core/library/application/singleton_application.cpp

   1 /*****************************************************************************\
   2 *                                                                             *
   3 *  Name   : singleton_application                                             *
   4 *  Author : Chris Koeritz                                                     *
   5 *                                                                             *
   6 *******************************************************************************
   7 * Copyright (c) 2006-$now By Author.  This program is free software; you can  *
   8 * redistribute it and/or modify it under the terms of the GNU General Public  *
   9 * License as published by the Free Software Foundation; either version 2 of   *
  10 * the License or (at your option) any later version.  This is online at:      *
  11 *     http://www.fsf.org/copyleft/gpl.html                                    *
  12 * Please send any updates to: fred@gruntose.com                               *
  13 \*****************************************************************************/
  14
  15 #include "singleton_application.h"
  16
  17 #include <basis/functions.h>
  18 #include <filesystem/filename.h>
  19
  20 using namespace basis;
  21 using namespace filesystem;
  22 using namespace processes;
  23
  24 namespace application {
  25
  26 singleton_application::singleton_application(const astring &application_name,
  27     const astring &user_name)
  28 : c_initial_try(0),
  29   _app_lock(new rendezvous(filename(application_name).basename().raw()
  30       + "__" + user_name)),
  31   _got_lock(false)
  32 {
  33 }
  34
  35 singleton_application::~singleton_application()
  36 {
  37   release_lock();
  38   WHACK(_app_lock);
  39 }
  40
  41 bool singleton_application::already_running()
  42 { return !allow_this_instance(); }
  43
  44 bool singleton_application::already_tried() const
  45 { return c_initial_try > 0; }
  46
  47 void singleton_application::release_lock()
  48 {
  49   if (_got_lock) {
  50     _app_lock->unlock();
  51     _got_lock = false;
  52   }
  53 }
  54
  55 bool singleton_application::allow_this_instance()
  56 {
  57   if (_got_lock) return true;  // already grabbed it.
  58
  59   if (!already_tried()) {
  60     _got_lock = _app_lock->lock(rendezvous::IMMEDIATE_RETURN);
  61     if (_got_lock) c_initial_try = 1;  // succeeded in locking.
  62     else c_initial_try = 2;  // failure.
  63   }
  64
  65   return _got_lock;
  66 }
  67
  68 } //namespace.
  69