//static bool isPod()
};
+// Provide DenseMapKeyInfo for all pointers.
template<typename T>
struct DenseMapKeyInfo<T*> {
static inline T* getEmptyKey() { return (T*)-1; }
static bool isPod() { return true; }
};
-template<typename KeyT, typename ValueT>
+template<typename KeyT, typename ValueT,
+ typename KeyInfoT = DenseMapKeyInfo<KeyT> >
class DenseMapIterator;
-template<typename KeyT, typename ValueT>
+template<typename KeyT, typename ValueT,
+ typename KeyInfoT = DenseMapKeyInfo<KeyT> >
class DenseMapConstIterator;
-template<typename KeyT, typename ValueT>
+template<typename KeyT, typename ValueT,
+ typename KeyInfoT = DenseMapKeyInfo<KeyT> >
class DenseMap {
typedef std::pair<KeyT, ValueT> BucketT;
unsigned NumBuckets;
BucketT *Buckets;
unsigned NumEntries;
+ unsigned NumTombstones;
DenseMap(const DenseMap &); // not implemented.
public:
- explicit DenseMap(unsigned NumInitBuckets = 8) {
+ explicit DenseMap(unsigned NumInitBuckets = 64) {
init(NumInitBuckets);
}
~DenseMap() {
delete[] (char*)Buckets;
}
- typedef DenseMapIterator<KeyT, ValueT> iterator;
- typedef DenseMapConstIterator<KeyT, ValueT> const_iterator;
+ typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
+ typedef DenseMapConstIterator<KeyT, ValueT, KeyInfoT> const_iterator;
inline iterator begin() {
- return DenseMapIterator<KeyT, ValueT>(Buckets, Buckets+NumBuckets);
+ return iterator(Buckets, Buckets+NumBuckets);
}
inline iterator end() {
- return DenseMapIterator<KeyT, ValueT>(Buckets+NumBuckets,
- Buckets+NumBuckets);
+ return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
}
inline const_iterator begin() const {
- return DenseMapConstIterator<KeyT, ValueT>(Buckets, Buckets+NumBuckets);
+ return const_iterator(Buckets, Buckets+NumBuckets);
}
inline const_iterator end() const {
- return DenseMapConstIterator<KeyT, ValueT>(Buckets+NumBuckets,
- Buckets+NumBuckets);
+ return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
}
bool empty() const { return NumEntries == 0; }
}
}
assert(NumEntries == 0 && "Node count imbalance!");
+ NumTombstones = 0;
}
/// count - Return true if the specified key is in the map.
return LookupBucketFor(Val, TheBucket);
}
- iterator find(const KeyT &Val) const {
+ iterator find(const KeyT &Val) {
BucketT *TheBucket;
if (LookupBucketFor(Val, TheBucket))
return iterator(TheBucket, Buckets+NumBuckets);
return end();
}
+ const_iterator find(const KeyT &Val) const {
+ BucketT *TheBucket;
+ if (LookupBucketFor(Val, TheBucket))
+ return const_iterator(TheBucket, Buckets+NumBuckets);
+ return end();
+ }
+
+ bool insert(const std::pair<KeyT, ValueT> &KV) {
+ BucketT *TheBucket;
+ if (LookupBucketFor(KV.first, TheBucket))
+ return false; // Already in map.
+
+ // Otherwise, insert the new element.
+ InsertIntoBucket(KV.first, KV.second, TheBucket);
+ return true;
+ }
bool erase(const KeyT &Val) {
BucketT *TheBucket;
TheBucket->second.~ValueT();
TheBucket->first = getTombstoneKey();
--NumEntries;
+ ++NumTombstones;
return true;
}
bool erase(iterator I) {
TheBucket->second.~ValueT();
TheBucket->first = getTombstoneKey();
--NumEntries;
+ ++NumTombstones;
return true;
}
- ValueT &operator[](const KeyT &Val) {
+ ValueT &operator[](const KeyT &Key) {
BucketT *TheBucket;
- if (LookupBucketFor(Val, TheBucket))
+ if (LookupBucketFor(Key, TheBucket))
return TheBucket->second;
- // If the load of the hash table is more than 3/4, grow it.
- if (NumEntries*4 >= NumBuckets*3) {
+ return InsertIntoBucket(Key, ValueT(), TheBucket)->second;
+ }
+
+private:
+ BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
+ BucketT *TheBucket) {
+ // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
+ // the buckets are empty (meaning that many are filled with tombstones),
+ // grow the table.
+ //
+ // The later case is tricky. For example, if we had one empty bucket with
+ // tons of tombstones, failing lookups (e.g. for insertion) would have to
+ // probe almost the entire table until it found the empty bucket. If the
+ // table completely filled with tombstones, no lookup would ever succeed,
+ // causing infinite loops in lookup.
+ if (NumEntries*4 >= NumBuckets*3 ||
+ NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
this->grow();
- LookupBucketFor(Val, TheBucket);
+ LookupBucketFor(Key, TheBucket);
}
++NumEntries;
- TheBucket->first = Val;
- new (&TheBucket->second) ValueT();
- return TheBucket->second;
+
+ // If we are writing over a tombstone, remember this.
+ if (TheBucket->first != getEmptyKey())
+ --NumTombstones;
+
+ TheBucket->first = Key;
+ new (&TheBucket->second) ValueT(Value);
+ return TheBucket;
}
-
-private:
+
static unsigned getHashValue(const KeyT &Val) {
- return DenseMapKeyInfo<KeyT>::getHashValue(Val);
+ return KeyInfoT::getHashValue(Val);
}
static const KeyT getEmptyKey() {
- return DenseMapKeyInfo<KeyT>::getEmptyKey();
+ return KeyInfoT::getEmptyKey();
}
static const KeyT getTombstoneKey() {
- return DenseMapKeyInfo<KeyT>::getTombstoneKey();
+ return KeyInfoT::getTombstoneKey();
}
/// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
void init(unsigned InitBuckets) {
NumEntries = 0;
+ NumTombstones = 0;
NumBuckets = InitBuckets;
assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 &&
"# initial buckets must be a power of two!");
// Double the number of buckets.
NumBuckets <<= 1;
+ NumTombstones = 0;
Buckets = (BucketT*)new char[sizeof(BucketT)*NumBuckets];
// Initialize all the keys to EmptyKey.
// Insert the key/value into the new table.
BucketT *DestBucket;
bool FoundVal = LookupBucketFor(B->first, DestBucket);
+ FoundVal = FoundVal; // silence warning.
assert(!FoundVal && "Key already in new map?");
DestBucket->first = B->first;
new (&DestBucket->second) ValueT(B->second);
}
};
-template<typename KeyT, typename ValueT>
+template<typename KeyT, typename ValueT, typename KeyInfoT>
class DenseMapIterator {
typedef std::pair<KeyT, ValueT> BucketT;
protected:
private:
void AdvancePastEmptyBuckets() {
- const KeyT Empty = DenseMapKeyInfo<KeyT>::getEmptyKey();
- const KeyT Tombstone = DenseMapKeyInfo<KeyT>::getTombstoneKey();
+ const KeyT Empty = KeyInfoT::getEmptyKey();
+ const KeyT Tombstone = KeyInfoT::getTombstoneKey();
while (Ptr != End && (Ptr->first == Empty || Ptr->first == Tombstone))
++Ptr;
}
};
-template<typename KeyT, typename ValueT>
-class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT> {
+template<typename KeyT, typename ValueT, typename KeyInfoT>
+class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> {
public:
DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
const std::pair<KeyT, ValueT> *E)
- : DenseMapIterator<KeyT, ValueT>(Pos, E) {
+ : DenseMapIterator<KeyT, ValueT, KeyInfoT>(Pos, E) {
}
const std::pair<KeyT, ValueT> &operator*() const {
return *this->Ptr;