Refine buffer channel

[chengduoZH]

• Send sends only one element, we should wake up only one receiver thread by calling notify_one, instead of notify_all.
• There are two possibilities for the return of Receive or Send:
  • the Channel was closed.
  • the Receive or Send of this Channel was called.
    we should separate the two possibilities.

[abhinavarora]

We want to make sure that writer_found_ is always false at the end of this function. I would rewrite it as follows:

bool ret = false;
if (!closed_) {
    std::unique_lock<std::mutex> channel_lock(mu_ch_);
    item = data;
    channel_lock.unlock();
    cv_channel_.notify_one();
    channel_lock.lock();
    cv_channel_.wait(channel_lock,
                     [this]() { return item == nullptr || closed_; });
    ret = true
  }
  writer_found_ = false;
  return ret;

[chengduoZH]

Done.

[abhinavarora]

Similarly I would prefer to rewrite this as follows:

bool ret = false;
if (!closed_) {
    std::unique_lock<std::mutex> lock_ch{mu_ch_};
    // Reader should wait for the writer to first write its data
    cv_channel_.wait(lock_ch, [this]() { return item != nullptr || closed_; });
    if (!closed_) {
      *data = std::move(*item);
      item = nullptr;
      lock_ch.unlock();
      ret = true;
    }
    cv_channel_.notify_one();
  }
  reader_found_ = false;
  return ret;

[chengduoZH]

Done.

[abhinavarora]

LGTM!

[abhinavarora]

LGTM