unikernel/duniverse/digestif/src-ocaml/xor.ml

@@ -0,0 +1,57 @@
+module Nat = struct
+  include Nativeint
+
+  let ( lxor ) = Nativeint.logxor
+end
+
+module type BUFFER = sig
+  type t
+
+  val length : t -> int
+  val sub : t -> int -> int -> t
+  val copy : t -> t
+  val benat_to_cpu : t -> int -> nativeint
+  val cpu_to_benat : t -> int -> nativeint -> unit
+end
+
+let imin (a : int) (b : int) = if a < b then a else b
+
+module Make (B : BUFFER) = struct
+  let size_of_long = Sys.word_size / 8
+
+  (* XXX(dinosaure): I'm not sure about this code. May be we don't need the
+     first loop and the _optimization_ is irrelevant. *)
+  let xor_into src src_off dst dst_off n =
+    let n = ref n in
+    let i = ref 0 in
+    while !n >= size_of_long do
+      B.cpu_to_benat dst (dst_off + !i)
+        Nat.(
+          B.benat_to_cpu dst (dst_off + !i)
+          lxor B.benat_to_cpu src (src_off + !i)) ;
+      n := !n - size_of_long ;
+      i := !i + size_of_long
+    done ;
+    while !n > 0 do
+      B.cpu_to_benat dst (dst_off + !i)
+        Nat.(
+          B.benat_to_cpu src (src_off + !i)
+          lxor B.benat_to_cpu dst (dst_off + !i)) ;
+      incr i ;
+      decr n
+    done
+
+  let xor_into a b n =
+    if n > imin (B.length a) (B.length b)
+    then raise (Invalid_argument "Baijiu.Xor.xor_inrot: buffers to small")
+    else xor_into a 0 b 0 n
+
+  let xor a b =
+    let l = imin (B.length a) (B.length b) in
+    let r = B.copy (B.sub b 0 l) in
+    xor_into a r l ;
+    r
+end
+
+module Bytes = Make (Digestif_by)
+module Bigstring = Make (Digestif_bi)