1 files changed, 55 insertions, 9 deletions

diff --git a/link.c b/link.c
index 60e701d..26372e7 100644
--- a/link.c
+++ b/link.c
@@ -1,30 +1,50 @@
 #include "link.h"
+#include "util.h"
 
 int
-list_len(struct link *list)
+list_len(struct link *head)
 {
 	struct link *iter;
 	int len;
 
+	ASSERT(head != NULL);
+
 	len = 0;
-	for (iter = list; iter; iter = iter->next)
+	for (iter = head->next; iter; iter = iter->next)
 		len += 1;
 
 	return len;
 }
 
+int
+list_ffind(struct link *head, struct link *link)
+{
+	struct link *iter;
+
+	ASSERT(head != NULL);
+
+	for (iter = head->next; iter && iter != link; iter = iter->next);
+
+	return (iter == link);
+}
+
 struct link *
-list_back(struct link *link)
+link_back(struct link *link)
 {
+	ASSERT(link != NULL);
+
 	for (; link->next; link = link->next);
+
 	return link;
 }
 
 void
-link_prepend(struct link *list, struct link *link)
+link_prepend(struct link *cur, struct link *link)
 {
-	link->prev = list->prev;
-	link->next = list;
+	ASSERT(cur != NULL && link != NULL);
+
+	link->prev = cur->prev;
+	link->next = cur;
 
 	if (link->prev)
 		link->prev->next = link;
@@ -33,10 +53,12 @@ link_prepend(struct link *list, struct link *link)
 }
 
 void
-link_append(struct link *list, struct link *link)
+link_append(struct link *cur, struct link *link)
 {
-	link->prev = list;
-	link->next = list->next;
+	ASSERT(cur != NULL && link != NULL);
+
+	link->prev = cur;
+	link->next = cur->next;
 
 	if (link->prev)
 		link->prev->next = link;
@@ -47,8 +69,32 @@ link_append(struct link *list, struct link *link)
 void
 link_pop(struct link *link)
 {
+	ASSERT(link != NULL);
+
 	if (link->prev)
 		link->prev->next = link->next;
 	if (link->next)
 		link->next->prev = link->prev;
 }
+
+struct link *
+link_iter(struct link *link, int n)
+{
+	int i;
+
+	for (i = 0; i < n; i++) {
+		if (!link) return NULL;
+		link = link->next;
+	}
+
+	return link;
+}
+
+void
+link_push_back(struct link *cur, struct link *link)
+{
+	struct link *back;
+
+	back = link_back(cur);
+	link_append(back, link);
+}