stack completed

I2_Dobble/stack.c

@@ -10,24 +10,47 @@
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data)
 {
+    StackNode *newNode = malloc(sizeof(StackNode));
+    if (!newNode)
+        return stack;
+    
+    newNode->data = data;
+    newNode->next = stack;
 
+    return newNode;
 }
 
 // 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 *newTopElement = stack->next;
+    free(stack);
 
+    return newTopElement;
 }
 
 // Returns the data of the top element.
 void *top(StackNode *stack)
 {
+    if (!stack)
+        return NULL;
 
+    return stack->data;
 }
 
 // Clears stack and releases all memory.
 void clearStack(StackNode *stack)
 {
+    StackNode *current = stack;
 
+    while (current)
+    {
+        StackNode *next = current->next;
+        free(current);
+        current = next;
+    }
 }

I2_Dobble/stack.h

@@ -8,6 +8,11 @@ The latest element is taken from the stack. */
 #include <stdlib.h>
 
 //TODO: passenden Datentyp als struct anlegen
+typedef struct stack
+{
+    void *data;
+    struct stack *next;
+} StackNode;
 
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data);