lemon/bits/alteration_notifier.h
author Alpar Juttner <alpar@cs.elte.hu>
Fri, 25 Jan 2008 14:52:50 +0000
changeset 63 1113f6d12c0c
child 107 31a2e6d28f61
permissions -rw-r--r--
Merge
     1 /* -*- C++ -*-
     2  *
     3  * This file is a part of LEMON, a generic C++ optimization library
     4  *
     5  * Copyright (C) 2003-2007
     6  * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
     7  * (Egervary Research Group on Combinatorial Optimization, EGRES).
     8  *
     9  * Permission to use, modify and distribute this software is granted
    10  * provided that this copyright notice appears in all copies. For
    11  * precise terms see the accompanying LICENSE file.
    12  *
    13  * This software is provided "AS IS" with no warranty of any kind,
    14  * express or implied, and with no claim as to its suitability for any
    15  * purpose.
    16  *
    17  */
    18 
    19 #ifndef LEMON_BITS_ALTERATION_NOTIFIER_H
    20 #define LEMON_BITS_ALTERATION_NOTIFIER_H
    21 
    22 #include <vector>
    23 #include <list>
    24 
    25 #include <lemon/bits/utility.h>
    26 
    27 ///\ingroup graphbits
    28 ///\file
    29 ///\brief Observer notifier for graph alteration observers.
    30 
    31 namespace lemon {
    32 
    33   /// \ingroup graphbits
    34   ///
    35   /// \brief Notifier class to notify observes about alterations in 
    36   /// a container.
    37   ///
    38   /// The simple graph's can be refered as two containers, one node container
    39   /// and one edge container. But they are not standard containers they
    40   /// does not store values directly they are just key continars for more
    41   /// value containers which are the node and edge maps.
    42   ///
    43   /// The graph's node and edge sets can be changed as we add or erase
    44   /// nodes and edges in the graph. Lemon would like to handle easily
    45   /// that the node and edge maps should contain values for all nodes or
    46   /// edges. If we want to check on every indicing if the map contains
    47   /// the current indicing key that cause a drawback in the performance
    48   /// in the library. We use another solution we notify all maps about
    49   /// an alteration in the graph, which cause only drawback on the
    50   /// alteration of the graph.
    51   ///
    52   /// This class provides an interface to the container. The \e first() and \e 
    53   /// next() member functions make possible to iterate on the keys of the
    54   /// container. The \e id() function returns an integer id for each key.
    55   /// The \e maxId() function gives back an upper bound of the ids.
    56   ///
    57   /// For the proper functonality of this class, we should notify it
    58   /// about each alteration in the container. The alterations have four type
    59   /// as \e add(), \e erase(), \e build() and \e clear(). The \e add() and
    60   /// \e erase() signals that only one or few items added or erased to or
    61   /// from the graph. If all items are erased from the graph or from an empty
    62   /// graph a new graph is builded then it can be signaled with the
    63   /// clear() and build() members. Important rule that if we erase items 
    64   /// from graph we should first signal the alteration and after that erase
    65   /// them from the container, on the other way on item addition we should
    66   /// first extend the container and just after that signal the alteration.
    67   ///
    68   /// The alteration can be observed with a class inherited from the
    69   /// \e ObserverBase nested class. The signals can be handled with
    70   /// overriding the virtual functions defined in the base class.  The
    71   /// observer base can be attached to the notifier with the 
    72   /// \e attach() member and can be detached with detach() function. The
    73   /// alteration handlers should not call any function which signals
    74   /// an other alteration in the same notifier and should not
    75   /// detach any observer from the notifier.
    76   ///
    77   /// Alteration observers try to be exception safe. If an \e add() or
    78   /// a \e clear() function throws an exception then the remaining
    79   /// observeres will not be notified and the fulfilled additions will
    80   /// be rolled back by calling the \e erase() or \e clear()
    81   /// functions. Thence the \e erase() and \e clear() should not throw
    82   /// exception. Actullay, it can be throw only 
    83   /// \ref AlterationObserver::ImmediateDetach ImmediateDetach
    84   /// exception which detach the observer from the notifier.
    85   ///
    86   /// There are some place when the alteration observing is not completly
    87   /// reliable. If we want to carry out the node degree in the graph
    88   /// as in the \ref InDegMap and we use the reverseEdge that cause 
    89   /// unreliable functionality. Because the alteration observing signals
    90   /// only erasing and adding but not the reversing it will stores bad
    91   /// degrees. The sub graph adaptors cannot signal the alterations because
    92   /// just a setting in the filter map can modify the graph and this cannot
    93   /// be watched in any way.
    94   ///
    95   /// \param _Container The container which is observed.
    96   /// \param _Item The item type which is obserbved.
    97   ///
    98   /// \author Balazs Dezso
    99 
   100   template <typename _Container, typename _Item>
   101   class AlterationNotifier {
   102   public:
   103 
   104     typedef True Notifier;
   105 
   106     typedef _Container Container;
   107     typedef _Item Item;
   108 
   109     /// \brief Exception which can be called from \e clear() and 
   110     /// \e erase().
   111     ///
   112     /// From the \e clear() and \e erase() function only this
   113     /// exception is allowed to throw. The exception immediatly
   114     /// detaches the current observer from the notifier. Because the
   115     /// \e clear() and \e erase() should not throw other exceptions
   116     /// it can be used to invalidate the observer.
   117     struct ImmediateDetach {};
   118 
   119     /// \brief ObserverBase is the base class for the observers.
   120     ///
   121     /// ObserverBase is the abstract base class for the observers.
   122     /// It will be notified about an item was inserted into or
   123     /// erased from the graph.
   124     ///
   125     /// The observer interface contains some pure virtual functions
   126     /// to override. The add() and erase() functions are
   127     /// to notify the oberver when one item is added or
   128     /// erased.
   129     ///
   130     /// The build() and clear() members are to notify the observer
   131     /// about the container is built from an empty container or
   132     /// is cleared to an empty container. 
   133     /// 
   134     /// \author Balazs Dezso
   135 
   136     class ObserverBase {
   137     protected:
   138       typedef AlterationNotifier Notifier;
   139 
   140       friend class AlterationNotifier;
   141 
   142       /// \brief Default constructor.
   143       ///
   144       /// Default constructor for ObserverBase.
   145       /// 
   146       ObserverBase() : _notifier(0) {}
   147 
   148       /// \brief Constructor which attach the observer into notifier.
   149       ///
   150       /// Constructor which attach the observer into notifier.
   151       ObserverBase(AlterationNotifier& nf) {
   152         attach(nf);
   153       }
   154 
   155       /// \brief Constructor which attach the obserever to the same notifier.
   156       ///
   157       /// Constructor which attach the obserever to the same notifier as
   158       /// the other observer is attached to. 
   159       ObserverBase(const ObserverBase& copy) {
   160 	if (copy.attached()) {
   161           attach(*copy.notifier());
   162 	}
   163       }
   164 	
   165       /// \brief Destructor
   166       virtual ~ObserverBase() {
   167         if (attached()) {
   168           detach();
   169         }
   170       }
   171 
   172       /// \brief Attaches the observer into an AlterationNotifier.
   173       ///
   174       /// This member attaches the observer into an AlterationNotifier.
   175       ///
   176       void attach(AlterationNotifier& nf) {
   177 	nf.attach(*this);
   178       }
   179       
   180       /// \brief Detaches the observer into an AlterationNotifier.
   181       ///
   182       /// This member detaches the observer from an AlterationNotifier.
   183       ///
   184       void detach() {
   185         _notifier->detach(*this);
   186       }
   187       
   188       /// \brief Gives back a pointer to the notifier which the map 
   189       /// attached into.
   190       ///
   191       /// This function gives back a pointer to the notifier which the map
   192       /// attached into.
   193       ///
   194       Notifier* notifier() const { return const_cast<Notifier*>(_notifier); }
   195       
   196       /// Gives back true when the observer is attached into a notifier.
   197       bool attached() const { return _notifier != 0; }
   198 
   199     private:
   200 
   201       ObserverBase& operator=(const ObserverBase& copy);
   202 
   203     protected:
   204       
   205       Notifier* _notifier;
   206       typename std::list<ObserverBase*>::iterator _index;
   207 
   208       /// \brief The member function to notificate the observer about an
   209       /// item is added to the container.
   210       ///
   211       /// The add() member function notificates the observer about an item
   212       /// is added to the container. It have to be overrided in the
   213       /// subclasses.
   214       virtual void add(const Item&) = 0;
   215 
   216       /// \brief The member function to notificate the observer about 
   217       /// more item is added to the container.
   218       ///
   219       /// The add() member function notificates the observer about more item
   220       /// is added to the container. It have to be overrided in the
   221       /// subclasses.
   222       virtual void add(const std::vector<Item>& items) = 0;
   223 
   224       /// \brief The member function to notificate the observer about an
   225       /// item is erased from the container.
   226       ///
   227       /// The erase() member function notificates the observer about an
   228       /// item is erased from the container. It have to be overrided in
   229       /// the subclasses.	
   230       virtual void erase(const Item&) = 0;
   231 
   232       /// \brief The member function to notificate the observer about 
   233       /// more item is erased from the container.
   234       ///
   235       /// The erase() member function notificates the observer about more item
   236       /// is erased from the container. It have to be overrided in the
   237       /// subclasses.
   238       virtual void erase(const std::vector<Item>& items) = 0;
   239 
   240       /// \brief The member function to notificate the observer about the
   241       /// container is built.
   242       ///
   243       /// The build() member function notificates the observer about the
   244       /// container is built from an empty container. It have to be
   245       /// overrided in the subclasses.
   246 
   247       virtual void build() = 0;
   248 
   249       /// \brief The member function to notificate the observer about all
   250       /// items are erased from the container.
   251       ///
   252       /// The clear() member function notificates the observer about all
   253       /// items are erased from the container. It have to be overrided in
   254       /// the subclasses.      
   255       virtual void clear() = 0;
   256 
   257     };
   258 	
   259   protected:
   260 
   261     const Container* container;
   262 
   263     typedef std::list<ObserverBase*> Observers; 
   264     Observers _observers;
   265 
   266 		
   267   public:
   268 
   269     /// \brief Default constructor.
   270     ///
   271     /// The default constructor of the AlterationNotifier. 
   272     /// It creates an empty notifier.
   273     AlterationNotifier() 
   274       : container(0) {}
   275 
   276     /// \brief Constructor.
   277     ///
   278     /// Constructor with the observed container parameter.
   279     AlterationNotifier(const Container& _container) 
   280       : container(&_container) {}
   281 
   282     /// \brief Copy Constructor of the AlterationNotifier. 
   283     ///
   284     /// Copy constructor of the AlterationNotifier. 
   285     /// It creates only an empty notifier because the copiable
   286     /// notifier's observers have to be registered still into that notifier.
   287     AlterationNotifier(const AlterationNotifier& _notifier) 
   288       : container(_notifier.container) {}
   289 
   290     /// \brief Destructor.
   291     ///		
   292     /// Destructor of the AlterationNotifier.
   293     ///
   294     ~AlterationNotifier() {
   295       typename Observers::iterator it;
   296       for (it = _observers.begin(); it != _observers.end(); ++it) {
   297 	(*it)->_notifier = 0;
   298       }
   299     }
   300 
   301     /// \brief Sets the container.
   302     ///
   303     /// Sets the container.
   304     void setContainer(const Container& _container) {
   305       container = &_container;
   306     }
   307 
   308   protected:
   309 
   310     AlterationNotifier& operator=(const AlterationNotifier&);
   311 
   312   public:
   313 
   314 
   315 
   316     /// \brief First item in the container.
   317     ///
   318     /// Returns the first item in the container. It is
   319     /// for start the iteration on the container.
   320     void first(Item& item) const {
   321       container->first(item);
   322     }
   323 
   324     /// \brief Next item in the container.
   325     ///
   326     /// Returns the next item in the container. It is
   327     /// for iterate on the container.
   328     void next(Item& item) const {
   329       container->next(item);
   330     }
   331 
   332     /// \brief Returns the id of the item.
   333     ///
   334     /// Returns the id of the item provided by the container.
   335     int id(const Item& item) const {
   336       return container->id(item);
   337     }
   338 
   339     /// \brief Returns the maximum id of the container.
   340     ///
   341     /// Returns the maximum id of the container.
   342     int maxId() const {
   343       return container->maxId(Item());
   344     }
   345 		
   346   protected:
   347 
   348     void attach(ObserverBase& observer) {
   349       observer._index = _observers.insert(_observers.begin(), &observer);
   350       observer._notifier = this;
   351     } 
   352 
   353     void detach(ObserverBase& observer) {
   354       _observers.erase(observer._index);
   355       observer._index = _observers.end();
   356       observer._notifier = 0;
   357     }
   358 
   359   public:
   360 	
   361     /// \brief Notifies all the registed observers about an item added to 
   362     /// the container.
   363     ///
   364     /// It notifies all the registed observers about an item added to 
   365     /// the container.
   366     /// 
   367     void add(const Item& item) {
   368       typename Observers::reverse_iterator it;
   369       try {
   370         for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
   371           (*it)->add(item);
   372         }
   373       } catch (...) {
   374         typename Observers::iterator jt;
   375         for (jt = it.base(); jt != _observers.end(); ++jt) {
   376           (*jt)->erase(item);
   377         }
   378         throw;
   379       }
   380     }	
   381 
   382     /// \brief Notifies all the registed observers about more item added to 
   383     /// the container.
   384     ///
   385     /// It notifies all the registed observers about more item added to 
   386     /// the container.
   387     /// 
   388     void add(const std::vector<Item>& items) {
   389       typename Observers::reverse_iterator it;
   390       try {
   391         for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
   392           (*it)->add(items);
   393         }
   394       } catch (...) {
   395         typename Observers::iterator jt;
   396         for (jt = it.base(); jt != _observers.end(); ++jt) {
   397           (*jt)->erase(items);
   398         }
   399         throw;
   400       }
   401     }	
   402 
   403     /// \brief Notifies all the registed observers about an item erased from 
   404     /// the container.
   405     ///	
   406     /// It notifies all the registed observers about an item erased from 
   407     /// the container.
   408     /// 
   409     void erase(const Item& item) throw() {
   410       typename Observers::iterator it = _observers.begin();
   411       while (it != _observers.end()) {
   412         try {
   413           (*it)->erase(item);
   414           ++it;
   415         } catch (const ImmediateDetach&) {
   416           it = _observers.erase(it);
   417           (*it)->_index = _observers.end();
   418           (*it)->_notifier = 0;
   419         }
   420       }
   421     }
   422 
   423     /// \brief Notifies all the registed observers about more item erased  
   424     /// from the container.
   425     ///	
   426     /// It notifies all the registed observers about more item erased from 
   427     /// the container.
   428     /// 
   429     void erase(const std::vector<Item>& items) {
   430       typename Observers::iterator it = _observers.begin();
   431       while (it != _observers.end()) {
   432         try {
   433           (*it)->erase(items);
   434           ++it;
   435         } catch (const ImmediateDetach&) {
   436           it = _observers.erase(it);
   437           (*it)->_index = _observers.end();
   438           (*it)->_notifier = 0;
   439         }
   440       }
   441     }
   442 
   443     /// \brief Notifies all the registed observers about the container is 
   444     /// built.
   445     ///		
   446     /// Notifies all the registed observers about the container is built
   447     /// from an empty container.
   448     void build() {
   449       typename Observers::reverse_iterator it;
   450       try {
   451         for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
   452           (*it)->build();
   453         }
   454       } catch (...) {
   455         typename Observers::iterator jt;
   456         for (jt = it.base(); jt != _observers.end(); ++jt) {
   457           (*jt)->clear();
   458         }
   459         throw;
   460       }
   461     }
   462 
   463     /// \brief Notifies all the registed observers about all items are 
   464     /// erased.
   465     ///
   466     /// Notifies all the registed observers about all items are erased
   467     /// from the container.
   468     void clear() {
   469       typename Observers::iterator it = _observers.begin();
   470       while (it != _observers.end()) {
   471         try {
   472           (*it)->clear();
   473           ++it;
   474         } catch (const ImmediateDetach&) {
   475           it = _observers.erase(it);
   476           (*it)->_index = _observers.end();
   477           (*it)->_notifier = 0;
   478         }
   479       }
   480     }
   481   };
   482 
   483 }
   484 
   485 #endif