js_of_lam_string.ml

(* Copyright (C) 2015 - 2016 Bloomberg Finance L.P.
 * Copyright (C) 2017 - Hongbo Zhang, Authors of ReScript  
 * 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. *)

module E = Js_exp_make

(* We use module B for string compilation, once the upstream can make changes to the
    patten match of range patterns, we can use module [A] which means [char] is [string] in js,
    currently, it follows the same patten of ocaml, [char] is [int]
*)

let const_char (i : char) = E.int ~c:i (Int32.of_int @@ Char.code i)

(* string [s[i]] expects to return a [ocaml_char] *)
let ref_string e e1 = E.string_index e e1

(* [s[i]] excepts to return a [ocaml_char]
   We use normal array for [bytes]
   TODO: we can use [Buffer] in the future
*)
let ref_byte e e0 = E.array_index e e0

(* {Bytes.set : bytes -> int -> char -> unit }*)
let set_byte e e0 e1 = E.assign (E.array_index e e0) e1

(**
   Note that [String.fromCharCode] also works, but it only 
   work for small arrays, however, for {bytes_to_string} it is likely the bytes 
   will become big
   {[
     String.fromCharCode.apply(null,[87,97])
       "Wa"
       String.fromCharCode(87,97)
       "Wa" 
   ]}
   This does not work for large arrays
   {[
     String.fromCharCode.apply(null, prim = Array[1048576]) 
       Maxiume call stack size exceeded
   ]}
*)
let bytes_to_string e =
  E.runtime_call Js_runtime_modules.bytes "bytes_to_string" [ e ]

let bytes_of_string s =
  E.runtime_call Js_runtime_modules.bytes "bytes_of_string" [ s ]