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#include "stack.h"
#include "calls.h"
#define QUANTITY_ADDRESSES 5
enum address_control { get_address, set_address };
void *heap_base;
void init_stack(stack *st)
{
*st = 0;
}
static void *address_management(void *address, enum address_control state)
{
enum { null = 0 };
static void *available_addresses[QUANTITY_ADDRESSES];
int i;
if(state == set_address) {
for(i = 0; i < QUANTITY_ADDRESSES; ++i) {
if(!available_addresses[i]) {
available_addresses[i] = address;
return null;
}
}
return null;
}
for(i = 0; i < QUANTITY_ADDRESSES; ++i) {
if(available_addresses[i]) {
address = available_addresses[i];
available_addresses[i] = 0;
return address;
}
}
return null;
}
void push_stack(stack *st, long num)
{
struct item *tmp;
tmp = address_management(0, get_address);
if(!tmp)
tmp = sys_alloc(sizeof(struct item));
if(!heap_base)
heap_base = tmp;
tmp->data = num;
tmp->next = *st;
*st = tmp;
}
long pop_stack(stack *st)
{
long num = (*st)->data;
address_management(*st, set_address);
*st = (*st)->next;
return num;
}
int is_empty_stack(const stack *st)
{
return *st ? 0 : 1;
}
long top_stack(const stack *st)
{
return (*st)->data;
}
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