stack.c

@@ -1,43 +1,33 @@
 #include <stdlib.h>
 #include "stack.h"
 
-typedef struct Stack_node {
+//TODO: grundlegende Stackfunktionen implementieren:
-    void *data;
+/*  * `push`: legt ein Element oben auf den Stack,
-    struct Stack_node *next;
+    * `pop`: entfernt das oberste Element,
-} StackNode;
+    * `top`: liefert das oberste Element zurück,
+    * `clearStack`: gibt den gesamten Speicher frei. */
 
-// Pushes data onto the stack.
+// Pushes data as pointer onto the stack.
-// Returns the new top of the stack.
+StackNode *push(StackNode *stack, void *data)
-StackNode *push(StackNode *stack, void *data) {
+{
-    StackNode *node = malloc(sizeof(StackNode));
-    if (!node) return stack;  // allocation failed → leave unchanged
 
-    node->data = data;
-    node->next = stack;
-    return node; // new top element
 }
 
-// Deletes the top element and returns the new stack top.
+// Deletes the top element of the stack (latest added element) and releases its memory. (Pointer to data has to be
-// Caller must free the *data* itself.
+// freed by caller.)
-StackNode *pop(StackNode *stack) {
+StackNode *pop(StackNode *stack)
-    if (!stack) return NULL;
+{
 
-    StackNode *next = stack->next;
-    free(stack);   // free only the node, NOT the data
-    return next;
 }
 
-// Returns the data at the top of the stack.
+// Returns the data of the top element.
-void *top(StackNode *stack) {
+void *top(StackNode *stack)
-    if (!stack) return NULL;
+{
-    return stack->data;
+
 }
 
-// Clears entire stack (but does NOT free the data).
+// Clears stack and releases all memory.
-void clearStack(StackNode *stack) {
+void clearStack(StackNode *stack)
-    while (stack) {
+{
-        StackNode *next = stack->next;
+
-        free(stack);
+}
-        stack = next;
-    }
-}