equal.ml

let[@inline] get x i = String.unsafe_get x i |> Char.code

external unsafe_get_int16 : string -> int -> int = "%caml_string_get16u"
let[@inline] get16 x i = unsafe_get_int16 x i

let equal ~ln a b =
  let l1 = ln asr 1 in
  let r = ref 0 in
  for i = 0 to pred l1 do r := !r lor (get16 a (i * 2) lxor get16 b (i * 2)) done ;
  for _ = 1 to ln land 1 do r := !r lor (get a (ln - 1) lxor get b (ln - 1)) done ;
  !r = 0

let equal a b =
  let al = String.length a in
  let bl = String.length b in
  if al <> bl
  then false
  else equal ~ln:al a b