Added ImmutableList, a companion ADT to ImmutableSet and ImmutableMap that is used to represent a purely functional list.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52911 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ted Kremenek 2008-06-30 18:07:38 +00:00
parent 5b388e40e4
commit 3771902e92

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//==--- ImmutableList.h - Immutable (functional) list interface --*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines the ImmutableList class.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_IMLIST_H
#define LLVM_ADT_IMLIST_H
#include "llvm/Support/Allocator.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/Support/DataTypes.h"
#include <cassert>
namespace llvm {
template <typename T> class ImmutableListFactory;
template <typename T>
class ImmutableListImpl : public FoldingSetNode {
T Head;
ImmutableListImpl* Tail;
ImmutableListImpl(const T& head, ImmutableListImpl* tail = 0)
: Head(head), Tail(tail) {}
friend class ImmutableListFactory<T>;
// Do not implement.
void operator=(const ImmutableListImpl&);
ImmutableListImpl(const ImmutableListImpl&);
public:
const T& getHead() const { return Head; }
ImmutableListImpl* getTail() const { return Tail; }
static inline void Profile(FoldingSetNodeID& ID, const T& H,
ImmutableListImpl* L){
ID.AddPointer(L);
ID.Add(H);
}
void Profile(FoldingSetNodeID& ID) {
Profile(ID, Head, Tail);
}
};
/// ImmutableList - This class represents an immutable (functional) list.
/// It is implemented as a smart pointer (wraps ImmutableListImpl), so it
/// it is intended to always be copied by value as if it were a pointer.
/// This interface matches ImmutableSet and ImmutableMap. ImmutableList
/// objects should almost never be created directly, and instead should
/// be created by ImmutableListFactory objects that manage the lifetime
/// of a group of lists. When the factory object is reclaimed, all lists
/// created by that factory are released as well.
template <typename T>
class ImmutableList {
public:
typedef T value_type;
typedef ImmutableListFactory<T> Factory;
private:
ImmutableListImpl<T>* X;
public:
// This constructor should normally only be called by ImmutableListFactory<T>.
// There may be cases, however, when one needs to extract the internal pointer
// and reconstruct a list object from that pointer.
ImmutableList(ImmutableListImpl<T>* x) : X(x) {}
ImmutableListImpl<T>* getInternalPointer() const {
return X;
}
class iterator {
ImmutableListImpl<T>* L;
public:
iterator() : L(0) {}
iterator(ImmutableList l) : L(l.getInternalPointer()) {}
iterator& operator++() { L = L->Tail; }
bool operator==(const iterator& I) const { return L == I.L; }
ImmutableList operator*() const { return L; }
};
iterator begin() const { return iterator(X); }
iterator end() const { return iterator(); }
bool isEmpty() const { return !X; }
bool isEqual(const ImmutableList& L) const { return X == L.X; }
bool operator==(const ImmutableList& L) const { return isEqual(L); }
const T& getHead() {
assert (!isEmpty() && "Cannot get the head of an empty list.");
return X->getHead();
}
ImmutableList getTail() {
return X ? X->getTail() : 0;
}
};
template <typename T>
class ImmutableListFactory {
typedef ImmutableListImpl<T> ListTy;
typedef FoldingSet<ListTy> CacheTy;
CacheTy Cache;
uintptr_t Allocator;
bool ownsAllocator() const {
return Allocator & 0x1 ? false : true;
}
BumpPtrAllocator& getAllocator() const {
return *reinterpret_cast<BumpPtrAllocator*>(Allocator & ~0x1);
}
public:
ImmutableListFactory()
: Allocator(reinterpret_cast<uintptr_t>(new BumpPtrAllocator())) {}
ImmutableListFactory(BumpPtrAllocator& Alloc)
: Allocator(reinterpret_cast<uintptr_t>(&Alloc) | 0x1) {}
~ImmutableListFactory() {
if (ownsAllocator()) delete &getAllocator();
}
ImmutableList<T> Concat(const T& Head, ImmutableList<T> Tail) {
// Profile the new list to see if it already exists in our cache.
FoldingSetNodeID ID;
void* InsertPos;
ListTy* TailImpl = Tail.getInternalPointer();
ListTy::Profile(ID, Head, TailImpl);
ListTy* L = Cache.FindNodeOrInsertPos(ID, InsertPos);
if (!L) {
// The list does not exist in our cache. Create it.
BumpPtrAllocator& A = getAllocator();
L = (ListTy*) A.Allocate<ListTy>();
new (L) ListTy(Head, TailImpl);
// Insert the new list into the cache.
Cache.InsertNode(L, InsertPos);
}
return L;
}
ImmutableList<T> Add(const T& D, ImmutableList<T> L) {
return Concat(D, L);
}
ImmutableList<T> GetEmptyList() const {
return ImmutableList<T>(0);
}
ImmutableList<T> Create(const T& X) {
return Concat(X, GetEmptyList());
}
};
} // end llvm namespace
#endif