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iterator.h
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1 //===- iterator.h - Utilities for using and defining iterators --*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef LLVM_ADT_ITERATOR_H
10 #define LLVM_ADT_ITERATOR_H
11 
13 #include <algorithm>
14 #include <cstddef>
15 #include <iterator>
16 #include <type_traits>
17 #include <utility>
18 
19 namespace llvm {
20 
21 /// CRTP base class which implements the entire standard iterator facade
22 /// in terms of a minimal subset of the interface.
23 ///
24 /// Use this when it is reasonable to implement most of the iterator
25 /// functionality in terms of a core subset. If you need special behavior or
26 /// there are performance implications for this, you may want to override the
27 /// relevant members instead.
28 ///
29 /// Note, one abstraction that this does *not* provide is implementing
30 /// subtraction in terms of addition by negating the difference. Negation isn't
31 /// always information preserving, and I can see very reasonable iterator
32 /// designs where this doesn't work well. It doesn't really force much added
33 /// boilerplate anyways.
34 ///
35 /// Another abstraction that this doesn't provide is implementing increment in
36 /// terms of addition of one. These aren't equivalent for all iterator
37 /// categories, and respecting that adds a lot of complexity for little gain.
38 ///
39 /// Classes wishing to use `iterator_facade_base` should implement the following
40 /// methods:
41 ///
42 /// Forward Iterators:
43 /// (All of the following methods)
44 /// - DerivedT &operator=(const DerivedT &R);
45 /// - bool operator==(const DerivedT &R) const;
46 /// - const T &operator*() const;
47 /// - T &operator*();
48 /// - DerivedT &operator++();
49 ///
50 /// Bidirectional Iterators:
51 /// (All methods of forward iterators, plus the following)
52 /// - DerivedT &operator--();
53 ///
54 /// Random-access Iterators:
55 /// (All methods of bidirectional iterators excluding the following)
56 /// - DerivedT &operator++();
57 /// - DerivedT &operator--();
58 /// (and plus the following)
59 /// - bool operator<(const DerivedT &RHS) const;
60 /// - DifferenceTypeT operator-(const DerivedT &R) const;
61 /// - DerivedT &operator+=(DifferenceTypeT N);
62 /// - DerivedT &operator-=(DifferenceTypeT N);
63 ///
64 template <typename DerivedT, typename IteratorCategoryT, typename T,
65  typename DifferenceTypeT = std::ptrdiff_t, typename PointerT = T *,
66  typename ReferenceT = T &>
68  : public std::iterator<IteratorCategoryT, T, DifferenceTypeT, PointerT,
69  ReferenceT> {
70 protected:
71  enum {
72  IsRandomAccess = std::is_base_of<std::random_access_iterator_tag,
73  IteratorCategoryT>::value,
74  IsBidirectional = std::is_base_of<std::bidirectional_iterator_tag,
75  IteratorCategoryT>::value,
76  };
77 
78  /// A proxy object for computing a reference via indirecting a copy of an
79  /// iterator. This is used in APIs which need to produce a reference via
80  /// indirection but for which the iterator object might be a temporary. The
81  /// proxy preserves the iterator internally and exposes the indirected
82  /// reference via a conversion operator.
84  friend iterator_facade_base;
85 
86  DerivedT I;
87 
88  ReferenceProxy(DerivedT I) : I(std::move(I)) {}
89 
90  public:
91  operator ReferenceT() const { return *I; }
92  };
93 
94 public:
95  DerivedT operator+(DifferenceTypeT n) const {
96  static_assert(std::is_base_of<iterator_facade_base, DerivedT>::value,
97  "Must pass the derived type to this template!");
98  static_assert(
100  "The '+' operator is only defined for random access iterators.");
101  DerivedT tmp = *static_cast<const DerivedT *>(this);
102  tmp += n;
103  return tmp;
104  }
105  friend DerivedT operator+(DifferenceTypeT n, const DerivedT &i) {
106  static_assert(
108  "The '+' operator is only defined for random access iterators.");
109  return i + n;
110  }
111  DerivedT operator-(DifferenceTypeT n) const {
112  static_assert(
114  "The '-' operator is only defined for random access iterators.");
115  DerivedT tmp = *static_cast<const DerivedT *>(this);
116  tmp -= n;
117  return tmp;
118  }
119 
120  DerivedT &operator++() {
121  static_assert(std::is_base_of<iterator_facade_base, DerivedT>::value,
122  "Must pass the derived type to this template!");
123  return static_cast<DerivedT *>(this)->operator+=(1);
124  }
125  DerivedT operator++(int) {
126  DerivedT tmp = *static_cast<DerivedT *>(this);
127  ++*static_cast<DerivedT *>(this);
128  return tmp;
129  }
130  DerivedT &operator--() {
131  static_assert(
133  "The decrement operator is only defined for bidirectional iterators.");
134  return static_cast<DerivedT *>(this)->operator-=(1);
135  }
136  DerivedT operator--(int) {
137  static_assert(
139  "The decrement operator is only defined for bidirectional iterators.");
140  DerivedT tmp = *static_cast<DerivedT *>(this);
141  --*static_cast<DerivedT *>(this);
142  return tmp;
143  }
144 
145  bool operator!=(const DerivedT &RHS) const {
146  return !static_cast<const DerivedT *>(this)->operator==(RHS);
147  }
148 
149  bool operator>(const DerivedT &RHS) const {
150  static_assert(
152  "Relational operators are only defined for random access iterators.");
153  return !static_cast<const DerivedT *>(this)->operator<(RHS) &&
154  !static_cast<const DerivedT *>(this)->operator==(RHS);
155  }
156  bool operator<=(const DerivedT &RHS) const {
157  static_assert(
159  "Relational operators are only defined for random access iterators.");
160  return !static_cast<const DerivedT *>(this)->operator>(RHS);
161  }
162  bool operator>=(const DerivedT &RHS) const {
163  static_assert(
165  "Relational operators are only defined for random access iterators.");
166  return !static_cast<const DerivedT *>(this)->operator<(RHS);
167  }
168 
169  PointerT operator->() { return &static_cast<DerivedT *>(this)->operator*(); }
170  PointerT operator->() const {
171  return &static_cast<const DerivedT *>(this)->operator*();
172  }
173  ReferenceProxy operator[](DifferenceTypeT n) {
174  static_assert(IsRandomAccess,
175  "Subscripting is only defined for random access iterators.");
176  return ReferenceProxy(static_cast<DerivedT *>(this)->operator+(n));
177  }
178  ReferenceProxy operator[](DifferenceTypeT n) const {
179  static_assert(IsRandomAccess,
180  "Subscripting is only defined for random access iterators.");
181  return ReferenceProxy(static_cast<const DerivedT *>(this)->operator+(n));
182  }
183 };
184 
185 /// CRTP base class for adapting an iterator to a different type.
186 ///
187 /// This class can be used through CRTP to adapt one iterator into another.
188 /// Typically this is done through providing in the derived class a custom \c
189 /// operator* implementation. Other methods can be overridden as well.
190 template <
191  typename DerivedT, typename WrappedIteratorT,
192  typename IteratorCategoryT =
193  typename std::iterator_traits<WrappedIteratorT>::iterator_category,
194  typename T = typename std::iterator_traits<WrappedIteratorT>::value_type,
195  typename DifferenceTypeT =
196  typename std::iterator_traits<WrappedIteratorT>::difference_type,
197  typename PointerT = typename std::conditional<
198  std::is_same<T, typename std::iterator_traits<
199  WrappedIteratorT>::value_type>::value,
200  typename std::iterator_traits<WrappedIteratorT>::pointer, T *>::type,
201  typename ReferenceT = typename std::conditional<
202  std::is_same<T, typename std::iterator_traits<
203  WrappedIteratorT>::value_type>::value,
204  typename std::iterator_traits<WrappedIteratorT>::reference, T &>::type>
206  : public iterator_facade_base<DerivedT, IteratorCategoryT, T,
207  DifferenceTypeT, PointerT, ReferenceT> {
208  using BaseT = typename iterator_adaptor_base::iterator_facade_base;
209 
210 protected:
211  WrappedIteratorT I;
212 
213  iterator_adaptor_base() = default;
214 
215  explicit iterator_adaptor_base(WrappedIteratorT u) : I(std::move(u)) {
216  static_assert(std::is_base_of<iterator_adaptor_base, DerivedT>::value,
217  "Must pass the derived type to this template!");
218  }
219 
220  const WrappedIteratorT &wrapped() const { return I; }
221 
222 public:
223  using difference_type = DifferenceTypeT;
224 
226  static_assert(
227  BaseT::IsRandomAccess,
228  "The '+=' operator is only defined for random access iterators.");
229  I += n;
230  return *static_cast<DerivedT *>(this);
231  }
233  static_assert(
234  BaseT::IsRandomAccess,
235  "The '-=' operator is only defined for random access iterators.");
236  I -= n;
237  return *static_cast<DerivedT *>(this);
238  }
239  using BaseT::operator-;
240  difference_type operator-(const DerivedT &RHS) const {
241  static_assert(
242  BaseT::IsRandomAccess,
243  "The '-' operator is only defined for random access iterators.");
244  return I - RHS.I;
245  }
246 
247  // We have to explicitly provide ++ and -- rather than letting the facade
248  // forward to += because WrappedIteratorT might not support +=.
249  using BaseT::operator++;
250  DerivedT &operator++() {
251  ++I;
252  return *static_cast<DerivedT *>(this);
253  }
254  using BaseT::operator--;
255  DerivedT &operator--() {
256  static_assert(
257  BaseT::IsBidirectional,
258  "The decrement operator is only defined for bidirectional iterators.");
259  --I;
260  return *static_cast<DerivedT *>(this);
261  }
262 
263  bool operator==(const DerivedT &RHS) const { return I == RHS.I; }
264  bool operator<(const DerivedT &RHS) const {
265  static_assert(
266  BaseT::IsRandomAccess,
267  "Relational operators are only defined for random access iterators.");
268  return I < RHS.I;
269  }
270 
271  ReferenceT operator*() const { return *I; }
272 };
273 
274 /// An iterator type that allows iterating over the pointees via some
275 /// other iterator.
276 ///
277 /// The typical usage of this is to expose a type that iterates over Ts, but
278 /// which is implemented with some iterator over T*s:
279 ///
280 /// \code
281 /// using iterator = pointee_iterator<SmallVectorImpl<T *>::iterator>;
282 /// \endcode
283 template <typename WrappedIteratorT,
284  typename T = typename std::remove_reference<
285  decltype(**std::declval<WrappedIteratorT>())>::type>
288  pointee_iterator<WrappedIteratorT, T>, WrappedIteratorT,
289  typename std::iterator_traits<WrappedIteratorT>::iterator_category,
290  T> {
291  pointee_iterator() = default;
292  template <typename U>
294  : pointee_iterator::iterator_adaptor_base(std::forward<U &&>(u)) {}
295 
296  T &operator*() const { return **this->I; }
297 };
298 
299 template <typename RangeT, typename WrappedIteratorT =
300  decltype(std::begin(std::declval<RangeT>()))>
302 make_pointee_range(RangeT &&Range) {
303  using PointeeIteratorT = pointee_iterator<WrappedIteratorT>;
304  return make_range(PointeeIteratorT(std::begin(std::forward<RangeT>(Range))),
305  PointeeIteratorT(std::end(std::forward<RangeT>(Range))));
306 }
307 
308 template <typename WrappedIteratorT,
309  typename T = decltype(&*std::declval<WrappedIteratorT>())>
311  : public iterator_adaptor_base<
312  pointer_iterator<WrappedIteratorT, T>, WrappedIteratorT,
313  typename std::iterator_traits<WrappedIteratorT>::iterator_category,
314  T> {
315  mutable T Ptr;
316 
317 public:
318  pointer_iterator() = default;
319 
320  explicit pointer_iterator(WrappedIteratorT u)
322 
323  T &operator*() { return Ptr = &*this->I; }
324  const T &operator*() const { return Ptr = &*this->I; }
325 };
326 
327 template <typename RangeT, typename WrappedIteratorT =
328  decltype(std::begin(std::declval<RangeT>()))>
330 make_pointer_range(RangeT &&Range) {
331  using PointerIteratorT = pointer_iterator<WrappedIteratorT>;
332  return make_range(PointerIteratorT(std::begin(std::forward<RangeT>(Range))),
333  PointerIteratorT(std::end(std::forward<RangeT>(Range))));
334 }
335 
336 // Wrapper iterator over iterator ItType, adding DataRef to the type of ItType,
337 // to create NodeRef = std::pair<InnerTypeOfItType, DataRef>.
338 template <typename ItType, typename NodeRef, typename DataRef>
340  : public iterator_adaptor_base<
341  WrappedPairNodeDataIterator<ItType, NodeRef, DataRef>, ItType,
342  typename std::iterator_traits<ItType>::iterator_category, NodeRef,
343  std::ptrdiff_t, NodeRef *, NodeRef &> {
346  typename std::iterator_traits<ItType>::iterator_category, NodeRef,
347  std::ptrdiff_t, NodeRef *, NodeRef &>;
348 
349  const DataRef DR;
350  mutable NodeRef NR;
351 
352 public:
353  WrappedPairNodeDataIterator(ItType Begin, const DataRef DR)
354  : BaseT(Begin), DR(DR) {
355  NR.first = DR;
356  }
357 
358  NodeRef &operator*() const {
359  NR.second = *this->I;
360  return NR;
361  }
362 };
363 
364 } // end namespace llvm
365 
366 #endif // LLVM_ADT_ITERATOR_H
const_iterator end(StringRef path)
Get end iterator over path.
Definition: Path.cpp:233
DerivedT operator-(DifferenceTypeT n) const
Definition: iterator.h:111
const_iterator begin(StringRef path, Style style=Style::native)
Get begin iterator over path.
Definition: Path.cpp:224
bool operator==(const DerivedT &RHS) const
Definition: iterator.h:263
This class represents lattice values for constants.
Definition: AllocatorList.h:23
bool operator!=(const DerivedT &RHS) const
Definition: iterator.h:145
ReferenceT operator*() const
Definition: iterator.h:271
bool operator>=(const DerivedT &RHS) const
Definition: iterator.h:162
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:156
A proxy object for computing a reference via indirecting a copy of an iterator.
Definition: iterator.h:83
DerivedT & operator-=(difference_type n)
Definition: iterator.h:232
Definition: BitVector.h:937
DerivedT & operator--()
Definition: iterator.h:130
bool operator<(const DerivedT &RHS) const
Definition: iterator.h:264
CRTP base class which implements the entire standard iterator facade in terms of a minimal subset of ...
Definition: iterator.h:67
WrappedPairNodeDataIterator(ItType Begin, const DataRef DR)
Definition: iterator.h:353
CRTP base class for adapting an iterator to a different type.
Definition: iterator.h:205
ReferenceProxy operator[](DifferenceTypeT n)
Definition: iterator.h:173
DerivedT & operator+=(difference_type n)
Definition: iterator.h:225
friend DerivedT operator+(DifferenceTypeT n, const DerivedT &i)
Definition: iterator.h:105
difference_type operator-(const DerivedT &RHS) const
Definition: iterator.h:240
DerivedT operator+(DifferenceTypeT n) const
Definition: iterator.h:95
iterator_adaptor_base(WrappedIteratorT u)
Definition: iterator.h:215
iterator_range< T > make_range(T x, T y)
Convenience function for iterating over sub-ranges.
ReferenceProxy operator[](DifferenceTypeT n) const
Definition: iterator.h:178
DerivedT & operator++()
Definition: iterator.h:120
PointerT operator->() const
Definition: iterator.h:170
An iterator type that allows iterating over the pointees via some other iterator. ...
Definition: iterator.h:286
T & operator*() const
Definition: iterator.h:296
A range adaptor for a pair of iterators.
pointer_iterator(WrappedIteratorT u)
Definition: iterator.h:320
NodeRef & operator*() const
Definition: iterator.h:358
const WrappedIteratorT & wrapped() const
Definition: iterator.h:220
#define I(x, y, z)
Definition: MD5.cpp:58
WrappedIteratorT I
Definition: iterator.h:211
iterator_range< pointee_iterator< WrappedIteratorT > > make_pointee_range(RangeT &&Range)
Definition: iterator.h:302
const T & operator*() const
Definition: iterator.h:324
DerivedT operator--(int)
Definition: iterator.h:136
DerivedT operator++(int)
Definition: iterator.h:125
bool operator>(const DerivedT &RHS) const
Definition: iterator.h:149
iterator_range< pointer_iterator< WrappedIteratorT > > make_pointer_range(RangeT &&Range)
Definition: iterator.h:330