void append()

in mcrouter/lib/carbon/CarbonQueueAppender.h [36:78]
33 lines of code
12 McCabe index (conditional complexity)

  void append(const folly::IOBuf& buf) {
    // IOBuf copy is a very expensive procedure (64 bytes object + atomic
    // operation), avoid incuring that cost for small buffers.
    if (!buf.empty() && !buf.isChained() && buf.length() <= kInlineIOBufLen &&
        storageIdx_ + buf.length() <= sizeOfStorage()) {
      push(buf.data(), buf.length());
      return;
    }

    finalizeLastIovec();

    if (nIovsUsed_ == kMaxIovecs) {
      coalesce();
    }

    assert(nIovsUsed_ < kMaxIovecs);

    struct iovec* nextIov = iovs_.data() + nIovsUsed_;
    const auto nFilled =
        buf.fillIov(nextIov, kMaxIovecs - nIovsUsed_).numIovecs;

    if (tcpZeroCopyThreshold_ && !applyZeroCopy_ &&
        buf.capacity() >= tcpZeroCopyThreshold_) {
      applyZeroCopy_ = true;
    }

    if (nFilled > 0) {
      nIovsUsed_ += nFilled;
      if (!head_) {
        head_ = buf;
      } else {
        head_->prependChain(buf.clone());
      }
    } else {
      if (buf.empty()) {
        return;
      }
      appendSlow(buf);
    }

    // If a push() comes after, it should not use the iovec we just filled in
    canUsePreviousIov_ = false;
  }