LLVM  8.0.1
iterator.h
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1 //===- iterator.h - Utilities for using and defining iterators --*- C++ -*-===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #ifndef LLVM_ADT_ITERATOR_H
11 #define LLVM_ADT_ITERATOR_H
12 
14 #include <algorithm>
15 #include <cstddef>
16 #include <iterator>
17 #include <type_traits>
18 #include <utility>
19 
20 namespace llvm {
21 
22 /// CRTP base class which implements the entire standard iterator facade
23 /// in terms of a minimal subset of the interface.
24 ///
25 /// Use this when it is reasonable to implement most of the iterator
26 /// functionality in terms of a core subset. If you need special behavior or
27 /// there are performance implications for this, you may want to override the
28 /// relevant members instead.
29 ///
30 /// Note, one abstraction that this does *not* provide is implementing
31 /// subtraction in terms of addition by negating the difference. Negation isn't
32 /// always information preserving, and I can see very reasonable iterator
33 /// designs where this doesn't work well. It doesn't really force much added
34 /// boilerplate anyways.
35 ///
36 /// Another abstraction that this doesn't provide is implementing increment in
37 /// terms of addition of one. These aren't equivalent for all iterator
38 /// categories, and respecting that adds a lot of complexity for little gain.
39 ///
40 /// Classes wishing to use `iterator_facade_base` should implement the following
41 /// methods:
42 ///
43 /// Forward Iterators:
44 /// (All of the following methods)
45 /// - DerivedT &operator=(const DerivedT &R);
46 /// - bool operator==(const DerivedT &R) const;
47 /// - const T &operator*() const;
48 /// - T &operator*();
49 /// - DerivedT &operator++();
50 ///
51 /// Bidirectional Iterators:
52 /// (All methods of forward iterators, plus the following)
53 /// - DerivedT &operator--();
54 ///
55 /// Random-access Iterators:
56 /// (All methods of bidirectional iterators excluding the following)
57 /// - DerivedT &operator++();
58 /// - DerivedT &operator--();
59 /// (and plus the following)
60 /// - bool operator<(const DerivedT &RHS) const;
61 /// - DifferenceTypeT operator-(const DerivedT &R) const;
62 /// - DerivedT &operator+=(DifferenceTypeT N);
63 /// - DerivedT &operator-=(DifferenceTypeT N);
64 ///
65 template <typename DerivedT, typename IteratorCategoryT, typename T,
66  typename DifferenceTypeT = std::ptrdiff_t, typename PointerT = T *,
67  typename ReferenceT = T &>
69  : public std::iterator<IteratorCategoryT, T, DifferenceTypeT, PointerT,
70  ReferenceT> {
71 protected:
72  enum {
73  IsRandomAccess = std::is_base_of<std::random_access_iterator_tag,
74  IteratorCategoryT>::value,
75  IsBidirectional = std::is_base_of<std::bidirectional_iterator_tag,
76  IteratorCategoryT>::value,
77  };
78 
79  /// A proxy object for computing a reference via indirecting a copy of an
80  /// iterator. This is used in APIs which need to produce a reference via
81  /// indirection but for which the iterator object might be a temporary. The
82  /// proxy preserves the iterator internally and exposes the indirected
83  /// reference via a conversion operator.
85  friend iterator_facade_base;
86 
87  DerivedT I;
88 
89  ReferenceProxy(DerivedT I) : I(std::move(I)) {}
90 
91  public:
92  operator ReferenceT() const { return *I; }
93  };
94 
95 public:
96  DerivedT operator+(DifferenceTypeT n) const {
97  static_assert(std::is_base_of<iterator_facade_base, DerivedT>::value,
98  "Must pass the derived type to this template!");
99  static_assert(
101  "The '+' operator is only defined for random access iterators.");
102  DerivedT tmp = *static_cast<const DerivedT *>(this);
103  tmp += n;
104  return tmp;
105  }
106  friend DerivedT operator+(DifferenceTypeT n, const DerivedT &i) {
107  static_assert(
109  "The '+' operator is only defined for random access iterators.");
110  return i + n;
111  }
112  DerivedT operator-(DifferenceTypeT n) const {
113  static_assert(
115  "The '-' operator is only defined for random access iterators.");
116  DerivedT tmp = *static_cast<const DerivedT *>(this);
117  tmp -= n;
118  return tmp;
119  }
120 
121  DerivedT &operator++() {
122  static_assert(std::is_base_of<iterator_facade_base, DerivedT>::value,
123  "Must pass the derived type to this template!");
124  return static_cast<DerivedT *>(this)->operator+=(1);
125  }
126  DerivedT operator++(int) {
127  DerivedT tmp = *static_cast<DerivedT *>(this);
128  ++*static_cast<DerivedT *>(this);
129  return tmp;
130  }
131  DerivedT &operator--() {
132  static_assert(
134  "The decrement operator is only defined for bidirectional iterators.");
135  return static_cast<DerivedT *>(this)->operator-=(1);
136  }
137  DerivedT operator--(int) {
138  static_assert(
140  "The decrement operator is only defined for bidirectional iterators.");
141  DerivedT tmp = *static_cast<DerivedT *>(this);
142  --*static_cast<DerivedT *>(this);
143  return tmp;
144  }
145 
146  bool operator!=(const DerivedT &RHS) const {
147  return !static_cast<const DerivedT *>(this)->operator==(RHS);
148  }
149 
150  bool operator>(const DerivedT &RHS) const {
151  static_assert(
153  "Relational operators are only defined for random access iterators.");
154  return !static_cast<const DerivedT *>(this)->operator<(RHS) &&
155  !static_cast<const DerivedT *>(this)->operator==(RHS);
156  }
157  bool operator<=(const DerivedT &RHS) const {
158  static_assert(
160  "Relational operators are only defined for random access iterators.");
161  return !static_cast<const DerivedT *>(this)->operator>(RHS);
162  }
163  bool operator>=(const DerivedT &RHS) const {
164  static_assert(
166  "Relational operators are only defined for random access iterators.");
167  return !static_cast<const DerivedT *>(this)->operator<(RHS);
168  }
169 
170  PointerT operator->() { return &static_cast<DerivedT *>(this)->operator*(); }
171  PointerT operator->() const {
172  return &static_cast<const DerivedT *>(this)->operator*();
173  }
174  ReferenceProxy operator[](DifferenceTypeT n) {
175  static_assert(IsRandomAccess,
176  "Subscripting is only defined for random access iterators.");
177  return ReferenceProxy(static_cast<DerivedT *>(this)->operator+(n));
178  }
179  ReferenceProxy operator[](DifferenceTypeT n) const {
180  static_assert(IsRandomAccess,
181  "Subscripting is only defined for random access iterators.");
182  return ReferenceProxy(static_cast<const DerivedT *>(this)->operator+(n));
183  }
184 };
185 
186 /// CRTP base class for adapting an iterator to a different type.
187 ///
188 /// This class can be used through CRTP to adapt one iterator into another.
189 /// Typically this is done through providing in the derived class a custom \c
190 /// operator* implementation. Other methods can be overridden as well.
191 template <
192  typename DerivedT, typename WrappedIteratorT,
193  typename IteratorCategoryT =
194  typename std::iterator_traits<WrappedIteratorT>::iterator_category,
195  typename T = typename std::iterator_traits<WrappedIteratorT>::value_type,
196  typename DifferenceTypeT =
197  typename std::iterator_traits<WrappedIteratorT>::difference_type,
198  typename PointerT = typename std::conditional<
199  std::is_same<T, typename std::iterator_traits<
200  WrappedIteratorT>::value_type>::value,
201  typename std::iterator_traits<WrappedIteratorT>::pointer, T *>::type,
202  typename ReferenceT = typename std::conditional<
203  std::is_same<T, typename std::iterator_traits<
204  WrappedIteratorT>::value_type>::value,
205  typename std::iterator_traits<WrappedIteratorT>::reference, T &>::type>
207  : public iterator_facade_base<DerivedT, IteratorCategoryT, T,
208  DifferenceTypeT, PointerT, ReferenceT> {
209  using BaseT = typename iterator_adaptor_base::iterator_facade_base;
210 
211 protected:
212  WrappedIteratorT I;
213 
214  iterator_adaptor_base() = default;
215 
216  explicit iterator_adaptor_base(WrappedIteratorT u) : I(std::move(u)) {
217  static_assert(std::is_base_of<iterator_adaptor_base, DerivedT>::value,
218  "Must pass the derived type to this template!");
219  }
220 
221  const WrappedIteratorT &wrapped() const { return I; }
222 
223 public:
224  using difference_type = DifferenceTypeT;
225 
227  static_assert(
228  BaseT::IsRandomAccess,
229  "The '+=' operator is only defined for random access iterators.");
230  I += n;
231  return *static_cast<DerivedT *>(this);
232  }
234  static_assert(
235  BaseT::IsRandomAccess,
236  "The '-=' operator is only defined for random access iterators.");
237  I -= n;
238  return *static_cast<DerivedT *>(this);
239  }
240  using BaseT::operator-;
241  difference_type operator-(const DerivedT &RHS) const {
242  static_assert(
243  BaseT::IsRandomAccess,
244  "The '-' operator is only defined for random access iterators.");
245  return I - RHS.I;
246  }
247 
248  // We have to explicitly provide ++ and -- rather than letting the facade
249  // forward to += because WrappedIteratorT might not support +=.
250  using BaseT::operator++;
251  DerivedT &operator++() {
252  ++I;
253  return *static_cast<DerivedT *>(this);
254  }
255  using BaseT::operator--;
256  DerivedT &operator--() {
257  static_assert(
258  BaseT::IsBidirectional,
259  "The decrement operator is only defined for bidirectional iterators.");
260  --I;
261  return *static_cast<DerivedT *>(this);
262  }
263 
264  bool operator==(const DerivedT &RHS) const { return I == RHS.I; }
265  bool operator<(const DerivedT &RHS) const {
266  static_assert(
267  BaseT::IsRandomAccess,
268  "Relational operators are only defined for random access iterators.");
269  return I < RHS.I;
270  }
271 
272  ReferenceT operator*() const { return *I; }
273 };
274 
275 /// An iterator type that allows iterating over the pointees via some
276 /// other iterator.
277 ///
278 /// The typical usage of this is to expose a type that iterates over Ts, but
279 /// which is implemented with some iterator over T*s:
280 ///
281 /// \code
282 /// using iterator = pointee_iterator<SmallVectorImpl<T *>::iterator>;
283 /// \endcode
284 template <typename WrappedIteratorT,
285  typename T = typename std::remove_reference<
286  decltype(**std::declval<WrappedIteratorT>())>::type>
289  pointee_iterator<WrappedIteratorT, T>, WrappedIteratorT,
290  typename std::iterator_traits<WrappedIteratorT>::iterator_category,
291  T> {
292  pointee_iterator() = default;
293  template <typename U>
295  : pointee_iterator::iterator_adaptor_base(std::forward<U &&>(u)) {}
296 
297  T &operator*() const { return **this->I; }
298 };
299 
300 template <typename RangeT, typename WrappedIteratorT =
301  decltype(std::begin(std::declval<RangeT>()))>
303 make_pointee_range(RangeT &&Range) {
304  using PointeeIteratorT = pointee_iterator<WrappedIteratorT>;
305  return make_range(PointeeIteratorT(std::begin(std::forward<RangeT>(Range))),
306  PointeeIteratorT(std::end(std::forward<RangeT>(Range))));
307 }
308 
309 template <typename WrappedIteratorT,
310  typename T = decltype(&*std::declval<WrappedIteratorT>())>
312  : public iterator_adaptor_base<
313  pointer_iterator<WrappedIteratorT, T>, WrappedIteratorT,
314  typename std::iterator_traits<WrappedIteratorT>::iterator_category,
315  T> {
316  mutable T Ptr;
317 
318 public:
319  pointer_iterator() = default;
320 
321  explicit pointer_iterator(WrappedIteratorT u)
323 
324  T &operator*() { return Ptr = &*this->I; }
325  const T &operator*() const { return Ptr = &*this->I; }
326 };
327 
328 template <typename RangeT, typename WrappedIteratorT =
329  decltype(std::begin(std::declval<RangeT>()))>
331 make_pointer_range(RangeT &&Range) {
332  using PointerIteratorT = pointer_iterator<WrappedIteratorT>;
333  return make_range(PointerIteratorT(std::begin(std::forward<RangeT>(Range))),
334  PointerIteratorT(std::end(std::forward<RangeT>(Range))));
335 }
336 
337 // Wrapper iterator over iterator ItType, adding DataRef to the type of ItType,
338 // to create NodeRef = std::pair<InnerTypeOfItType, DataRef>.
339 template <typename ItType, typename NodeRef, typename DataRef>
341  : public iterator_adaptor_base<
342  WrappedPairNodeDataIterator<ItType, NodeRef, DataRef>, ItType,
343  typename std::iterator_traits<ItType>::iterator_category, NodeRef,
344  std::ptrdiff_t, NodeRef *, NodeRef &> {
347  typename std::iterator_traits<ItType>::iterator_category, NodeRef,
348  std::ptrdiff_t, NodeRef *, NodeRef &>;
349 
350  const DataRef DR;
351  mutable NodeRef NR;
352 
353 public:
354  WrappedPairNodeDataIterator(ItType Begin, const DataRef DR)
355  : BaseT(Begin), DR(DR) {
356  NR.first = DR;
357  }
358 
359  NodeRef &operator*() const {
360  NR.second = *this->I;
361  return NR;
362  }
363 };
364 
365 } // end namespace llvm
366 
367 #endif // LLVM_ADT_ITERATOR_H
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:259
DerivedT operator-(DifferenceTypeT n) const
Definition: iterator.h:112
const_iterator begin(StringRef path, Style style=Style::native)
Get begin iterator over path.
Definition: Path.cpp:250
bool operator==(const DerivedT &RHS) const
Definition: iterator.h:264
This class represents lattice values for constants.
Definition: AllocatorList.h:24
bool operator!=(const DerivedT &RHS) const
Definition: iterator.h:146
ReferenceT operator*() const
Definition: iterator.h:272
bool operator>=(const DerivedT &RHS) const
Definition: iterator.h:163
This provides a very simple, boring adaptor for a begin and end iterator into a range type...
bool operator<=(const DerivedT &RHS) const
Definition: iterator.h:157
A proxy object for computing a reference via indirecting a copy of an iterator.
Definition: iterator.h:84
DerivedT & operator-=(difference_type n)
Definition: iterator.h:233
Definition: BitVector.h:938
DerivedT & operator--()
Definition: iterator.h:131
#define T
bool operator<(const DerivedT &RHS) const
Definition: iterator.h:265
CRTP base class which implements the entire standard iterator facade in terms of a minimal subset of ...
Definition: iterator.h:68
WrappedPairNodeDataIterator(ItType Begin, const DataRef DR)
Definition: iterator.h:354
CRTP base class for adapting an iterator to a different type.
Definition: iterator.h:206
ReferenceProxy operator[](DifferenceTypeT n)
Definition: iterator.h:174
DerivedT & operator+=(difference_type n)
Definition: iterator.h:226
friend DerivedT operator+(DifferenceTypeT n, const DerivedT &i)
Definition: iterator.h:106
difference_type operator-(const DerivedT &RHS) const
Definition: iterator.h:241
DerivedT operator+(DifferenceTypeT n) const
Definition: iterator.h:96
iterator_adaptor_base(WrappedIteratorT u)
Definition: iterator.h:216
iterator_range< T > make_range(T x, T y)
Convenience function for iterating over sub-ranges.
ReferenceProxy operator[](DifferenceTypeT n) const
Definition: iterator.h:179
DerivedT & operator++()
Definition: iterator.h:121
PointerT operator->() const
Definition: iterator.h:171
An iterator type that allows iterating over the pointees via some other iterator. ...
Definition: iterator.h:287
T & operator*() const
Definition: iterator.h:297
A range adaptor for a pair of iterators.
pointer_iterator(WrappedIteratorT u)
Definition: iterator.h:321
NodeRef & operator*() const
Definition: iterator.h:359
const WrappedIteratorT & wrapped() const
Definition: iterator.h:221
#define I(x, y, z)
Definition: MD5.cpp:58
WrappedIteratorT I
Definition: iterator.h:212
iterator_range< pointee_iterator< WrappedIteratorT > > make_pointee_range(RangeT &&Range)
Definition: iterator.h:303
const T & operator*() const
Definition: iterator.h:325
DerivedT operator--(int)
Definition: iterator.h:137
DerivedT operator++(int)
Definition: iterator.h:126
bool operator>(const DerivedT &RHS) const
Definition: iterator.h:150
iterator_range< pointer_iterator< WrappedIteratorT > > make_pointer_range(RangeT &&Range)
Definition: iterator.h:331