| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License |
| |
| #ifndef __GATE_HPP__ |
| #define __GATE_HPP__ |
| |
| #include <condition_variable> |
| #include <mutex> |
| |
| #include <stout/synchronized.hpp> |
| |
| namespace process { |
| |
| // A Gate abstracts the concept of something that can "only happen |
| // once and every one else needs to queue up and wait until that thing |
| // happens" ... kind of like a gate that can only ever open. |
| // |
| // NOTE: historically a gate could be opened and _closed_ allowing but |
| // those semantics are no longer needed so they have been removed in |
| // order to simplify the implementation. |
| // |
| // TODO(benh): Consider removing this entirely and using `Once` for |
| // cleanup of a `ProcessBase` instead of a `Gate`. |
| class Gate |
| { |
| public: |
| // Opens the gate and notifies all the waiters. |
| void open() |
| { |
| synchronized (mutex) { |
| opened = true; |
| cond.notify_all(); |
| } |
| } |
| |
| // Blocks the current thread until the gate has been opened. |
| void wait() |
| { |
| synchronized (mutex) { |
| while (!opened) { |
| synchronized_wait(&cond, &mutex); |
| } |
| } |
| } |
| |
| private: |
| bool opened = false; |
| std::mutex mutex; |
| std::condition_variable cond; |
| }; |
| |
| } // namespace process { |
| |
| #endif // __GATE_HPP__ |