(* Title: Pure/General/xml.ML
ID: $Id$
Author: David Aspinall, Stefan Berghofer and Markus Wenzel
Basic support for XML.
*)
signature XML =
sig
val header: string
val text: string -> string
val cdata: string -> string
val element: string -> (string * string) list -> string list -> string
datatype tree =
Elem of string * (string * string) list * tree list
| Text of string
val string_of_tree: tree -> string
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 scan_comment_whspc : string list -> unit * string list
val tree_of_string: string -> tree
end;
structure XML: XML =
struct
(** string based representation (small scale) **)
val header = "<?xml version=\"1.0\"?>\n";
(* text and character data *)
fun decode "<" = "<"
| decode ">" = ">"
| decode "&" = "&"
| decode "'" = "'"
| decode """ = "\""
| decode c = c;
fun encode "<" = "<"
| encode ">" = ">"
| encode "&" = "&"
| encode "'" = "'"
| encode "\"" = """
| encode c = c;
val text = Library.translate_string encode;
val cdata = enclose "<![CDATA[" "]]>";
(* 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 **)
datatype tree =
Elem of string * (string * string) list * tree list
| Text of string;
fun string_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;
in Buffer.content (string_of tree Buffer.empty) end;
(** XML parsing **)
fun err s (xs, _) =
"XML parsing error: " ^ s ^ "\nfound: " ^ quote (Symbol.beginning 100 xs);
val scan_whspc = Scan.any Symbol.is_blank;
val scan_special = $$ "&" ^^ Symbol.scan_id ^^ $$ ";" >> decode;
val parse_chars = Scan.repeat1 (Scan.unless (scan_whspc -- $$ "<")
(scan_special || Scan.one Symbol.not_eof)) >> implode;
val parse_cdata = Scan.this_string "<![CDATA[" |--
(Scan.repeat (Scan.unless (Scan.this_string "]]>") (Scan.one Symbol.not_eof)) >>
implode) --| Scan.this_string "]]>";
val parse_att =
Symbol.scan_id --| scan_whspc --| $$ "=" --| 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;