1 files changed, 41 insertions, 3 deletions

diff --git a/04_exercise/arena/arena_list.c b/04_exercise/arena/arena_list.c
index f4b4eb3..822f8f0 100644
--- a/04_exercise/arena/arena_list.c
+++ b/04_exercise/arena/arena_list.c
@@ -23,7 +23,7 @@ Node *listPopFront(List *list) {
     return front;
 }
 
-Node *listPopBack(List list) { return NULL; }
+Node *listPopBack(List* list) { return NULL; }
 
 void listPushFront(List *list, Node *new) {
     if (list->first == NULL) {
@@ -32,17 +32,20 @@ void listPushFront(List *list, Node *new) {
         list->last = new;
         return;
     }
+    new->prev = NULL;
     new->next = list->first;
     new->next->prev = new;
     list->first = new;
 }
 
-void listPushBack(List list, Node *value) {}
+void listPushBack(List* list, Node *value) {}
 
 ArenaList alInit(Node *arena, size_t size) {
     ArenaList al;
     al.activeList = (List){.first = NULL, .last = NULL};
     al.freeList = (List){.first = arena, .last = &arena[size - 1]};
+    al.arena = arena;
+    al.size = size;
     arena[0] = (Node){.value = NULL, .prev = NULL, .next = &arena[1]};
     for (size_t i = 1; i < size - 1; ++i) {
         arena[i] = (Node){.value = NULL, .prev = &arena[i - 1], .next = &arena[i + 1]};
@@ -60,4 +63,39 @@ int alPush(ArenaList* al, void *value) {
     current->value = value;
     listPushFront(&al->activeList, current);
     return 0;
-}
\ No newline at end of file
+}
+
+
+
+int alRemoveElem(ArenaList*  al, void * value){
+    for(size_t i = 0; i < al->size; ++i) {
+        if(al->arena[i].value == value) {
+            return alRemove(al, &al->arena[i]);
+        }
+    }
+    return -1;
+}
+
+int alRemove(ArenaList*  al, Node * node) {
+    //TODO Should we check that the node is actually in the active list
+    //Maybe as an assert that gets optimized out
+    if(node == al->activeList.first) {
+        listPopFront(&al->activeList);
+        listPushFront(&al->freeList, node);
+        return 0;
+    }
+    if(node == al->activeList.last) {
+        listPopBack(&al->activeList);
+        listPushFront(&al->freeList, node);
+        return 0;
+    }
+    // The node is somewhere in the middle
+    Node * prev = node ->prev;
+    Node * next = node ->next;
+
+    next->prev = prev;
+    prev->next = next;
+
+    listPushFront(&al->freeList, node);
+    return 0;
+}