WPILibC++  2020.3.2
SmallSet.h
1 //===- llvm/ADT/SmallSet.h - 'Normally small' sets --------------*- 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 // This file defines the SmallSet class.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef WPIUTIL_WPI_SMALLSET_H
15 #define WPIUTIL_WPI_SMALLSET_H
16 
17 #include "wpi/SmallPtrSet.h"
18 #include "wpi/SmallVector.h"
19 #include "wpi/Compiler.h"
20 #include "wpi/iterator.h"
21 #include "wpi/type_traits.h"
22 #include <cstddef>
23 #include <functional>
24 #include <optional>
25 #include <set>
26 #include <type_traits>
27 #include <utility>
28 
29 namespace wpi {
30 
33 template <typename T, unsigned N, typename C>
35  : public iterator_facade_base<SmallSetIterator<T, N, C>,
36  std::forward_iterator_tag, T> {
37 private:
38  using SetIterTy = typename std::set<T, C>::const_iterator;
39  using VecIterTy = typename SmallVector<T, N>::const_iterator;
41 
44  union {
45  SetIterTy SetIter;
46  VecIterTy VecIter;
47  };
48 
49  bool isSmall;
50 
51 public:
52  SmallSetIterator(SetIterTy SetIter) : SetIter(SetIter), isSmall(false) {}
53 
54  SmallSetIterator(VecIterTy VecIter) : VecIter(VecIter), isSmall(true) {}
55 
56  // Spell out destructor, copy/move constructor and assignment operators for
57  // MSVC STL, where set<T>::const_iterator is not trivially copy constructible.
58  ~SmallSetIterator() {
59  if (isSmall)
60  VecIter.~VecIterTy();
61  else
62  SetIter.~SetIterTy();
63  }
64 
65  SmallSetIterator(const SmallSetIterator &Other) : isSmall(Other.isSmall) {
66  if (isSmall)
67  VecIter = Other.VecIter;
68  else
69  // Use placement new, to make sure SetIter is properly constructed, even
70  // if it is not trivially copy-able (e.g. in MSVC).
71  new (&SetIter) SetIterTy(Other.SetIter);
72  }
73 
74  SmallSetIterator(SmallSetIterator &&Other) : isSmall(Other.isSmall) {
75  if (isSmall)
76  VecIter = std::move(Other.VecIter);
77  else
78  // Use placement new, to make sure SetIter is properly constructed, even
79  // if it is not trivially copy-able (e.g. in MSVC).
80  new (&SetIter) SetIterTy(std::move(Other.SetIter));
81  }
82 
83  SmallSetIterator& operator=(const SmallSetIterator& Other) {
84  // Call destructor for SetIter, so it gets properly destroyed if it is
85  // not trivially destructible in case we are setting VecIter.
86  if (!isSmall)
87  SetIter.~SetIterTy();
88 
89  isSmall = Other.isSmall;
90  if (isSmall)
91  VecIter = Other.VecIter;
92  else
93  new (&SetIter) SetIterTy(Other.SetIter);
94  return *this;
95  }
96 
97  SmallSetIterator& operator=(SmallSetIterator&& Other) {
98  // Call destructor for SetIter, so it gets properly destroyed if it is
99  // not trivially destructible in case we are setting VecIter.
100  if (!isSmall)
101  SetIter.~SetIterTy();
102 
103  isSmall = Other.isSmall;
104  if (isSmall)
105  VecIter = std::move(Other.VecIter);
106  else
107  new (&SetIter) SetIterTy(std::move(Other.SetIter));
108  return *this;
109  }
110 
111  bool operator==(const SmallSetIterator &RHS) const {
112  if (isSmall != RHS.isSmall)
113  return false;
114  if (isSmall)
115  return VecIter == RHS.VecIter;
116  return SetIter == RHS.SetIter;
117  }
118 
119  SmallSetIterator &operator++() { // Preincrement
120  if (isSmall)
121  VecIter++;
122  else
123  SetIter++;
124  return *this;
125  }
126 
127  const T &operator*() const { return isSmall ? *VecIter : *SetIter; }
128 };
129 
134 template <typename T, unsigned N, typename C = std::less<T>>
135 class SmallSet {
139  SmallVector<T, N> Vector;
140  std::set<T, C> Set;
141 
142  using VIterator = typename SmallVector<T, N>::const_iterator;
143  using mutable_iterator = typename SmallVector<T, N>::iterator;
144 
145  // In small mode SmallPtrSet uses linear search for the elements, so it is
146  // not a good idea to choose this value too high. You may consider using a
147  // DenseSet<> instead if you expect many elements in the set.
148  static_assert(N <= 32, "N should be small");
149 
150 public:
151  using size_type = size_t;
153 
154  SmallSet() = default;
155 
156  LLVM_NODISCARD bool empty() const {
157  return Vector.empty() && Set.empty();
158  }
159 
160  size_type size() const {
161  return isSmall() ? Vector.size() : Set.size();
162  }
163 
165  size_type count(const T &V) const {
166  if (isSmall()) {
167  // Since the collection is small, just do a linear search.
168  return vfind(V) == Vector.end() ? 0 : 1;
169  } else {
170  return Set.count(V);
171  }
172  }
173 
179  // FIXME: Add iterators that abstract over the small and large form, and then
180  // return those here.
181  std::pair<std::nullopt_t, bool> insert(const T &V) {
182  if (!isSmall())
183  return std::make_pair(std::nullopt, Set.insert(V).second);
184 
185  VIterator I = vfind(V);
186  if (I != Vector.end()) // Don't reinsert if it already exists.
187  return std::make_pair(std::nullopt, false);
188  if (Vector.size() < N) {
189  Vector.push_back(V);
190  return std::make_pair(std::nullopt, true);
191  }
192 
193  // Otherwise, grow from vector to set.
194  while (!Vector.empty()) {
195  Set.insert(Vector.back());
196  Vector.pop_back();
197  }
198  Set.insert(V);
199  return std::make_pair(std::nullopt, true);
200  }
201 
202  template <typename IterT>
203  void insert(IterT I, IterT E) {
204  for (; I != E; ++I)
205  insert(*I);
206  }
207 
208  bool erase(const T &V) {
209  if (!isSmall())
210  return Set.erase(V);
211  for (mutable_iterator I = Vector.begin(), E = Vector.end(); I != E; ++I)
212  if (*I == V) {
213  Vector.erase(I);
214  return true;
215  }
216  return false;
217  }
218 
219  void clear() {
220  Vector.clear();
221  Set.clear();
222  }
223 
224  const_iterator begin() const {
225  if (isSmall())
226  return {Vector.begin()};
227  return {Set.begin()};
228  }
229 
230  const_iterator end() const {
231  if (isSmall())
232  return {Vector.end()};
233  return {Set.end()};
234  }
235 
236 private:
237  bool isSmall() const { return Set.empty(); }
238 
239  VIterator vfind(const T &V) const {
240  for (VIterator I = Vector.begin(), E = Vector.end(); I != E; ++I)
241  if (*I == V)
242  return I;
243  return Vector.end();
244  }
245 };
246 
249 template <typename PointeeType, unsigned N>
250 class SmallSet<PointeeType*, N> : public SmallPtrSet<PointeeType*, N> {};
251 
252 } // end namespace wpi
253 
254 #endif // LLVM_ADT_SMALLSET_H
wpi::SmallPtrSet< PointeeType *, N >
wpi
WPILib C++ utilities (wpiutil) namespace.
Definition: EventLoopRunner.h:17
wpi::SmallSet::insert
std::pair< std::nullopt_t, bool > insert(const T &V)
insert - Insert an element into the set if it isn't already there.
Definition: SmallSet.h:181
wpi::SmallSet
SmallSet - This maintains a set of unique values, optimizing for the case when the set is small (less...
Definition: SmallSet.h:135
wpi::iterator_facade_base
CRTP base class which implements the entire standard iterator facade in terms of a minimal subset of ...
Definition: iterator.h:68
wpi::SmallVector
This is a 'vector' (really, a variable-sized array), optimized for the case when the array is small.
Definition: SmallVector.h:856
wpi::SmallSetIterator
SmallSetIterator - This class implements a const_iterator for SmallSet by delegating to the underlyin...
Definition: SmallSet.h:34
wpi::SmallSet::count
size_type count(const T &V) const
count - Return 1 if the element is in the set, 0 otherwise.
Definition: SmallSet.h:165