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#pragma once
#include "base/assert.hpp"
#include "base/macros.hpp"
#include "base/thread_checker.hpp"
#include "std/condition_variable.hpp"
#include "std/mutex.hpp"
#include "std/queue.hpp"
#include "std/shared_ptr.hpp"
#include "std/thread.hpp"
namespace my
{
/// This class wraps a sequential worker thread, that performs tasks
/// one-by-one. This class is not thread-safe, so, it should be
/// instantiated, used and destroyed on the same thread.
template <typename Task>
class WorkerThread
{
public:
WorkerThread(int maxTasks)
: m_maxTasks(maxTasks), m_shouldFinish(false), m_workerThread(&WorkerThread::Worker, this)
{
}
~WorkerThread()
{
ASSERT(m_threadChecker.CalledOnOriginalThread(), ());
if (IsRunning())
RunUntilIdleAndStop();
ASSERT(!IsRunning(), ());
}
/// Pushes new task into worker thread's queue. If the queue is
/// full, current thread is blocked.
///
/// \param task A callable object that will be called by worker thread.
void Push(shared_ptr<Task> task)
{
ASSERT(m_threadChecker.CalledOnOriginalThread(), ());
ASSERT(IsRunning(), ());
unique_lock<mutex> lock(m_mutex);
m_condNotFull.wait(lock, [this]()
{
return m_tasks.size() < m_maxTasks;
});
m_tasks.push(task);
m_condNonEmpty.notify_one();
}
/// Runs worker thread until it'll become idle. After that,
/// terminates worker thread.
void RunUntilIdleAndStop()
{
ASSERT(m_threadChecker.CalledOnOriginalThread(), ());
ASSERT(IsRunning(), ());
{
lock_guard<mutex> lock(m_mutex);
m_shouldFinish = true;
m_condNonEmpty.notify_one();
}
m_workerThread.join();
}
/// \return True if worker thread is running, false otherwise.
inline bool IsRunning() const
{
ASSERT(m_threadChecker.CalledOnOriginalThread(), ());
return m_workerThread.joinable();
}
private:
void Worker()
{
shared_ptr<Task> task;
while (true)
{
{
unique_lock<mutex> lock(m_mutex);
m_condNonEmpty.wait(lock, [this]()
{
return m_shouldFinish || !m_tasks.empty();
});
if (m_shouldFinish && m_tasks.empty())
break;
task = m_tasks.front();
m_tasks.pop();
m_condNotFull.notify_one();
}
(*task)();
}
}
/// Maximum number of tasks in the queue.
int const m_maxTasks;
queue<shared_ptr<Task>> m_tasks;
/// When true, worker thread should finish all tasks in the queue
/// and terminate.
bool m_shouldFinish;
mutex m_mutex;
condition_variable m_condNotFull;
condition_variable m_condNonEmpty;
thread m_workerThread;
#ifdef DEBUG
ThreadChecker m_threadChecker;
#endif
DISALLOW_COPY_AND_MOVE(WorkerThread);
}; // class WorkerThread
} // namespace my
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