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//===- ScopedHashTable.h - A simple scoped hash table ---------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements an efficient scoped hash table, which is useful for
// things like dominator-based optimizations. This allows clients to do things
// like this:
//
// ScopedHashTable<int, int> HT;
// {
// ScopedHashTableScope<int, int> Scope1(HT);
// HT.insert(0, 0);
// HT.insert(1, 1);
// {
// ScopedHashTableScope<int, int> Scope2(HT);
// HT.insert(0, 42);
// }
// }
//
// Looking up the value for "0" in the Scope2 block will return 42. Looking
// up the value for 0 before 42 is inserted or after Scope2 is popped will
// return 0.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_SCOPEDHASHTABLE_H
#define LLVM_ADT_SCOPEDHASHTABLE_H
#include <cassert>
#include "llvm/ADT/DenseMap.h"
namespace llvm {
template <typename K, typename V>
class ScopedHashTable;
template <typename K, typename V>
class ScopedHashTableVal {
ScopedHashTableVal *NextInScope;
ScopedHashTableVal *NextForKey;
K Key;
V Val;
public:
ScopedHashTableVal(ScopedHashTableVal *nextInScope,
ScopedHashTableVal *nextForKey, const K &key, const V &val)
: NextInScope(nextInScope), NextForKey(nextForKey), Key(key), Val(val) {
}
const K &getKey() const { return Key; }
const V &getValue() const { return Val; }
V &getValue() { return Val; }
ScopedHashTableVal *getNextForKey() { return NextForKey; }
const ScopedHashTableVal *getNextForKey() const { return NextForKey; }
public:
ScopedHashTableVal *getNextInScope() { return NextInScope; }
};
template <typename K, typename V>
class ScopedHashTableScope {
/// HT - The hashtable that we are active for.
ScopedHashTable<K, V> &HT;
/// PrevScope - This is the scope that we are shadowing in HT.
ScopedHashTableScope *PrevScope;
/// LastValInScope - This is the last value that was inserted for this scope
/// or null if none have been inserted yet.
ScopedHashTableVal<K,V> *LastValInScope;
void operator=(ScopedHashTableScope&); // DO NOT IMPLEMENT
ScopedHashTableScope(ScopedHashTableScope&); // DO NOT IMPLEMENT
public:
ScopedHashTableScope(ScopedHashTable<K, V> &HT);
~ScopedHashTableScope();
private:
friend class ScopedHashTable<K, V>;
ScopedHashTableVal<K, V> *getLastValInScope() { return LastValInScope; }
void setLastValInScope(ScopedHashTableVal<K,V> *Val) { LastValInScope = Val; }
};
template <typename K, typename V>
class ScopedHashTableIterator {
ScopedHashTableVal<K,V> *Node;
public:
ScopedHashTableIterator(ScopedHashTableVal<K,V> *node) : Node(node){}
V &operator*() const {
assert(Node && "Dereference end()");
return Node->getValue();
}
V *operator->() const {
return &Node->getValue();
}
bool operator==(const ScopedHashTableIterator &RHS) const {
return Node == RHS.Node;
}
bool operator!=(const ScopedHashTableIterator &RHS) const {
return Node != RHS.Node;
}
inline ScopedHashTableIterator& operator++() { // Preincrement
assert(Node && "incrementing past end()");
Node = Node->getNextForKey();
return *this;
}
ScopedHashTableIterator operator++(int) { // Postincrement
ScopedHashTableIterator tmp = *this; ++*this; return tmp;
}
};
template <typename K, typename V>
class ScopedHashTable {
DenseMap<K, ScopedHashTableVal<K,V>*> TopLevelMap;
ScopedHashTableScope<K, V> *CurScope;
ScopedHashTable(const ScopedHashTable&); // NOT YET IMPLEMENTED
void operator=(const ScopedHashTable&); // NOT YET IMPLEMENTED
friend class ScopedHashTableScope<K, V>;
public:
ScopedHashTable() : CurScope(0) {}
~ScopedHashTable() {
assert(CurScope == 0 && TopLevelMap.empty() && "Scope imbalance!");
}
void insert(const K &Key, const V &Val) {
assert(CurScope && "No scope active!");
ScopedHashTableVal<K,V> *&KeyEntry = TopLevelMap[Key];
KeyEntry = new ScopedHashTableVal<K,V>(CurScope->getLastValInScope(),
KeyEntry, Key, Val);
CurScope->setLastValInScope(KeyEntry);
}
typedef ScopedHashTableIterator<K, V> iterator;
iterator end() { return iterator(0); }
iterator begin(const K &Key) {
typename DenseMap<K, ScopedHashTableVal<K,V>*>::iterator I =
TopLevelMap.find(Key);
if (I == TopLevelMap.end()) return end();
return iterator(I->second);
}
};
/// ScopedHashTableScope ctor - Install this as the current scope for the hash
/// table.
template <typename K, typename V>
ScopedHashTableScope<K, V>::ScopedHashTableScope(ScopedHashTable<K, V> &ht)
: HT(ht) {
PrevScope = HT.CurScope;
HT.CurScope = this;
LastValInScope = 0;
}
template <typename K, typename V>
ScopedHashTableScope<K, V>::~ScopedHashTableScope() {
assert(HT.CurScope == this && "Scope imbalance!");
HT.CurScope = PrevScope;
// Pop and delete all values corresponding to this scope.
while (ScopedHashTableVal<K, V> *ThisEntry = LastValInScope) {
// Pop this value out of the TopLevelMap.
if (ThisEntry->getNextForKey() == 0) {
assert(HT.TopLevelMap[ThisEntry->getKey()] == ThisEntry &&
"Scope imbalance!");
HT.TopLevelMap.erase(ThisEntry->getKey());
} else {
ScopedHashTableVal<K,V> *&KeyEntry = HT.TopLevelMap[ThisEntry->getKey()];
assert(KeyEntry == ThisEntry && "Scope imbalance!");
KeyEntry = ThisEntry->getNextForKey();
}
// Pop this value out of the scope.
LastValInScope = ThisEntry->getNextInScope();
// Delete this entry.
delete ThisEntry;
}
}
} // end namespace llvm
#endif
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