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#pragma once
#include "base/assert.hpp"
#include "base/task_loop.hpp"
#include "base/thread.hpp"
#include "base/thread_checker.hpp"
#include <chrono>
#include <condition_variable>
#include <mutex>
#include <queue>
#include <utility>
#include <vector>
namespace base
{
namespace thread_pool
{
namespace delayed
{
// This class represents a simple thread pool with a queue of tasks.
//
// *NOTE* This class IS NOT thread-safe, it must be destroyed on the
// same thread it was created, but Push* methods are thread-safe.
class ThreadPool : public TaskLoop
{
public:
using Clock = std::chrono::steady_clock;
using Duration = Clock::duration;
using TimePoint = Clock::time_point;
enum class Exit
{
ExecPending,
SkipPending
};
explicit ThreadPool(size_t threadsCount = 1, Exit e = Exit::SkipPending);
~ThreadPool() override;
// Pushes task to the end of the thread's queue of immediate tasks.
// Returns false when the thread is shut down.
//
// The task |t| is going to be executed after all immediate tasks
// that were pushed pushed before it.
bool Push(Task && t) override;
bool Push(Task const & t) override;
// Pushes task to the thread's queue of delayed tasks. Returns false
// when the thread is shut down.
//
// The task |t| is going to be executed not earlier than after
// |delay|. No other guarantees about execution order are made. In
// particular, when executing:
//
// PushDelayed(3ms, task1);
// PushDelayed(1ms, task2);
//
// there is no guarantee that |task2| will be executed before |task1|.
//
// NOTE: current implementation depends on the fact that
// steady_clock is the same for different threads.
bool PushDelayed(Duration const & delay, Task && t);
bool PushDelayed(Duration const & delay, Task const & t);
// Sends a signal to the thread to shut down. Returns false when the
// thread was shut down previously.
bool Shutdown(Exit e);
// Sends a signal to the thread to shut down and waits for completion.
void ShutdownAndJoin();
static TimePoint Now() { return Clock::now(); }
private:
enum QueueType
{
QUEUE_TYPE_IMMEDIATE,
QUEUE_TYPE_DELAYED,
QUEUE_TYPE_COUNT
};
struct DelayedTask
{
template <typename T>
DelayedTask(TimePoint const & when, T && task) : m_when(when), m_task(std::forward<T>(task))
{
}
bool operator<(DelayedTask const & rhs) const { return m_when < rhs.m_when; }
bool operator>(DelayedTask const & rhs) const { return rhs < *this; }
TimePoint m_when = {};
Task m_task = {};
};
using ImmediateQueue = std::queue<Task>;
using DelayedQueue =
std::priority_queue<DelayedTask, std::vector<DelayedTask>, std::greater<DelayedTask>>;
template <typename Fn>
bool TouchQueues(Fn && fn)
{
std::lock_guard<std::mutex> lk(m_mu);
if (m_shutdown)
return false;
fn();
m_cv.notify_one();
return true;
}
void ProcessTasks();
std::vector<threads::SimpleThread> m_threads;
std::mutex m_mu;
std::condition_variable m_cv;
bool m_shutdown = false;
Exit m_exit = Exit::SkipPending;
ImmediateQueue m_immediate;
DelayedQueue m_delayed;
ThreadChecker m_checker;
};
} // namespace delayed
} // namespace thread_pool
} // namespace base
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