DenseMap.h revision 28f72279f5aaf34ba62ae00ca3b8bb94d8b91f70 
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 = 64) {
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 insert(const std::pair<KeyT, ValueT> &KV) {
115    BucketT *TheBucket;
116    if (LookupBucketFor(KV.first, TheBucket))
117      return false; // Already in map.
118
119    // Otherwise, insert the new element.
120    InsertIntoBucket(KV.first, KV.second, TheBucket);
121    return true;
122  }
123
124  bool erase(const KeyT &Val) {
125    BucketT *TheBucket;
126    if (!LookupBucketFor(Val, TheBucket))
127      return false; // not in map.
128
129    TheBucket->second.~ValueT();
130    TheBucket->first = getTombstoneKey();
131    --NumEntries;
132    return true;
133  }
134  bool erase(iterator I) {
135    BucketT *TheBucket = &*I;
136    TheBucket->second.~ValueT();
137    TheBucket->first = getTombstoneKey();
138    --NumEntries;
139    return true;
140  }
141
142  ValueT &operator[](const KeyT &Key) {
143    BucketT *TheBucket;
144    if (LookupBucketFor(Key, TheBucket))
145      return TheBucket->second;
146
147    return InsertIntoBucket(Key, ValueT(), TheBucket)->second;
148  }
149
150private:
151  BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
152                            BucketT *TheBucket) {
153    // If the load of the hash table is more than 3/4, grow it.
154    if (NumEntries*4 >= NumBuckets*3) {
155      this->grow();
156      LookupBucketFor(Key, TheBucket);
157    }
158    ++NumEntries;
159    TheBucket->first = Key;
160    new (&TheBucket->second) ValueT(Value);
161    return TheBucket;
162  }
163
164  static unsigned getHashValue(const KeyT &Val) {
165    return DenseMapKeyInfo<KeyT>::getHashValue(Val);
166  }
167  static const KeyT getEmptyKey() {
168    return DenseMapKeyInfo<KeyT>::getEmptyKey();
169  }
170  static const KeyT getTombstoneKey() {
171    return DenseMapKeyInfo<KeyT>::getTombstoneKey();
172  }
173
174  /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
175  /// FoundBucket.  If the bucket contains the key and a value, this returns
176  /// true, otherwise it returns a bucket with an empty marker or tombstone and
177  /// returns false.
178  bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
179    unsigned BucketNo = getHashValue(Val);
180    unsigned ProbeAmt = 1;
181    BucketT *BucketsPtr = Buckets;
182
183    // FoundTombstone - Keep track of whether we find a tombstone while probing.
184    BucketT *FoundTombstone = 0;
185    const KeyT EmptyKey = getEmptyKey();
186    const KeyT TombstoneKey = getTombstoneKey();
187    assert(Val != EmptyKey && Val != TombstoneKey &&
188           "Empty/Tombstone value shouldn't be inserted into map!");
189
190    while (1) {
191      BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
192      // Found Val's bucket?  If so, return it.
193      if (ThisBucket->first == Val) {
194        FoundBucket = ThisBucket;
195        return true;
196      }
197
198      // If we found an empty bucket, the key doesn't exist in the set.
199      // Insert it and return the default value.
200      if (ThisBucket->first == EmptyKey) {
201        // If we've already seen a tombstone while probing, fill it in instead
202        // of the empty bucket we eventually probed to.
203        if (FoundTombstone) ThisBucket = FoundTombstone;
204        FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
205        return false;
206      }
207
208      // If this is a tombstone, remember it.  If Val ends up not in the map, we
209      // prefer to return it than something that would require more probing.
210      if (ThisBucket->first == TombstoneKey && !FoundTombstone)
211        FoundTombstone = ThisBucket;  // Remember the first tombstone found.
212
213      // Otherwise, it's a hash collision or a tombstone, continue quadratic
214      // probing.
215      BucketNo += ProbeAmt++;
216    }
217  }
218
219  void init(unsigned InitBuckets) {
220    NumEntries = 0;
221    NumBuckets = InitBuckets;
222    assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 &&
223           "# initial buckets must be a power of two!");
224    Buckets = (BucketT*)new char[sizeof(BucketT)*InitBuckets];
225    // Initialize all the keys to EmptyKey.
226    const KeyT EmptyKey = getEmptyKey();
227    for (unsigned i = 0; i != InitBuckets; ++i)
228      new (&Buckets[i].first) KeyT(EmptyKey);
229  }
230
231  void grow() {
232    unsigned OldNumBuckets = NumBuckets;
233    BucketT *OldBuckets = Buckets;
234
235    // Double the number of buckets.
236    NumBuckets <<= 1;
237    Buckets = (BucketT*)new char[sizeof(BucketT)*NumBuckets];
238
239    // Initialize all the keys to EmptyKey.
240    const KeyT EmptyKey = getEmptyKey();
241    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
242      new (&Buckets[i].first) KeyT(EmptyKey);
243
244    // Insert all the old elements.
245    const KeyT TombstoneKey = getTombstoneKey();
246    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
247      if (B->first != EmptyKey && B->first != TombstoneKey) {
248        // Insert the key/value into the new table.
249        BucketT *DestBucket;
250        bool FoundVal = LookupBucketFor(B->first, DestBucket);
251        FoundVal = FoundVal; // silence warning.
252        assert(!FoundVal && "Key already in new map?");
253        DestBucket->first = B->first;
254        new (&DestBucket->second) ValueT(B->second);
255
256        // Free the value.
257        B->second.~ValueT();
258      }
259      B->first.~KeyT();
260    }
261
262    // Free the old table.
263    delete[] (char*)OldBuckets;
264  }
265};
266
267template<typename KeyT, typename ValueT>
268class DenseMapIterator {
269  typedef std::pair<KeyT, ValueT> BucketT;
270protected:
271  const BucketT *Ptr, *End;
272public:
273  DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
274    AdvancePastEmptyBuckets();
275  }
276
277  std::pair<KeyT, ValueT> &operator*() const {
278    return *const_cast<BucketT*>(Ptr);
279  }
280  std::pair<KeyT, ValueT> *operator->() const {
281    return const_cast<BucketT*>(Ptr);
282  }
283
284  bool operator==(const DenseMapIterator &RHS) const {
285    return Ptr == RHS.Ptr;
286  }
287  bool operator!=(const DenseMapIterator &RHS) const {
288    return Ptr != RHS.Ptr;
289  }
290
291  inline DenseMapIterator& operator++() {          // Preincrement
292    ++Ptr;
293    AdvancePastEmptyBuckets();
294    return *this;
295  }
296  DenseMapIterator operator++(int) {        // Postincrement
297    DenseMapIterator tmp = *this; ++*this; return tmp;
298  }
299
300private:
301  void AdvancePastEmptyBuckets() {
302    const KeyT Empty = DenseMapKeyInfo<KeyT>::getEmptyKey();
303    const KeyT Tombstone = DenseMapKeyInfo<KeyT>::getTombstoneKey();
304
305    while (Ptr != End && (Ptr->first == Empty || Ptr->first == Tombstone))
306      ++Ptr;
307  }
308};
309
310template<typename KeyT, typename ValueT>
311class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT> {
312public:
313  DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
314                        const std::pair<KeyT, ValueT> *E)
315    : DenseMapIterator<KeyT, ValueT>(Pos, E) {
316  }
317  const std::pair<KeyT, ValueT> &operator*() const {
318    return *this->Ptr;
319  }
320  const std::pair<KeyT, ValueT> *operator->() const {
321    return this->Ptr;
322  }
323};
324
325} // end namespace llvm
326
327#endif
328