libpg_and_libevent.cpp

    // Asynchronous PostgreSQL INSERT.

    glim::NsecTimer timer;
    std::unique_ptr<PGconn, void(*)(PGconn*)> pg (PQconnectStart (pcs.c_str()), PQfinish);
    if (pg.get() == nullptr || PQstatus (pg.get()) == CONNECTION_BAD) GTHROW ("!PQconnectStart");
    int sock = PQsocket (pg.get());

    auto evBase = EvServ::instance()->evbase();
    event_callback_fn cbcoroInvokeFromCallback = [](evutil_socket_t, short, void* cbcoro) {((CBCoro*) cbcoro)->invokeFromCallback();};
    std::unique_ptr<struct event, void(*)(struct event*)> evRead (event_new (evBase.get(), sock, EV_READ, cbcoroInvokeFromCallback, cbcoro), event_free);
    std::unique_ptr<struct event, void(*)(struct event*)> evWrite (event_new (evBase.get(), sock, EV_WRITE, cbcoroInvokeFromCallback, cbcoro), event_free);
    auto waitFor = [&](int sock, short events) {
      cbcoro->yieldForCallback ([&]() {event_add (events == EV_READ ? evRead.get() : evWrite.get(), nullptr);});
    };

    for (;;) {
      auto pollStatus = PQconnectPoll (pg.get()); if (pollStatus == PGRES_POLLING_FAILED) GTHROW ("!PQconnectPoll");
      if (pollStatus == PGRES_POLLING_OK) break;
      waitFor (sock, pollStatus == PGRES_POLLING_READING ? EV_READ : EV_WRITE);
    }
    PQsetnonblocking (pg.get(), 1);
    log_info ("logWindowOnerror: Connected to PostgreSQL! (In " << timer.seconds (3) << " seconds).");

    timer.restart();
    GSTRING_ON_STACK (sql, 256) << "BEGIN;";
    sql << "DELETE FROM window_onerror_log WHERE time < now() - interval '30 days';";
    sql << "INSERT INTO window_onerror_log (error) VALUES (" << PQescapeLiteral (pg.get(), post.data(), post.size()) << ");";
    sql << "COMMIT";
    int rc = PQsendQuery (pg.get(), sql.c_str());
    if (!rc) GTHROW (PQerrorMessage (pg.get()));

    auto nextResult = [&]()->std::unique_ptr<PGresult, void(*)(PGresult*)> {
      while (PQisBusy (pg.get()) == 1) {
        waitFor (sock, EV_READ);
        if (!PQconsumeInput (pg.get())) GTHROW (PQerrorMessage (pg.get()));
        while (PQflush (pg.get()) == 1) waitFor (sock, EV_WRITE);
      }
      return std::unique_ptr<PGresult, void(*)(PGresult*)> (PQgetResult (pg.get()), PQclear);
    };
    while (auto pr = nextResult()) {
      ExecStatusType status = PQresultStatus (pr.get());
      if (status == PGRES_COMMAND_OK) log_info ("logWindowOnerror: PGRES_COMMAND_OK");
      else if (status == PGRES_TUPLES_OK) {
        int rows = PQntuples (pr.get()), columns = PQnfields (pr.get());
        GSTRING_ON_STACK (got, 64); for (int row = 0; row < rows; ++row) for (int col = 0; col < columns; ++col) got << "; " << PQgetvalue (pr.get(), row, col);
        log_info ("logWindowOnerror: PGRES_TUPLES_OK" << got);
      } else log_info ("logWindowOnerror: PGresult: " << PQresStatus (status) << "; " << PQresultErrorMessage (pr.get()));
    }
    log_info ("logWindowOnerror: INSERT in " << timer.seconds (3) << " seconds.");

    evhtp_send_reply (req, HTTP_OK); evhtp_request_resume (req);

What's this? Where is a coroutine from?