From ddb7d43143ff664948f27cd2cd4e18bdfcce6118 Mon Sep 17 00:00:00 2001
From: Stefan Zabka <zabkaste@hu-berlin.de>
Date: Thu, 11 Jun 2020 01:00:56 +0200
Subject: Forgot arena folder

---
 04_exercise/arena/arena_list.c | 63 ++++++++++++++++++++++++++++++++++++++++++
 04_exercise/arena/arena_list.h | 36 ++++++++++++++++++++++++
 04_exercise/arena/arena_test.c | 18 ++++++++++++
 3 files changed, 117 insertions(+)
 create mode 100644 04_exercise/arena/arena_list.c
 create mode 100644 04_exercise/arena/arena_list.h
 create mode 100644 04_exercise/arena/arena_test.c

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
diff --git a/04_exercise/arena/arena_list.h b/04_exercise/arena/arena_list.h
new file mode 100644
index 0000000..86bf805
--- /dev/null
+++ b/04_exercise/arena/arena_list.h
@@ -0,0 +1,36 @@
+//
+// Created by stefan on 10.06.20.
+//
+
+#ifndef BETRIEBSYSTEME_ARENA_LIST_H
+#define BETRIEBSYSTEME_ARENA_LIST_H
+
+#include <stdlib.h>
+typedef struct Node {
+    void * value;
+    struct Node * next;
+    struct Node * prev;
+} Node;
+
+typedef struct List {
+    Node * first;
+    Node * last;
+} List;
+// This structure manages an arena / memory slab to be used
+typedef struct ArenaList {
+    List freeList;
+    List activeList;
+} ArenaList;
+
+//Initializes the node array
+ArenaList alInit(Node * arena, size_t size);
+// Return -1 if the List is full
+int alPush(ArenaList*  al, void * value);
+
+// Return -1 if the Node was already deleted
+int alRemove(ArenaList*  al, Node * node);
+
+// Return -1 if the Node was already deleted
+int alRemoveElem(ArenaList*  al, void * value);
+
+#endif // BETRIEBSYSTEME_ARENA_LIST_H
diff --git a/04_exercise/arena/arena_test.c b/04_exercise/arena/arena_test.c
new file mode 100644
index 0000000..b0927f1
--- /dev/null
+++ b/04_exercise/arena/arena_test.c
@@ -0,0 +1,18 @@
+//
+// Created by stefan on 10.06.20.
+//
+#include "arena_list.h"
+#include <stdio.h>
+int main() {
+    Node arena[5];
+    ArenaList al = alInit(arena, 5);
+    int data[5] = {1, 2, 3, 4, 5};
+    for (int i = 0; i < 5; ++i) {
+        alPush(&al, &data[4 - i]);
+    }
+
+    for (Node *cur = al.activeList.first; cur != NULL; cur = cur->next) {
+        printf("Got digit %d \n", *(int *)cur->value);
+    }
+
+}
-- 
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