More efficient Richpp.

We build the rich XML at once without generating the printed string.

2 files changed, 84 insertions, 93 deletions

diff --git a/lib/richpp.ml b/lib/richpp.ml
index 442050cf89..c4a9c39d5a 100644
--- a/lib/richpp.ml
+++ b/lib/richpp.ml
@@ -15,126 +15,117 @@ type 'annotation located = {
   endpos     : int
 }
 
-type context =
+type 'a stack =
 | Leaf
-| Node of string * xml list * context
+| Node of string * 'a located gxml list * int * 'a stack
+
+type 'a context = {
+  mutable stack : 'a stack;
+  (** Pending opened nodes *)
+  mutable offset : int;
+  (** Quantity of characters printed so far *)
+  mutable annotations : 'a option Int.Map.t;
+  (** Map associating annotations to indexes *)
+  mutable index : int;
+  (** Current index of annotations *)
+}
+
+(** We use Format to introduce tags inside the pretty-printed document.
+    Each inserted tag is a fresh index that we keep in sync with the contents
+    of annotations.
 
+    We build an XML tree on the fly, by plugging ourselves in Format tag
+    marking functions. As those functions are called when actually writing to
+    the device, the resulting tree is correct.
+*)
 let rich_pp annotate ppcmds =
-  (** First, we use Format to introduce tags inside the pretty-printed document.
-      Each inserted tag is a fresh index that we keep in sync with the contents
-      of annotations.
-
-      We build an XML tree on the fly, by plugging ourselves in Format tag
-      marking functions. As those functions are called when actually writing to
-      the device, the resulting tree is correct.
-  *)
-  let annotations = ref [] in
-  let index = ref (-1) in
+
+  let context = {
+    stack = Leaf;
+    offset = 0;
+    annotations = Int.Map.empty;
+    index = (-1);
+  } in
+
   let pp_tag obj =
-    let () = incr index in
-    let () = annotations := obj :: !annotations in
-    string_of_int !index
+    let index = context.index + 1 in
+    let () = context.index <- index in
+    let obj = annotate obj in
+    let () = context.annotations <- Int.Map.add index obj context.annotations in
+    string_of_int index
   in
 
   let pp_buffer = Buffer.create 13 in
 
-  let push_pcdata context =
+  let push_pcdata () =
     (** Push the optional PCData on the above node *)
-    if (Buffer.length pp_buffer = 0) then ()
-    else match !context with
+    let len = Buffer.length pp_buffer in
+    if len = 0 then ()
+    else match context.stack with
     | Leaf -> assert false
-    | Node (node, child, ctx) ->
+    | Node (node, child, pos, ctx) ->
       let data = Buffer.contents pp_buffer in
       let () = Buffer.clear pp_buffer in
-      context := Node (node, PCData data :: child, ctx)
+      let () = context.stack <- Node (node, PCData data :: child, pos, ctx) in
+      context.offset <- context.offset + len
   in
 
-  let open_xml_tag context tag =
-    let () = push_pcdata context in
-    context := Node (tag, [], !context)
+  let open_xml_tag tag =
+    let () = push_pcdata () in
+    context.stack <- Node (tag, [], context.offset, context.stack)
   in
 
-  let close_xml_tag context tag =
-    let () = push_pcdata context in
-    match !context with
+  let close_xml_tag tag =
+    let () = push_pcdata () in
+    match context.stack with
     | Leaf -> assert false
-    | Node (node, child, ctx) ->
+    | Node (node, child, pos, ctx) ->
       let () = assert (String.equal tag node) in
-      let xml = Element (node, [], List.rev child) in
+      let annotation =
+        try Int.Map.find (int_of_string node) context.annotations
+        with _ -> None
+      in
+      let annotation = {
+        annotation = annotation;
+        startpos = pos;
+        endpos = context.offset;
+      } in
+      let xml = Element (node, annotation, List.rev child) in
       match ctx with
       | Leaf ->
         (** Final node: we keep the result in a dummy context *)
-        context := Node ("", [xml], Leaf)
-      | Node (node, child, ctx) ->
-        context := Node (node, xml :: child, ctx)
+        context.stack <- Node ("", [xml], 0, Leaf)
+      | Node (node, child, pos, ctx) ->
+        context.stack <- Node (node, xml :: child, pos, ctx)
   in
 
-  let xml_pp = Format.(
-
-    let ft = formatter_of_buffer pp_buffer in
+  let open Format in
 
-    let context = ref Leaf in
+  let ft = formatter_of_buffer pp_buffer in
 
-    let tag_functions = {
-      mark_open_tag = (fun tag -> let () = open_xml_tag context tag in "");
-      mark_close_tag = (fun tag -> let () = close_xml_tag context tag in "");
-      print_open_tag = ignore;
-      print_close_tag = ignore;
-    } in
+  let tag_functions = {
+    mark_open_tag = (fun tag -> let () = open_xml_tag tag in "");
+    mark_close_tag = (fun tag -> let () = close_xml_tag tag in "");
+    print_open_tag = ignore;
+    print_close_tag = ignore;
+  } in
 
-    pp_set_formatter_tag_functions ft tag_functions;
-    pp_set_mark_tags ft true;
+  pp_set_formatter_tag_functions ft tag_functions;
+  pp_set_mark_tags ft true;
 
-    (** The whole output must be a valid document. To that
-        end, we nest the document inside <pp> tags. *)
-    pp_open_tag ft "pp";
-    Pp.(pp_with ~pp_tag ft ppcmds);
-    pp_close_tag ft ();
+  (** The whole output must be a valid document. To that
+      end, we nest the document inside <pp> tags. *)
+  pp_open_tag ft "pp";
+  Pp.(pp_with ~pp_tag ft ppcmds);
+  pp_close_tag ft ();
 
-    (** Get the resulting XML tree. *)
-    let () = pp_print_flush ft () in
-    let () = assert (Buffer.length pp_buffer = 0) in
-    match !context with
-    | Node ("", [xml], Leaf) -> xml
-    | _ -> assert false
-  )
-  in
-  (** Second, we retrieve the final function that relates
-      each tag to an annotation. *)
-  let objs = CArray.rev_of_list !annotations in
-  let get index = annotate objs.(index) in
-
-  (** Third, the low-level XML is turned into a high-level
-      semi-structured document that contains a located annotation in
-      every node. During the traversal of the low-level XML document,
-      we build a raw string representation of the pretty-print. *)
-  let rec node buffer = function
-    | Element (index, [], cs) ->
-      let startpos, endpos, cs = children buffer cs in
-      let annotation = try get (int_of_string index) with _ -> None in
-      (Element (index, { annotation; startpos; endpos }, cs), endpos)
-
-    | PCData s ->
-      Buffer.add_string buffer s;
-      (PCData s, Buffer.length buffer)
-
-    | _ ->
-      assert false (* Because of the form of XML produced by Format. *)
-
-  and children buffer cs =
-    let startpos   = Buffer.length buffer in
-    let cs, endpos =
-      List.fold_left (fun (cs, endpos) c ->
-        let c, endpos = node buffer c in
-        (c :: cs, endpos)
-      ) ([], startpos) cs
-    in
-    (startpos, endpos, List.rev cs)
-  in
-  let xml, _ = node pp_buffer xml_pp in
+  (** Get the resulting XML tree. *)
+  let () = pp_print_flush ft () in
+  let () = assert (Buffer.length pp_buffer = 0) in
+  match context.stack with
+  | Node ("", [xml], 0, Leaf) -> xml
+  | _ -> assert false
 
-  (** We return the raw pretty-printing and its annotations tree. *)
-  (Buffer.contents pp_buffer, xml)
 
 let annotations_positions xml =
   let rec node accu = function
diff --git a/lib/richpp.mli b/lib/richpp.mli
index 446ee1a046..bf80c8dc8c 100644
--- a/lib/richpp.mli
+++ b/lib/richpp.mli
@@ -17,13 +17,13 @@ type 'annotation located = {
 }
 
 (** [rich_pp get_annotations ppcmds] returns the interpretation
-    of [ppcmds] as a string as well as a semi-structured document
+    of [ppcmds] as a semi-structured document
     that represents (located) annotations of this string.
     The [get_annotations] function is used to convert tags into the desired
     annotation. If this function returns [None], then no annotation is put. *)
 val rich_pp :
   (Pp.Tag.t -> 'annotation option) -> Pp.std_ppcmds ->
-  string * 'annotation located Xml_datatype.gxml
+  'annotation located Xml_datatype.gxml
 
 (** [annotations_positions ssdoc] returns a list associating each
     annotations with its position in the string from which [ssdoc] is