Source file `metadataCharEncoding.ml`

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module type T = sig
  val convert :
    ?source:[ `ISO_8859_1 | `UTF_8 | `UTF_16 | `UTF_16LE | `UTF_16BE ] ->
    string ->
    string
end

module Naive : T = struct
  let convert ?source s =
    let source = match source with None -> `UTF_8 | Some x -> x in
    let endianness = ref `BE in
    let buf = Buffer.create 10 in
    match source with
      | (`UTF_16 | `UTF_16LE | `UTF_16BE) as source ->
          let get_char =
            match source with
              | `UTF_16LE -> String.get_utf_16le_uchar
              | `UTF_16BE -> String.get_utf_16be_uchar
              | `UTF_16 -> (
                  match !endianness with
                    | `LE -> String.get_utf_16le_uchar
                    | `BE -> String.get_utf_16be_uchar)
          in
          let len = String.length s in
          let rec f pos =
            if pos = len then Buffer.contents buf
            else if pos + 2 <= len && s.[pos] = '\xfe' && s.[pos] = '\xff' then (
              endianness := `BE;
              f (pos + 2))
            else if pos + 2 <= len && s.[pos] = '\xff' && s.[pos] = '\xfe' then (
              endianness := `LE;
              f (pos + 2))
            else (
              let d = get_char s pos in
              let c = Uchar.utf_decode_uchar d in
              Buffer.add_utf_8_uchar buf c;
              f (pos + Uchar.utf_decode_length d))
          in
          f 0
      | `UTF_8 -> s
      | _ -> s
end