let big_int_of_byte_list l =
let rec continue = function
[] -> Big_int.zero_big_int
| [n] -> Big_int.big_int_of_int (n land 0xff)
| n::l ->
Big_int.add_int_big_int (n land 0xff) (Big_int.mult_int_big_int 0x100 (continue l))
in
continue l