author | wenzelm |
Sun, 29 Mar 2020 19:42:59 +0200 | |
changeset 71620 | 5a4ccef7f310 |
parent 71456 | 09c850e82258 |
child 73556 | 192bcee4f8b8 |
permissions | -rw-r--r-- |
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(* Title: Pure/PIDE/yxml.ML |
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Author: Makarius |
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Efficient text representation of XML trees using extra characters X |
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and Y -- no escaping, may nest marked text verbatim. Suitable for |
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direct inlining into plain text. |
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Markup <elem att="val" ...>...body...</elem> is encoded as: |
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X Y name Y att=val ... X |
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... |
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body |
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... |
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X Y X |
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*) |
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signature YXML = |
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sig |
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val X: Symbol.symbol |
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val Y: Symbol.symbol |
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val embed_controls: string -> string |
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inner syntax supports inlined YXML according to Term_XML (particularly useful for producing text under program control);
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val detect: string -> bool |
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val traverse: (string -> 'a -> 'a) -> XML.tree -> 'a -> 'a |
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val string_of_body: XML.body -> string |
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val string_of: XML.tree -> string |
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val write_body: Path.T -> XML.body -> unit |
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val output_markup: Markup.T -> string * string |
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val output_markup_elem: Markup.T -> (string * string) * string |
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val parse_body: string -> XML.body |
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val parse: string -> XML.tree |
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val content_of: string -> string |
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val is_wellformed: string -> bool |
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end; |
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structure YXML: YXML = |
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struct |
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(** string representation **) |
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(* idempotent recoding of certain low ASCII control characters *) |
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robust representation of low ASCII control characters within XML/YXML text;
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robust representation of low ASCII control characters within XML/YXML text;
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fun pseudo_utf8 c = |
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if Symbol.is_ascii_control c |
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then chr 192 ^ chr (128 + ord c) |
c2f176a38448
robust representation of low ASCII control characters within XML/YXML text;
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parents:
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else c; |
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robust representation of low ASCII control characters within XML/YXML text;
wenzelm
parents:
31469
diff
changeset
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46 |
|
43772
c825594fd0c1
clarified YXML.embed_controls -- this is idempotent and cannot be nested;
wenzelm
parents:
43731
diff
changeset
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fun embed_controls str = |
34095
c2f176a38448
robust representation of low ASCII control characters within XML/YXML text;
wenzelm
parents:
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if exists_string Symbol.is_ascii_control str |
c2f176a38448
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parents:
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then translate_string pseudo_utf8 str |
c2f176a38448
robust representation of low ASCII control characters within XML/YXML text;
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parents:
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else str; |
c2f176a38448
robust representation of low ASCII control characters within XML/YXML text;
wenzelm
parents:
31469
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|
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robust representation of low ASCII control characters within XML/YXML text;
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parents:
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(* markers *) |
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val X_char = Char.chr 5; |
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val Y_char = Char.chr 6; |
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val X = String.str X_char; |
ac2abc987cf9
accomodate Poly/ML repository version, which treats singleton strings as boxed;
wenzelm
parents:
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val Y = String.str Y_char; |
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val XY = X ^ Y; |
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val XYX = XY ^ X; |
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wenzelm
parents:
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changeset
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fun detect s = Char.contains s X_char orelse Char.contains s Y_char; |
43731
70072780e095
inner syntax supports inlined YXML according to Term_XML (particularly useful for producing text under program control);
wenzelm
parents:
43728
diff
changeset
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(* output *) |
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fun traverse string = |
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let |
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fun attrib (a, x) = string Y #> string a #> string "=" #> string x; |
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fun tree (XML.Elem ((name, atts), ts)) = |
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string XY #> string name #> fold attrib atts #> string X #> |
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fold tree ts #> |
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string XYX |
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| tree (XML.Text s) = string s; |
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in tree end; |
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fun string_of_body body = Buffer.empty |> fold (traverse Buffer.add) body |> Buffer.content; |
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val string_of = string_of_body o single; |
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fun write_body path body = |
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path |> File.open_output (fn file => |
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fold (traverse (fn s => fn () => File.output file s)) body ()); |
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more scalable protocol_message: use XML.body directly (Output.output hook is not required);
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(* markup elements *) |
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val Z = chr 0; |
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val Z_text = [XML.Text Z]; |
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fun output_markup (markup as (name, atts)) = |
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if Markup.is_empty markup then Markup.no_output |
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else (XY ^ name ^ implode (map (fn (a, x) => Y ^ a ^ "=" ^ x) atts) ^ X, XYX); |
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fun output_markup_elem markup = |
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let val [bg1, bg2, en] = space_explode Z (string_of (XML.wrap_elem ((markup, Z_text), Z_text))) |
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in ((bg1, bg2), en) end; |
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(** efficient YXML parsing **) |
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local |
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(* splitting *) |
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val split_string = |
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Substring.full #> |
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Substring.tokens (fn c => c = X_char) #> |
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map (Substring.fields (fn c => c = Y_char) #> map Substring.string); |
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(* structural errors *) |
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fun err msg = raise Fail ("Malformed YXML: " ^ msg); |
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fun err_attribute () = err "bad attribute"; |
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fun err_element () = err "bad element"; |
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fun err_unbalanced "" = err "unbalanced element" |
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| err_unbalanced name = err ("unbalanced element " ^ quote name); |
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(* stack operations *) |
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fun add x ((elem, body) :: pending) = (elem, x :: body) :: pending; |
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fun push "" _ _ = err_element () |
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| push name atts pending = ((name, atts), []) :: pending; |
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fun pop ((("", _), _) :: _) = err_unbalanced "" |
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| pop ((markup, body) :: pending) = add (XML.Elem (markup, rev body)) pending; |
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(* parsing *) |
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fun parse_attrib s = |
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(case first_field "=" s of |
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NONE => err_attribute () |
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| SOME ("", _) => err_attribute () |
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| SOME att => att); |
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fun parse_chunk ["", ""] = pop |
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| parse_chunk ("" :: name :: atts) = push name (map parse_attrib atts) |
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| parse_chunk txts = fold (add o XML.Text) txts; |
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in |
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fun parse_body source = |
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(case fold parse_chunk (split_string source) [(("", []), [])] of |
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[(("", _), result)] => rev result |
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| ((name, _), _) :: _ => err_unbalanced name); |
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fun parse source = |
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(case parse_body source of |
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YXML.parse: allow text without markup, potentially empty;
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[result] => result |
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| [] => XML.Text "" |
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| _ => err "multiple results"); |
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end; |
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val content_of = parse_body #> XML.content_of; |
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wenzelm
parents:
70996
diff
changeset
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fun is_wellformed s = string_of_body (parse_body s) = s |
09c850e82258
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wenzelm
parents:
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handle Fail _ => false; |
09c850e82258
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parents:
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end; |