manage the underlying ML process in Scala;

--- a/src/Pure/General/file.scala	Mon Mar 07 14:53:28 2016 +0100
+++ b/src/Pure/General/file.scala	Mon Mar 07 15:21:50 2016 +0100
@@ -108,6 +108,15 @@
   def shell_path(file: JFile): String = shell_quote(standard_path(file))
 
 
+  /* directory entries */
+
+  def check_dir(path: Path): Path =
+    if (path.is_dir) path else error("No such directory: " + path)
+
+  def check_file(path: Path): Path =
+    if (path.is_file) path else error("No such file: " + path)
+
+
   /* find files */
 
   def find_files(start: JFile, pred: JFile => Boolean = _ => true): List[JFile] =

--- a/src/Pure/ML/ml_syntax.scala	Mon Mar 07 14:53:28 2016 +0100
+++ b/src/Pure/ML/ml_syntax.scala	Mon Mar 07 15:21:50 2016 +0100
@@ -33,4 +33,7 @@
 
   def print_string_raw(str: String): String =
     quote(UTF8.bytes(str).iterator.map(print_chr(_)).mkString)
+
+  def print_list[A](f: A => String)(list: List[A]): String =
+    "[" + commas(list.map(f)) + "]"
 }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/Pure/System/ml_process.scala	Mon Mar 07 15:21:50 2016 +0100
@@ -0,0 +1,102 @@
+/*  Title:      Pure/System/ml_process.scala
+    Author:     Makarius
+
+The underlying ML process.
+*/
+
+package isabelle
+
+
+object ML_Process
+{
+  def apply(options: Options,
+    heap: String = "",
+    args: List[String] = Nil,
+    process_socket: String = "",
+    secure: Boolean = false,
+    modes: List[String] = Nil): Bash.Process =
+  {
+    val load_heaps =
+    {
+      if (heap == "RAW_ML_SYSTEM") Nil
+      else if (heap.iterator.contains('/')) {
+        val heap_path = Path.explode(heap)
+        if (!heap_path.is_file) error("Bad heap file: " + heap_path)
+        List(heap_path)
+      }
+      else {
+        val dirs = Isabelle_System.find_logics_dirs()
+        val heap_name = if (heap == "") Isabelle_System.getenv_strict("ISABELLE_LOGIC") else heap
+        dirs.map(_ + Path.basic(heap_name)).find(_.is_file) match {
+          case Some(heap_path) => List(heap_path)
+          case None =>
+            error("Unknown logic " + quote(heap) + " -- no heap file found in:\n" +
+              cat_lines(dirs.map(dir => "  " + dir.implode)))
+        }
+      }
+    }
+
+    val eval_heaps =
+      load_heaps.map(load_heap =>
+        "PolyML.SaveState.loadState " + ML_Syntax.print_string_raw(File.platform_path(load_heap)) +
+        " handle exn => (TextIO.output (TextIO.stdErr, General.exnMessage exn ^ " +
+        ML_Syntax.print_string_raw(": " + load_heap.toString + "\n") +
+        "); OS.Process.exit OS.Process.failure)")
+
+    val eval_exit =
+      if (load_heaps.isEmpty) {
+        List(
+          if (Platform.is_windows)
+            "fun exit 0 = OS.Process.exit OS.Process.success" +
+            " | exit 1 = OS.Process.exit OS.Process.failure" +
+            " | exit rc = OS.Process.exit (RunCall.unsafeCast (Word8.fromInt rc))"
+          else
+            "fun exit rc = Posix.Process.exit (Word8.fromInt rc)"
+        )
+      }
+      else Nil
+
+    val eval_secure = if (secure) List("Secure.set_secure ()") else Nil
+
+    val eval_modes =
+      if (modes.isEmpty) Nil
+      else List("Print_Mode.add_modes " + ML_Syntax.print_list(ML_Syntax.print_string_raw _)(modes))
+
+
+    // options
+    val isabelle_process_options = Isabelle_System.tmp_file("options")
+    File.write(isabelle_process_options, YXML.string_of_body(options.encode))
+    val bash_env = Map("ISABELLE_PROCESS_OPTIONS" -> File.standard_path(isabelle_process_options))
+    val eval_options = List("Options.load_default ()")
+
+    val eval_process =
+      if (process_socket == "") Nil
+      else List("Isabelle_Process.init " + ML_Syntax.print_string_raw(process_socket))
+
+    val bash_script =
+      """
+        [ -z "$ISABELLE_TMP_PREFIX" ] && ISABELLE_TMP_PREFIX=/tmp/isabelle
+
+        export ISABELLE_PID="$$"
+        export ISABELLE_TMP="$ISABELLE_TMP_PREFIX$ISABELLE_PID"
+        mkdir -p "$ISABELLE_TMP"
+        chmod $(umask -S) "$ISABELLE_TMP"
+
+        librarypath "$ML_HOME"
+        "$ML_HOME/poly" -q -i $ML_OPTIONS "$@"
+        RC="$?"
+
+        rm -f "$ISABELLE_PROCESS_OPTIONS"
+        rmdir "$ISABELLE_TMP"
+
+        exit "$RC"
+      """
+
+    val bash_args =
+      List("-c", bash_script, "ml_process") :::
+      (eval_heaps ::: eval_exit ::: eval_secure ::: eval_modes ::: eval_options ::: eval_process).
+        map(eval => List("--eval", eval)).flatten ::: args
+
+    Bash.process(null, bash_env, false, bash_args:_*)
+  }
+}

--- a/src/Pure/build-jars	Mon Mar 07 14:53:28 2016 +0100
+++ b/src/Pure/build-jars	Mon Mar 07 15:21:50 2016 +0100
@@ -81,6 +81,7 @@
   System/isabelle_charset.scala
   System/isabelle_process.scala
   System/isabelle_system.scala
+  System/ml_process.scala
   System/options.scala
   System/platform.scala
   System/posix_interrupt.scala