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#ifndef ROMKATV_GITSTATUS_THREAD_POOL_H_
#define ROMKATV_GITSTATUS_THREAD_POOL_H_
#include <condition_variable>
#include <cstddef>
#include <cstdint>
#include <functional>
#include <mutex>
#include <queue>
#include <thread>
#include <tuple>
#include <utility>
#include "time.h"
namespace gitstatus {
class ThreadPool {
public:
explicit ThreadPool(size_t num_threads);
ThreadPool(ThreadPool&&) = delete;
// Waits for the currently running functions to finish.
// Does NOT wait for the queue of functions to drain.
// If you want the latter, call Wait() manually.
~ThreadPool();
// Runs `f` on one of the threads at or after time `t`. Can be called
// from any thread. Can be called concurrently.
//
// Does not block.
void Schedule(Time t, std::function<void()> f);
void Schedule(std::function<void()> f) { Schedule(Clock::now(), std::move(f)); }
// Blocks until the work queue is empty and there are no currently
// running functions.
void Wait();
size_t num_threads() const { return threads_.size(); }
private:
struct Work {
bool operator<(const Work& w) const { return std::tie(w.t, w.idx) < std::tie(t, idx); }
Time t;
int64_t idx;
mutable std::function<void()> f;
};
void Loop(size_t tid);
int64_t last_idx_ = 0;
int64_t num_inflight_;
bool exit_ = false;
// Do we have a thread waiting on sleeper_cv_?
bool have_sleeper_ = false;
std::mutex mutex_;
// Any number of threads can wait on this condvar. Always without a timeout.
std::condition_variable cv_;
// At most one thread can wait on this condvar at a time. Always with a timeout.
std::condition_variable sleeper_cv_;
// Signalled when the work queue is empty and there is nothing inflight.
std::condition_variable idle_cv_;
std::priority_queue<Work> work_;
std::vector<std::thread> threads_;
};
void InitGlobalThreadPool(size_t num_threads);
ThreadPool* GlobalThreadPool();
} // namespace gitstatus
#endif // ROMKATV_GITSTATUS_THREAD_POOL_H_
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