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/*
* ThreadPool.h, part of VCMI engine
*
* Authors: listed in file AUTHORS in main folder
*
* License: GNU General Public License v2.0 or later
* Full text of license available in license.txt file, in main folder
*
*/
#pragma once
#include "BlockingQueue.h"
#include <boost/thread/future.hpp>
#include <boost/thread/condition_variable.hpp>
VCMI_LIB_NAMESPACE_BEGIN
typedef std::function<void()> TRMGfunction ;
typedef std::optional<TRMGfunction> TRMGJob;
//Credit to https://github.com/Liam0205/toy-threadpool/tree/master/yuuki
class DLL_LINKAGE ThreadPool
{
private:
using Lock = boost::unique_lock<boost::shared_mutex>;
mutable boost::shared_mutex mx;
mutable boost::condition_variable_any cv;
mutable boost::once_flag once;
bool isInitialized = false;
bool stopping = false;
bool canceling = false;
public:
ThreadPool();
~ThreadPool();
void init(size_t numThreads);
void spawn();
void terminate();
void cancel();
public:
bool initialized() const;
bool running() const;
int size() const;
private:
bool isRunning() const;
public:
auto async(std::function<void()>&& f) const -> boost::future<void>;
private:
std::vector<boost::thread> workers;
mutable BlockingQueue<TRMGfunction> tasks;
};
ThreadPool::ThreadPool() :
once(BOOST_ONCE_INIT)
{};
ThreadPool::~ThreadPool()
{
terminate();
}
inline void ThreadPool::init(size_t numThreads)
{
boost::call_once(once, [this, numThreads]()
{
Lock lock(mx);
stopping = false;
canceling = false;
workers.reserve(numThreads);
for (size_t i = 0; i < numThreads; ++i)
{
workers.emplace_back(std::bind(&ThreadPool::spawn, this));
}
isInitialized = true;
});
}
bool ThreadPool::isRunning() const
{
return isInitialized && !stopping && !canceling;
}
inline bool ThreadPool::initialized() const
{
Lock lock(mx);
return isInitialized;
}
inline bool ThreadPool::running() const
{
Lock lock(mx);
return isRunning();
}
inline int ThreadPool::size() const
{
Lock lock(mx);
return workers.size();
}
inline void ThreadPool::spawn()
{
while(true)
{
bool pop = false;
TRMGfunction task;
{
Lock lock(mx);
cv.wait(lock, [this, &pop, &task]
{
pop = tasks.pop(task);
return canceling || stopping || pop;
});
}
if (canceling || (stopping && !pop))
{
return;
}
task();
}
}
inline void ThreadPool::terminate()
{
{
Lock lock(mx);
if (isRunning())
{
stopping = true;
}
else
{
return;
}
}
cv.notify_all();
for (auto& worker : workers)
{
worker.join();
}
}
inline void ThreadPool::cancel()
{
{
Lock lock(mx);
if (running())
{
canceling = true;
}
else
{
return;
}
}
tasks.clear();
cv.notify_all();
for (auto& worker : workers)
{
worker.join();
}
}
auto ThreadPool::async(std::function<void()>&& f) const -> boost::future<void>
{
using TaskT = boost::packaged_task<void>;
{
Lock lock(mx);
if (stopping || canceling)
{
throw std::runtime_error("Delegating task to a threadpool that has been terminated or canceled.");
}
}
auto task = std::make_shared<TaskT>(f);
boost::future<void> fut = task->get_future();
tasks.emplace([task]() -> void
{
(*task)();
});
cv.notify_one();
return fut;
}
VCMI_LIB_NAMESPACE_END
|
