sixel_allocator_ref(
    sixel_allocator_t /* in */ *allocator)  /* allocator object to be
                                               increment reference counter */
{
    /* precondition */
    assert(allocator);

    /* TODO: be thread safe */
    ++allocator->ref;
}
sixel_allocator_ref(
    sixel_allocator_t   *allocator)   
{
     
    assert(allocator);

     
    ++allocator->ref;
}