1 files changed, 63 insertions, 0 deletions
diff --git a/04_exercise/arena/arena_list.c b/04_exercise/arena/arena_list.c
new file mode 100644
index 0000000..f4b4eb3
--- /dev/null
+++ b/04_exercise/arena/arena_list.c
@@ -0,0 +1,63 @@
+//
+// Created by stefan on 10.06.20.
+//
+#include "arena_list.h"
+
+Node *listPopFront(List *list) {
+    Node *front = list->first;
+    if (front == NULL) {
+        return NULL;
+    }
+
+    list->first = front->next;
+    if (front == list->last) {
+        // Only Node in the list
+        list->last = NULL;
+        return front;
+    }
+
+    if (front->next != NULL) {
+        list->first->prev = NULL;
+        front->next = NULL;
+    }
+    return front;
+}
+
+Node *listPopBack(List list) { return NULL; }
+
+void listPushFront(List *list, Node *new) {
+    if (list->first == NULL) {
+        // List was empty
+        list->first = new;
+        list->last = new;
+        return;
+    }
+    new->next = list->first;
+    new->next->prev = new;
+    list->first = new;
+}
+
+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]};
+    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]};
+    }
+    arena[size - 1] = (Node){.value = NULL, .prev = &arena[size - 2], .next = NULL};
+    return al;
+}
+
+int alPush(ArenaList* al, void *value) {
+    Node *current = listPopFront(&al->freeList);
+    // List is empty
+    if (current == NULL) {
+        return -1;
+    }
+    current->value = value;
+    listPushFront(&al->activeList, current);
+    return 0;
+}
+\ No newline at end of file