sample.60

Define (heap_alloc align size)
    Begin {
        Let start
            Let start (Fetch uint32 heap_top)
            In
            Cond {
            | [align > 4]
                Let c [[align / 4] - 1]
                In
                (and [start + c] (complement c))
            | True
                start
            }
        In
        Begin {
            Let limit (Fetch uint32 heap_limit)
            In
            When Or [start > limit] [size > [4 * [limit - start]]] {
                (die "Failed to allocate memory.")
            }
        }
        (Store uint32 heap_top [start + [[size + 3] / 4]])
        start
    }