MLton.Random.seed

[Stephen Weeks]

What is correct failure mode for MLton.Random.{seed,useed} when they are unable
to read 4 bytes from /dev/random?  Right now, they are implemented as follows,
and raise Fail if they are unable to read 4 bytes.

      (* Linux specific.  Uses /dev/random and /dev/urandom to get a
       * random word.
       *)
      local
	 fun make (file, name) () =
	    let
	       val buf = Word8Array.array (4, 0w0)
	       val fd =
		  let
		     open Posix.FileSys
		  in
		     openf (file, O_RDONLY, O.flags [])
		  end
	       val n = Posix.IO.readArr (fd, {buf = buf, i = 0, sz = SOME 4})
	       val _ = Posix.IO.close fd
	       val _ =
		  if 4 = n
		     then ()
		  else raise Fail name
	    in
	       Pack32Little.subArr (buf, 0)
	    end
      in
	 val seed = make ("/dev/random", "Random.seed")
	 val useed = make ("/dev/urandom", "Random.useed")
      end