WaitingTaskHolder.h

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#ifndef FWCore_Concurrency_WaitingTaskHolder_h
#define FWCore_Concurrency_WaitingTaskHolder_h
// -*- C++ -*-
//
// Package:     FWCore/Concurrency
// Class  :     WaitingTaskHolder
//
//
// Original Author:  FWCore
//         Created:  Fri, 18 Nov 2016 20:30:42 GMT
//
 
// system include files
#include <cassert>
 
// user include files
#include "FWCore/Concurrency/interface/WaitingTask.h"
 
// forward declarations
 
namespace edm {
  class WaitingTaskHolder {
  public:
    WaitingTaskHolder() : m_task(nullptr) {}
 
    explicit WaitingTaskHolder(edm::WaitingTask* iTask) : m_task(iTask) { m_task->increment_ref_count(); }
    ~WaitingTaskHolder() {
      if (m_task) {
        doneWaiting(std::exception_ptr{});
      }
    }
 
    WaitingTaskHolder(const WaitingTaskHolder& iHolder) : m_task(iHolder.m_task) { m_task->increment_ref_count(); }
 
    WaitingTaskHolder(WaitingTaskHolder&& iOther) : m_task(iOther.m_task) { iOther.m_task = nullptr; }
 
    WaitingTaskHolder& operator=(const WaitingTaskHolder& iRHS) {
      WaitingTaskHolder tmp(iRHS);
      std::swap(m_task, tmp.m_task);
      return *this;
    }
 
    WaitingTaskHolder& operator=(WaitingTaskHolder&& iRHS) {
      WaitingTaskHolder tmp(std::move(iRHS));
      std::swap(m_task, tmp.m_task);
      return *this;
    }
 
    // ---------- const member functions ---------------------
    bool taskHasFailed() const { return m_task->exceptionPtr() != nullptr; }
 
    // ---------- static member functions --------------------
 
    // ---------- member functions ---------------------------
 
    void presetTaskAsFailed(std::exception_ptr iExcept) {
      if (iExcept) {
        m_task->dependentTaskFailed(iExcept);
      }
    }
 
    void doneWaiting(std::exception_ptr iExcept) {
      if (iExcept) {
        m_task->dependentTaskFailed(iExcept);
      }
      //spawn can run the task before we finish
      // doneWaiting and some other thread might
      // try to reuse this object. Resetting
      // before spawn avoids problems
      auto task = m_task;
      m_task = nullptr;
      if (0 == task->decrement_ref_count()) {
        tbb::task::spawn(*task);
      }
    }
 
  private:
    // ---------- member data --------------------------------
    WaitingTask* m_task;
  };
}  // namespace edm
 
#endif