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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
13#include "llvm/ADT/iterator_range.h"
14#include <algorithm>
15#include <cstddef>
16#include <iterator>
17#include <type_traits>
18#include <utility>
19
20namespace 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///
65template <typename DerivedT, typename IteratorCategoryT, typename T,
66 typename DifferenceTypeT = std::ptrdiff_t, typename PointerT = T *,
67 typename ReferenceT = T &>
68class iterator_facade_base
69 : public std::iterator<IteratorCategoryT, T, DifferenceTypeT, PointerT,
70 ReferenceT> {
71protected:
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.
84 class ReferenceProxy {
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
95public:
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(
100 IsRandomAccess,
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(
108 IsRandomAccess,
109 "The '+' operator is only defined for random access iterators.");
110 return i + n;
111 }
112 DerivedT operator-(DifferenceTypeT n) const {
113 static_assert(
114 IsRandomAccess,
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(
133 IsBidirectional,
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(
139 IsBidirectional,
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(
152 IsRandomAccess,
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(
159 IsRandomAccess,
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(
165 IsRandomAccess,
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.
191template <
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,
206 // Don't provide these, they are mostly to act as aliases below.
207 typename WrappedTraitsT = std::iterator_traits<WrappedIteratorT>>
208class iterator_adaptor_base
209 : public iterator_facade_base<DerivedT, IteratorCategoryT, T,
210 DifferenceTypeT, PointerT, ReferenceT> {
211 using BaseT = typename iterator_adaptor_base::iterator_facade_base;
212
213protected:
214 WrappedIteratorT I;
215
216 iterator_adaptor_base() = default;
217
218 explicit iterator_adaptor_base(WrappedIteratorT u) : I(std::move(u)) {
219 static_assert(std::is_base_of<iterator_adaptor_base, DerivedT>::value,
220 "Must pass the derived type to this template!");
221 }
222
223 const WrappedIteratorT &wrapped() const { return I; }
224
225public:
226 using difference_type = DifferenceTypeT;
227
228 DerivedT &operator+=(difference_type n) {
229 static_assert(
230 BaseT::IsRandomAccess,
231 "The '+=' operator is only defined for random access iterators.");
232 I += n;
233 return *static_cast<DerivedT *>(this);
234 }
235 DerivedT &operator-=(difference_type n) {
236 static_assert(
237 BaseT::IsRandomAccess,
238 "The '-=' operator is only defined for random access iterators.");
239 I -= n;
240 return *static_cast<DerivedT *>(this);
241 }
242 using BaseT::operator-;
243 difference_type operator-(const DerivedT &RHS) const {
244 static_assert(
245 BaseT::IsRandomAccess,
246 "The '-' operator is only defined for random access iterators.");
247 return I - RHS.I;
248 }
249
250 // We have to explicitly provide ++ and -- rather than letting the facade
251 // forward to += because WrappedIteratorT might not support +=.
252 using BaseT::operator++;
253 DerivedT &operator++() {
254 ++I;
255 return *static_cast<DerivedT *>(this);
256 }
257 using BaseT::operator--;
258 DerivedT &operator--() {
259 static_assert(
260 BaseT::IsBidirectional,
261 "The decrement operator is only defined for bidirectional iterators.");
262 --I;
263 return *static_cast<DerivedT *>(this);
264 }
265
266 bool operator==(const DerivedT &RHS) const { return I == RHS.I; }
267 bool operator<(const DerivedT &RHS) const {
268 static_assert(
269 BaseT::IsRandomAccess,
270 "Relational operators are only defined for random access iterators.");
271 return I < RHS.I;
272 }
273
274 ReferenceT operator*() const { return *I; }
275};
276
277/// An iterator type that allows iterating over the pointees via some
278/// other iterator.
279///
280/// The typical usage of this is to expose a type that iterates over Ts, but
281/// which is implemented with some iterator over T*s:
282///
283/// \code
284/// using iterator = pointee_iterator<SmallVectorImpl<T *>::iterator>;
285/// \endcode
286template <typename WrappedIteratorT,
287 typename T = typename std::remove_reference<
288 decltype(**std::declval<WrappedIteratorT>())>::type>
289struct pointee_iterator
290 : iterator_adaptor_base<
291 pointee_iterator<WrappedIteratorT, T>, WrappedIteratorT,
292 typename std::iterator_traits<WrappedIteratorT>::iterator_category,
293 T> {
294 pointee_iterator() = default;
295 template <typename U>
296 pointee_iterator(U &&u)
297 : pointee_iterator::iterator_adaptor_base(std::forward<U &&>(u)) {}
298
299 T &operator*() const { return **this->I; }
300};
301
302template <typename RangeT, typename WrappedIteratorT =
303 decltype(std::begin(std::declval<RangeT>()))>
304iterator_range<pointee_iterator<WrappedIteratorT>>
305make_pointee_range(RangeT &&Range) {
306 using PointeeIteratorT = pointee_iterator<WrappedIteratorT>;
307 return make_range(PointeeIteratorT(std::begin(std::forward<RangeT>(Range))),
308 PointeeIteratorT(std::end(std::forward<RangeT>(Range))));
309}
310
311template <typename WrappedIteratorT,
312 typename T = decltype(&*std::declval<WrappedIteratorT>())>
313class pointer_iterator
314 : public iterator_adaptor_base<pointer_iterator<WrappedIteratorT, T>,
315 WrappedIteratorT, T> {
316 mutable T Ptr;
317
318public:
319 pointer_iterator() = default;
320
321 explicit pointer_iterator(WrappedIteratorT u)
322 : pointer_iterator::iterator_adaptor_base(std::move(u)) {}
323
324 T &operator*() { return Ptr = &*this->I; }
325 const T &operator*() const { return Ptr = &*this->I; }
326};
327
328template <typename RangeT, typename WrappedIteratorT =
329 decltype(std::begin(std::declval<RangeT>()))>
330iterator_range<pointer_iterator<WrappedIteratorT>>
331make_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} // end namespace llvm
338
339#endif // LLVM_ADT_ITERATOR_H
340

Warning: That file was not part of the compilation database. It may have many parsing errors.