#include <stdlib.h>
#include "stack.h"

StackNode *push(StackNode *stack, void *data)
{
    StackNode *node = malloc(sizeof(StackNode));
    if (node == NULL) return stack;
    node->data = data;
    node->next = stack;
    return node;
}

StackNode *pop(StackNode *stack)
{
    if (stack == NULL) return NULL;
    StackNode *next = stack->next;
    free(stack);
    return next;
}

void *top(StackNode *stack)
{
    if (stack == NULL) return NULL;
    return stack->data;
}

void clearStack(StackNode *stack)
{
    while (stack != NULL) {
        StackNode *next = stack->next;
        free(stack);
        stack = next;
    }
}