SPIRV-Cross/include/spirv_cross/thread_group.hpp

/*
 * Copyright 2015-2016 ARM Limited
 *
 * 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 SPIRV_CROSS_THREAD_GROUP_HPP
#define SPIRV_CROSS_THREAD_GROUP_HPP

#include <thread>
#include <condition_variable>
#include <mutex>

namespace spirv_cross
{
template <typename T, unsigned Size>
class ThreadGroup
{
public:
	ThreadGroup(T *impl)
	{
		for (unsigned i = 0; i < Size; i++)
			workers[i].start(&impl[i]);
	}

	void run()
	{
		for (auto &worker : workers)
			worker.run();
	}

	void wait()
	{
		for (auto &worker : workers)
			worker.wait();
	}

private:
	struct Thread
	{
		enum State
		{
			Idle,
			Running,
			Dying
		};
		State state = Idle;

		void start(T *impl)
		{
			worker = std::thread([impl, this]
			                     {
				                     for (;;)
				                     {
					                     {
						                     std::unique_lock<std::mutex> l{ lock };
						                     cond.wait(l, [this]
						                               {
							                               return state != Idle;
							                           });
						                     if (state == Dying)
							                     break;
					                     }

					                     impl->main();

					                     std::lock_guard<std::mutex> l{ lock };
					                     state = Idle;
					                     cond.notify_one();
				                     }
				                 });
		}

		void wait()
		{
			std::unique_lock<std::mutex> l{ lock };
			cond.wait(l, [this]
			          {
				          return state == Idle;
				      });
		}

		void run()
		{
			std::lock_guard<std::mutex> l{ lock };
			state = Running;
			cond.notify_one();
		}

		~Thread()
		{
			if (worker.joinable())
			{
				{
					std::lock_guard<std::mutex> l{ lock };
					state = Dying;
					cond.notify_one();
				}
				worker.join();
			}
		}
		std::thread worker;
		std::condition_variable cond;
		std::mutex lock;
	};
	Thread workers[Size];
};
}

#endif