		if (!*fromnext)
+			break;
+		fromnext = &(*fromnext)->next;
+	}
+
+	return false;
+}
+
+bool typesafe_dlist_member(const struct dlist_head *head,
+			   const struct dlist_item *item)
+{
+	const struct dlist_item *fromhead = head->hitem.next;
+	const struct dlist_item *fromitem = item->next;
+
+	if (!item->prev || !item->next)
+		return false;
+
+	while (fromhead != &head->hitem && fromitem != item) {
+		if (fromitem == &head->hitem || fromhead == item)
+			return true;
+		fromhead = fromhead->next;
+		fromitem = fromitem->next;
+	}
+
+	return false;
+}
+
 #if 0
 static void hash_consistency_check(struct thash_head *head)
 {