1 //===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
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.
8 //===----------------------------------------------------------------------===//
10 // This file defines the DenseMap class.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_ADT_DENSEMAP_H
15 #define LLVM_ADT_DENSEMAP_H
17 #include "llvm/Support/DataTypes.h"
24 struct DenseMapKeyInfo {
25 //static inline T getEmptyKey();
26 //static inline T getTombstoneKey();
27 //static unsigned getHashValue(const T &Val);
31 // Provide DenseMapKeyInfo for all pointers.
33 struct DenseMapKeyInfo<T*> {
34 static inline T* getEmptyKey() { return (T*)-1; }
35 static inline T* getTombstoneKey() { return (T*)-2; }
36 static unsigned getHashValue(const T *PtrVal) {
37 return (unsigned)((uintptr_t)PtrVal >> 4) ^
38 (unsigned)((uintptr_t)PtrVal >> 9);
40 static bool isPod() { return true; }
43 template<typename KeyT, typename ValueT,
44 typename KeyInfoT = DenseMapKeyInfo<KeyT> >
45 class DenseMapIterator;
46 template<typename KeyT, typename ValueT,
47 typename KeyInfoT = DenseMapKeyInfo<KeyT> >
48 class DenseMapConstIterator;
50 template<typename KeyT, typename ValueT,
51 typename KeyInfoT = DenseMapKeyInfo<KeyT> >
53 typedef std::pair<KeyT, ValueT> BucketT;
58 unsigned NumTombstones;
59 DenseMap(const DenseMap &); // not implemented.
61 explicit DenseMap(unsigned NumInitBuckets = 64) {
65 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
66 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
67 if (P->first != EmptyKey && P->first != TombstoneKey)
71 delete[] (char*)Buckets;
74 typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
75 typedef DenseMapConstIterator<KeyT, ValueT, KeyInfoT> const_iterator;
76 inline iterator begin() {
77 return iterator(Buckets, Buckets+NumBuckets);
79 inline iterator end() {
80 return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
82 inline const_iterator begin() const {
83 return const_iterator(Buckets, Buckets+NumBuckets);
85 inline const_iterator end() const {
86 return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
89 bool empty() const { return NumEntries == 0; }
90 unsigned size() const { return NumEntries; }
93 const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
94 for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
95 if (P->first != EmptyKey && P->first != TombstoneKey) {
101 assert(NumEntries == 0 && "Node count imbalance!");
105 /// count - Return true if the specified key is in the map.
106 bool count(const KeyT &Val) const {
108 return LookupBucketFor(Val, TheBucket);
111 iterator find(const KeyT &Val) {
113 if (LookupBucketFor(Val, TheBucket))
114 return iterator(TheBucket, Buckets+NumBuckets);
117 const_iterator find(const KeyT &Val) const {
119 if (LookupBucketFor(Val, TheBucket))
120 return const_iterator(TheBucket, Buckets+NumBuckets);
124 bool insert(const std::pair<KeyT, ValueT> &KV) {
126 if (LookupBucketFor(KV.first, TheBucket))
127 return false; // Already in map.
129 // Otherwise, insert the new element.
130 InsertIntoBucket(KV.first, KV.second, TheBucket);
134 bool erase(const KeyT &Val) {
136 if (!LookupBucketFor(Val, TheBucket))
137 return false; // not in map.
139 TheBucket->second.~ValueT();
140 TheBucket->first = getTombstoneKey();
145 bool erase(iterator I) {
146 BucketT *TheBucket = &*I;
147 TheBucket->second.~ValueT();
148 TheBucket->first = getTombstoneKey();
154 ValueT &operator[](const KeyT &Key) {
156 if (LookupBucketFor(Key, TheBucket))
157 return TheBucket->second;
159 return InsertIntoBucket(Key, ValueT(), TheBucket)->second;
163 BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
164 BucketT *TheBucket) {
165 // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
166 // the buckets are empty (meaning that many are filled with tombstones),
169 // The later case is tricky. For example, if we had one empty bucket with
170 // tons of tombstones, failing lookups (e.g. for insertion) would have to
171 // probe almost the entire table until it found the empty bucket. If the
172 // table completely filled with tombstones, no lookup would ever succeed,
173 // causing infinite loops in lookup.
174 if (NumEntries*4 >= NumBuckets*3 ||
175 NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
177 LookupBucketFor(Key, TheBucket);
181 // If we are writing over a tombstone, remember this.
182 if (TheBucket->first != getEmptyKey())
185 TheBucket->first = Key;
186 new (&TheBucket->second) ValueT(Value);
190 static unsigned getHashValue(const KeyT &Val) {
191 return KeyInfoT::getHashValue(Val);
193 static const KeyT getEmptyKey() {
194 return KeyInfoT::getEmptyKey();
196 static const KeyT getTombstoneKey() {
197 return KeyInfoT::getTombstoneKey();
200 /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
201 /// FoundBucket. If the bucket contains the key and a value, this returns
202 /// true, otherwise it returns a bucket with an empty marker or tombstone and
204 bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
205 unsigned BucketNo = getHashValue(Val);
206 unsigned ProbeAmt = 1;
207 BucketT *BucketsPtr = Buckets;
209 // FoundTombstone - Keep track of whether we find a tombstone while probing.
210 BucketT *FoundTombstone = 0;
211 const KeyT EmptyKey = getEmptyKey();
212 const KeyT TombstoneKey = getTombstoneKey();
213 assert(Val != EmptyKey && Val != TombstoneKey &&
214 "Empty/Tombstone value shouldn't be inserted into map!");
217 BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
218 // Found Val's bucket? If so, return it.
219 if (ThisBucket->first == Val) {
220 FoundBucket = ThisBucket;
224 // If we found an empty bucket, the key doesn't exist in the set.
225 // Insert it and return the default value.
226 if (ThisBucket->first == EmptyKey) {
227 // If we've already seen a tombstone while probing, fill it in instead
228 // of the empty bucket we eventually probed to.
229 if (FoundTombstone) ThisBucket = FoundTombstone;
230 FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
234 // If this is a tombstone, remember it. If Val ends up not in the map, we
235 // prefer to return it than something that would require more probing.
236 if (ThisBucket->first == TombstoneKey && !FoundTombstone)
237 FoundTombstone = ThisBucket; // Remember the first tombstone found.
239 // Otherwise, it's a hash collision or a tombstone, continue quadratic
241 BucketNo += ProbeAmt++;
245 void init(unsigned InitBuckets) {
248 NumBuckets = InitBuckets;
249 assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 &&
250 "# initial buckets must be a power of two!");
251 Buckets = (BucketT*)new char[sizeof(BucketT)*InitBuckets];
252 // Initialize all the keys to EmptyKey.
253 const KeyT EmptyKey = getEmptyKey();
254 for (unsigned i = 0; i != InitBuckets; ++i)
255 new (&Buckets[i].first) KeyT(EmptyKey);
259 unsigned OldNumBuckets = NumBuckets;
260 BucketT *OldBuckets = Buckets;
262 // Double the number of buckets.
265 Buckets = (BucketT*)new char[sizeof(BucketT)*NumBuckets];
267 // Initialize all the keys to EmptyKey.
268 const KeyT EmptyKey = getEmptyKey();
269 for (unsigned i = 0, e = NumBuckets; i != e; ++i)
270 new (&Buckets[i].first) KeyT(EmptyKey);
272 // Insert all the old elements.
273 const KeyT TombstoneKey = getTombstoneKey();
274 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
275 if (B->first != EmptyKey && B->first != TombstoneKey) {
276 // Insert the key/value into the new table.
278 bool FoundVal = LookupBucketFor(B->first, DestBucket);
279 FoundVal = FoundVal; // silence warning.
280 assert(!FoundVal && "Key already in new map?");
281 DestBucket->first = B->first;
282 new (&DestBucket->second) ValueT(B->second);
290 // Free the old table.
291 delete[] (char*)OldBuckets;
295 template<typename KeyT, typename ValueT, typename KeyInfoT>
296 class DenseMapIterator {
297 typedef std::pair<KeyT, ValueT> BucketT;
299 const BucketT *Ptr, *End;
301 DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
302 AdvancePastEmptyBuckets();
305 std::pair<KeyT, ValueT> &operator*() const {
306 return *const_cast<BucketT*>(Ptr);
308 std::pair<KeyT, ValueT> *operator->() const {
309 return const_cast<BucketT*>(Ptr);
312 bool operator==(const DenseMapIterator &RHS) const {
313 return Ptr == RHS.Ptr;
315 bool operator!=(const DenseMapIterator &RHS) const {
316 return Ptr != RHS.Ptr;
319 inline DenseMapIterator& operator++() { // Preincrement
321 AdvancePastEmptyBuckets();
324 DenseMapIterator operator++(int) { // Postincrement
325 DenseMapIterator tmp = *this; ++*this; return tmp;
329 void AdvancePastEmptyBuckets() {
330 const KeyT Empty = KeyInfoT::getEmptyKey();
331 const KeyT Tombstone = KeyInfoT::getTombstoneKey();
333 while (Ptr != End && (Ptr->first == Empty || Ptr->first == Tombstone))
338 template<typename KeyT, typename ValueT, typename KeyInfoT>
339 class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> {
341 DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
342 const std::pair<KeyT, ValueT> *E)
343 : DenseMapIterator<KeyT, ValueT, KeyInfoT>(Pos, E) {
345 const std::pair<KeyT, ValueT> &operator*() const {
348 const std::pair<KeyT, ValueT> *operator->() const {
353 } // end namespace llvm