Add Jambon's tree printer

Makefile

@@ -8,7 +8,7 @@ DOC = cpdfunicodedata cpdferror cpdfdebug cpdfjson cpdfstrftime cpdfcoord \
       cpdfsqueeze cpdfdraft cpdfspot cpdfpagelabels cpdfcreate cpdfannot \
       cpdfxobject cpdfimpose cpdfchop cpdftweak cpdftexttopdf cpdftoc \
       cpdfjpeg cpdfjpeg2000 cpdfpng cpdfimage cpdfdraw cpdfcomposition \
-      cpdfshape cpdfcolours cpdfdrawcontrol cpdfua cpdfcommand
+      cpdfshape cpdfcolours cpdfdrawcontrol cpdfprinttree cpdfua cpdfcommand
 
 MODS = $(NONDOC) $(DOC)
 

cpdfprinttree.ml

@@ -0,0 +1,24 @@
+(* Courtesy Martin Jambon, in the public domain. *)
+let rec titer f = function
+  | [] -> ()
+  | [x] -> f true x
+  | x :: tl -> f false x; titer f tl
+
+let to_buffer ?(line_prefix = "") ~get_name ~get_children buf x =
+  let rec print_root indent x =
+    Printf.bprintf buf "%s\n" (get_name x);
+    let children = get_children x in
+      titer (print_child indent) children
+  and print_child indent is_last x =
+    let line = if is_last then "└── " else "├── " in
+      Printf.bprintf buf "%s%s" indent line;
+      let extra_indent = if is_last then "    " else "│   " in
+        print_root (indent ^ extra_indent) x
+  in
+    Buffer.add_string buf line_prefix;
+    print_root line_prefix x
+
+let to_string ?line_prefix ~get_name ~get_children x =
+  let buf = Buffer.create 1000 in
+    to_buffer ?line_prefix ~get_name ~get_children buf x;
+    Buffer.contents buf

cpdfprinttree.mli

@@ -0,0 +1,5 @@
+(** Print trees *)
+
+val to_buffer : ?line_prefix: string -> get_name: ('a -> string) -> get_children: ('a -> 'a list) -> Buffer.t -> 'a -> unit
+
+val to_string : ?line_prefix: string -> get_name: ('a -> string) -> get_children: ('a -> 'a list) -> 'a -> string