Reworked version of stack_structure.c

stack_structure2.c

/*
A Stack structure implementation
(c) 2015 mooxmirror
*/

#include <stdlib.h>
#include <stdio.h>

#define STACK_TYPE int
#define STACK_TYPE_NULL NULL

typedef struct stack stack;
typedef struct stack_item stack_item;
typedef STACK_TYPE stack_value;

struct stack
{
	stack_item * top;
};
struct stack_item
{
	stack_value value;
	stack_item * next;
};

stack * 		stack_new();
void			stack_delete(stack * s);
stack_value 		stack_peek(stack * s);
stack_value 		stack_pull(stack * s);
void 			stack_put(stack * s, stack_value v);
int			stack_empty(stack * s);

/** IMPLEMENTATION **/
stack * stack_new()
{
	stack * s = (stack *) malloc(sizeof(stack));
	s->top = NULL;
	return s;
}
void stack_delete(stack * s)
{
	stack_item * current = s->top;
	while (current != NULL) {
		stack_item * next = current->next;
		free(current);
		current = next;
	}
	free(s);
}
stack_value stack_peek(stack * s)
{
	stack_item * top = s->top;
	if (top != NULL)
		return top->value;
	
	return STACK_TYPE_NULL;
}
stack_value stack_pull(stack * s)
{
	stack_item * top = s->top;
	
	if (top != NULL)
	{
		stack_value value = top->value;
		stack_item * tmp = top->next;
		s->top = tmp;
		free(top);
		
		return value;
	}
	
	return STACK_TYPE_NULL;
}
void stack_put(stack * s, stack_value value)
{
	stack_item * top = s->top;
	stack_item * next = malloc(sizeof(stack_item));
	next->value = value;
	next->next = top;
	s->top = next;
}
int stack_empty(stack * s)
{
	return s->top == NULL;
}

/** RUNTIME **/
int main(void)
{
	stack * my_stack = stack_new();

	stack_put(my_stack, 13);
	
	printf("%d\n", stack_peek(my_stack));
	stack_pull(my_stack);
	
	stack_delete(my_stack);
	
	return 0;
}