Stoppable.h

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012-2015 Ripple Labs Inc.
 
    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.
 
    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================
 
#ifndef RIPPLE_CORE_STOPPABLE_H_INCLUDED
#define RIPPLE_CORE_STOPPABLE_H_INCLUDED
 
#include <ripple/beast/core/LockFreeStack.h>
#include <ripple/beast/utility/Journal.h>
#include <ripple/core/ClosureCounter.h>
#include <ripple/core/Job.h>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <mutex>
 
namespace ripple {
 
// Give a reasonable name for the JobCounter
using JobCounter = ClosureCounter<void, Job&>;
 
class RootStoppable;
 
class Stoppable
{
protected:
    Stoppable(std::string name, RootStoppable& root);
 
public:
    Stoppable(std::string name, Stoppable& parent);
 
    virtual ~Stoppable();
 
    RootStoppable&
    getRoot()
    {
        return m_root;
    }
 
    void
    setParent(Stoppable& parent);
 
    bool
    isStopping() const;
 
    bool
    isStopped() const;
 
    bool
    areChildrenStopped() const;
 
    /* JobQueue uses this method for Job counting. */
    inline JobCounter&
    jobCounter();
 
    bool
    alertable_sleep_until(std::chrono::system_clock::time_point const& t);
 
protected:
    void
    stopped();
 
private:
    virtual void
    onPrepare();
 
    virtual void
    onStart();
 
    virtual void
    onStop();
 
    virtual void
    onChildrenStopped();
 
    friend class RootStoppable;
 
    struct Child;
    using Children = beast::LockFreeStack<Child>;
 
    struct Child : Children::Node
    {
        Child(Stoppable* stoppable_) : stoppable(stoppable_)
        {
        }
 
        Stoppable* stoppable;
    };
 
    void
    prepareRecursive();
    void
    startRecursive();
    void
    stopAsyncRecursive(beast::Journal j);
    void
    stopRecursive(beast::Journal j);
 
    std::string m_name;
    RootStoppable& m_root;
    Child m_child;
    // TODO [C++20]: Use std::atomic_flag instead.
    std::atomic<bool> m_stopped{false};
    std::atomic<bool> m_childrenStopped{false};
    Children m_children;
    std::condition_variable m_cv;
    std::mutex m_mut;
    bool m_is_stopping = false;
    bool hasParent_{false};
};
 
//------------------------------------------------------------------------------
 
class RootStoppable : public Stoppable
{
public:
    explicit RootStoppable(std::string name);
 
    virtual ~RootStoppable();
 
    bool
    isStopping() const;
 
    void
    start();
 
    void
    stop(beast::Journal j);
 
    bool
    started() const
    {
        return startExited_;
    }
 
    /* JobQueue uses this method for Job counting. */
    JobCounter&
    jobCounter()
    {
        return jobCounter_;
    }
 
    bool
    alertable_sleep_until(std::chrono::system_clock::time_point const& t);
 
private:
    // TODO [C++20]: Use std::atomic_flag instead.
    std::atomic<bool> startEntered_{false};
    std::atomic<bool> startExited_{false};
    std::atomic<bool> stopEntered_{false};
    std::mutex m_;
    std::condition_variable c_;
    JobCounter jobCounter_;
};
//------------------------------------------------------------------------------
 
JobCounter&
Stoppable::jobCounter()
{
    return m_root.jobCounter();
}
 
//------------------------------------------------------------------------------
 
inline bool
RootStoppable::alertable_sleep_until(
    std::chrono::system_clock::time_point const& t)
{
    std::unique_lock<std::mutex> lock(m_);
    if (stopEntered_)
        return true;
    // TODO [C++20]: When `stopEntered_` is changed to a `std::atomic_flag`,
    // this call to `load` needs to change to a call to `test`.
    return c_.wait_until(lock, t, [this] { return stopEntered_.load(); });
}
 
inline bool
Stoppable::alertable_sleep_until(std::chrono::system_clock::time_point const& t)
{
    return m_root.alertable_sleep_until(t);
}
 
}  // namespace ripple
 
#endif