void AsyncFizzBase::deliverAppData()

in fizz/protocol/AsyncFizzBase.cpp [241:308]
59 lines of code
17 McCabe index (conditional complexity)

void AsyncFizzBase::deliverAppData(std::unique_ptr<folly::IOBuf> data) {
  if (data) {
    appBytesReceived_ += data->computeChainDataLength();
  }

  if (appDataBuf_) {
    if (data) {
      appDataBuf_->prependChain(std::move(data));
    }
    data = std::move(appDataBuf_);
  }

  while (readCallback_ && data) {
    if (readCallback_->isBufferMovable()) {
      return readCallback_->readBufferAvailable(std::move(data));
    } else {
      folly::io::Cursor cursor(data.get());
      size_t available = 0;
      while ((available = cursor.totalLength()) != 0 && readCallback_ &&
             !readCallback_->isBufferMovable()) {
        void* buf = nullptr;
        size_t buflen = 0;
        try {
          readCallback_->getReadBuffer(&buf, &buflen);
        } catch (const AsyncSocketException& ase) {
          return deliverError(ase);
        } catch (const std::exception& e) {
          AsyncSocketException ase(
              AsyncSocketException::BAD_ARGS,
              folly::to<std::string>("getReadBuffer() threw ", e.what()));
          return deliverError(ase);
        } catch (...) {
          AsyncSocketException ase(
              AsyncSocketException::BAD_ARGS,
              "getReadBuffer() threw unknown exception");
          return deliverError(ase);
        }
        if (buflen == 0 || buf == nullptr) {
          AsyncSocketException ase(
              AsyncSocketException::BAD_ARGS,
              "getReadBuffer() returned empty buffer");
          return deliverError(ase);
        }

        size_t bytesToRead = std::min(buflen, available);
        cursor.pull(buf, bytesToRead);
        readCallback_->readDataAvailable(bytesToRead);
      }

      // If we have data left, it means the read callback changed and we need
      // to save the remaining data (if any)
      if (available != 0) {
        std::unique_ptr<folly::IOBuf> remainingData;
        cursor.clone(remainingData, available);
        data = std::move(remainingData);
      } else {
        // Out of data. Reset the data pointer to end the loop
        data.reset();
      }
    }
  }

  if (data) {
    appDataBuf_ = std::move(data);
  }

  checkBufLen();
}