1 files changed, 87 insertions, 0 deletions
diff --git a/lib/render/escape.ml b/lib/render/escape.ml
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index 0000000..53fdd46
--- /dev/null
+++ b/lib/render/escape.ml
@@ -0,0 +1,87 @@
+type flavour = Latex | Groff | Html | Xml | Ics | None_
+
+let all = [ Latex; Groff; Html; Xml; Ics; None_ ]
+
+let to_string = function
+  | Latex -> "latex" | Groff -> "groff" | Html -> "html"
+  | Xml -> "xml" | Ics -> "ics" | None_ -> "none"
+
+let of_string = function
+  | "latex" -> Some Latex | "groff" -> Some Groff | "html" -> Some Html
+  | "xml" -> Some Xml | "ics" -> Some Ics | "none" -> Some None_
+  | _ -> None
+
+let of_extension = function
+  | ".tex" -> Some Latex
+  | ".ms" | ".mom" | ".me" -> Some Groff
+  | ".html" | ".htm" -> Some Html
+  | ".xml" -> Some Xml
+  | ".ics" -> Some Ics
+  | ".md" | ".adoc" | ".txt" -> Some None_
+  | _ -> None
+
+(* Replace each character with its expansion, in ONE pass. A sequence of
+   String.concat replacements would double-escape: "&" -> "\\&" then the
+   backslash rule would rewrite the backslash it just introduced. *)
+let expand f s =
+  let b = Buffer.create (String.length s + 16) in
+  String.iter (fun c -> Buffer.add_string b (f c)) s;
+  Buffer.contents b
+
+let latex = function
+  | '\\' -> "\\textbackslash{}"
+  | '{' -> "\\{" | '}' -> "\\}"
+  | '$' -> "\\$" | '&' -> "\\&" | '#' -> "\\#"
+  | '_' -> "\\_" | '%' -> "\\%"
+  | '^' -> "\\textasciicircum{}"
+  | '~' -> "\\textasciitilde{}"
+  | c -> String.make 1 c
+
+let html = function
+  | '&' -> "&amp;" | '<' -> "&lt;" | '>' -> "&gt;"
+  | '"' -> "&quot;" | '\'' -> "&#39;"
+  | c -> String.make 1 c
+
+let ics = function
+  | '\\' -> "\\\\" | ';' -> "\\;" | ',' -> "\\,"
+  | '\n' -> "\\n" | '\r' -> ""
+  | c -> String.make 1 c
+
+(* groff: a backslash starts an escape, and a '.' or '\'' in COLUMN ONE starts a
+   request. \& is the zero-width non-printing character that defuses it. *)
+let groff s =
+  let escaped = expand (function '\\' -> "\\e" | c -> String.make 1 c) s in
+  if String.length escaped > 0 && (escaped.[0] = '.' || escaped.[0] = '\'') then "\\&" ^ escaped
+  else escaped
+
+let apply flavour s =
+  match flavour with
+  | Latex -> expand latex s
+  | Groff -> groff s
+  | Html | Xml -> expand html s
+  | Ics -> expand ics s
+  | None_ -> s
+
+(* RFC 5545 section 3.1. A continuation byte is 0x80-0xBF; backing off to a
+   non-continuation byte keeps every fold on a character boundary. *)
+let fold_ics line =
+  let n = String.length line in
+  let b = Buffer.create (n + (n / 70) + 8) in
+  let is_cont c = Char.code c land 0xC0 = 0x80 in
+  let rec go pos first =
+    let limit = if first then 75 else 74 (* the leading space costs one octet *) in
+    if n - pos <= limit then (
+      if not first then Buffer.add_char b ' ';
+      Buffer.add_string b (String.sub line pos (n - pos));
+      Buffer.add_string b "\r\n")
+    else begin
+      let cut = ref (pos + limit) in
+      while !cut > pos && is_cont line.[!cut] do decr cut done;
+      if not first then Buffer.add_char b ' ';
+      Buffer.add_string b (String.sub line pos (!cut - pos));
+      Buffer.add_string b "\r\n";
+      go !cut false
+    end
+  in
+  go 0 true;
+  Buffer.contents b