Double/stack.c

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

// Pushes data as pointer onto the stack.
StackNode *push(StackNode *stack, void *data)
{
    StackNode *node = (StackNode*)malloc(sizeof(StackNode));
    if (node == NULL) return stack; // allocation failed, return unchanged stack
    node->data = data;
    node->next = stack;
    return node;
}

// 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 *next = stack->next;
    free(stack);
    return next;
}

// Returns the data of the top element.
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;
    }
}