diff --git a/src/Pure/PIDE/command.ML b/src/Pure/PIDE/command.ML
--- a/src/Pure/PIDE/command.ML
+++ b/src/Pure/PIDE/command.ML
@@ -1,504 +1,504 @@
 (*  Title:      Pure/PIDE/command.ML
     Author:     Makarius
 
 Prover command execution: read -- eval -- print.
 *)
 
 signature COMMAND =
 sig
   type blob = {file_node: string, src_path: Path.T, content: (SHA1.digest * string list) option}
   val read_file: Path.T -> Position.T -> bool -> Path.T -> Token.file
   val read_thy: Toplevel.state -> theory
   val read: Keyword.keywords -> theory -> Path.T-> (unit -> theory) ->
     blob Exn.result list * int -> Token.T list -> Toplevel.transition
   val read_span: Keyword.keywords -> Toplevel.state -> Path.T -> (unit -> theory) ->
     Command_Span.span -> Toplevel.transition
   type eval
   val eval_command_id: eval -> Document_ID.command
   val eval_exec_id: eval -> Document_ID.exec
   val eval_eq: eval * eval -> bool
   val eval_running: eval -> bool
   val eval_finished: eval -> bool
   val eval_result_command: eval -> Toplevel.transition
   val eval_result_state: eval -> Toplevel.state
   val eval: Keyword.keywords -> Path.T -> (unit -> theory) ->
     blob Exn.result list * int -> Document_ID.command -> Token.T list -> eval -> eval
   type print
   type print_fn = Toplevel.transition -> Toplevel.state -> unit
   val print0: {pri: int, print_fn: print_fn} -> eval -> print
   val print: bool -> (string * string list) list -> Keyword.keywords -> string ->
     eval -> print list -> print list option
   val parallel_print: print -> bool
   type print_function =
     {keywords: Keyword.keywords, command_name: string, args: string list, exec_id: Document_ID.exec} ->
       {delay: Time.time option, pri: int, persistent: bool, strict: bool, print_fn: print_fn} option
   val print_function: string -> print_function -> unit
   val no_print_function: string -> unit
   type exec = eval * print list
   val init_exec: theory option -> exec
   val no_exec: exec
   val exec_ids: exec option -> Document_ID.exec list
   val exec: Document_ID.execution -> exec -> unit
   val exec_parallel_prints: Document_ID.execution -> Future.task list -> exec -> exec option
 end;
 
 structure Command: COMMAND =
 struct
 
 (** main phases of execution **)
 
 fun task_context group f =
   f
   |> Future.interruptible_task
   |> Future.task_context "Command.run_process" group;
 
 
 (* read *)
 
 type blob = {file_node: string, src_path: Path.T, content: (SHA1.digest * string list) option};
 
 fun read_file_node file_node master_dir pos delimited src_path =
   let
     val _ =
       if Context_Position.pide_reports ()
       then Position.report pos (Markup.language_path delimited) else ();
 
     fun read_file () =
       let
         val path = File.check_file (File.full_path master_dir src_path);
         val text = File.read path;
         val file_pos = Path.position path;
       in (text, file_pos) end;
 
     fun read_url () =
       let
-        val text = Isabelle_System.download file_node;
+        val text = Bytes.content (Isabelle_System.download file_node);
         val file_pos = Position.file file_node;
       in (text, file_pos) end;
 
     val (text, file_pos) =
       (case try Url.explode file_node of
         NONE => read_file ()
       | SOME (Url.File _) => read_file ()
       | _ => read_url ());
 
     val lines = split_lines text;
     val digest = SHA1.digest text;
   in {src_path = src_path, lines = lines, digest = digest, pos = Position.copy_id pos file_pos} end
   handle ERROR msg => error (msg ^ Position.here pos);
 
 val read_file = read_file_node "";
 
 local
 
 fun blob_file src_path lines digest file_node =
   let
     val file_pos =
       Position.file file_node |>
       (case Position.id_of (Position.thread_data ()) of
         NONE => I
       | SOME exec_id => Position.put_id exec_id);
   in {src_path = src_path, lines = lines, digest = digest, pos = file_pos} end
 
 fun resolve_files master_dir (blobs, blobs_index) toks =
   (case Outer_Syntax.parse_spans toks of
     [Command_Span.Span (Command_Span.Command_Span _, _)] =>
       (case try (nth toks) blobs_index of
         SOME tok =>
           let
             val source = Token.input_of tok;
             val pos = Input.pos_of source;
             val delimited = Input.is_delimited source;
 
             fun make_file (Exn.Res {file_node, src_path, content = NONE}) =
                   Exn.interruptible_capture (fn () =>
                     read_file_node file_node master_dir pos delimited src_path) ()
               | make_file (Exn.Res {file_node, src_path, content = SOME (digest, lines)}) =
                   (Position.report pos (Markup.language_path delimited);
                     Exn.Res (blob_file src_path lines digest file_node))
               | make_file (Exn.Exn e) = Exn.Exn e;
             val files = map make_file blobs;
           in
             toks |> map_index (fn (i, tok) =>
               if i = blobs_index then Token.put_files files tok else tok)
           end
       | NONE => toks)
   | _ => toks);
 
 fun reports_of_token keywords tok =
   let
     val malformed_symbols =
       Input.source_explode (Token.input_of tok)
       |> map_filter (fn (sym, pos) =>
           if Symbol.is_malformed sym
           then SOME ((pos, Markup.bad ()), "Malformed symbolic character") else NONE);
     val is_malformed = Token.is_error tok orelse not (null malformed_symbols);
     val reports = Token.reports keywords tok @ Token.completion_report tok @ malformed_symbols;
   in (is_malformed, reports) end;
 
 in
 
 fun read_thy st = Toplevel.theory_of st
   handle Toplevel.UNDEF => Pure_Syn.bootstrap_thy;
 
 fun read keywords thy master_dir init blobs_info span =
   let
     val command_reports = Outer_Syntax.command_reports thy;
     val token_reports = map (reports_of_token keywords) span;
     val _ = Position.reports_text (maps #2 token_reports @ maps command_reports span);
 
     val core_range = Token.core_range_of span;
     val tr =
       if exists #1 token_reports
       then Toplevel.malformed (#1 core_range) "Malformed command syntax"
       else Outer_Syntax.parse_span thy init (resolve_files master_dir blobs_info span);
     val _ =
       if Toplevel.is_ignored tr orelse Toplevel.is_malformed tr then ()
       else Position.report (#1 core_range) (Markup.command_span (Toplevel.name_of tr));
   in tr end;
 
 end;
 
 fun read_span keywords st master_dir init =
   Command_Span.content #> read keywords (read_thy st) master_dir init ([], ~1);
 
 
 (* eval *)
 
 type eval_state = {failed: bool, command: Toplevel.transition, state: Toplevel.state};
 
 fun init_eval_state opt_thy =
  {failed = false,
   command = Toplevel.empty,
   state =
     (case opt_thy of
       NONE => Toplevel.init_toplevel ()
     | SOME thy => Toplevel.theory_toplevel thy)};
 
 datatype eval =
   Eval of
     {command_id: Document_ID.command, exec_id: Document_ID.exec, eval_process: eval_state lazy};
 
 fun eval_command_id (Eval {command_id, ...}) = command_id;
 
 fun eval_exec_id (Eval {exec_id, ...}) = exec_id;
 val eval_eq = op = o apply2 eval_exec_id;
 
 val eval_running = Execution.is_running_exec o eval_exec_id;
 fun eval_finished (Eval {eval_process, ...}) = Lazy.is_finished eval_process;
 
 fun eval_result (Eval {eval_process, ...}) =
   Exn.release (Lazy.finished_result eval_process);
 
 val eval_result_command = #command o eval_result;
 val eval_result_state = #state o eval_result;
 
 local
 
 fun reset_state keywords tr st0 = Toplevel.setmp_thread_position tr (fn () =>
   let
     val name = Toplevel.name_of tr;
     val res =
       if Keyword.is_theory_body keywords name then Toplevel.reset_theory st0
       else if Keyword.is_proof keywords name then Toplevel.reset_proof st0
       else if Keyword.is_theory_end keywords name then
         (case Toplevel.reset_notepad st0 of
           NONE => Toplevel.reset_theory st0
         | some => some)
       else NONE;
   in
     (case res of
       NONE => st0
     | SOME st => (Output.error_message (Toplevel.type_error tr ^ " -- using reset state"); st))
   end) ();
 
 fun run keywords int tr st =
   if Future.proofs_enabled 1 andalso Keyword.is_diag keywords (Toplevel.name_of tr) then
     let
       val (tr1, tr2) = Toplevel.fork_presentation tr;
       val _ =
         Execution.fork {name = "Toplevel.diag", pos = Toplevel.pos_of tr, pri = ~1}
           (fn () => Toplevel.command_exception int tr1 st);
     in Toplevel.command_errors int tr2 st end
   else Toplevel.command_errors int tr st;
 
 fun check_token_comments ctxt tok =
   (Document_Output.check_comments ctxt (Input.source_explode (Token.input_of tok)); [])
     handle exn =>
       if Exn.is_interrupt exn then Exn.reraise exn
       else Runtime.exn_messages exn;
 
 fun check_span_comments ctxt span tr =
   Toplevel.setmp_thread_position tr (fn () => maps (check_token_comments ctxt) span) ();
 
 fun report_indent tr st =
   (case try Toplevel.proof_of st of
     SOME prf =>
       let val keywords = Thy_Header.get_keywords (Proof.theory_of prf) in
         if Keyword.command_kind keywords (Toplevel.name_of tr) = SOME Keyword.prf_script then
           (case try (Thm.nprems_of o #goal o Proof.goal) prf of
             NONE => ()
           | SOME 0 => ()
           | SOME n =>
               let val report = Markup.markup_only (Markup.command_indent (n - 1));
               in Toplevel.setmp_thread_position tr (fn () => Output.report [report]) () end)
         else ()
       end
   | NONE => ());
 
 fun status tr m =
   Toplevel.setmp_thread_position tr (fn () => Output.status [Markup.markup_only m]) ();
 
 fun eval_state keywords span tr ({state, ...}: eval_state) =
   let
     val _ = Thread_Attributes.expose_interrupt ();
 
     val st = reset_state keywords tr state;
 
     val _ = report_indent tr st;
     val _ = status tr Markup.running;
     val (errs1, result) = run keywords true tr st;
     val errs2 =
       (case result of
         NONE => []
       | SOME st' => check_span_comments (Toplevel.presentation_context st') span tr);
     val errs = errs1 @ errs2;
     val _ = List.app (Future.error_message (Toplevel.pos_of tr)) errs;
   in
     (case result of
       NONE =>
         let
           val _ = status tr Markup.failed;
           val _ = status tr Markup.finished;
           val _ = if null errs then (status tr Markup.canceled; Exn.interrupt ()) else ();
         in {failed = true, command = tr, state = st} end
     | SOME st' =>
         let
           val _ =
             if Keyword.is_theory_end keywords (Toplevel.name_of tr) andalso
               can (Toplevel.end_theory Position.none) st'
             then status tr Markup.finalized else ();
           val _ = status tr Markup.finished;
         in {failed = false, command = tr, state = st'} end)
   end;
 
 in
 
 fun eval keywords master_dir init blobs_info command_id span eval0 =
   let
     val exec_id = Document_ID.make ();
     fun process () =
       let
         val eval_state0 = eval_result eval0;
         val thy = read_thy (#state eval_state0);
         val tr =
           Position.setmp_thread_data (Position.id_only (Document_ID.print exec_id))
             (fn () =>
               read keywords thy master_dir init blobs_info span |> Toplevel.exec_id exec_id) ();
       in eval_state keywords span tr eval_state0 end;
   in
     Eval {command_id = command_id, exec_id = exec_id,
       eval_process = Lazy.lazy_name "Command.eval" process}
   end;
 
 end;
 
 
 (* print *)
 
 datatype print = Print of
  {name: string, args: string list, delay: Time.time option, pri: int, persistent: bool,
   exec_id: Document_ID.exec, print_process: unit lazy};
 
 fun print_exec_id (Print {exec_id, ...}) = exec_id;
 val print_eq = op = o apply2 print_exec_id;
 
 type print_fn = Toplevel.transition -> Toplevel.state -> unit;
 
 type print_function =
   {keywords: Keyword.keywords, command_name: string, args: string list, exec_id: Document_ID.exec} ->
     {delay: Time.time option, pri: int, persistent: bool, strict: bool, print_fn: print_fn} option;
 
 local
 
 val print_functions =
   Synchronized.var "Command.print_functions" ([]: (string * print_function) list);
 
 fun print_error tr opt_context e =
   (Toplevel.setmp_thread_position tr o Runtime.controlled_execution opt_context) e ()
     handle exn =>
       if Exn.is_interrupt exn then Exn.reraise exn
       else List.app (Future.error_message (Toplevel.pos_of tr)) (Runtime.exn_messages exn);
 
 fun print_finished (Print {print_process, ...}) = Lazy.is_finished print_process;
 
 fun print_persistent (Print {persistent, ...}) = persistent;
 
 val overlay_ord = prod_ord string_ord (list_ord string_ord);
 
 fun make_print (name, args) {delay, pri, persistent, strict, print_fn} eval =
   let
     val exec_id = Document_ID.make ();
     fun process () =
       let
         val {failed, command, state = st', ...} = eval_result eval;
         val tr = Toplevel.exec_id exec_id command;
         val opt_context = try Toplevel.generic_theory_of st';
       in
         if failed andalso strict then ()
         else print_error tr opt_context (fn () => print_fn tr st')
       end;
   in
     Print {
       name = name, args = args, delay = delay, pri = pri, persistent = persistent,
       exec_id = exec_id, print_process = Lazy.lazy_name "Command.print" process}
   end;
 
 fun bad_print name_args exn =
   make_print name_args {delay = NONE, pri = 0, persistent = false,
     strict = false, print_fn = fn _ => fn _ => Exn.reraise exn};
 
 in
 
 fun print0 {pri, print_fn} =
   make_print ("", [serial_string ()])
     {delay = NONE, pri = pri, persistent = true, strict = true, print_fn = print_fn};
 
 fun print command_visible command_overlays keywords command_name eval old_prints =
   let
     val print_functions = Synchronized.value print_functions;
 
     fun new_print (name, args) get_pr =
       let
         val params =
          {keywords = keywords,
           command_name = command_name,
           args = args,
           exec_id = eval_exec_id eval};
       in
         (case Exn.capture (Runtime.controlled_execution NONE get_pr) params of
           Exn.Res NONE => NONE
         | Exn.Res (SOME pr) => SOME (make_print (name, args) pr eval)
         | Exn.Exn exn => SOME (bad_print (name, args) exn eval))
       end;
 
     fun get_print (name, args) =
       (case find_first (fn Print print => (#name print, #args print) = (name, args)) old_prints of
         NONE =>
           (case AList.lookup (op =) print_functions name of
             NONE =>
               SOME (bad_print (name, args) (ERROR ("Missing print function " ^ quote name)) eval)
           | SOME get_pr => new_print (name, args) get_pr)
       | some => some);
 
     val retained_prints =
       filter (fn print => print_finished print andalso print_persistent print) old_prints;
     val visible_prints =
       if command_visible then
         fold (fn (name, _) => cons (name, [])) print_functions command_overlays
         |> sort_distinct overlay_ord
         |> map_filter get_print
       else [];
     val new_prints = visible_prints @ retained_prints;
   in
     if eq_list print_eq (old_prints, new_prints) then NONE else SOME new_prints
   end;
 
 fun parallel_print (Print {pri, ...}) =
   pri <= 0 orelse (Future.enabled () andalso Options.default_bool "parallel_print");
 
 fun print_function name f =
   Synchronized.change print_functions (fn funs =>
    (if name = "" then error "Unnamed print function" else ();
     if not (AList.defined (op =) funs name) then ()
     else warning ("Redefining command print function: " ^ quote name);
     AList.update (op =) (name, f) funs));
 
 fun no_print_function name =
   Synchronized.change print_functions (filter_out (equal name o #1));
 
 end;
 
 val _ =
   print_function "Execution.print"
     (fn {args, exec_id, ...} =>
       if null args then
         SOME {delay = NONE, pri = Task_Queue.urgent_pri + 2, persistent = false, strict = false,
           print_fn = fn _ => fn _ => Execution.fork_prints exec_id}
       else NONE);
 
 val _ =
   print_function "print_state"
     (fn {keywords, command_name, ...} =>
       if Options.default_bool "editor_output_state" andalso Keyword.is_printed keywords command_name
       then
         SOME {delay = NONE, pri = Task_Queue.urgent_pri + 1, persistent = false, strict = false,
           print_fn = fn _ => fn st =>
             if Toplevel.is_proof st then Output.state (Toplevel.string_of_state st)
             else ()}
       else NONE);
 
 
 (* combined execution *)
 
 type exec = eval * print list;
 
 fun init_exec opt_thy : exec =
   (Eval
     {command_id = Document_ID.none, exec_id = Document_ID.none,
       eval_process = Lazy.value (init_eval_state opt_thy)}, []);
 
 val no_exec = init_exec NONE;
 
 fun exec_ids NONE = []
   | exec_ids (SOME (eval, prints)) = eval_exec_id eval :: map print_exec_id prints;
 
 local
 
 fun run_process execution_id exec_id process =
   let val group = Future.worker_subgroup () in
     if Execution.running execution_id exec_id [group] then
       ignore (task_context group (fn () => Lazy.force_result {strict = true} process) ())
     else ()
   end;
 
 fun ignore_process process =
   Lazy.is_running process orelse Lazy.is_finished process;
 
 fun run_eval execution_id (Eval {exec_id, eval_process, ...}) =
   if Lazy.is_finished eval_process then ()
   else run_process execution_id exec_id eval_process;
 
 fun fork_print execution_id deps (Print {name, delay, pri, exec_id, print_process, ...}) =
   let
     val group = Future.worker_subgroup ();
     fun fork () =
       ignore ((singleton o Future.forks)
         {name = name, group = SOME group, deps = deps, pri = pri, interrupts = true}
         (fn () =>
           if ignore_process print_process then ()
           else run_process execution_id exec_id print_process));
   in
     (case delay of
       NONE => fork ()
     | SOME d => ignore (Event_Timer.request {physical = true} (Time.now () + d) fork))
   end;
 
 fun run_print execution_id (print as Print {exec_id, print_process, ...}) =
   if ignore_process print_process then ()
   else if parallel_print print then fork_print execution_id [] print
   else run_process execution_id exec_id print_process;
 
 in
 
 fun exec execution_id (eval, prints) =
   (run_eval execution_id eval; List.app (run_print execution_id) prints);
 
 fun exec_parallel_prints execution_id deps (exec as (Eval {eval_process, ...}, prints)) =
   if Lazy.is_finished eval_process
   then (List.app (fork_print execution_id deps) prints; NONE)
   else SOME exec;
 
 end;
 
 end;
diff --git a/src/Pure/System/isabelle_system.ML b/src/Pure/System/isabelle_system.ML
--- a/src/Pure/System/isabelle_system.ML
+++ b/src/Pure/System/isabelle_system.ML
@@ -1,186 +1,186 @@
 (*  Title:      Pure/System/isabelle_system.ML
     Author:     Makarius
 
 Isabelle system support.
 *)
 
 signature ISABELLE_SYSTEM =
 sig
   val bash_process: Bash.params -> Process_Result.T
   val bash_output: string -> string * int
   val bash: string -> int
   val bash_functions: unit -> string list
   val check_bash_function: Proof.context -> string * Position.T -> string
   val absolute_path: Path.T -> string
   val make_directory: Path.T -> Path.T
   val copy_dir: Path.T -> Path.T -> unit
   val copy_file: Path.T -> Path.T -> unit
   val copy_file_base: Path.T * Path.T -> Path.T -> unit
   val create_tmp_path: string -> string -> Path.T
   val with_tmp_file: string -> string -> (Path.T -> 'a) -> 'a
   val rm_tree: Path.T -> unit
   val with_tmp_dir: string -> (Path.T -> 'a) -> 'a
-  val download: string -> string
+  val download: string -> Bytes.T
   val download_file: string -> Path.T -> unit
-  val decode_base64: string -> string
-  val encode_base64: string -> string
+  val decode_base64: Bytes.T -> Bytes.T
+  val encode_base64: Bytes.T -> Bytes.T
   val isabelle_id: unit -> string
   val isabelle_identifier: unit -> string option
   val isabelle_heading: unit -> string
   val isabelle_name: unit -> string
   val identification: unit -> string
 end;
 
 structure Isabelle_System: ISABELLE_SYSTEM =
 struct
 
 (* bash *)
 
 val absolute_path = Path.implode o File.absolute_path;
 
 fun bash_process params =
   let
     val {script, input, cwd, putenv, redirect, timeout, description} =
       Bash.dest_params params;
     val run =
       [Bash.server_run, script, input,
         let open XML.Encode in YXML.string_of_body (option (string o absolute_path) cwd) end,
         let open XML.Encode in YXML.string_of_body o list (pair string string) end
           (("ISABELLE_TMP", getenv "ISABELLE_TMP") :: putenv),
         Value.print_bool redirect,
         Value.print_real (Time.toReal timeout),
         description];
 
     val address = Options.default_string \<^system_option>\<open>bash_process_address\<close>;
     val password = Options.default_string \<^system_option>\<open>bash_process_password\<close>;
 
     val _ = address = "" andalso raise Fail "Bad bash_process server address";
     fun with_streams f = Socket_IO.with_streams' f address password;
 
     fun kill (SOME uuid) =
           with_streams (fn s => Byte_Message.write_message_string (#2 s) [Bash.server_kill, uuid])
       | kill NONE = ();
   in
     Thread_Attributes.uninterruptible (fn restore_attributes => fn () =>
       let
         fun err () = raise Fail "Malformed result from bash_process server";
         fun loop maybe_uuid s =
           (case restore_attributes Byte_Message.read_message_string (#1 s) of
             SOME (head :: args) =>
               if head = Bash.server_uuid andalso length args = 1 then
                 loop (SOME (hd args)) s
               else if head = Bash.server_interrupt andalso null args then
                 raise Exn.Interrupt
               else if head = Bash.server_failure andalso length args = 1 then
                 raise Fail (hd args)
               else if head = Bash.server_result andalso length args >= 4 then
                 let
                   val a :: b :: c :: d :: lines = args;
                   val rc = Value.parse_int a;
                   val (elapsed, cpu) = apply2 (Time.fromMilliseconds o Value.parse_int) (b, c);
                   val (out_lines, err_lines) = chop (Value.parse_int d) lines;
                 in
                   if rc = Process_Result.timeout_rc then raise Timeout.TIMEOUT elapsed
                   else
                     Process_Result.make
                      {rc = rc,
                       out_lines = out_lines,
                       err_lines = err_lines,
                       timing = {elapsed = elapsed, cpu = cpu, gc = Time.zeroTime}}
                  end
                else err ()
           | _ => err ())
           handle exn => (kill maybe_uuid; Exn.reraise exn);
       in with_streams (fn s => (Byte_Message.write_message_string (#2 s) run; loop NONE s)) end) ()
   end;
 
 val bash = Bash.script #> bash_process #> Process_Result.print #> Process_Result.rc;
 
 fun bash_output s =
   let
     val res = bash_process (Bash.script s);
     val _ = warning (Process_Result.err res);
   in (Process_Result.out res, Process_Result.rc res) end;
 
 
 (* bash functions *)
 
 fun bash_functions () =
   bash_process (Bash.script "declare -Fx")
   |> Process_Result.check
   |> Process_Result.out_lines
   |> map_filter (space_explode " " #> try List.last);
 
 fun check_bash_function ctxt arg =
   Completion.check_entity Markup.bash_functionN
     (bash_functions () |> map (rpair Position.none)) ctxt arg;
 
 
 (* directory and file operations *)
 
 fun scala_function name = ignore o Scala.function name o map absolute_path;
 
 fun make_directory path = (scala_function "make_directory" [path]; path);
 
 fun copy_dir src dst = scala_function "copy_dir" [src, dst];
 
 fun copy_file src dst = scala_function "copy_file" [src, dst];
 
 fun copy_file_base (base_dir, src) target_dir =
   ignore (Scala.function "copy_file_base"
     [absolute_path base_dir, Path.implode src, absolute_path target_dir]);
 
 
 (* tmp files *)
 
 fun create_tmp_path name ext =
   let
     val path = File.tmp_path (Path.basic (name ^ serial_string ()) |> Path.ext ext);
     val _ = File.exists path andalso
       raise Fail ("Temporary file already exists: " ^ Path.print path);
   in path end;
 
 fun with_tmp_file name ext f =
   let val path = create_tmp_path name ext
   in Exn.release (Exn.capture f path before ignore (try File.rm path)) end;
 
 
 (* tmp dirs *)
 
 fun rm_tree path = scala_function "rm_tree" [path];
 
 fun with_tmp_dir name f =
   let val path = create_tmp_path name ""
   in Exn.release (Exn.capture f (make_directory path) before ignore (try rm_tree path)) end;
 
 
 (* download file *)
 
-val download = Scala.function1 "download";
+val download = Bytes.string #> Scala.function1_bytes "download";
 
-fun download_file url path = File.write path (download url);
+fun download_file url path = Bytes.write path (download url);
 
 
 (* base64 *)
 
-val decode_base64 = Scala.function1 "decode_base64";
-val encode_base64 = Scala.function1 "encode_base64";
+val decode_base64 = Scala.function1_bytes "decode_base64";
+val encode_base64 = Scala.function1_bytes "encode_base64";
 
 
 (* Isabelle distribution identification *)
 
 fun isabelle_id () = Scala.function1 "isabelle_id" "";
 
 fun isabelle_identifier () = try getenv_strict "ISABELLE_IDENTIFIER";
 
 fun isabelle_heading () =
   (case isabelle_identifier () of
     NONE => ""
   | SOME version => " (" ^ version ^ ")");
 
 fun isabelle_name () = getenv_strict "ISABELLE_NAME";
 
 fun identification () =
   "Isabelle" ^ (case try isabelle_id () of SOME id => "/" ^ id | NONE => "") ^ isabelle_heading ();
 
 end;