MapVector.h revision 353358
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