This utility function, to join the zoo that the Quagga linked-list
implementation has accumulated, does an insert-before while returning
the newly allocated node.
It is similar to:
- listnode_add_after(), but
- complementary direction
- returns allocated node
- list_add_node_prev(), but
- supports before == NULL
- returns allocated node
In general, the entire linked-list implementation is in bad shape, and
while it needs a cleanup / rewrite / replacement, this would both cause
significant conflicts and block other cleanups...
Signed-off-by: David Lamparter <equi...@opensourcerouting.org>
---
lib/linklist.c | 38 ++++++++++++++++++++++++++++++++++++++
lib/linklist.h | 1 +
2 files changed, 39 insertions(+)
diff --git a/lib/linklist.c b/lib/linklist.c
index 02e91f1..052d47c 100644
--- a/lib/linklist.c
+++ b/lib/linklist.c
@@ -162,6 +162,44 @@ listnode_add_after (struct list *list, struct listnode
*pp, void *val)
list->count++;
}
+struct listnode *
+listnode_add_before (struct list *list, struct listnode *pp, void *val)
+{
+ struct listnode *nn;
+
+ assert (val != NULL);
+
+ nn = listnode_new ();
+ nn->data = val;
+
+ if (pp == NULL)
+ {
+ if (list->tail)
+ list->tail->next = nn;
+ else
+ list->head = nn;
+
+ nn->prev = list->tail;
+ nn->next = pp;
+
+ list->tail = nn;
+ }
+ else
+ {
+ if (pp->prev)
+ pp->prev->next = nn;
+ else
+ list->head = nn;
+
+ nn->prev = pp->prev;
+ nn->next = pp;
+
+ pp->prev = nn;
+ }
+ list->count++;
+ return nn;
+}
+
/* Move given listnode to tail of the list */
void
listnode_move_to_tail (struct list *l, struct listnode *n)
diff --git a/lib/linklist.h b/lib/linklist.h
index 6209c8b..96aaf43 100644
--- a/lib/linklist.h
+++ b/lib/linklist.h
@@ -68,6 +68,7 @@ extern void list_free (struct list *);
extern void listnode_add (struct list *, void *);
extern void listnode_add_sort (struct list *, void *);
extern void listnode_add_after (struct list *, struct listnode *, void *);
+extern struct listnode *listnode_add_before (struct list *, struct listnode *,
void *);
extern void listnode_move_to_tail (struct list *, struct listnode *);
extern void listnode_delete (struct list *, void *);
extern struct listnode *listnode_lookup (struct list *, void *);
--
2.7.3
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