Shinichiro Hamaji | 702befc | 2016-01-27 17:21:39 +0900 | [diff] [blame^] | 1 | // Copyright 2016 Google Inc. All rights reserved |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | // you may not use this file except in compliance with the License. |
| 5 | // You may obtain a copy of the License at |
| 6 | // |
| 7 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | // |
| 9 | // Unless required by applicable law or agreed to in writing, software |
| 10 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | // See the License for the specific language governing permissions and |
| 13 | // limitations under the License. |
| 14 | |
| 15 | #include "thread_pool.h" |
| 16 | |
| 17 | #include <stack> |
| 18 | #include <vector> |
| 19 | |
| 20 | #include "condvar.h" |
| 21 | #include "mutex.h" |
| 22 | #include "thread.h" |
| 23 | |
| 24 | class ThreadPoolImpl : public ThreadPool { |
| 25 | public: |
| 26 | explicit ThreadPoolImpl(int num_threads) |
| 27 | : is_waiting_(false) { |
| 28 | threads_.reserve(num_threads); |
| 29 | for (int i = 0; i < num_threads; i++) { |
| 30 | threads_.push_back(thread([this]() { Loop(); })); |
| 31 | } |
| 32 | } |
| 33 | |
| 34 | virtual ~ThreadPoolImpl() override { |
| 35 | } |
| 36 | |
| 37 | virtual void Submit(function<void(void)> task) override { |
| 38 | unique_lock<mutex> lock(mu_); |
| 39 | tasks_.push(task); |
| 40 | cond_.notify_one(); |
| 41 | } |
| 42 | |
| 43 | virtual void Wait() override { |
| 44 | { |
| 45 | unique_lock<mutex> lock(mu_); |
| 46 | is_waiting_ = true; |
| 47 | cond_.notify_all(); |
| 48 | } |
| 49 | |
| 50 | for (thread& th : threads_) { |
| 51 | th.join(); |
| 52 | } |
| 53 | } |
| 54 | |
| 55 | private: |
| 56 | void Loop() { |
| 57 | while (true) { |
| 58 | function<void(void)> task; |
| 59 | { |
| 60 | unique_lock<mutex> lock(mu_); |
| 61 | if (tasks_.empty()) { |
| 62 | if (is_waiting_) |
| 63 | return; |
| 64 | cond_.wait(lock); |
| 65 | } |
| 66 | |
| 67 | if (tasks_.empty()) |
| 68 | continue; |
| 69 | |
| 70 | task = tasks_.top(); |
| 71 | tasks_.pop(); |
| 72 | } |
| 73 | task(); |
| 74 | } |
| 75 | } |
| 76 | |
| 77 | vector<thread> threads_; |
| 78 | mutex mu_; |
| 79 | condition_variable cond_; |
| 80 | stack<function<void(void)>> tasks_; |
| 81 | bool is_waiting_; |
| 82 | }; |
| 83 | |
| 84 | ThreadPool* NewThreadPool(int num_threads) { |
| 85 | return new ThreadPoolImpl(num_threads); |
| 86 | } |