function isTokenCharCode (c) {
  switch (c) {
    case 0x22:
    case 0x28:
    case 0x29:
    case 0x2c:
    case 0x2f:
    case 0x3a:
    case 0x3b:
    case 0x3c:
    case 0x3d:
    case 0x3e:
    case 0x3f:
    case 0x40:
    case 0x5b:
    case 0x5c:
    case 0x5d:
    case 0x7b:
    case 0x7d:
      // DQUOTE and "(),/:;<=>?@[\]{}"
      return false
    default:
      // VCHAR %x21-7E
      return c >= 0x21 && c <= 0x7e
  }
}
@see https://tools.ietf.org/html/rfc7230#section-3.2.6
@param {number} c
@returns {boolean}