edm::CallOnceNoWait Class Reference

#include "FWCore/Utilities/interface/CallOnceNoWait.h"

Public Member Functions
	CallOnceNoWait ()
template<typename T >
void	operator() (T iCall)

Private Attributes
std::atomic< bool >	m_called

Detailed Description

Description: Thread safe way to do something 1 time

Usage: This class allows one to safely do a 'non-side-effect' operation 1 time in a job. An example use would be

void myFunc( int iValue) {
static CallOnceNoWait message;
message([&]() { edm::LogInfo("IWantToKnow")<<"called with "<<iValue; } );

The important thing to remember, is there is no guarantee that the operation being run finishes before a thread which doesn't get to run the operation reaches the code following the call. Therefore it is useful to suppress messages but should not be used to do something like filling a container with values since the filling is not guaranteed to complete before another thread skips the call.

Definition at line 40 of file CallOnceNoWait.h.

Constructor & Destructor Documentation

edm::CallOnceNoWait::CallOnceNoWait ( )

inline

Definition at line 43 of file CallOnceNoWait.h.

: m_called(false) {}

Member Function Documentation

template<typename T >

void edm::CallOnceNoWait::operator() ( T  iCall )

inline

Definition at line 46 of file CallOnceNoWait.h.

References m_called.

                             {
      bool expected = false;
      if(m_called.compare_exchange_strong(expected, true, std::memory_order_acq_rel)) {
        iCall();
      }
    }

Member Data Documentation

std::atomic<bool> edm::CallOnceNoWait::m_called

private

Definition at line 54 of file CallOnceNoWait.h.

Referenced by operator()().