Method WaitUntilWritten

library/cpp/neh/https.cpp:838–867

            }

            void WaitUntilWritten() {
#if defined(FIONWRITE)
                if (Y_LIKELY(Cont_)) {
                    int err;
                    int nbytes = Max<int>();
                    TDuration tout = TDuration::MilliSeconds(10);

                    while (((err = ioctl(S_, FIONWRITE, &nbytes)) == 0) && nbytes) {
                        err = NCoro::PollT(Cont_, S_, CONT_POLL_READ, tout);

                        if (!err) {
                            //wait complete, cause have some data
                            break;
                        }

                        if (err != ETIMEDOUT) {
                            ythrow TSystemError(err) << TStringBuf("request failed");
                        }

                        tout = tout * 2;
                    }

                    if (err) {
                        ythrow TSystemError() << TStringBuf("ioctl() failed");
                    }
                } else {
                    ythrow TSslException() << TStringBuf("No cont available");
                }
#endif
            }

            void AcquireCont(TCont* c) {
                Cont_ = c;