linked_list: Add `linked_list` type.

This is a type generic doubly linked list implementation.

I used the implementation from DevkitPro's libnds library as a baseline.

Link to libnds implementation:
https://github.com/devkitPro/libnds/blob/master/source/arm9/linkedlist.c

1 files changed, 59 insertions, 0 deletions

diff --git a/linked_list.c b/linked_list.c
new file mode 100644
index 0000000..792da4d
--- /dev/null
+++ b/linked_list.c
@@ -0,0 +1,59 @@
+#include <stdlib.h>
+#include "linked_list.h"
+
+linked_list *add_node(linked_list **tail, void *data) {
+	if (tail == NULL) {
+		return NULL;
+	} else {
+		linked_list *node = calloc(1, sizeof(linked_list));
+		if (node == NULL) {
+			return NULL;
+		} else {
+			node->next = NULL;
+			node->data = data;
+
+			if (*tail == NULL) {
+				node->prev = NULL;
+				*tail = node;
+			} else {
+				(*tail)->next = node;
+				node->prev = *tail;
+			}
+
+			return node;
+		}
+	}
+}
+
+
+void remove_node(linked_list *node) {
+	if (node != NULL) {
+		if (node->prev != NULL) {
+			node->prev->next = node->next;
+		}
+
+		if (node->next != NULL) {
+			node->next->prev = node->prev;
+		}
+
+		free(node);
+	}
+}
+
+linked_list *get_head(linked_list *node) {
+	linked_list *head;
+	for (head = node; head != NULL && head->prev != NULL; head = head->prev);
+	return head;
+}
+
+linked_list *get_tail(linked_list *node) {
+	linked_list *tail;
+	for (tail = node; tail != NULL && tail->next != NULL; tail = tail->next);
+	return tail;
+}
+
+int linked_list_size(linked_list *tail) {
+	int i = 0;
+	for (linked_list *node = tail; node != NULL; node = node->prev, ++i);
+	return i;
+}