include/llvm/ADT/DenseMap.h

   1 //===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // 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/MathExtras.h"
  18 #include "llvm/Support/PointerLikeTypeTraits.h"
  19 #include "llvm/Support/type_traits.h"
  20 #include "llvm/ADT/DenseMapInfo.h"
  21 #include <algorithm>
  22 #include <iterator>
  23 #include <new>
  24 #include <utility>
  25 #include <cassert>
  26 #include <cstddef>
  27 #include <cstring>
  28
  29 namespace llvm {
  30
  31 template<typename KeyT, typename ValueT,
  32          typename KeyInfoT = DenseMapInfo<KeyT>,
  33          typename ValueInfoT = DenseMapInfo<ValueT>, bool IsConst = false>
  34 class DenseMapIterator;
  35
  36 template<typename KeyT, typename ValueT,
  37          typename KeyInfoT = DenseMapInfo<KeyT>,
  38          typename ValueInfoT = DenseMapInfo<ValueT> >
  39 class DenseMap {
  40   typedef std::pair<KeyT, ValueT> BucketT;
  41   unsigned NumBuckets;
  42   BucketT *Buckets;
  43
  44   unsigned NumEntries;
  45   unsigned NumTombstones;
  46 public:
  47   typedef KeyT key_type;
  48   typedef ValueT mapped_type;
  49   typedef BucketT value_type;
  50
  51   DenseMap(const DenseMap &other) {
  52     NumBuckets = 0;
  53     CopyFrom(other);
  54   }
  55
  56   explicit DenseMap(unsigned NumInitBuckets = 64) {
  57     init(NumInitBuckets);
  58   }
  59
  60   template<typename InputIt>
  61   DenseMap(const InputIt &I, const InputIt &E) {
  62     init(64);
  63     insert(I, E);
  64   }
  65
  66   ~DenseMap() {
  67     const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
  68     for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
  69       if (!KeyInfoT::isEqual(P->first, EmptyKey) &&
  70           !KeyInfoT::isEqual(P->first, TombstoneKey))
  71         P->second.~ValueT();
  72       P->first.~KeyT();
  73     }
  74 #ifndef NDEBUG
  75     memset(Buckets, 0x5a, sizeof(BucketT)*NumBuckets);
  76 #endif
  77     operator delete(Buckets);
  78   }
  79
  80   typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
  81   typedef DenseMapIterator<KeyT, ValueT,
  82                            KeyInfoT, ValueInfoT, true> const_iterator;
  83   inline iterator begin() {
  84     // When the map is empty, avoid the overhead of AdvancePastEmptyBuckets().
  85     return empty() ? end() : iterator(Buckets, Buckets+NumBuckets);
  86   }
  87   inline iterator end() {
  88     return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
  89   }
  90   inline const_iterator begin() const {
  91     return empty() ? end() : const_iterator(Buckets, Buckets+NumBuckets);
  92   }
  93   inline const_iterator end() const {
  94     return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
  95   }
  96
  97   bool empty() const { return NumEntries == 0; }
  98   unsigned size() const { return NumEntries; }
  99
 100   /// Grow the densemap so that it has at least Size buckets. Does not shrink
 101   void resize(size_t Size) { grow(Size); }
 102
 103   void clear() {
 104     if (NumEntries == 0 && NumTombstones == 0) return;
 105
 106     // If the capacity of the array is huge, and the # elements used is small,
 107     // shrink the array.
 108     if (NumEntries * 4 < NumBuckets && NumBuckets > 64) {
 109       shrink_and_clear();
 110       return;
 111     }
 112
 113     const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
 114     for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
 115       if (!KeyInfoT::isEqual(P->first, EmptyKey)) {
 116         if (!KeyInfoT::isEqual(P->first, TombstoneKey)) {
 117           P->second.~ValueT();
 118           --NumEntries;
 119         }
 120         P->first = EmptyKey;
 121       }
 122     }
 123     assert(NumEntries == 0 && "Node count imbalance!");
 124     NumTombstones = 0;
 125   }
 126
 127   /// count - Return true if the specified key is in the map.
 128   bool count(const KeyT &Val) const {
 129     BucketT *TheBucket;
 130     return LookupBucketFor(Val, TheBucket);
 131   }
 132
 133   iterator find(const KeyT &Val) {
 134     BucketT *TheBucket;
 135     if (LookupBucketFor(Val, TheBucket))
 136       return iterator(TheBucket, Buckets+NumBuckets);
 137     return end();
 138   }
 139   const_iterator find(const KeyT &Val) const {
 140     BucketT *TheBucket;
 141     if (LookupBucketFor(Val, TheBucket))
 142       return const_iterator(TheBucket, Buckets+NumBuckets);
 143     return end();
 144   }
 145
 146   /// lookup - Return the entry for the specified key, or a default
 147   /// constructed value if no such entry exists.
 148   ValueT lookup(const KeyT &Val) const {
 149     BucketT *TheBucket;
 150     if (LookupBucketFor(Val, TheBucket))
 151       return TheBucket->second;
 152     return ValueT();
 153   }
 154
 155   // Inserts key,value pair into the map if the key isn't already in the map.
 156   // If the key is already in the map, it returns false and doesn't update the
 157   // value.
 158   std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) {
 159     BucketT *TheBucket;
 160     if (LookupBucketFor(KV.first, TheBucket))
 161       return std::make_pair(iterator(TheBucket, Buckets+NumBuckets),
 162                             false); // Already in map.
 163
 164     // Otherwise, insert the new element.
 165     TheBucket = InsertIntoBucket(KV.first, KV.second, TheBucket);
 166     return std::make_pair(iterator(TheBucket, Buckets+NumBuckets),
 167                           true);
 168   }
 169
 170   /// insert - Range insertion of pairs.
 171   template<typename InputIt>
 172   void insert(InputIt I, InputIt E) {
 173     for (; I != E; ++I)
 174       insert(*I);
 175   }
 176
 177
 178   bool erase(const KeyT &Val) {
 179     BucketT *TheBucket;
 180     if (!LookupBucketFor(Val, TheBucket))
 181       return false; // not in map.
 182
 183     TheBucket->second.~ValueT();
 184     TheBucket->first = getTombstoneKey();
 185     --NumEntries;
 186     ++NumTombstones;
 187     return true;
 188   }
 189   void erase(iterator I) {
 190     BucketT *TheBucket = &*I;
 191     TheBucket->second.~ValueT();
 192     TheBucket->first = getTombstoneKey();
 193     --NumEntries;
 194     ++NumTombstones;
 195   }
 196
 197   void swap(DenseMap& RHS) {
 198     std::swap(NumBuckets, RHS.NumBuckets);
 199     std::swap(Buckets, RHS.Buckets);
 200     std::swap(NumEntries, RHS.NumEntries);
 201     std::swap(NumTombstones, RHS.NumTombstones);
 202   }
 203
 204   value_type& FindAndConstruct(const KeyT &Key) {
 205     BucketT *TheBucket;
 206     if (LookupBucketFor(Key, TheBucket))
 207       return *TheBucket;
 208
 209     return *InsertIntoBucket(Key, ValueT(), TheBucket);
 210   }
 211
 212   ValueT &operator[](const KeyT &Key) {
 213     return FindAndConstruct(Key).second;
 214   }
 215
 216   DenseMap& operator=(const DenseMap& other) {
 217     CopyFrom(other);
 218     return *this;
 219   }
 220
 221   /// isPointerIntoBucketsArray - Return true if the specified pointer points
 222   /// somewhere into the DenseMap's array of buckets (i.e. either to a key or
 223   /// value in the DenseMap).
 224   bool isPointerIntoBucketsArray(const void *Ptr) const {
 225     return Ptr >= Buckets && Ptr < Buckets+NumBuckets;
 226   }
 227
 228   /// getPointerIntoBucketsArray() - Return an opaque pointer into the buckets
 229   /// array.  In conjunction with the previous method, this can be used to
 230   /// determine whether an insertion caused the DenseMap to reallocate.
 231   const void *getPointerIntoBucketsArray() const { return Buckets; }
 232
 233 private:
 234   void CopyFrom(const DenseMap& other) {
 235     if (NumBuckets != 0 &&
 236         (!isPodLike<KeyInfoT>::value || !isPodLike<ValueInfoT>::value)) {
 237       const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
 238       for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
 239         if (!KeyInfoT::isEqual(P->first, EmptyKey) &&
 240             !KeyInfoT::isEqual(P->first, TombstoneKey))
 241           P->second.~ValueT();
 242         P->first.~KeyT();
 243       }
 244     }
 245
 246     NumEntries = other.NumEntries;
 247     NumTombstones = other.NumTombstones;
 248
 249     if (NumBuckets) {
 250 #ifndef NDEBUG
 251       memset(Buckets, 0x5a, sizeof(BucketT)*NumBuckets);
 252 #endif
 253       operator delete(Buckets);
 254     }
 255     Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT) *
 256                                                  other.NumBuckets));
 257
 258     if (isPodLike<KeyInfoT>::value && isPodLike<ValueInfoT>::value)
 259       memcpy(Buckets, other.Buckets, other.NumBuckets * sizeof(BucketT));
 260     else
 261       for (size_t i = 0; i < other.NumBuckets; ++i) {
 262         new (&Buckets[i].first) KeyT(other.Buckets[i].first);
 263         if (!KeyInfoT::isEqual(Buckets[i].first, getEmptyKey()) &&
 264             !KeyInfoT::isEqual(Buckets[i].first, getTombstoneKey()))
 265           new (&Buckets[i].second) ValueT(other.Buckets[i].second);
 266       }
 267     NumBuckets = other.NumBuckets;
 268   }
 269
 270   BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
 271                             BucketT *TheBucket) {
 272     // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
 273     // the buckets are empty (meaning that many are filled with tombstones),
 274     // grow the table.
 275     //
 276     // The later case is tricky.  For example, if we had one empty bucket with
 277     // tons of tombstones, failing lookups (e.g. for insertion) would have to
 278     // probe almost the entire table until it found the empty bucket.  If the
 279     // table completely filled with tombstones, no lookup would ever succeed,
 280     // causing infinite loops in lookup.
 281     ++NumEntries;
 282     if (NumEntries*4 >= NumBuckets*3 ||
 283         NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
 284       this->grow(NumBuckets * 2);
 285       LookupBucketFor(Key, TheBucket);
 286     }
 287
 288     // If we are writing over a tombstone, remember this.
 289     if (!KeyInfoT::isEqual(TheBucket->first, getEmptyKey()))
 290       --NumTombstones;
 291
 292     TheBucket->first = Key;
 293     new (&TheBucket->second) ValueT(Value);
 294     return TheBucket;
 295   }
 296
 297   static unsigned getHashValue(const KeyT &Val) {
 298     return KeyInfoT::getHashValue(Val);
 299   }
 300   static const KeyT getEmptyKey() {
 301     return KeyInfoT::getEmptyKey();
 302   }
 303   static const KeyT getTombstoneKey() {
 304     return KeyInfoT::getTombstoneKey();
 305   }
 306
 307   /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
 308   /// FoundBucket.  If the bucket contains the key and a value, this returns
 309   /// true, otherwise it returns a bucket with an empty marker or tombstone and
 310   /// returns false.
 311   bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
 312     unsigned BucketNo = getHashValue(Val);
 313     unsigned ProbeAmt = 1;
 314     BucketT *BucketsPtr = Buckets;
 315
 316     // FoundTombstone - Keep track of whether we find a tombstone while probing.
 317     BucketT *FoundTombstone = 0;
 318     const KeyT EmptyKey = getEmptyKey();
 319     const KeyT TombstoneKey = getTombstoneKey();
 320     assert(!KeyInfoT::isEqual(Val, EmptyKey) &&
 321            !KeyInfoT::isEqual(Val, TombstoneKey) &&
 322            "Empty/Tombstone value shouldn't be inserted into map!");
 323
 324     while (1) {
 325       BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
 326       // Found Val's bucket?  If so, return it.
 327       if (KeyInfoT::isEqual(ThisBucket->first, Val)) {
 328         FoundBucket = ThisBucket;
 329         return true;
 330       }
 331
 332       // If we found an empty bucket, the key doesn't exist in the set.
 333       // Insert it and return the default value.
 334       if (KeyInfoT::isEqual(ThisBucket->first, EmptyKey)) {
 335         // If we've already seen a tombstone while probing, fill it in instead
 336         // of the empty bucket we eventually probed to.
 337         if (FoundTombstone) ThisBucket = FoundTombstone;
 338         FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
 339         return false;
 340       }
 341
 342       // If this is a tombstone, remember it.  If Val ends up not in the map, we
 343       // prefer to return it than something that would require more probing.
 344       if (KeyInfoT::isEqual(ThisBucket->first, TombstoneKey) && !FoundTombstone)
 345         FoundTombstone = ThisBucket;  // Remember the first tombstone found.
 346
 347       // Otherwise, it's a hash collision or a tombstone, continue quadratic
 348       // probing.
 349       BucketNo += ProbeAmt++;
 350     }
 351   }
 352
 353   void init(unsigned InitBuckets) {
 354     NumEntries = 0;
 355     NumTombstones = 0;
 356     NumBuckets = InitBuckets;
 357     assert(InitBuckets && (InitBuckets & (InitBuckets-1)) == 0 &&
 358            "# initial buckets must be a power of two!");
 359     Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*InitBuckets));
 360     // Initialize all the keys to EmptyKey.
 361     const KeyT EmptyKey = getEmptyKey();
 362     for (unsigned i = 0; i != InitBuckets; ++i)
 363       new (&Buckets[i].first) KeyT(EmptyKey);
 364   }
 365
 366   void grow(unsigned AtLeast) {
 367     unsigned OldNumBuckets = NumBuckets;
 368     BucketT *OldBuckets = Buckets;
 369
 370     // Double the number of buckets.
 371     while (NumBuckets < AtLeast)
 372       NumBuckets <<= 1;
 373     NumTombstones = 0;
 374     Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets));
 375
 376     // Initialize all the keys to EmptyKey.
 377     const KeyT EmptyKey = getEmptyKey();
 378     for (unsigned i = 0, e = NumBuckets; i != e; ++i)
 379       new (&Buckets[i].first) KeyT(EmptyKey);
 380
 381     // Insert all the old elements.
 382     const KeyT TombstoneKey = getTombstoneKey();
 383     for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
 384       if (!KeyInfoT::isEqual(B->first, EmptyKey) &&
 385           !KeyInfoT::isEqual(B->first, TombstoneKey)) {
 386         // Insert the key/value into the new table.
 387         BucketT *DestBucket;
 388         bool FoundVal = LookupBucketFor(B->first, DestBucket);
 389         FoundVal = FoundVal; // silence warning.
 390         assert(!FoundVal && "Key already in new map?");
 391         DestBucket->first = B->first;
 392         new (&DestBucket->second) ValueT(B->second);
 393
 394         // Free the value.
 395         B->second.~ValueT();
 396       }
 397       B->first.~KeyT();
 398     }
 399
 400 #ifndef NDEBUG
 401     memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets);
 402 #endif
 403     // Free the old table.
 404     operator delete(OldBuckets);
 405   }
 406
 407   void shrink_and_clear() {
 408     unsigned OldNumBuckets = NumBuckets;
 409     BucketT *OldBuckets = Buckets;
 410
 411     // Reduce the number of buckets.
 412     NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1)
 413                                  : 64;
 414     NumTombstones = 0;
 415     Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets));
 416
 417     // Initialize all the keys to EmptyKey.
 418     const KeyT EmptyKey = getEmptyKey();
 419     for (unsigned i = 0, e = NumBuckets; i != e; ++i)
 420       new (&Buckets[i].first) KeyT(EmptyKey);
 421
 422     // Free the old buckets.
 423     const KeyT TombstoneKey = getTombstoneKey();
 424     for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
 425       if (!KeyInfoT::isEqual(B->first, EmptyKey) &&
 426           !KeyInfoT::isEqual(B->first, TombstoneKey)) {
 427         // Free the value.
 428         B->second.~ValueT();
 429       }
 430       B->first.~KeyT();
 431     }
 432
 433 #ifndef NDEBUG
 434     memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets);
 435 #endif
 436     // Free the old table.
 437     operator delete(OldBuckets);
 438
 439     NumEntries = 0;
 440   }
 441 };
 442
 443 template<typename KeyT, typename ValueT,
 444          typename KeyInfoT, typename ValueInfoT, bool IsConst>
 445 class DenseMapIterator {
 446   typedef std::pair<KeyT, ValueT> Bucket;
 447   typedef DenseMapIterator<KeyT, ValueT,
 448                            KeyInfoT, ValueInfoT, true> ConstIterator;
 449   friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, ValueInfoT, true>;
 450 public:
 451   typedef ptrdiff_t difference_type;
 452   typedef typename conditional<IsConst, const Bucket, Bucket>::type value_type;
 453   typedef value_type *pointer;
 454   typedef value_type &reference;
 455   typedef std::forward_iterator_tag iterator_category;
 456 private:
 457   pointer Ptr, End;
 458 public:
 459   DenseMapIterator() : Ptr(0), End(0) {}
 460
 461   DenseMapIterator(pointer Pos, pointer E) : Ptr(Pos), End(E) {
 462     AdvancePastEmptyBuckets();
 463   }
 464
 465   // If IsConst is true this is a converting constructor from iterator to
 466   // const_iterator and the default copy constructor is used.
 467   // Otherwise this is a copy constructor for iterator.
 468   DenseMapIterator(const DenseMapIterator<KeyT, ValueT,
 469                                           KeyInfoT, ValueInfoT, false>& I)
 470     : Ptr(I.Ptr), End(I.End) {}
 471
 472   reference operator*() const {
 473     return *Ptr;
 474   }
 475   pointer operator->() const {
 476     return Ptr;
 477   }
 478
 479   bool operator==(const ConstIterator &RHS) const {
 480     return Ptr == RHS.operator->();
 481   }
 482   bool operator!=(const ConstIterator &RHS) const {
 483     return Ptr != RHS.operator->();
 484   }
 485
 486   inline DenseMapIterator& operator++() {  // Preincrement
 487     ++Ptr;
 488     AdvancePastEmptyBuckets();
 489     return *this;
 490   }
 491   DenseMapIterator operator++(int) {  // Postincrement
 492     DenseMapIterator tmp = *this; ++*this; return tmp;
 493   }
 494
 495 private:
 496   void AdvancePastEmptyBuckets() {
 497     const KeyT Empty = KeyInfoT::getEmptyKey();
 498     const KeyT Tombstone = KeyInfoT::getTombstoneKey();
 499
 500     while (Ptr != End &&
 501            (KeyInfoT::isEqual(Ptr->first, Empty) ||
 502             KeyInfoT::isEqual(Ptr->first, Tombstone)))
 503       ++Ptr;
 504   }
 505 };
 506
 507 } // end namespace llvm
 508
 509 #endif