Method Select

cxx/Net.cpp:516–529

		std::unordered_map<std::shared_ptr<Socket>, int> pending;

		void Select(const std::shared_ptr<Socket>& sock, int add, int remove)
		{
			std::lock_guard<std::mutex> g(mutexPending);
			int oldFlags = sock->selectorFlags;
			int newFlags = (oldFlags & ~remove) | add;
			if (oldFlags != newFlags)
			{
				sock->selectorFlags = newFlags;
				auto rc = pending.insert(std::make_pair(sock, newFlags));
				if (false == rc.second) // 已经存在，更新flags
					rc.first->second = newFlags;
				Wakeup();
			}
		}

		int wakeupfds[2];
		bool loop = true;