COIN-OR::LEMON - Graph Library

source: lemon-1.0/lemon/bits/alteration_notifier.h @ 233:28239207a8a3

Last change on this file since 233:28239207a8a3 was 230:af4e8ba94294, checked in by Balazs Dezso <deba@…>, 11 years ago

Fix ImmediateDetach? in AlterationObserver? (ticket #130)

File size: 15.6 KB
Line 
1/* -*- mode: C++; indent-tabs-mode: nil; -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library.
4 *
5 * Copyright (C) 2003-2008
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/core.h>
26
27///\ingroup graphbits
28///\file
29///\brief Observer notifier for graph alteration observers.
30
31namespace 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  template <typename _Container, typename _Item>
99  class AlterationNotifier {
100  public:
101
102    typedef True Notifier;
103
104    typedef _Container Container;
105    typedef _Item Item;
106
107    /// \brief Exception which can be called from \e clear() and
108    /// \e erase().
109    ///
110    /// From the \e clear() and \e erase() function only this
111    /// exception is allowed to throw. The exception immediatly
112    /// detaches the current observer from the notifier. Because the
113    /// \e clear() and \e erase() should not throw other exceptions
114    /// it can be used to invalidate the observer.
115    struct ImmediateDetach {};
116
117    /// \brief ObserverBase is the base class for the observers.
118    ///
119    /// ObserverBase is the abstract base class for the observers.
120    /// It will be notified about an item was inserted into or
121    /// erased from the graph.
122    ///
123    /// The observer interface contains some pure virtual functions
124    /// to override. The add() and erase() functions are
125    /// to notify the oberver when one item is added or
126    /// erased.
127    ///
128    /// The build() and clear() members are to notify the observer
129    /// about the container is built from an empty container or
130    /// is cleared to an empty container.
131
132    class ObserverBase {
133    protected:
134      typedef AlterationNotifier Notifier;
135
136      friend class AlterationNotifier;
137
138      /// \brief Default constructor.
139      ///
140      /// Default constructor for ObserverBase.
141      ///
142      ObserverBase() : _notifier(0) {}
143
144      /// \brief Constructor which attach the observer into notifier.
145      ///
146      /// Constructor which attach the observer into notifier.
147      ObserverBase(AlterationNotifier& nf) {
148        attach(nf);
149      }
150
151      /// \brief Constructor which attach the obserever to the same notifier.
152      ///
153      /// Constructor which attach the obserever to the same notifier as
154      /// the other observer is attached to.
155      ObserverBase(const ObserverBase& copy) {
156        if (copy.attached()) {
157          attach(*copy.notifier());
158        }
159      }
160
161      /// \brief Destructor
162      virtual ~ObserverBase() {
163        if (attached()) {
164          detach();
165        }
166      }
167
168      /// \brief Attaches the observer into an AlterationNotifier.
169      ///
170      /// This member attaches the observer into an AlterationNotifier.
171      ///
172      void attach(AlterationNotifier& nf) {
173        nf.attach(*this);
174      }
175
176      /// \brief Detaches the observer into an AlterationNotifier.
177      ///
178      /// This member detaches the observer from an AlterationNotifier.
179      ///
180      void detach() {
181        _notifier->detach(*this);
182      }
183
184      /// \brief Gives back a pointer to the notifier which the map
185      /// attached into.
186      ///
187      /// This function gives back a pointer to the notifier which the map
188      /// attached into.
189      ///
190      Notifier* notifier() const { return const_cast<Notifier*>(_notifier); }
191
192      /// Gives back true when the observer is attached into a notifier.
193      bool attached() const { return _notifier != 0; }
194
195    private:
196
197      ObserverBase& operator=(const ObserverBase& copy);
198
199    protected:
200
201      Notifier* _notifier;
202      typename std::list<ObserverBase*>::iterator _index;
203
204      /// \brief The member function to notificate the observer about an
205      /// item is added to the container.
206      ///
207      /// The add() member function notificates the observer about an item
208      /// is added to the container. It have to be overrided in the
209      /// subclasses.
210      virtual void add(const Item&) = 0;
211
212      /// \brief The member function to notificate the observer about
213      /// more item is added to the container.
214      ///
215      /// The add() member function notificates the observer about more item
216      /// is added to the container. It have to be overrided in the
217      /// subclasses.
218      virtual void add(const std::vector<Item>& items) = 0;
219
220      /// \brief The member function to notificate the observer about an
221      /// item is erased from the container.
222      ///
223      /// The erase() member function notificates the observer about an
224      /// item is erased from the container. It have to be overrided in
225      /// the subclasses.
226      virtual void erase(const Item&) = 0;
227
228      /// \brief The member function to notificate the observer about
229      /// more item is erased from the container.
230      ///
231      /// The erase() member function notificates the observer about more item
232      /// is erased from the container. It have to be overrided in the
233      /// subclasses.
234      virtual void erase(const std::vector<Item>& items) = 0;
235
236      /// \brief The member function to notificate the observer about the
237      /// container is built.
238      ///
239      /// The build() member function notificates the observer about the
240      /// container is built from an empty container. It have to be
241      /// overrided in the subclasses.
242
243      virtual void build() = 0;
244
245      /// \brief The member function to notificate the observer about all
246      /// items are erased from the container.
247      ///
248      /// The clear() member function notificates the observer about all
249      /// items are erased from the container. It have to be overrided in
250      /// the subclasses.
251      virtual void clear() = 0;
252
253    };
254
255  protected:
256
257    const Container* container;
258
259    typedef std::list<ObserverBase*> Observers;
260    Observers _observers;
261
262
263  public:
264
265    /// \brief Default constructor.
266    ///
267    /// The default constructor of the AlterationNotifier.
268    /// It creates an empty notifier.
269    AlterationNotifier()
270      : container(0) {}
271
272    /// \brief Constructor.
273    ///
274    /// Constructor with the observed container parameter.
275    AlterationNotifier(const Container& _container)
276      : container(&_container) {}
277
278    /// \brief Copy Constructor of the AlterationNotifier.
279    ///
280    /// Copy constructor of the AlterationNotifier.
281    /// It creates only an empty notifier because the copiable
282    /// notifier's observers have to be registered still into that notifier.
283    AlterationNotifier(const AlterationNotifier& _notifier)
284      : container(_notifier.container) {}
285
286    /// \brief Destructor.
287    ///
288    /// Destructor of the AlterationNotifier.
289    ///
290    ~AlterationNotifier() {
291      typename Observers::iterator it;
292      for (it = _observers.begin(); it != _observers.end(); ++it) {
293        (*it)->_notifier = 0;
294      }
295    }
296
297    /// \brief Sets the container.
298    ///
299    /// Sets the container.
300    void setContainer(const Container& _container) {
301      container = &_container;
302    }
303
304  protected:
305
306    AlterationNotifier& operator=(const AlterationNotifier&);
307
308  public:
309
310
311
312    /// \brief First item in the container.
313    ///
314    /// Returns the first item in the container. It is
315    /// for start the iteration on the container.
316    void first(Item& item) const {
317      container->first(item);
318    }
319
320    /// \brief Next item in the container.
321    ///
322    /// Returns the next item in the container. It is
323    /// for iterate on the container.
324    void next(Item& item) const {
325      container->next(item);
326    }
327
328    /// \brief Returns the id of the item.
329    ///
330    /// Returns the id of the item provided by the container.
331    int id(const Item& item) const {
332      return container->id(item);
333    }
334
335    /// \brief Returns the maximum id of the container.
336    ///
337    /// Returns the maximum id of the container.
338    int maxId() const {
339      return container->maxId(Item());
340    }
341
342  protected:
343
344    void attach(ObserverBase& observer) {
345      observer._index = _observers.insert(_observers.begin(), &observer);
346      observer._notifier = this;
347    }
348
349    void detach(ObserverBase& observer) {
350      _observers.erase(observer._index);
351      observer._index = _observers.end();
352      observer._notifier = 0;
353    }
354
355  public:
356
357    /// \brief Notifies all the registed observers about an item added to
358    /// the container.
359    ///
360    /// It notifies all the registed observers about an item added to
361    /// the container.
362    ///
363    void add(const Item& item) {
364      typename Observers::reverse_iterator it;
365      try {
366        for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
367          (*it)->add(item);
368        }
369      } catch (...) {
370        typename Observers::iterator jt;
371        for (jt = it.base(); jt != _observers.end(); ++jt) {
372          (*jt)->erase(item);
373        }
374        throw;
375      }
376    }
377
378    /// \brief Notifies all the registed observers about more item added to
379    /// the container.
380    ///
381    /// It notifies all the registed observers about more item added to
382    /// the container.
383    ///
384    void add(const std::vector<Item>& items) {
385      typename Observers::reverse_iterator it;
386      try {
387        for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
388          (*it)->add(items);
389        }
390      } catch (...) {
391        typename Observers::iterator jt;
392        for (jt = it.base(); jt != _observers.end(); ++jt) {
393          (*jt)->erase(items);
394        }
395        throw;
396      }
397    }
398
399    /// \brief Notifies all the registed observers about an item erased from
400    /// the container.
401    ///
402    /// It notifies all the registed observers about an item erased from
403    /// the container.
404    ///
405    void erase(const Item& item) throw() {
406      typename Observers::iterator it = _observers.begin();
407      while (it != _observers.end()) {
408        try {
409          (*it)->erase(item);
410          ++it;
411        } catch (const ImmediateDetach&) {
412          (*it)->_index = _observers.end();
413          (*it)->_notifier = 0;
414          it = _observers.erase(it);
415        }
416      }
417    }
418
419    /// \brief Notifies all the registed observers about more item erased
420    /// from the container.
421    ///
422    /// It notifies all the registed observers about more item erased from
423    /// the container.
424    ///
425    void erase(const std::vector<Item>& items) {
426      typename Observers::iterator it = _observers.begin();
427      while (it != _observers.end()) {
428        try {
429          (*it)->erase(items);
430          ++it;
431        } catch (const ImmediateDetach&) {
432          (*it)->_index = _observers.end();
433          (*it)->_notifier = 0;
434          it = _observers.erase(it);
435        }
436      }
437    }
438
439    /// \brief Notifies all the registed observers about the container is
440    /// built.
441    ///
442    /// Notifies all the registed observers about the container is built
443    /// from an empty container.
444    void build() {
445      typename Observers::reverse_iterator it;
446      try {
447        for (it = _observers.rbegin(); it != _observers.rend(); ++it) {
448          (*it)->build();
449        }
450      } catch (...) {
451        typename Observers::iterator jt;
452        for (jt = it.base(); jt != _observers.end(); ++jt) {
453          (*jt)->clear();
454        }
455        throw;
456      }
457    }
458
459    /// \brief Notifies all the registed observers about all items are
460    /// erased.
461    ///
462    /// Notifies all the registed observers about all items are erased
463    /// from the container.
464    void clear() {
465      typename Observers::iterator it = _observers.begin();
466      while (it != _observers.end()) {
467        try {
468          (*it)->clear();
469          ++it;
470        } catch (const ImmediateDetach&) {
471          (*it)->_index = _observers.end();
472          (*it)->_notifier = 0;
473          it = _observers.erase(it);
474        }
475      }
476    }
477  };
478
479}
480
481#endif
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