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iteratoradapter.hxx VIGRA

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35 
36 
37 #ifndef VIGRA_ITERATORADAPTER_HXX
38 #define VIGRA_ITERATORADAPTER_HXX
39 
40 namespace vigra {
41 
42 /********************************************************/
43 /* */
44 /* IteratorAdaptor */
45 /* */
46 /********************************************************/
47 
48 /** \brief Quickly create 1-dimensional iterator adapters.
49 
50  This class supports the easy creation of 1D iterator adapters out
51  of existing iterators. To use it, you must first implement a policy class
52  that defines the iterator's behavior. The policy is used to
53  instantiate the IteratorAdapter template, which thus automatically
54  obtains all required functions of an STL-compatible iterator.
55  General information on how this works can be found on the
56  <a href="http://www.boost.org/libs/utility/iterator_adaptors.htm">Boost Iterator Adaptor</a>
57  page, although there are some differences in the details of the
58  boost and VIGRA implementations.
59  Here is an example policy class that just exports the behaviour
60  of the underlying iterator:
61 
62  \code
63  template <class Iterator>
64  class TrivialIteratorAdaptorPolicy
65  {
66  public:
67  // the underlying iterator
68  typedef Iterator BaseType;
69 
70  // the adaptor's value type
71  typedef typename Iterator::value_type value_type;
72 
73  // the adaptor's difference type (result of 'iter1 - iter2',
74  // argument of 'iter[n]')
75  typedef typename Iterator::difference_type difference_type;
76 
77  // the adaptor's reference type (result of '*iter')
78  typedef typename Iterator::reference reference;
79 
80  // the adaptor's index_reference type (result of 'iter[n]')
81  typedef typename Iterator::index_reference index_reference;
82 
83  // the adaptor's pointer type (result of 'iter.operator->()')
84  typedef typename Iterator::pointer pointer;
85 
86  // the adaptor's iterator category
87  typedef typename Iterator::iterator_category iterator_category;
88 
89  // do some additional initialization in the adaptor's constructor
90  static void initialize(BaseType & d) {}
91 
92  // called by '*iter', 'iter->'
93  static reference dereference(BaseType const & d)
94  { return *d; }
95 
96  // called by 'iter[n]'
97  static index_reference dereference(BaseType d, difference_type n)
98  { return d[n]; }
99 
100  // called by 'iter1 == iter2', 'iter1 != iter2'
101  static bool equal(BaseType const & d1, BaseType const & d2)
102  { return d1 == d2; }
103 
104  // called by 'iter1 < iter2', 'iter1 <= iter2', 'iter1 > iter2', 'iter1 >= iter2'
105  static bool less(BaseType const & d1, BaseType const & d2)
106  { return d1 < d2; }
107 
108  // called by 'iter1 - iter2'
109  static difference_type difference(BaseType const & d1, BaseType const & d2)
110  { return d1 - d2; }
111 
112  // called by '++iter', 'iter++'
113  static void increment(BaseType & d)
114  { ++d; }
115 
116  // called by '--iter', 'iter--'
117  static void decrement(BaseType & d)
118  { --d; }
119 
120  // called by 'iter += n', 'iter -= n'
121  static void advance(BaseType & d, difference_type n)
122  { d += n; }
123  };
124  \endcode
125 
126  This policy class is used like this:
127 
128  \code
129  SomeIterator iter = ...;
130 
131  vigra::IteratorAdaptor<vigra::TrivialIteratorAdaptorPolicy<SomeIterator> > iter_adaptor(iter);
132  \endcode
133 
134  By changing the definition of the policy members, a wide range of
135  adaptor behaviors can be achieved. If the base iterator isn't a
136  random access iterator, just drop the functions that cannot be implemented.
137  This simply means that some adaptor functions may not be called,
138  as one would expect from an iterator that doesn't support random access.
139  Note also that the <TT>BaseType</TT> needs not be an iterator -
140  it can be any type that contains the information necessary for the
141  adaptor to do it's work.
142 
143  <b>\#include</b> <vigra/iteratoradapter.hxx><br>
144  Namespace: vigra
145 
146 */
147 template <class Policy>
149 {
150  public:
151 
152  typedef typename Policy::BaseType BaseType;
153  typedef typename Policy::value_type value_type;
154  typedef typename Policy::difference_type difference_type;
155  typedef typename Policy::reference reference;
156  typedef typename Policy::index_reference index_reference;
157  typedef typename Policy::pointer pointer;
158  typedef typename Policy::iterator_category iterator_category;
159 
161  : adaptee_()
162  {}
163 
164  /** Construct from an instance of the policy class' BaseType
165  Note that the functions of the adaptor implement the
166  interface of an random access iterator as defined in the
167  C++ standard, so there is no need for explicit documentation.
168  */
169  explicit IteratorAdaptor(BaseType const & o)
170  : adaptee_(o)
171  {
172  Policy::initialize(adaptee_);
173  }
174 
176  : adaptee_(o.adaptee_)
177  {}
178 
179  IteratorAdaptor & operator=(BaseType const & o)
180  {
181  if(this != &o)
182  {
183  adaptee_ = o;
184  Policy::initialize(adaptee_);
185  }
186  return *this;
187  }
188 
189  IteratorAdaptor & operator=(IteratorAdaptor const & o)
190  {
191  if(this != &o)
192  adaptee_ = o.adaptee_;
193  return *this;
194  }
195 
196  IteratorAdaptor & operator+=(difference_type d)
197  {
198  Policy::advance(adaptee_, d);
199  return *this;
200  }
201 
202  IteratorAdaptor operator+(difference_type d) const
203  {
204  return IteratorAdaptor(*this) += d;
205  }
206 
207  IteratorAdaptor & operator-=(difference_type d)
208  {
209  Policy::advance(adaptee_, -d);
210  return *this;
211  }
212 
213  IteratorAdaptor operator-(difference_type d) const
214  {
215  return IteratorAdaptor(*this) -= d;
216  }
217 
218  IteratorAdaptor & operator++()
219  {
220  Policy::increment(adaptee_);
221  return *this;
222  }
223 
224  IteratorAdaptor operator++(int)
225  {
226  IteratorAdaptor res(*this);
227  Policy::increment(adaptee_);
228  return res;
229  }
230 
231  IteratorAdaptor & operator--()
232  {
233  Policy::decrement(adaptee_);
234  return *this;
235  }
236 
237  IteratorAdaptor operator--(int)
238  {
239  IteratorAdaptor res(*this);
240  Policy::decrement(adaptee_);
241  return res;
242  }
243 
244  bool operator==(IteratorAdaptor const & o) const
245  {
246  return Policy::equal(adaptee_, o.adaptee_);
247  }
248 
249  bool operator!=(IteratorAdaptor const & o) const
250  {
251  return !Policy::equal(adaptee_, o.adaptee_);
252  }
253 
254  bool operator<(IteratorAdaptor const & o) const
255  {
256  return Policy::less(adaptee_, o.adaptee_);
257  }
258 
259  bool operator<=(IteratorAdaptor const & o) const
260  {
261  return !Policy::less(o.adaptee_, adaptee_);
262  }
263 
264  bool operator>(IteratorAdaptor const & o) const
265  {
266  return Policy::less(o.adaptee_, adaptee_);
267  }
268 
269  bool operator>=(IteratorAdaptor const & o) const
270  {
271  return !Policy::less(adaptee_, o.adaptee_);
272  }
273 
274  difference_type operator-(IteratorAdaptor const & o) const
275  {
276  return Policy::difference(adaptee_, o.adaptee_);
277  }
278 
279  reference operator*() const
280  {
281  return Policy::dereference(adaptee_);
282  }
283 
284  index_reference operator[](difference_type d) const
285  {
286  return Policy::dereference(adaptee_, d);
287  }
288 
289  pointer operator->() const
290  {
291  return &Policy::dereference(adaptee_);
292  }
293 
294  protected:
295 
296  BaseType adaptee_;
297 };
298 
299 } // namespace vigra
300 
301 
302 #endif /* VIGRA_ITERATORADAPTER_HXX */
IteratorAdaptor(BaseType const &o)
Definition: iteratoradapter.hxx:169
Quickly create 1-dimensional iterator adapters.
Definition: iteratoradapter.hxx:148

© Ullrich Köthe (ullrich.koethe@iwr.uni-heidelberg.de)
Heidelberg Collaboratory for Image Processing, University of Heidelberg, Germany

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