// that happens, then we will have buffered bytes that are needed by the SSLSocket!
        // This check is imperfect: it doesn't tell us whether a handshake will succeed, just
        // that it will almost certainly fail because the proxy has sent unexpected data.
        if (source?.buffer?.exhausted() == false || sink?.buffer?.exhausted() == false) {
          throw IOException("TLS tunnel buffered too many bytes!")
        }

1DFC          ; valid                                  # 6.0  COMBINING DOUBLE INVERTED BREVE BELOW
1DFD          ; valid                                  # 5.2  COMBINING ALMOST EQUAL TO BELOW
1DFE..1DFF    ; valid                                  # 5.0  COMBINING LEFT ARROWHEAD ABOVE..COMBINING RIGHT ARROWHEAD AND DOWN ARROWHEAD BELOW