module Net::IMAP::SASL::GS2Header

def gs2_saslname_encode(str)
  str = str.encode("UTF-8")
  # Regexp#match raises "invalid byte sequence" for invalid UTF-8
  NO_NULL_CHARS.match str or
    raise ArgumentError, "invalid saslname: %p" % [str]
  str
    .gsub(?=, "=3D")
    .gsub(?,, "=2C")
end