ImmutableList.h revision 30389141c9c7270b4733ec0b9bc5ad58541f39da 
1//==--- ImmutableList.h - Immutable (functional) list interface --*- C++ -*-==//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines the ImmutableList class.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_ADT_IMLIST_H
15#define LLVM_ADT_IMLIST_H
16
17#include "llvm/Support/Allocator.h"
18#include "llvm/ADT/FoldingSet.h"
19#include "llvm/Support/DataTypes.h"
20#include <cassert>
21
22namespace llvm {
23
24template <typename T> class ImmutableListFactory;
25
26template <typename T>
27class ImmutableListImpl : public FoldingSetNode {
28  T Head;
29  ImmutableListImpl* Tail;
30
31  ImmutableListImpl(const T& head, ImmutableListImpl* tail = 0)
32    : Head(head), Tail(tail) {}
33
34  friend class ImmutableListFactory<T>;
35
36  // Do not implement.
37  void operator=(const ImmutableListImpl&);
38  ImmutableListImpl(const ImmutableListImpl&);
39
40public:
41  const T& getHead() const { return Head; }
42  ImmutableListImpl* getTail() const { return Tail; }
43
44  static inline void Profile(FoldingSetNodeID& ID, const T& H,
45                             ImmutableListImpl* L){
46    ID.AddPointer(L);
47    ID.Add(H);
48  }
49
50  void Profile(FoldingSetNodeID& ID) {
51    Profile(ID, Head, Tail);
52  }
53};
54
55/// ImmutableList - This class represents an immutable (functional) list.
56///  It is implemented as a smart pointer (wraps ImmutableListImpl), so it
57///  it is intended to always be copied by value as if it were a pointer.
58///  This interface matches ImmutableSet and ImmutableMap.  ImmutableList
59///  objects should almost never be created directly, and instead should
60///  be created by ImmutableListFactory objects that manage the lifetime
61///  of a group of lists.  When the factory object is reclaimed, all lists
62///  created by that factory are released as well.
63template <typename T>
64class ImmutableList {
65public:
66  typedef T value_type;
67  typedef ImmutableListFactory<T> Factory;
68
69private:
70  ImmutableListImpl<T>* X;
71
72public:
73  // This constructor should normally only be called by ImmutableListFactory<T>.
74  // There may be cases, however, when one needs to extract the internal pointer
75  // and reconstruct a list object from that pointer.
76  ImmutableList(ImmutableListImpl<T>* x) : X(x) {}
77
78  ImmutableListImpl<T>* getInternalPointer() const {
79    return X;
80  }
81
82  class iterator {
83    ImmutableListImpl<T>* L;
84  public:
85    iterator() : L(0) {}
86    iterator(ImmutableList l) : L(l.getInternalPointer()) {}
87
88    iterator& operator++() { L = L->Tail; return *this; }
89    bool operator==(const iterator& I) const { return L == I.L; }
90    ImmutableList operator*() const { return L; }
91  };
92
93  /// begin - Returns an iterator referring to the head of the list, or
94  ///  an iterator denoting the end of the list if the list is empty.
95  iterator begin() const { return iterator(X); }
96
97  /// end - Returns an iterator denoting the end of the list.  This iterator
98  ///  does not refer to a valid list element.
99  iterator end() const { return iterator(); }
100
101  /// isEmpty - Returns true if the list is empty.
102  bool isEmpty() const { return !X; }
103
104  /// isEqual - Returns true if two lists are equal.  Because all lists created
105  ///  from the same ImmutableListFactory are uniqued, this has O(1) complexity
106  ///  because it the contents of the list do not need to be compared.  Note
107  ///  that you should only compare two lists created from the same
108  ///  ImmutableListFactory.
109  bool isEqual(const ImmutableList& L) const { return X == L.X; }
110
111  bool operator==(const ImmutableList& L) const { return isEqual(L); }
112
113  /// getHead - Returns the head of the list.
114  const T& getHead() {
115    assert (!isEmpty() && "Cannot get the head of an empty list.");
116    return X->getHead();
117  }
118
119  /// getTail - Returns the tail of the list, which is another (possibly empty)
120  ///  ImmutableList.
121  ImmutableList getTail() {
122    return X ? X->getTail() : 0;
123  }
124};
125
126template <typename T>
127class ImmutableListFactory {
128  typedef ImmutableListImpl<T> ListTy;
129  typedef FoldingSet<ListTy>   CacheTy;
130
131  CacheTy Cache;
132  uintptr_t Allocator;
133
134  bool ownsAllocator() const {
135    return Allocator & 0x1 ? false : true;
136  }
137
138  BumpPtrAllocator& getAllocator() const {
139    return *reinterpret_cast<BumpPtrAllocator*>(Allocator & ~0x1);
140  }
141
142public:
143  ImmutableListFactory()
144    : Allocator(reinterpret_cast<uintptr_t>(new BumpPtrAllocator())) {}
145
146  ImmutableListFactory(BumpPtrAllocator& Alloc)
147  : Allocator(reinterpret_cast<uintptr_t>(&Alloc) | 0x1) {}
148
149  ~ImmutableListFactory() {
150    if (ownsAllocator()) delete &getAllocator();
151  }
152
153  ImmutableList<T> Concat(const T& Head, ImmutableList<T> Tail) {
154    // Profile the new list to see if it already exists in our cache.
155    FoldingSetNodeID ID;
156    void* InsertPos;
157
158    ListTy* TailImpl = Tail.getInternalPointer();
159    ListTy::Profile(ID, Head, TailImpl);
160    ListTy* L = Cache.FindNodeOrInsertPos(ID, InsertPos);
161
162    if (!L) {
163      // The list does not exist in our cache.  Create it.
164      BumpPtrAllocator& A = getAllocator();
165      L = (ListTy*) A.Allocate<ListTy>();
166      new (L) ListTy(Head, TailImpl);
167
168      // Insert the new list into the cache.
169      Cache.InsertNode(L, InsertPos);
170    }
171
172    return L;
173  }
174
175  ImmutableList<T> Add(const T& D, ImmutableList<T> L) {
176    return Concat(D, L);
177  }
178
179  ImmutableList<T> GetEmptyList() const {
180    return ImmutableList<T>(0);
181  }
182
183  ImmutableList<T> Create(const T& X) {
184    return Concat(X, GetEmptyList());
185  }
186};
187
188} // end llvm namespace
189
190#endif
191