sixel_allocator_free(
    sixel_allocator_t   /* in */ *allocator,  /* allocator object */
    void                /* in */ *p)          /* existing buffer to be freed */
{
    /* precondition */
    assert(allocator);
    assert(allocator->fn_free);

    allocator->fn_free(p);
}
sixel_allocator_free(
    sixel_allocator_t     *allocator,   
    void                  *p)           
{
     
    assert(allocator);
    assert(allocator->fn_free);

    allocator->fn_free(p);
}