1//===- llvm/ADT/MapVector.h - Map w/ deterministic value order --*- 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// This file implements a map that provides insertion order iteration. The
10// interface is purposefully minimal. The key is assumed to be cheap to copy
11// and 2 copies are kept, one for indexing in a DenseMap, one for iteration in
12// a std::vector.
13//
14//===----------------------------------------------------------------------===//
15
16#ifndef LLVM_ADT_MAPVECTOR_H
17#define LLVM_ADT_MAPVECTOR_H
18
19#include "llvm/ADT/DenseMap.h"
20#include "llvm/ADT/SmallVector.h"
21#include <algorithm>
22#include <cassert>
23#include <cstddef>
24#include <iterator>
25#include <type_traits>
26#include <utility>
27#include <vector>
28
29namespace llvm {
30
31/// This class implements a map that also provides access to all stored values
32/// in a deterministic order. The values are kept in a std::vector and the
33/// mapping is done with DenseMap from Keys to indexes in that vector.
34template<typename KeyT, typename ValueT,
35 typename MapType = DenseMap<KeyT, unsigned>,
36 typename VectorType = std::vector<std::pair<KeyT, ValueT>>>
37class MapVector {
38 MapType Map;
39 VectorType Vector;
40
41 static_assert(
42 std::is_integral<typename MapType::mapped_type>::value,
43 "The mapped_type of the specified Map must be an integral type");
44
45public:
46 using value_type = typename VectorType::value_type;
47 using size_type = typename VectorType::size_type;
48
49 using iterator = typename VectorType::iterator;
50 using const_iterator = typename VectorType::const_iterator;
51 using reverse_iterator = typename VectorType::reverse_iterator;
52 using const_reverse_iterator = typename VectorType::const_reverse_iterator;
53
54 /// Clear the MapVector and return the underlying vector.
55 VectorType takeVector() {
56 Map.clear();
57 return std::move(Vector);
58 }
59
60 size_type size() const { return Vector.size(); }
61
62 /// Grow the MapVector so that it can contain at least \p NumEntries items
63 /// before resizing again.
64 void reserve(size_type NumEntries) {
65 Map.reserve(NumEntries);
66 Vector.reserve(NumEntries);
67 }
68
69 iterator begin() { return Vector.begin(); }
70 const_iterator begin() const { return Vector.begin(); }
71 iterator end() { return Vector.end(); }
72 const_iterator end() const { return Vector.end(); }
73
74 reverse_iterator rbegin() { return Vector.rbegin(); }
75 const_reverse_iterator rbegin() const { return Vector.rbegin(); }
76 reverse_iterator rend() { return Vector.rend(); }
77 const_reverse_iterator rend() const { return Vector.rend(); }
78
79 bool empty() const {
80 return Vector.empty();
81 }
82
83 std::pair<KeyT, ValueT> &front() { return Vector.front(); }
84 const std::pair<KeyT, ValueT> &front() const { return Vector.front(); }
85 std::pair<KeyT, ValueT> &back() { return Vector.back(); }
86 const std::pair<KeyT, ValueT> &back() const { return Vector.back(); }
87
88 void clear() {
89 Map.clear();
90 Vector.clear();
91 }
92
93 void swap(MapVector &RHS) {
94 std::swap(Map, RHS.Map);
95 std::swap(Vector, RHS.Vector);
96 }
97
98 ValueT &operator[](const KeyT &Key) {
99 std::pair<KeyT, typename MapType::mapped_type> Pair = std::make_pair(Key, 0);
100 std::pair<typename MapType::iterator, bool> Result = Map.insert(Pair);
101 auto &I = Result.first->second;
102 if (Result.second) {
103 Vector.push_back(std::make_pair(Key, ValueT()));
104 I = Vector.size() - 1;
105 }
106 return Vector[I].second;
107 }
108
109 // Returns a copy of the value. Only allowed if ValueT is copyable.
110 ValueT lookup(const KeyT &Key) const {
111 static_assert(std::is_copy_constructible<ValueT>::value,
112 "Cannot call lookup() if ValueT is not copyable.");
113 typename MapType::const_iterator Pos = Map.find(Key);
114 return Pos == Map.end()? ValueT() : Vector[Pos->second].second;
115 }
116
117 std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) {
118 std::pair<KeyT, typename MapType::mapped_type> Pair = std::make_pair(KV.first, 0);
119 std::pair<typename MapType::iterator, bool> Result = Map.insert(Pair);
120 auto &I = Result.first->second;
121 if (Result.second) {
122 Vector.push_back(std::make_pair(KV.first, KV.second));
123 I = Vector.size() - 1;
124 return std::make_pair(std::prev(end()), true);
125 }
126 return std::make_pair(begin() + I, false);
127 }
128
129 std::pair<iterator, bool> insert(std::pair<KeyT, ValueT> &&KV) {
130 // Copy KV.first into the map, then move it into the vector.
131 std::pair<KeyT, typename MapType::mapped_type> Pair = std::make_pair(KV.first, 0);
132 std::pair<typename MapType::iterator, bool> Result = Map.insert(Pair);
133 auto &I = Result.first->second;
134 if (Result.second) {
135 Vector.push_back(std::move(KV));
136 I = Vector.size() - 1;
137 return std::make_pair(std::prev(end()), true);
138 }
139 return std::make_pair(begin() + I, false);
140 }
141
142 size_type count(const KeyT &Key) const {
143 typename MapType::const_iterator Pos = Map.find(Key);
144 return Pos == Map.end()? 0 : 1;
145 }
146
147 iterator find(const KeyT &Key) {
148 typename MapType::const_iterator Pos = Map.find(Key);
149 return Pos == Map.end()? Vector.end() :
150 (Vector.begin() + Pos->second);
151 }
152
153 const_iterator find(const KeyT &Key) const {
154 typename MapType::const_iterator Pos = Map.find(Key);
155 return Pos == Map.end()? Vector.end() :
156 (Vector.begin() + Pos->second);
157 }
158
159 /// Remove the last element from the vector.
160 void pop_back() {
161 typename MapType::iterator Pos = Map.find(Vector.back().first);
162 Map.erase(Pos);
163 Vector.pop_back();
164 }
165
166 /// Remove the element given by Iterator.
167 ///
168 /// Returns an iterator to the element following the one which was removed,
169 /// which may be end().
170 ///
171 /// \note This is a deceivingly expensive operation (linear time). It's
172 /// usually better to use \a remove_if() if possible.
173 typename VectorType::iterator erase(typename VectorType::iterator Iterator) {
174 Map.erase(Iterator->first);
175 auto Next = Vector.erase(Iterator);
176 if (Next == Vector.end())
177 return Next;
178
179 // Update indices in the map.
180 size_t Index = Next - Vector.begin();
181 for (auto &I : Map) {
182 assert(I.second != Index && "Index was already erased!");
183 if (I.second > Index)
184 --I.second;
185 }
186 return Next;
187 }
188
189 /// Remove all elements with the key value Key.
190 ///
191 /// Returns the number of elements removed.
192 size_type erase(const KeyT &Key) {
193 auto Iterator = find(Key);
194 if (Iterator == end())
195 return 0;
196 erase(Iterator);
197 return 1;
198 }
199
200 /// Remove the elements that match the predicate.
201 ///
202 /// Erase all elements that match \c Pred in a single pass. Takes linear
203 /// time.
204 template <class Predicate> void remove_if(Predicate Pred);
205};
206
207template <typename KeyT, typename ValueT, typename MapType, typename VectorType>
208template <class Function>
209void MapVector<KeyT, ValueT, MapType, VectorType>::remove_if(Function Pred) {
210 auto O = Vector.begin();
211 for (auto I = O, E = Vector.end(); I != E; ++I) {
212 if (Pred(*I)) {
213 // Erase from the map.
214 Map.erase(I->first);
215 continue;
216 }
217
218 if (I != O) {
219 // Move the value and update the index in the map.
220 *O = std::move(*I);
221 Map[O->first] = O - Vector.begin();
222 }
223 ++O;
224 }
225 // Erase trailing entries in the vector.
226 Vector.erase(O, Vector.end());
227}
228
229/// A MapVector that performs no allocations if smaller than a certain
230/// size.
231template <typename KeyT, typename ValueT, unsigned N>
232struct SmallMapVector
233 : MapVector<KeyT, ValueT, SmallDenseMap<KeyT, unsigned, N>,
234 SmallVector<std::pair<KeyT, ValueT>, N>> {
235};
236
237} // end namespace llvm
238
239#endif // LLVM_ADT_MAPVECTOR_H
240