ast_utf8_string.ml

(* Copyright (C) 2015-2016 Bloomberg Finance L.P.
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * In addition to the permissions granted to you by the LGPL, you may combine
 * or link a "work that uses the Library" with a publicly distributed version
 * of this file to produce a combined library or application, then distribute
 * that combined work under the terms of your choosing, with no requirement
 * to comply with the obligations normally placed on you by section 4 of the
 * LGPL version 3 (or the corresponding section of a later version of the LGPL
 * should you choose to use a later version).
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *)



type error = 
  | Invalid_code_point 
  | Unterminated_backslash
  | Invalid_escape_code of char 
  | Invalid_hex_escape
  | Invalid_unicode_escape

let pp_error fmt err = 
  Format.pp_print_string fmt @@  match err with 
  | Invalid_code_point -> "Invalid code point"
  | Unterminated_backslash -> "\\ ended unexpectedly"
  | Invalid_escape_code c -> "Invalid escape code: " ^ String.make 1 c 
  | Invalid_hex_escape -> 
    "Invalid \\x escape"
  | Invalid_unicode_escape -> "Invalid \\u escape"



type exn += Error of int  (* offset *) * error 




let error ~loc error = 
  raise (Error (loc, error))

(** Note the [loc] really should be the utf8-offset, it has nothing to do with our 
    escaping mechanism
*)
(* we can not just print new line in ES5 
   seems we don't need 
   escape "\b" "\f" 
   we need escape "\n" "\r" since 
   ocaml multiple-line allows [\n]
   visual input while es5 string 
   does not*)

let rec check_and_transform (loc : int ) buf s byte_offset s_len =
  if byte_offset = s_len then ()
  else 
    let current_char = s.[byte_offset] in 
    match Ext_utf8.classify current_char with 
    | Single 92 (* '\\' *) -> 
      escape_code (loc + 1) buf s (byte_offset+1) s_len
    | Single 34 ->
      Buffer.add_string buf "\\\"";
      check_and_transform (loc + 1) buf s (byte_offset + 1) s_len
    | Single 39 -> 
      Buffer.add_string buf "\\'";
      check_and_transform (loc + 1) buf s (byte_offset + 1) s_len 
    | Single 10 ->          
      Buffer.add_string buf "\\n";
      check_and_transform (loc + 1) buf s (byte_offset + 1) s_len 
    | Single 13 -> 
      Buffer.add_string buf "\\r";
      check_and_transform (loc + 1) buf s (byte_offset + 1) s_len 
    | Single _ -> 
      Buffer.add_char buf current_char;
      check_and_transform (loc + 1) buf s (byte_offset + 1) s_len 

    | Invalid 
    | Cont _ -> error ~loc Invalid_code_point
    | Leading (n,_) -> 
      let i' = Ext_utf8.next s ~remaining:n  byte_offset in
      if i' < 0 then 
        error ~loc Invalid_code_point
      else 
        begin 
          for k = byte_offset to i' do 
            Buffer.add_char buf s.[k]; 
          done;   
          check_and_transform (loc + 1 ) buf s (i' + 1) s_len 
        end
(* we share the same escape sequence with js *)        
and escape_code loc buf s offset s_len = 
  if offset >= s_len then 
    error ~loc Unterminated_backslash
  else
    Buffer.add_char buf '\\'; 
  let cur_char = s.[offset] in
  match cur_char with 
  | '\\'
  | 'b' 
  | 't' 
  | 'n' 
  | 'v'
  | 'f'
  | 'r' 
  | '0' 
  | '$'
    -> 
    begin 
      Buffer.add_char buf cur_char ;
      check_and_transform (loc + 1) buf s (offset + 1) s_len 
    end 
  | 'u' -> 
    begin 
      Buffer.add_char buf cur_char;
      unicode (loc + 1) buf s (offset + 1) s_len 
    end 
  | 'x' -> begin 
      Buffer.add_char buf cur_char ; 
      two_hex (loc + 1) buf s (offset + 1) s_len 
    end 
  | _ -> error ~loc (Invalid_escape_code cur_char)
and two_hex loc buf s offset s_len = 
  if offset + 1 >= s_len then 
    error ~loc Invalid_hex_escape;
  (*Location.raise_errorf ~loc "\\x need at least two chars";*)
  let a, b = s.[offset], s.[offset + 1] in 
  if Ext_char.valid_hex a && Ext_char.valid_hex b then 
    begin 
      Buffer.add_char buf a ; 
      Buffer.add_char buf b ; 
      check_and_transform (loc + 2) buf s (offset + 2) s_len 
    end
  else
    error ~loc Invalid_hex_escape
(*Location.raise_errorf ~loc "%c%c is not a valid hex code" a b*)

and unicode loc buf s offset s_len = 
  if offset + 3 >= s_len then 
    error ~loc Invalid_unicode_escape
  (*Location.raise_errorf ~loc "\\u need at least four chars"*)
  ;
  let a0,a1,a2,a3 = s.[offset], s.[offset+1], s.[offset+2], s.[offset+3] in
  if 
    Ext_char.valid_hex a0 &&
    Ext_char.valid_hex a1 &&
    Ext_char.valid_hex a2 &&
    Ext_char.valid_hex a3 then 
    begin 
      Buffer.add_char buf a0;
      Buffer.add_char buf a1;
      Buffer.add_char buf a2;
      Buffer.add_char buf a3;  
      check_and_transform (loc + 4) buf s  (offset + 4) s_len 
    end 
  else
    error ~loc Invalid_unicode_escape 
(*Location.raise_errorf ~loc "%c%c%c%c is not a valid unicode point"
  a0 a1 a2 a3 *)
(* http://www.2ality.com/2015/01/es6-strings.html
   console.log('\uD83D\uDE80'); (* ES6*)
   console.log('\u{1F680}');
*)   









let transform_test s =
  let s_len = String.length s in 
  let buf = Buffer.create (s_len * 2) in
  check_and_transform 0 buf s 0 s_len;
  Buffer.contents buf

let transform loc s = 
  let s_len = String.length s in 
  let buf = Buffer.create (s_len * 2) in
  try
    check_and_transform 0 buf s 0 s_len;
    Buffer.contents buf 
  with
    Error (offset, error)
    ->  Location.raise_errorf ~loc "Offset: %d, %a" offset pp_error error