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356 lines
11 KiB
C++
356 lines
11 KiB
C++
//===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by Chris Lattner and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines the DenseMap class.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ADT_DENSEMAP_H
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#define LLVM_ADT_DENSEMAP_H
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#include "llvm/Support/DataTypes.h"
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#include <cassert>
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#include <utility>
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namespace llvm {
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template<typename T>
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struct DenseMapKeyInfo {
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//static inline T getEmptyKey();
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//static inline T getTombstoneKey();
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//static unsigned getHashValue(const T &Val);
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//static bool isPod()
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};
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// Provide DenseMapKeyInfo for all pointers.
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template<typename T>
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struct DenseMapKeyInfo<T*> {
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static inline T* getEmptyKey() { return (T*)-1; }
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static inline T* getTombstoneKey() { return (T*)-2; }
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static unsigned getHashValue(const T *PtrVal) {
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return (unsigned)((uintptr_t)PtrVal >> 4) ^
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(unsigned)((uintptr_t)PtrVal >> 9);
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}
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static bool isPod() { return true; }
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};
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template<typename KeyT, typename ValueT,
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typename KeyInfoT = DenseMapKeyInfo<KeyT> >
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class DenseMapIterator;
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template<typename KeyT, typename ValueT,
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typename KeyInfoT = DenseMapKeyInfo<KeyT> >
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class DenseMapConstIterator;
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template<typename KeyT, typename ValueT,
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typename KeyInfoT = DenseMapKeyInfo<KeyT> >
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class DenseMap {
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typedef std::pair<KeyT, ValueT> BucketT;
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unsigned NumBuckets;
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BucketT *Buckets;
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unsigned NumEntries;
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unsigned NumTombstones;
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DenseMap(const DenseMap &); // not implemented.
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public:
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explicit DenseMap(unsigned NumInitBuckets = 64) {
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init(NumInitBuckets);
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}
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~DenseMap() {
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const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
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for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
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if (P->first != EmptyKey && P->first != TombstoneKey)
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P->second.~ValueT();
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P->first.~KeyT();
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}
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delete[] (char*)Buckets;
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}
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typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
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typedef DenseMapConstIterator<KeyT, ValueT, KeyInfoT> const_iterator;
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inline iterator begin() {
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return iterator(Buckets, Buckets+NumBuckets);
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}
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inline iterator end() {
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return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
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}
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inline const_iterator begin() const {
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return const_iterator(Buckets, Buckets+NumBuckets);
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}
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inline const_iterator end() const {
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return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
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}
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bool empty() const { return NumEntries == 0; }
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unsigned size() const { return NumEntries; }
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void clear() {
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const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
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for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
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if (P->first != EmptyKey && P->first != TombstoneKey) {
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P->first = EmptyKey;
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P->second.~ValueT();
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--NumEntries;
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}
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}
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assert(NumEntries == 0 && "Node count imbalance!");
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NumTombstones = 0;
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}
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/// count - Return true if the specified key is in the map.
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bool count(const KeyT &Val) const {
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BucketT *TheBucket;
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return LookupBucketFor(Val, TheBucket);
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}
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iterator find(const KeyT &Val) {
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BucketT *TheBucket;
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if (LookupBucketFor(Val, TheBucket))
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return iterator(TheBucket, Buckets+NumBuckets);
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return end();
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}
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const_iterator find(const KeyT &Val) const {
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BucketT *TheBucket;
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if (LookupBucketFor(Val, TheBucket))
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return const_iterator(TheBucket, Buckets+NumBuckets);
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return end();
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}
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bool insert(const std::pair<KeyT, ValueT> &KV) {
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BucketT *TheBucket;
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if (LookupBucketFor(KV.first, TheBucket))
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return false; // Already in map.
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// Otherwise, insert the new element.
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InsertIntoBucket(KV.first, KV.second, TheBucket);
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return true;
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}
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bool erase(const KeyT &Val) {
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BucketT *TheBucket;
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if (!LookupBucketFor(Val, TheBucket))
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return false; // not in map.
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TheBucket->second.~ValueT();
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TheBucket->first = getTombstoneKey();
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--NumEntries;
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++NumTombstones;
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return true;
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}
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bool erase(iterator I) {
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BucketT *TheBucket = &*I;
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TheBucket->second.~ValueT();
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TheBucket->first = getTombstoneKey();
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--NumEntries;
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++NumTombstones;
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return true;
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}
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ValueT &operator[](const KeyT &Key) {
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BucketT *TheBucket;
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if (LookupBucketFor(Key, TheBucket))
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return TheBucket->second;
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return InsertIntoBucket(Key, ValueT(), TheBucket)->second;
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}
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private:
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BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
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BucketT *TheBucket) {
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// If the load of the hash table is more than 3/4, or if fewer than 1/8 of
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// the buckets are empty (meaning that many are filled with tombstones),
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// grow the table.
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//
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// The later case is tricky. For example, if we had one empty bucket with
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// tons of tombstones, failing lookups (e.g. for insertion) would have to
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// probe almost the entire table until it found the empty bucket. If the
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// table completely filled with tombstones, no lookup would ever succeed,
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// causing infinite loops in lookup.
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if (NumEntries*4 >= NumBuckets*3 ||
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NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
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this->grow();
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LookupBucketFor(Key, TheBucket);
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}
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++NumEntries;
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// If we are writing over a tombstone, remember this.
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if (TheBucket->first != getEmptyKey())
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--NumTombstones;
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TheBucket->first = Key;
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new (&TheBucket->second) ValueT(Value);
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return TheBucket;
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}
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static unsigned getHashValue(const KeyT &Val) {
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return KeyInfoT::getHashValue(Val);
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}
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static const KeyT getEmptyKey() {
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return KeyInfoT::getEmptyKey();
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}
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static const KeyT getTombstoneKey() {
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return KeyInfoT::getTombstoneKey();
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}
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/// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
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/// FoundBucket. If the bucket contains the key and a value, this returns
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/// true, otherwise it returns a bucket with an empty marker or tombstone and
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/// returns false.
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bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
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unsigned BucketNo = getHashValue(Val);
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unsigned ProbeAmt = 1;
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BucketT *BucketsPtr = Buckets;
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// FoundTombstone - Keep track of whether we find a tombstone while probing.
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BucketT *FoundTombstone = 0;
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const KeyT EmptyKey = getEmptyKey();
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const KeyT TombstoneKey = getTombstoneKey();
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assert(Val != EmptyKey && Val != TombstoneKey &&
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"Empty/Tombstone value shouldn't be inserted into map!");
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while (1) {
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BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
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// Found Val's bucket? If so, return it.
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if (ThisBucket->first == Val) {
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FoundBucket = ThisBucket;
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return true;
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}
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// If we found an empty bucket, the key doesn't exist in the set.
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// Insert it and return the default value.
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if (ThisBucket->first == EmptyKey) {
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// If we've already seen a tombstone while probing, fill it in instead
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// of the empty bucket we eventually probed to.
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if (FoundTombstone) ThisBucket = FoundTombstone;
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FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
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return false;
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}
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// If this is a tombstone, remember it. If Val ends up not in the map, we
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// prefer to return it than something that would require more probing.
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if (ThisBucket->first == TombstoneKey && !FoundTombstone)
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FoundTombstone = ThisBucket; // Remember the first tombstone found.
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// Otherwise, it's a hash collision or a tombstone, continue quadratic
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// probing.
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BucketNo += ProbeAmt++;
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}
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}
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void init(unsigned InitBuckets) {
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NumEntries = 0;
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NumTombstones = 0;
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NumBuckets = InitBuckets;
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assert(InitBuckets && (InitBuckets & InitBuckets-1) == 0 &&
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"# initial buckets must be a power of two!");
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Buckets = (BucketT*)new char[sizeof(BucketT)*InitBuckets];
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// Initialize all the keys to EmptyKey.
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const KeyT EmptyKey = getEmptyKey();
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for (unsigned i = 0; i != InitBuckets; ++i)
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new (&Buckets[i].first) KeyT(EmptyKey);
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}
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void grow() {
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unsigned OldNumBuckets = NumBuckets;
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BucketT *OldBuckets = Buckets;
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// Double the number of buckets.
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NumBuckets <<= 1;
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NumTombstones = 0;
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Buckets = (BucketT*)new char[sizeof(BucketT)*NumBuckets];
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// Initialize all the keys to EmptyKey.
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const KeyT EmptyKey = getEmptyKey();
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for (unsigned i = 0, e = NumBuckets; i != e; ++i)
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new (&Buckets[i].first) KeyT(EmptyKey);
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// Insert all the old elements.
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const KeyT TombstoneKey = getTombstoneKey();
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for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
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if (B->first != EmptyKey && B->first != TombstoneKey) {
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// Insert the key/value into the new table.
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BucketT *DestBucket;
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bool FoundVal = LookupBucketFor(B->first, DestBucket);
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FoundVal = FoundVal; // silence warning.
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assert(!FoundVal && "Key already in new map?");
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DestBucket->first = B->first;
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new (&DestBucket->second) ValueT(B->second);
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// Free the value.
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B->second.~ValueT();
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}
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B->first.~KeyT();
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}
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// Free the old table.
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delete[] (char*)OldBuckets;
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}
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};
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template<typename KeyT, typename ValueT, typename KeyInfoT>
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class DenseMapIterator {
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typedef std::pair<KeyT, ValueT> BucketT;
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protected:
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const BucketT *Ptr, *End;
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public:
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DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
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AdvancePastEmptyBuckets();
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}
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std::pair<KeyT, ValueT> &operator*() const {
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return *const_cast<BucketT*>(Ptr);
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}
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std::pair<KeyT, ValueT> *operator->() const {
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return const_cast<BucketT*>(Ptr);
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}
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bool operator==(const DenseMapIterator &RHS) const {
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return Ptr == RHS.Ptr;
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}
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bool operator!=(const DenseMapIterator &RHS) const {
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return Ptr != RHS.Ptr;
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}
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inline DenseMapIterator& operator++() { // Preincrement
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++Ptr;
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AdvancePastEmptyBuckets();
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return *this;
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}
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DenseMapIterator operator++(int) { // Postincrement
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DenseMapIterator tmp = *this; ++*this; return tmp;
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}
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private:
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void AdvancePastEmptyBuckets() {
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const KeyT Empty = KeyInfoT::getEmptyKey();
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const KeyT Tombstone = KeyInfoT::getTombstoneKey();
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while (Ptr != End && (Ptr->first == Empty || Ptr->first == Tombstone))
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++Ptr;
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}
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};
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template<typename KeyT, typename ValueT, typename KeyInfoT>
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class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> {
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public:
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DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
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const std::pair<KeyT, ValueT> *E)
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: DenseMapIterator<KeyT, ValueT, KeyInfoT>(Pos, E) {
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}
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const std::pair<KeyT, ValueT> &operator*() const {
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return *this->Ptr;
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}
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const std::pair<KeyT, ValueT> *operator->() const {
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return this->Ptr;
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}
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};
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} // end namespace llvm
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#endif
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