task_runner.hpp

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#ifndef OTBR_COMMON_TASK_RUNNER_HPP_
#define OTBR_COMMON_TASK_RUNNER_HPP_
 
#include <openthread-br/config.h>
 
#include <chrono>
#include <functional>
#include <future>
#include <mutex>
#include <queue>
#include <set>
 
#include "common/code_utils.hpp"
#include "common/mainloop.hpp"
#include "common/time.hpp"
 
namespace otbr {
 
class TaskRunner : public MainloopProcessor, private NonCopyable
{
public:
    template <class T> using Task = std::function<T(void)>;
 
    typedef uint64_t TaskId;
 
    TaskRunner(void);
 
    ~TaskRunner(void) override;
 
    void Post(Task<void> aTask);
 
    TaskId Post(Milliseconds aDelay, Task<void> aTask);
 
    void Cancel(TaskId aTaskId);
 
    template <class T> T PostAndWait(const Task<T> &aTask)
    {
        std::promise<T> pro;
 
        Post([&pro, &aTask]() { pro.set_value(aTask()); });
 
        return pro.get_future().get();
    }
 
    void Update(MainloopContext &aMainloop) override;
    void Process(const MainloopContext &aMainloop) override;
 
private:
    enum
    {
        kRead  = 0,
        kWrite = 1,
    };
 
    struct DelayedTask
    {
        friend class Comparator;
 
        struct Comparator
        {
            bool operator()(const DelayedTask &aLhs, const DelayedTask &aRhs) const { return aRhs < aLhs; }
        };
 
        DelayedTask(TaskId aTaskId, Milliseconds aDelay, Task<void> aTask)
            : mTaskId(aTaskId)
            , mDeadline(Clock::now() + aDelay)
            , mTask(std::move(aTask))
        {
        }
 
        bool operator<(const DelayedTask &aOther) const
        {
            return mDeadline <= aOther.mDeadline || (mDeadline == aOther.mDeadline && mTaskId < aOther.mTaskId);
        }
 
        Timepoint GetTimeExecute(void) const { return mDeadline; }
 
        TaskId     mTaskId;
        Timepoint  mDeadline;
        Task<void> mTask;
    };
 
    TaskId PushTask(Milliseconds aDelay, Task<void> aTask);
    void   PopTasks(void);
 
    // The event fds which are used to wakeup the mainloop
    // when there are pending tasks in the task queue.
    int mEventFd[2];
 
    std::priority_queue<DelayedTask, std::vector<DelayedTask>, DelayedTask::Comparator> mTaskQueue;
 
    std::set<TaskId> mActiveTaskIds;
    TaskId           mNextTaskId = 1;
 
    // The mutex which protects the `mTaskQueue` from being
    // simultaneously accessed by multiple threads.
    std::mutex mTaskQueueMutex;
};
 
} // namespace otbr
 
#endif // OTBR_COMMON_TASK_RUNNER_HPP_