src/Pure/General/xml.ML

-(*  Title:      Pure/General/xml.ML
-    ID:         $Id$
-    Author:     David Aspinall, Stefan Berghofer and Markus Wenzel
-
-Basic support for XML.
-*)
-
-signature XML =
-sig
-  (* string functions *)
-  val header: string
-  val text: string -> string
-  val text_charref: string -> string
-  val cdata: string -> string
-  type attributes = (string * string) list
-  val element: string -> attributes -> string list -> string
-  (* tree functions *)
-  datatype tree =
-      Elem of string * attributes * tree list
-    | Text of string    (* native string, subject to XML.text on output *)
-    | Rawtext of string (* XML string: output directly, not parsed      *)
-  type content = tree list
-  type element = string * attributes * content
-  val string_of_tree: tree -> string
-  val buffer_of_tree: tree -> Buffer.T
-  val parse_string : string -> string option
-  val parse_content: string list -> tree list * string list
-  val parse_elem: string list -> tree * string list
-  val parse_document: string list -> (string option * tree) * string list
-  val tree_of_string: string -> tree
-  val scan_comment_whspc : string list -> unit * string list
-end;
-
-structure XML: XML =
-struct
-
-(** string based representation (small scale) **)
-
-val header = "<?xml version=\"1.0\"?>\n";
-
-
-(* text and character data *)
-
-fun decode "&lt;" = "<"
-  | decode "&gt;" = ">"
-  | decode "&amp;" = "&"
-  | decode "&apos;" = "'"
-  | decode "&quot;" = "\""
-  | decode c = c;
-
-fun encode "<" = "&lt;"
-  | encode ">" = "&gt;"
-  | encode "&" = "&amp;"
-  | encode "'" = "&apos;"
-  | encode "\"" = "&quot;"
-  | encode c = c;
-
-fun encode_charref c = "&#" ^ Int.toString (ord c) ^ ";"
-
-val text = Library.translate_string encode
-
-val text_charref = translate_string encode_charref;
-
-val cdata = enclose "<![CDATA[" "]]>\n"
-
-
-(* elements *)
-
-fun attribute (a, x) = a ^ " = \"" ^ text x ^ "\"";
-
-fun element name atts cs =
-  let val elem = space_implode " " (name :: map attribute atts) in
-    if null cs then enclose "<" "/>" elem
-    else enclose "<" ">" elem ^ implode cs ^ enclose "</" ">" name
-  end;
-
-
-
-
-(** explicit XML trees **)
-
-type attributes = (string * string) list
-
-datatype tree =
-    Elem of string * attributes * tree list
-  | Text of string
-  | Rawtext of string;
-
-type content = tree list
-
-type element = string * attributes * content
-
-fun buffer_of_tree tree =
-  let
-    fun string_of (Elem (name, atts, ts)) buf =
-        let val buf' =
-          buf |> Buffer.add "<"
-          |> fold Buffer.add (separate " " (name :: map attribute atts))
-        in
-          if null ts then
-            buf' |> Buffer.add "/>"
-          else
-            buf' |> Buffer.add ">"
-            |> fold string_of ts
-            |> Buffer.add "</" |> Buffer.add name |> Buffer.add ">"
-        end
-      | string_of (Text s) buf = Buffer.add (text s) buf
-      | string_of (Rawtext s) buf = Buffer.add s buf;
-  in string_of tree Buffer.empty end;
-
-val string_of_tree = Buffer.content o buffer_of_tree;
-
-
-
-(** XML parsing **)
-
-fun err s (xs, _) =
-  "XML parsing error: " ^ s ^ "\nfound: " ^ quote (Symbol.beginning 100 xs);
-
-val scan_whspc = Scan.many Symbol.is_blank;
-
-val scan_special = $$ "&" ^^ Symbol.scan_id ^^ $$ ";" >> decode;
-
-val parse_chars = Scan.repeat1 (Scan.unless ((* scan_whspc -- *)$$ "<")
-  (scan_special || Scan.one Symbol.not_eof)) >> implode;
-
-val parse_string = Scan.read Symbol.stopper parse_chars o explode;
-
-val parse_cdata = Scan.this_string "<![CDATA[" |--
-  (Scan.repeat (Scan.unless (Scan.this_string "]]>") (Scan.one Symbol.not_eof)) >>
-    implode) --| Scan.this_string "]]>";
-
-val parse_att =
-  Symbol.scan_id --| scan_whspc --| $$ "=" --| scan_whspc --
-  (($$ "\"" || $$ "'") :-- (fn s => (Scan.repeat (Scan.unless ($$ s)
-    (scan_special || Scan.one Symbol.not_eof)) >> implode) --| $$ s) >> snd);
-
-val parse_comment = Scan.this_string "<!--" --
-  Scan.repeat (Scan.unless (Scan.this_string "-->") (Scan.one Symbol.not_eof)) --
-  Scan.this_string "-->";
-
-val scan_comment_whspc =
-  (scan_whspc >> K()) --| (Scan.repeat (parse_comment |-- (scan_whspc >> K())));
-
-val parse_pi = Scan.this_string "<?" |--
-  Scan.repeat (Scan.unless (Scan.this_string "?>") (Scan.one Symbol.not_eof)) --|
-  Scan.this_string "?>";
-
-fun parse_content xs =
-  ((Scan.optional ((* scan_whspc |-- *) parse_chars >> (single o Text)) [] --
-    (Scan.repeat ((* scan_whspc |-- *)
-       (   parse_elem >> single
-        || parse_cdata >> (single o Text)
-        || parse_pi >> K []
-        || parse_comment >> K []) --
-       Scan.optional ((* scan_whspc |-- *) parse_chars >> (single o Text)) []
-         >> op @) >> flat) >> op @)(* --| scan_whspc*)) xs
-
-and parse_elem xs =
-  ($$ "<" |-- Symbol.scan_id --
-    Scan.repeat (scan_whspc |-- parse_att) --| scan_whspc :-- (fn (s, _) =>
-      !! (err "Expected > or />")
-        (Scan.this_string "/>" >> K []
-         || $$ ">" |-- parse_content --|
-            !! (err ("Expected </" ^ s ^ ">"))
-              (Scan.this_string ("</" ^ s) --| scan_whspc --| $$ ">"))) >>
-    (fn ((s, atts), ts) => Elem (s, atts, ts))) xs;
-
-val parse_document =
-  Scan.option (Scan.this_string "<!DOCTYPE" -- scan_whspc |--
-    (Scan.repeat (Scan.unless ($$ ">")
-      (Scan.one Symbol.not_eof)) >> implode) --| $$ ">" --| scan_whspc) --
-  parse_elem;
-
-fun tree_of_string s =
-  (case Scan.finite Symbol.stopper (Scan.error (!! (err "Malformed element")
-      (scan_whspc |-- parse_elem --| scan_whspc))) (Symbol.explode s) of
-    (x, []) => x
-  | (_, ys) => error ("XML parsing error: Unprocessed input\n" ^ Symbol.beginning 100 ys));
-
-end;