QuicSocket::WriteResult QuicTransportBase::writeBufMeta()

in quic/api/QuicTransportBase.cpp [2117:2191]
69 lines of code
17 McCabe index (conditional complexity)

QuicSocket::WriteResult QuicTransportBase::writeBufMeta(
    StreamId id,
    const BufferMeta& data,
    bool eof,
    ByteEventCallback* cb) {
  if (isReceivingStream(conn_->nodeType, id)) {
    return folly::makeUnexpected(LocalErrorCode::INVALID_OPERATION);
  }
  if (closeState_ != CloseState::OPEN) {
    return folly::makeUnexpected(LocalErrorCode::CONNECTION_CLOSED);
  }
  FOLLY_MAYBE_UNUSED auto self = sharedGuard();
  try {
    // Check whether stream exists before calling getStream to avoid
    // creating a peer stream if it does not exist yet.
    if (!conn_->streamManager->streamExists(id)) {
      return folly::makeUnexpected(LocalErrorCode::STREAM_NOT_EXISTS);
    }
    auto stream = conn_->streamManager->getStream(id);
    if (!stream->writable()) {
      return folly::makeUnexpected(LocalErrorCode::STREAM_CLOSED);
    }
    if (!stream->dsrSender) {
      return folly::makeUnexpected(LocalErrorCode::INVALID_OPERATION);
    }
    if (stream->currentWriteOffset == 0 && stream->writeBuffer.empty()) {
      // If nothing has been written to writeBuffer ever, meta writing isn't
      // allowed.
      return folly::makeUnexpected(LocalErrorCode::INVALID_OPERATION);
    }
    // Register DeliveryCallback for the data + eof offset.
    if (cb) {
      auto dataLength = data.length + (eof ? 1 : 0);
      if (dataLength) {
        auto currentLargestWriteOffset = getLargestWriteOffsetSeen(*stream);
        registerDeliveryCallback(
            id, currentLargestWriteOffset + dataLength - 1, cb);
      }
    }
    bool wasAppLimitedOrIdle = false;
    if (conn_->congestionController) {
      wasAppLimitedOrIdle = conn_->congestionController->isAppLimited();
      wasAppLimitedOrIdle |= conn_->streamManager->isAppIdle();
    }
    writeBufMetaToQuicStream(*stream, data, eof);
    // If we were previously app limited restart pacing with the current rate.
    if (wasAppLimitedOrIdle && conn_->pacer) {
      conn_->pacer->reset();
    }
    updateWriteLooper(true);
  } catch (const QuicTransportException& ex) {
    VLOG(4) << __func__ << " streamId=" << id << " " << ex.what() << " "
            << *this;
    exceptionCloseWhat_ = ex.what();
    closeImpl(QuicError(
        QuicErrorCode(ex.errorCode()), std::string("writeChain() error")));
    return folly::makeUnexpected(LocalErrorCode::TRANSPORT_ERROR);
  } catch (const QuicInternalException& ex) {
    VLOG(4) << __func__ << " streamId=" << id << " " << ex.what() << " "
            << *this;
    exceptionCloseWhat_ = ex.what();
    closeImpl(QuicError(
        QuicErrorCode(ex.errorCode()), std::string("writeChain() error")));
    return folly::makeUnexpected(ex.errorCode());
  } catch (const std::exception& ex) {
    VLOG(4) << __func__ << " streamId=" << id << " " << ex.what() << " "
            << *this;
    exceptionCloseWhat_ = ex.what();
    closeImpl(QuicError(
        QuicErrorCode(TransportErrorCode::INTERNAL_ERROR),
        std::string("writeChain() error")));
    return folly::makeUnexpected(LocalErrorCode::INTERNAL_ERROR);
  }
  return folly::unit;
}