 
   /// Lookahead buffer used for UTF-8 decoding.  New bytes are inserted at LSB,
   /// and bytes are read at MSB.
-  var _decodeLookahead: UInt32 = 0
+  internal var _decodeLookahead: UInt32 = 0
 
   /// Flags with layout: `0bxxxx_yyyy`.
   ///

  /// Returns `true` if the LSB bytes in `buffer` are well-formed UTF-8 code
  /// unit sequence.
  @warn_unused_result
  static func _isValidUTF8(buffer: UInt32, validBytes: UInt8) -> Bool {
    _sanityCheck(validBytes & 0b0000_1111 != 0,
        "input buffer should not be empty")


  public static func isContinuation(byte: CodeUnit) -> Bool {
    return byte & 0b11_00__0000 == 0b10_00__0000
  }
}

/// A codec for [UTF-16](http://www.unicode.org/glossary/#UTF_16).
