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) const {
113 if (LookupBucketFor(Val, TheBucket))
114 return iterator(TheBucket, Buckets+NumBuckets);
118 bool insert(const std::pair<KeyT, ValueT> &KV) {
120 if (LookupBucketFor(KV.first, TheBucket))
121 return false; // Already in map.
123 // Otherwise, insert the new element.
124 InsertIntoBucket(KV.first, KV.second, TheBucket);
128 bool erase(const KeyT &Val) {
130 if (!LookupBucketFor(Val, TheBucket))
131 return false; // not in map.
133 TheBucket->second.~ValueT();
134 TheBucket->first = getTombstoneKey();
139 bool erase(iterator I) {
140 BucketT *TheBucket = &*I;
141 TheBucket->second.~ValueT();
142 TheBucket->first = getTombstoneKey();
148 ValueT &operator[](const KeyT &Key) {
150 if (LookupBucketFor(Key, TheBucket))
151 return TheBucket->second;
153 return InsertIntoBucket(Key, ValueT(), TheBucket)->second;
157 BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
158 BucketT *TheBucket) {
159 // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
160 // the buckets are empty (meaning that many are filled with tombstones),
163 // The later case is tricky. For example, if we had one empty bucket with
164 // tons of tombstones, failing lookups (e.g. for insertion) would have to
165 // probe almost the entire table until it found the empty bucket. If the
166 // table completely filled with tombstones, no lookup would ever succeed,
167 // causing infinite loops in lookup.
168 if (NumEntries*4 >= NumBuckets*3 ||
169 NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
171 LookupBucketFor(Key, TheBucket);
175 // If we are writing over a tombstone, remember this.
176 if (TheBucket->first != getEmptyKey())
179 TheBucket->first = Key;
180 new (&TheBucket->second) ValueT(Value);
184 static unsigned getHashValue(const KeyT &Val) {
185 return KeyInfoT::getHashValue(Val);
187 static const KeyT getEmptyKey() {
188 return KeyInfoT::getEmptyKey();
190 static const KeyT getTombstoneKey() {
191 return KeyInfoT::getTombstoneKey();
194 /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
195 /// FoundBucket. If the bucket contains the key and a value, this returns
196 /// true, otherwise it returns a bucket with an empty marker or tombstone and
198 bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
199 unsigned BucketNo = getHashValue(Val);
200 unsigned ProbeAmt = 1;
201 BucketT *BucketsPtr = Buckets;
203 // FoundTombstone - Keep track of whether we find a tombstone while probing.
204 BucketT *FoundTombstone = 0;
205 const KeyT EmptyKey = getEmptyKey();
206 const KeyT TombstoneKey = getTombstoneKey();
207 assert(Val != EmptyKey && Val != TombstoneKey &&
208 "Empty/Tombstone value shouldn't be inserted into map!");
211 BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
212 // Found Val's bucket? If so, return it.
213 if (ThisBucket->first == Val) {
214 FoundBucket = ThisBucket;
218 // If we found an empty bucket, the key doesn't exist in the set.
219 // Insert it and return the default value.
220 if (ThisBucket->first == EmptyKey) {
221 // If we've already seen a tombstone while probing, fill it in instead
222 // of the empty bucket we eventually probed to.
223 if (FoundTombstone) ThisBucket = FoundTombstone;
224 FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
228 // If this is a tombstone, remember it. If Val ends up not in the map, we
229 // prefer to return it than something that would require more probing.
230 if (ThisBucket->first == TombstoneKey && !FoundTombstone)
231 FoundTombstone = ThisBucket; // Remember the first tombstone found.
233 // Otherwise, it's a hash collision or a tombstone, continue quadratic
235 BucketNo += ProbeAmt++;
239 void init(unsigned InitBuckets) {
242 NumBuckets = InitBuckets;
243 assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 &&
244 "# initial buckets must be a power of two!");
245 Buckets = (BucketT*)new char[sizeof(BucketT)*InitBuckets];
246 // Initialize all the keys to EmptyKey.
247 const KeyT EmptyKey = getEmptyKey();
248 for (unsigned i = 0; i != InitBuckets; ++i)
249 new (&Buckets[i].first) KeyT(EmptyKey);
253 unsigned OldNumBuckets = NumBuckets;
254 BucketT *OldBuckets = Buckets;
256 // Double the number of buckets.
259 Buckets = (BucketT*)new char[sizeof(BucketT)*NumBuckets];
261 // Initialize all the keys to EmptyKey.
262 const KeyT EmptyKey = getEmptyKey();
263 for (unsigned i = 0, e = NumBuckets; i != e; ++i)
264 new (&Buckets[i].first) KeyT(EmptyKey);
266 // Insert all the old elements.
267 const KeyT TombstoneKey = getTombstoneKey();
268 for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
269 if (B->first != EmptyKey && B->first != TombstoneKey) {
270 // Insert the key/value into the new table.
272 bool FoundVal = LookupBucketFor(B->first, DestBucket);
273 FoundVal = FoundVal; // silence warning.
274 assert(!FoundVal && "Key already in new map?");
275 DestBucket->first = B->first;
276 new (&DestBucket->second) ValueT(B->second);
284 // Free the old table.
285 delete[] (char*)OldBuckets;
289 template<typename KeyT, typename ValueT, typename KeyInfoT>
290 class DenseMapIterator {
291 typedef std::pair<KeyT, ValueT> BucketT;
293 const BucketT *Ptr, *End;
295 DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
296 AdvancePastEmptyBuckets();
299 std::pair<KeyT, ValueT> &operator*() const {
300 return *const_cast<BucketT*>(Ptr);
302 std::pair<KeyT, ValueT> *operator->() const {
303 return const_cast<BucketT*>(Ptr);
306 bool operator==(const DenseMapIterator &RHS) const {
307 return Ptr == RHS.Ptr;
309 bool operator!=(const DenseMapIterator &RHS) const {
310 return Ptr != RHS.Ptr;
313 inline DenseMapIterator& operator++() { // Preincrement
315 AdvancePastEmptyBuckets();
318 DenseMapIterator operator++(int) { // Postincrement
319 DenseMapIterator tmp = *this; ++*this; return tmp;
323 void AdvancePastEmptyBuckets() {
324 const KeyT Empty = KeyInfoT::getEmptyKey();
325 const KeyT Tombstone = KeyInfoT::getTombstoneKey();
327 while (Ptr != End && (Ptr->first == Empty || Ptr->first == Tombstone))
332 template<typename KeyT, typename ValueT, typename KeyInfoT>
333 class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> {
335 DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
336 const std::pair<KeyT, ValueT> *E)
337 : DenseMapIterator<KeyT, ValueT>(Pos, E) {
339 const std::pair<KeyT, ValueT> &operator*() const {
342 const std::pair<KeyT, ValueT> *operator->() const {
347 } // end namespace llvm