PendingSaves.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_APP_PENDINGSAVES_H_INCLUDED
#define RIPPLE_APP_PENDINGSAVES_H_INCLUDED
 
#include <xrpl/protocol/Protocol.h>
#include <condition_variable>
#include <map>
#include <mutex>
 
namespace ripple {
 
class PendingSaves
{
private:
    std::mutex mutable mutex_;
    std::map<LedgerIndex, bool> map_;
    std::condition_variable await_;
 
public:
    bool
    startWork(LedgerIndex seq)
    {
        std::lock_guard lock(mutex_);
 
        auto it = map_.find(seq);
 
        if ((it == map_.end()) || it->second)
        {
            // Work done or another thread is doing it
            return false;
        }
 
        it->second = true;
        return true;
    }
 
    void
    finishWork(LedgerIndex seq)
    {
        std::lock_guard lock(mutex_);
 
        map_.erase(seq);
        await_.notify_all();
    }
 
    bool
    pending(LedgerIndex seq)
    {
        std::lock_guard lock(mutex_);
        return map_.find(seq) != map_.end();
    }
 
    bool
    shouldWork(LedgerIndex seq, bool isSynchronous)
    {
        std::unique_lock<std::mutex> lock(mutex_);
        do
        {
            auto it = map_.find(seq);
 
            if (it == map_.end())
            {
                map_.emplace(seq, false);
                return true;
            }
 
            if (!isSynchronous)
            {
                // Already dispatched
                return false;
            }
 
            if (!it->second)
            {
                // Scheduled, but not dispatched
                return true;
            }
 
            // Already in progress, just need to wait
            await_.wait(lock);
 
        } while (true);
    }
 
    std::map<LedgerIndex, bool>
    getSnapshot() const
    {
        std::lock_guard lock(mutex_);
 
        return map_;
    }
};
 
}  // namespace ripple
 
#endif