#include <string.h>
#include "stack-man.h"

typedef struct
{
    int begin;
    int end;
} alloc_t;

bool_t
stack_manager_init (stack_man_t *st)
{
    st->total_size = 0;

    return array_create (&st->allocations, sizeof (alloc_t));
}

bool_t
stack_manager_alloc (stack_man_t *st, int size, int *offset)
{
    array_t *new_allocs;
    alloc_t *all;
    size_t n_allocs;
    size_t i;
    int location;
    alloc_t *tail;

    if (!array_create (&new_allocs, sizeof (alloc_t)))
	return FALSE;

    all = array_get_data (&st->allocations, &n_allocs);
    location = 0;
    for (i = 0; i < n_allocs; ++i)
    {
	if (!array_append (&new_allocs, 1, &tail))
            goto out;

	memcpy (tail, all, sizeof (alloc_t));

	if (all->begin - location >= size)
	    break;
	
	location = all->end;
	all++;
    }

    if (!array_append (&new_allocs, 1, &tail))
	goto out;

    if (location + size > st->total_size)
	st->total_size = location + size;
    
    tail->begin = location;
    tail->end = location + size;

    for (; i < n_allocs; ++i)
    {
	if (!array_append (&new_allocs, 1, &tail))
	    goto out;

	memcpy (tail, all, sizeof (alloc_t));
	all++;
    }

    *offset = location;

    array_free (&st->allocations);
    st->allocations = new_allocs;
    
    return TRUE;

out:
    array_free (&new_allocs);
    return FALSE;
}

void
stack_manager_free (stack_man_t *st, int offset)
{
    alloc_t *alloc;
    size_t n_allocs;
    int i, d;

    alloc = array_get_data (&st->allocations, &n_allocs);

    d = 0;
    for (i = 0; i < n_allocs; ++i)
    {
        if (alloc[i].begin == offset)
            d++;
        else
            alloc[i - d] = alloc[i];
    }
        
    array_delete_tail (&st->allocations, d);
}