From 2c2bdb8b66e386e14b5cc1a35abfbf242dcf2018 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@lysator.liu.se>
Date: Mon, 4 Feb 2019 00:36:57 +0100
Subject: Work on propper memmory management for linked lists.

---
 linked_list.inc.h | 72 ++++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 55 insertions(+), 17 deletions(-)

(limited to 'linked_list.inc.h')

diff --git a/linked_list.inc.h b/linked_list.inc.h
index 260eaf0d..a878d075 100644
--- a/linked_list.inc.h
+++ b/linked_list.inc.h
@@ -4,21 +4,29 @@
 
 int CONSTRUCTOR_DECL ( LLIST(TYPE) ) {
 	this->length = 0;
-	this->head = NULL;
-	this->tail = NULL;
-	this->cur = NULL;
+	NEW(LINK(TYPE), head);
+	NEW(LINK(TYPE), tail);
+	this->head = head;
+	this->tail = tail;
+	head->after = tail;
+	tail->before = head;
+	this->cur  = head;
 	return 0;
 }
 
-int LLIST_FREE(TYPE) (LLIST(TYPE)* this ) {
+int FREE_DECL( LLIST(TYPE) ) {
 	LINK(TYPE) *node, *next;
-	node = this->head;
-	while (node != NULL) {
+	node = this->head->after;
+	while (node->after != NULL) {
 		next = node->after;
-		FFREE(TYPE, node->value);
-		free(node);
+		if (node->value != NULL) {
+			FFREE(TYPE, node->value);
+		}
+		// free(node);
 		node = next;
 	}
+	free (this->head);
+	free (this->tail);
 	this->length = 0;
 	return 0;
 }
@@ -30,25 +38,32 @@ int CONSTRUCTOR_DECL ( LINK(TYPE) ) {
 	return 0;
 }
 
+int CONSTRUCTOR_DECL ( LINK(TYPE), TYPE* val ) {
+	this->before = NULL;
+	this->after  = NULL;
+	this->value  = val;
+	return 0;
+}
+
 int LLIST_CONS(TYPE) ( LLIST(TYPE)* lst, TYPE* val) {
-	NEW(LINK(TYPE), l);
-	l->after = lst->head;
-	if (l->after != NULL) {
-		l->after->before = l;
-	}
-	lst->head = l;
-	l->value = val;
+	NEW(LINK(TYPE), l, val);
+
+	l->after = lst->head->after;
+	lst->head->after = l;
+	l->after->before = l;
+	l->before = lst->head;
 	++lst->length;
 
+	// TODO do I want to change that?
 	lst->cur = l;
 
 	return 0;
 }
 
 int DEEP_COPY(LLIST(TYPE)) ( LLIST(TYPE)* dest, LLIST(TYPE)* src ) {
-	LINK(TYPE)* n = src->head;
+	LINK(TYPE)* n = src->head->after;
 
-	while (n != NULL) {
+	while (n->after != NULL) {
 		NEW(TYPE, cpy);
 		DEEP_COPY(TYPE)(cpy, n->value);
 		LLIST_CONS(TYPE) ( dest, cpy );
@@ -58,4 +73,27 @@ int DEEP_COPY(LLIST(TYPE)) ( LLIST(TYPE)* dest, LLIST(TYPE)* src ) {
 	return 0;
 }
 
+/*
+ * TODO
+ * this or cons links wrong, creating infinite loops.
+ */
+int APPEND(LLIST(TYPE)) ( LLIST(TYPE)* dest, LLIST(TYPE)* new ) {
+
+	dest->tail->before->after = new->head->after;
+	new->head->after->before = dest->tail->before;
+	LINK(TYPE)* old_tail = dest->tail;
+	dest->tail = new->tail;
+	dest->length += new->length;
+
+	// free(old_tail);
+	// free(new->head);
+
+	/*
+	 * TODO `new` can now be handled as an empty husk.
+	 * Somehow it needs to be collected
+	 */
+
+	return 0;
+}
+
 #endif /* TYPE */
-- 
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