DenseMap.h revision 137d4b253384adce88bfa2a1c37695d90f0a9d6c
1//===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by Chris Lattner and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the DenseMap class. 11// 12//===----------------------------------------------------------------------===// 13 14#ifndef LLVM_ADT_DENSEMAP_H 15#define LLVM_ADT_DENSEMAP_H 16 17#include "llvm/Support/DataTypes.h" 18#include <cassert> 19#include <utility> 20 21namespace llvm { 22 23template<typename T> 24struct DenseMapKeyInfo { 25 //static inline T getEmptyKey(); 26 //static inline T getTombstoneKey(); 27 //static unsigned getHashValue(const T &Val); 28 //static bool isPod() 29}; 30 31template<typename T> 32struct DenseMapKeyInfo<T*> { 33 static inline T* getEmptyKey() { return (T*)-1; } 34 static inline T* getTombstoneKey() { return (T*)-2; } 35 static unsigned getHashValue(const T *PtrVal) { 36 return (unsigned)((uintptr_t)PtrVal >> 4) ^ 37 (unsigned)((uintptr_t)PtrVal >> 9); 38 } 39 static bool isPod() { return true; } 40}; 41 42template<typename KeyT, typename ValueT> 43class DenseMapIterator; 44template<typename KeyT, typename ValueT> 45class DenseMapConstIterator; 46 47template<typename KeyT, typename ValueT> 48class DenseMap { 49 typedef std::pair<KeyT, ValueT> BucketT; 50 unsigned NumBuckets; 51 BucketT *Buckets; 52 53 unsigned NumEntries; 54 DenseMap(const DenseMap &); // not implemented. 55public: 56 explicit DenseMap(unsigned NumInitBuckets = 8) { 57 init(NumInitBuckets); 58 } 59 ~DenseMap() { 60 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 61 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 62 if (P->first != EmptyKey && P->first != TombstoneKey) 63 P->second.~ValueT(); 64 P->first.~KeyT(); 65 } 66 delete[] (char*)Buckets; 67 } 68 69 typedef DenseMapIterator<KeyT, ValueT> iterator; 70 typedef DenseMapConstIterator<KeyT, ValueT> const_iterator; 71 inline iterator begin() { 72 return DenseMapIterator<KeyT, ValueT>(Buckets, Buckets+NumBuckets); 73 } 74 inline iterator end() { 75 return DenseMapIterator<KeyT, ValueT>(Buckets+NumBuckets, 76 Buckets+NumBuckets); 77 } 78 inline const_iterator begin() const { 79 return DenseMapConstIterator<KeyT, ValueT>(Buckets, Buckets+NumBuckets); 80 } 81 inline const_iterator end() const { 82 return DenseMapConstIterator<KeyT, ValueT>(Buckets+NumBuckets, 83 Buckets+NumBuckets); 84 } 85 86 bool empty() const { return NumEntries == 0; } 87 unsigned size() const { return NumEntries; } 88 89 void clear() { 90 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey(); 91 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) { 92 if (P->first != EmptyKey && P->first != TombstoneKey) { 93 P->first = EmptyKey; 94 P->second.~ValueT(); 95 --NumEntries; 96 } 97 } 98 assert(NumEntries == 0 && "Node count imbalance!"); 99 } 100 101 /// count - Return true if the specified key is in the map. 102 bool count(const KeyT &Val) const { 103 BucketT *TheBucket; 104 return LookupBucketFor(Val, TheBucket); 105 } 106 107 iterator find(const KeyT &Val) const { 108 BucketT *TheBucket; 109 if (LookupBucketFor(Val, TheBucket)) 110 return iterator(TheBucket, Buckets+NumBuckets); 111 return end(); 112 } 113 114 bool erase(const KeyT &Val) { 115 BucketT *TheBucket; 116 if (!LookupBucketFor(Val, TheBucket)) 117 return false; // not in map. 118 119 TheBucket->second.~ValueT(); 120 TheBucket->first = getTombstoneKey(); 121 --NumEntries; 122 return true; 123 } 124 bool erase(iterator I) { 125 BucketT *TheBucket = &*I; 126 TheBucket->second.~ValueT(); 127 TheBucket->first = getTombstoneKey(); 128 --NumEntries; 129 return true; 130 } 131 132 ValueT &operator[](const KeyT &Val) { 133 BucketT *TheBucket; 134 if (LookupBucketFor(Val, TheBucket)) 135 return TheBucket->second; 136 137 // If the load of the hash table is more than 3/4, grow it. 138 if (NumEntries*4 >= NumBuckets*3) { 139 this->grow(); 140 LookupBucketFor(Val, TheBucket); 141 } 142 ++NumEntries; 143 TheBucket->first = Val; 144 new (&TheBucket->second) ValueT(); 145 return TheBucket->second; 146 } 147 148private: 149 static unsigned getHashValue(const KeyT &Val) { 150 return DenseMapKeyInfo<KeyT>::getHashValue(Val); 151 } 152 static const KeyT getEmptyKey() { 153 return DenseMapKeyInfo<KeyT>::getEmptyKey(); 154 } 155 static const KeyT getTombstoneKey() { 156 return DenseMapKeyInfo<KeyT>::getTombstoneKey(); 157 } 158 159 /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in 160 /// FoundBucket. If the bucket contains the key and a value, this returns 161 /// true, otherwise it returns a bucket with an empty marker or tombstone and 162 /// returns false. 163 bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const { 164 unsigned BucketNo = getHashValue(Val); 165 unsigned ProbeAmt = 1; 166 BucketT *BucketsPtr = Buckets; 167 168 // FoundTombstone - Keep track of whether we find a tombstone while probing. 169 BucketT *FoundTombstone = 0; 170 const KeyT EmptyKey = getEmptyKey(); 171 const KeyT TombstoneKey = getTombstoneKey(); 172 assert(Val != EmptyKey && Val != TombstoneKey && 173 "Empty/Tombstone value shouldn't be inserted into map!"); 174 175 while (1) { 176 BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1)); 177 // Found Val's bucket? If so, return it. 178 if (ThisBucket->first == Val) { 179 FoundBucket = ThisBucket; 180 return true; 181 } 182 183 // If we found an empty bucket, the key doesn't exist in the set. 184 // Insert it and return the default value. 185 if (ThisBucket->first == EmptyKey) { 186 // If we've already seen a tombstone while probing, fill it in instead 187 // of the empty bucket we eventually probed to. 188 if (FoundTombstone) ThisBucket = FoundTombstone; 189 FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket; 190 return false; 191 } 192 193 // If this is a tombstone, remember it. If Val ends up not in the map, we 194 // prefer to return it than something that would require more probing. 195 if (ThisBucket->first == TombstoneKey && !FoundTombstone) 196 FoundTombstone = ThisBucket; // Remember the first tombstone found. 197 198 // Otherwise, it's a hash collision or a tombstone, continue quadratic 199 // probing. 200 BucketNo += ProbeAmt++; 201 } 202 } 203 204 void init(unsigned InitBuckets) { 205 NumEntries = 0; 206 NumBuckets = InitBuckets; 207 assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 && 208 "# initial buckets must be a power of two!"); 209 Buckets = (BucketT*)new char[sizeof(BucketT)*InitBuckets]; 210 // Initialize all the keys to EmptyKey. 211 const KeyT EmptyKey = getEmptyKey(); 212 for (unsigned i = 0; i != InitBuckets; ++i) 213 new (&Buckets[i].first) KeyT(EmptyKey); 214 } 215 216 void grow() { 217 unsigned OldNumBuckets = NumBuckets; 218 BucketT *OldBuckets = Buckets; 219 220 // Double the number of buckets. 221 NumBuckets <<= 1; 222 Buckets = (BucketT*)new char[sizeof(BucketT)*NumBuckets]; 223 224 // Initialize all the keys to EmptyKey. 225 const KeyT EmptyKey = getEmptyKey(); 226 for (unsigned i = 0, e = NumBuckets; i != e; ++i) 227 new (&Buckets[i].first) KeyT(EmptyKey); 228 229 // Insert all the old elements. 230 const KeyT TombstoneKey = getTombstoneKey(); 231 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) { 232 if (B->first != EmptyKey && B->first != TombstoneKey) { 233 // Insert the key/value into the new table. 234 BucketT *DestBucket; 235 bool FoundVal = LookupBucketFor(B->first, DestBucket); 236 FoundVal = FoundVal; // silence warning. 237 assert(!FoundVal && "Key already in new map?"); 238 DestBucket->first = B->first; 239 new (&DestBucket->second) ValueT(B->second); 240 241 // Free the value. 242 B->second.~ValueT(); 243 } 244 B->first.~KeyT(); 245 } 246 247 // Free the old table. 248 delete[] (char*)OldBuckets; 249 } 250}; 251 252template<typename KeyT, typename ValueT> 253class DenseMapIterator { 254 typedef std::pair<KeyT, ValueT> BucketT; 255protected: 256 const BucketT *Ptr, *End; 257public: 258 DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) { 259 AdvancePastEmptyBuckets(); 260 } 261 262 std::pair<KeyT, ValueT> &operator*() const { 263 return *const_cast<BucketT*>(Ptr); 264 } 265 std::pair<KeyT, ValueT> *operator->() const { 266 return const_cast<BucketT*>(Ptr); 267 } 268 269 bool operator==(const DenseMapIterator &RHS) const { 270 return Ptr == RHS.Ptr; 271 } 272 bool operator!=(const DenseMapIterator &RHS) const { 273 return Ptr != RHS.Ptr; 274 } 275 276 inline DenseMapIterator& operator++() { // Preincrement 277 ++Ptr; 278 AdvancePastEmptyBuckets(); 279 return *this; 280 } 281 DenseMapIterator operator++(int) { // Postincrement 282 DenseMapIterator tmp = *this; ++*this; return tmp; 283 } 284 285private: 286 void AdvancePastEmptyBuckets() { 287 const KeyT Empty = DenseMapKeyInfo<KeyT>::getEmptyKey(); 288 const KeyT Tombstone = DenseMapKeyInfo<KeyT>::getTombstoneKey(); 289 290 while (Ptr != End && (Ptr->first == Empty || Ptr->first == Tombstone)) 291 ++Ptr; 292 } 293}; 294 295template<typename KeyT, typename ValueT> 296class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT> { 297public: 298 DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos, 299 const std::pair<KeyT, ValueT> *E) 300 : DenseMapIterator<KeyT, ValueT>(Pos, E) { 301 } 302 const std::pair<KeyT, ValueT> &operator*() const { 303 return *this->Ptr; 304 } 305 const std::pair<KeyT, ValueT> *operator->() const { 306 return this->Ptr; 307 } 308}; 309 310} // end namespace llvm 311 312#endif 313