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// Copyright 2016 Google Inc. All rights reserved
//
// 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.
#include "thread_pool.h"
#include <stack>
#include <vector>
#include "condvar.h"
#include "mutex.h"
#include "thread.h"
class ThreadPoolImpl : public ThreadPool {
public:
explicit ThreadPoolImpl(int num_threads)
: is_waiting_(false) {
threads_.reserve(num_threads);
for (int i = 0; i < num_threads; i++) {
threads_.push_back(thread([this]() { Loop(); }));
}
}
virtual ~ThreadPoolImpl() override {
}
virtual void Submit(function<void(void)> task) override {
unique_lock<mutex> lock(mu_);
tasks_.push(task);
cond_.notify_one();
}
virtual void Wait() override {
{
unique_lock<mutex> lock(mu_);
is_waiting_ = true;
cond_.notify_all();
}
for (thread& th : threads_) {
th.join();
}
}
private:
void Loop() {
while (true) {
function<void(void)> task;
{
unique_lock<mutex> lock(mu_);
if (tasks_.empty()) {
if (is_waiting_)
return;
cond_.wait(lock);
}
if (tasks_.empty())
continue;
task = tasks_.top();
tasks_.pop();
}
task();
}
}
vector<thread> threads_;
mutex mu_;
condition_variable cond_;
stack<function<void(void)>> tasks_;
bool is_waiting_;
};
ThreadPool* NewThreadPool(int num_threads) {
return new ThreadPoolImpl(num_threads);
}