io_list.h

//------------------------------------------------------------------------------
/*
    This file is part of rippled: https://github.com/ripple/rippled
    Copyright (c) 2012, 2013 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_SERVER_IO_LIST_H_INCLUDED
#define RIPPLE_SERVER_IO_LIST_H_INCLUDED
 
#include <boost/container/flat_map.hpp>
 
#include <condition_variable>
#include <functional>
#include <memory>
#include <mutex>
#include <stdexcept>
#include <type_traits>
#include <utility>
 
namespace ripple {
 
class io_list final
{
public:
    class work
    {
        template <class = void>
        void
        destroy();
 
        friend class io_list;
        io_list* ios_ = nullptr;
 
    public:
        virtual ~work()
        {
            destroy();
        }
 
        io_list&
        ios()
        {
            return *ios_;
        }
 
        virtual void
        close() = 0;
    };
 
private:
    template <class = void>
    void
    destroy();
 
    std::mutex m_;
    std::size_t n_ = 0;
    bool closed_ = false;
    std::condition_variable cv_;
    boost::container::flat_map<work*, std::weak_ptr<work>> map_;
    std::function<void(void)> f_;
 
public:
    io_list() = default;
 
    ~io_list()
    {
        destroy();
    }
 
    bool
    closed() const
    {
        return closed_;
    }
 
    template <class T, class... Args>
    std::shared_ptr<T>
    emplace(Args&&... args);
 
    template <class Finisher>
    void
    close(Finisher&& f);
 
    void
    close()
    {
        close([] {});
    }
 
    template <class = void>
    void
    join();
};
 
//------------------------------------------------------------------------------
 
template <class>
void
io_list::work::destroy()
{
    if (!ios_)
        return;
    std::function<void(void)> f;
    {
        std::lock_guard lock(ios_->m_);
        ios_->map_.erase(this);
        if (--ios_->n_ == 0 && ios_->closed_)
        {
            std::swap(f, ios_->f_);
            ios_->cv_.notify_all();
        }
    }
    if (f)
        f();
}
 
template <class>
void
io_list::destroy()
{
    close();
    join();
}
 
template <class T, class... Args>
std::shared_ptr<T>
io_list::emplace(Args&&... args)
{
    static_assert(
        std::is_base_of<work, T>::value, "T must derive from io_list::work");
    if (closed_)
        return nullptr;
    auto sp = std::make_shared<T>(std::forward<Args>(args)...);
    decltype(sp) dead;
 
    std::lock_guard lock(m_);
    if (!closed_)
    {
        ++n_;
        sp->work::ios_ = this;
        map_.emplace(sp.get(), sp);
    }
    else
    {
        std::swap(sp, dead);
    }
    return sp;
}
 
template <class Finisher>
void
io_list::close(Finisher&& f)
{
    std::unique_lock<std::mutex> lock(m_);
    if (closed_)
        return;
    closed_ = true;
    auto map = std::move(map_);
    if (!map.empty())
    {
        f_ = std::forward<Finisher>(f);
        lock.unlock();
        for (auto const& p : map)
            if (auto sp = p.second.lock())
                sp->close();
    }
    else
    {
        lock.unlock();
        f();
    }
}
 
template <class>
void
io_list::join()
{
    std::unique_lock<std::mutex> lock(m_);
    cv_.wait(lock, [&] { return closed_ && n_ == 0; });
}
 
}  // namespace ripple
 
#endif