1 files changed, 54 insertions, 0 deletions
diff --git a/link.c b/link.c
new file mode 100644
index 0000000..60e701d
--- /dev/null
+++ b/link.c
@@ -0,0 +1,54 @@
+#include "link.h"
+
+int
+list_len(struct link *list)
+{
+	struct link *iter;
+	int len;
+
+	len = 0;
+	for (iter = list; iter; iter = iter->next)
+		len += 1;
+
+	return len;
+}
+
+struct link *
+list_back(struct link *link)
+{
+	for (; link->next; link = link->next);
+	return link;
+}
+
+void
+link_prepend(struct link *list, struct link *link)
+{
+	link->prev = list->prev;
+	link->next = list;
+
+	if (link->prev)
+		link->prev->next = link;
+	if (link->next)
+		link->next->prev = link;
+}
+
+void
+link_append(struct link *list, struct link *link)
+{
+	link->prev = list;
+	link->next = list->next;
+
+	if (link->prev)
+		link->prev->next = link;
+	if (link->next)
+		link->next->prev = link;
+}
+
+void
+link_pop(struct link *link)
+{
+	if (link->prev)
+		link->prev->next = link->next;
+	if (link->next)
+		link->next->prev = link->prev;
+}