ParagonIE_Sodium_Crypto::secretstream_xchacha20poly1305_rekey

    public static function secretstream_xchacha20poly1305_rekey(&$state)
    {
        $st = ParagonIE_Sodium_Core_SecretStream_State::fromString($state);
        # unsigned char new_key_and_inonce[crypto_stream_chacha20_ietf_KEYBYTES +
        # crypto_secretstream_xchacha20poly1305_INONCEBYTES];
        # size_t        i;
        # for (i = 0U; i < crypto_stream_chacha20_ietf_KEYBYTES; i++) {
        #     new_key_and_inonce[i] = state->k[i];
        # }
        $new_key_and_inonce = $st->getKey();

        # for (i = 0U; i < crypto_secretstream_xchacha20poly1305_INONCEBYTES; i++) {
        #     new_key_and_inonce[crypto_stream_chacha20_ietf_KEYBYTES + i] =
        #         STATE_INONCE(state)[i];
        # }
        $new_key_and_inonce .= ParagonIE_Sodium_Core_Util::substR($st->getNonce(), 0, 8);

        # crypto_stream_chacha20_ietf_xor(new_key_and_inonce, new_key_and_inonce,
        #                                 sizeof new_key_and_inonce,
        #                                 state->nonce, state->k);

        $st->rekey(ParagonIE_Sodium_Core_ChaCha20::ietfStreamXorIc(
            $new_key_and_inonce,
            $st->getCombinedNonce(),
            $st->getKey(),
            ParagonIE_Sodium_Core_Util::store64_le(0)
        ));

        # for (i = 0U; i < crypto_stream_chacha20_ietf_KEYBYTES; i++) {
        #     state->k[i] = new_key_and_inonce[i];
        # }
        # for (i = 0U; i < crypto_secretstream_xchacha20poly1305_INONCEBYTES; i++) {
        #     STATE_INONCE(state)[i] =
        #          new_key_and_inonce[crypto_stream_chacha20_ietf_KEYBYTES + i];
        # }
        # _crypto_secretstream_xchacha20poly1305_counter_reset(state);
        $st->counterReset();

        $state = $st->toString();
    }