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//===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by Chris Lattner and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the DenseMap class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_DENSEMAP_H
#define LLVM_ADT_DENSEMAP_H
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/MathExtras.h"
#include <cassert>
#include <utility>
namespace llvm {
template<typename T>
struct DenseMapKeyInfo {
//static inline T getEmptyKey();
//static inline T getTombstoneKey();
//static unsigned getHashValue(const T &Val);
//static bool isPod()
};
// Provide DenseMapKeyInfo for all pointers.
template<typename T>
struct DenseMapKeyInfo<T*> {
static inline T* getEmptyKey() { return reinterpret_cast<T*>(-1); }
static inline T* getTombstoneKey() { return reinterpret_cast<T*>(-2); }
static unsigned getHashValue(const T *PtrVal) {
return (unsigned(uintptr_t(PtrVal)) >> 4) ^
(unsigned(uintptr_t(PtrVal)) >> 9);
}
static bool isPod() { return true; }
};
template<typename KeyT, typename ValueT,
typename KeyInfoT = DenseMapKeyInfo<KeyT> >
class DenseMapIterator;
template<typename KeyT, typename ValueT,
typename KeyInfoT = DenseMapKeyInfo<KeyT> >
class DenseMapConstIterator;
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 = 64) {
init(NumInitBuckets);
}
~DenseMap() {
const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
if (P->first != EmptyKey && P->first != TombstoneKey)
P->second.~ValueT();
P->first.~KeyT();
}
delete[] reinterpret_cast<char*>(Buckets);
}
typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
typedef DenseMapConstIterator<KeyT, ValueT, KeyInfoT> const_iterator;
inline iterator begin() {
return iterator(Buckets, Buckets+NumBuckets);
}
inline iterator end() {
return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
}
inline const_iterator begin() const {
return const_iterator(Buckets, Buckets+NumBuckets);
}
inline const_iterator end() const {
return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
}
bool empty() const { return NumEntries == 0; }
unsigned size() const { return NumEntries; }
void clear() {
// If the capacity of the array is huge, and the # elements used is small,
// shrink the array.
if (NumEntries * 4 < NumBuckets && NumBuckets > 64) {
shrink_and_clear();
return;
}
const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
if (P->first != EmptyKey) {
if (P->first != TombstoneKey) {
P->second.~ValueT();
--NumEntries;
}
P->first = EmptyKey;
}
}
assert(NumEntries == 0 && "Node count imbalance!");
NumTombstones = 0;
}
/// count - Return true if the specified key is in the map.
bool count(const KeyT &Val) const {
BucketT *TheBucket;
return LookupBucketFor(Val, TheBucket);
}
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;
if (!LookupBucketFor(Val, TheBucket))
return false; // not in map.
TheBucket->second.~ValueT();
TheBucket->first = getTombstoneKey();
--NumEntries;
++NumTombstones;
return true;
}
bool erase(iterator I) {
BucketT *TheBucket = &*I;
TheBucket->second.~ValueT();
TheBucket->first = getTombstoneKey();
--NumEntries;
++NumTombstones;
return true;
}
ValueT &operator[](const KeyT &Key) {
BucketT *TheBucket;
if (LookupBucketFor(Key, TheBucket))
return TheBucket->second;
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(Key, TheBucket);
}
++NumEntries;
// If we are writing over a tombstone, remember this.
if (TheBucket->first != getEmptyKey())
--NumTombstones;
TheBucket->first = Key;
new (&TheBucket->second) ValueT(Value);
return TheBucket;
}
static unsigned getHashValue(const KeyT &Val) {
return KeyInfoT::getHashValue(Val);
}
static const KeyT getEmptyKey() {
return KeyInfoT::getEmptyKey();
}
static const KeyT getTombstoneKey() {
return KeyInfoT::getTombstoneKey();
}
/// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
/// FoundBucket. If the bucket contains the key and a value, this returns
/// true, otherwise it returns a bucket with an empty marker or tombstone and
/// returns false.
bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
unsigned BucketNo = getHashValue(Val);
unsigned ProbeAmt = 1;
BucketT *BucketsPtr = Buckets;
// FoundTombstone - Keep track of whether we find a tombstone while probing.
BucketT *FoundTombstone = 0;
const KeyT EmptyKey = getEmptyKey();
const KeyT TombstoneKey = getTombstoneKey();
assert(Val != EmptyKey && Val != TombstoneKey &&
"Empty/Tombstone value shouldn't be inserted into map!");
while (1) {
BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
// Found Val's bucket? If so, return it.
if (ThisBucket->first == Val) {
FoundBucket = ThisBucket;
return true;
}
// If we found an empty bucket, the key doesn't exist in the set.
// Insert it and return the default value.
if (ThisBucket->first == EmptyKey) {
// If we've already seen a tombstone while probing, fill it in instead
// of the empty bucket we eventually probed to.
if (FoundTombstone) ThisBucket = FoundTombstone;
FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
return false;
}
// If this is a tombstone, remember it. If Val ends up not in the map, we
// prefer to return it than something that would require more probing.
if (ThisBucket->first == TombstoneKey && !FoundTombstone)
FoundTombstone = ThisBucket; // Remember the first tombstone found.
// Otherwise, it's a hash collision or a tombstone, continue quadratic
// probing.
BucketNo += ProbeAmt++;
}
}
void init(unsigned InitBuckets) {
NumEntries = 0;
NumTombstones = 0;
NumBuckets = InitBuckets;
assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 &&
"# initial buckets must be a power of two!");
Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*InitBuckets]);
// Initialize all the keys to EmptyKey.
const KeyT EmptyKey = getEmptyKey();
for (unsigned i = 0; i != InitBuckets; ++i)
new (&Buckets[i].first) KeyT(EmptyKey);
}
void grow() {
unsigned OldNumBuckets = NumBuckets;
BucketT *OldBuckets = Buckets;
// Double the number of buckets.
NumBuckets <<= 1;
NumTombstones = 0;
Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*NumBuckets]);
// Initialize all the keys to EmptyKey.
const KeyT EmptyKey = getEmptyKey();
for (unsigned i = 0, e = NumBuckets; i != e; ++i)
new (&Buckets[i].first) KeyT(EmptyKey);
// Insert all the old elements.
const KeyT TombstoneKey = getTombstoneKey();
for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
if (B->first != EmptyKey && B->first != TombstoneKey) {
// 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);
// Free the value.
B->second.~ValueT();
}
B->first.~KeyT();
}
// Free the old table.
delete[] reinterpret_cast<char*>(OldBuckets);
}
void shrink_and_clear() {
unsigned OldNumBuckets = NumBuckets;
BucketT *OldBuckets = Buckets;
// Reduce the number of buckets.
NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1)
: 64;
NumTombstones = 0;
Buckets = reinterpret_cast<BucketT*>(new char[sizeof(BucketT)*NumBuckets]);
// Initialize all the keys to EmptyKey.
const KeyT EmptyKey = getEmptyKey();
for (unsigned i = 0, e = NumBuckets; i != e; ++i)
new (&Buckets[i].first) KeyT(EmptyKey);
// Free the old buckets.
const KeyT TombstoneKey = getTombstoneKey();
for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
if (B->first != EmptyKey && B->first != TombstoneKey) {
// Free the value.
B->second.~ValueT();
}
B->first.~KeyT();
}
// Free the old table.
delete[] reinterpret_cast<char*>(OldBuckets);
NumEntries = 0;
}
};
template<typename KeyT, typename ValueT, typename KeyInfoT>
class DenseMapIterator {
typedef std::pair<KeyT, ValueT> BucketT;
protected:
const BucketT *Ptr, *End;
public:
DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
AdvancePastEmptyBuckets();
}
std::pair<KeyT, ValueT> &operator*() const {
return *const_cast<BucketT*>(Ptr);
}
std::pair<KeyT, ValueT> *operator->() const {
return const_cast<BucketT*>(Ptr);
}
bool operator==(const DenseMapIterator &RHS) const {
return Ptr == RHS.Ptr;
}
bool operator!=(const DenseMapIterator &RHS) const {
return Ptr != RHS.Ptr;
}
inline DenseMapIterator& operator++() { // Preincrement
++Ptr;
AdvancePastEmptyBuckets();
return *this;
}
DenseMapIterator operator++(int) { // Postincrement
DenseMapIterator tmp = *this; ++*this; return tmp;
}
private:
void AdvancePastEmptyBuckets() {
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, 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, KeyInfoT>(Pos, E) {
}
const std::pair<KeyT, ValueT> &operator*() const {
return *this->Ptr;
}
const std::pair<KeyT, ValueT> *operator->() const {
return this->Ptr;
}
};
} // end namespace llvm
#endif
|