stack.c

stack.c

@@ -10,24 +10,49 @@
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data)
 {
+    StackNode *newNode = createNode(data); // Speicher für neuen Knoten
+                                           // reservieren
 
+    if (newNode == NULL)
+    { // wenn Speicher nicht reserviert werden konnte, wird
+        // stack unverändert zurückgegeben
+        return stack;
+    }
+
+    newNode->next = stack; // pointer verschieben
+
+    return newNode; // Zeiger auf neuen Speicherbereich zurückgeben
 }
 
 // Deletes the top element of the stack (latest added element) and releases its memory. (Pointer to data has to be
 // freed by caller.)
 StackNode *pop(StackNode *stack)
 {
+    if (stack == NULL)
+        return NULL;
 
+    StackNode *nextNode = stack->next;
+
+    free(stack);
+
+    stack = NULL;
+
+    return nextNode;
 }
 
 // Returns the data of the top element.
-void *top(StackNode *stack)
-{
-
-}
+void *top(StackNode *stack) { return stack != NULL ? stack->data : NULL; }
 
 // Clears stack and releases all memory.
 void clearStack(StackNode *stack)
+{
+    while (stack != NULL)
     {
 
+        StackNode *next = stack->next;
+        free(stack);
+        stack = next;
+    }
+
+    return NULL;
 }