g2log: An efficient asynchronous logger using C++11

/** ==========================================================================
* 2010 by KjellKod.cc. This is PUBLIC DOMAIN to use at your own risk and comes
* with no warranties. This code is yours to share, use and modify with no
* strings attached and no restrictions or obligations.
* ============================================================================
*
* Example of a Active Object, using C++0x std::thread mechanisms to make it
* safe for thread communication.
*
* This was originally published at http://sites.google.com/site/kjellhedstrom2/active-object-with-cpp0x
* and inspired from Herb Sutter's C++0x Active Object
* http://herbsutter.com/2010/07/12/effective-concurrency-prefer-using-active-objects-instead-of-naked-threads
*
* The code below uses JustSoftware Solutions Inc std::thread implementation
* http://www.justsoftwaresolutions.co.uk
*
* Last update 2011-06-23, by Kjell Hedstrom,
* e-mail: hedstrom at kjellkod dot cc
* linkedin: http://linkedin.com/se/kjellkod */


#include "active.h"
#include <cassert>

using namespace kjellkod;

Active::Active(): done_(false){}

Active::~Active() {
  Callback quit_token = std::bind(&Active::doDone, this);
  send(quit_token); // tell thread to exit
  thd_.join();
}

// Add asynchronously a work-message to queue
void Active::send(Callback msg_){
  mq_.push(msg_);
}


// Will wait for msgs if queue is empty
// A great explanation of how this is done (using Qt's library):
// http://doc.qt.nokia.com/stable/qwaitcondition.html
void Active::run() {
  while (!done_) {
    // wait till job is available, then retrieve it and
    // executes the retrieved job in this thread (background)
    Callback func;
    mq_.wait_and_pop(func);
    func();
  }
}

// Factory: safe construction of object before thread start
std::unique_ptr<Active> Active::createActive(){
  std::unique_ptr<Active> aPtr(new Active());
  aPtr->thd_ = std::thread(&Active::run, aPtr.get());
  return aPtr;
}