54 lines
1.2 KiB
C
54 lines
1.2 KiB
C
#include <stdlib.h>
|
|
#include "stack.h"
|
|
|
|
// TODO: grundlegende Stackfunktionen implementieren:
|
|
/* * `push`: legt ein Element oben auf den Stack,
|
|
* `pop`: entfernt das oberste Element,
|
|
* `top`: liefert das oberste Element zurück,
|
|
* `clearStack`: gibt den gesamten Speicher frei. */
|
|
|
|
// Pushes data as pointer onto the stack.
|
|
StackNode *push(StackNode *stack, void *data)
|
|
{
|
|
// if(!data)
|
|
// return 0; -> nicht notwendig
|
|
|
|
StackNode *newNode = calloc(1, sizeof(StackNode)); // Speicher reserviert für data und prev, jeweils nur zeiger
|
|
if (!newNode)
|
|
return NULL;
|
|
|
|
newNode->prev = stack;
|
|
newNode->data = data;
|
|
|
|
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)
|
|
return NULL;
|
|
StackNode *prev = stack->prev;
|
|
free(stack);
|
|
|
|
return prev;
|
|
}
|
|
|
|
// 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) // Annahme: erstes Element: prev = NULL;
|
|
{
|
|
if (!stack)
|
|
return;
|
|
|
|
clearStack(stack->prev);
|
|
free(stack);
|
|
} |