1// Copyright 2011 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef V8_SMART_POINTERS_H_
6#define V8_SMART_POINTERS_H_
7
8namespace v8 {
9namespace internal {
10
11
12template<typename Deallocator, typename T>
13class SmartPointerBase {
14 public:
15  // Default constructor. Constructs an empty scoped pointer.
16  SmartPointerBase() : p_(NULL) {}
17
18  // Constructs a scoped pointer from a plain one.
19  explicit SmartPointerBase(T* ptr) : p_(ptr) {}
20
21  // Copy constructor removes the pointer from the original to avoid double
22  // freeing.
23  SmartPointerBase(const SmartPointerBase<Deallocator, T>& rhs)
24      : p_(rhs.p_) {
25    const_cast<SmartPointerBase<Deallocator, T>&>(rhs).p_ = NULL;
26  }
27
28  T* operator->() const { return p_; }
29
30  T& operator*() const { return *p_; }
31
32  T* get() const { return p_; }
33
34  // You can use [n] to index as if it was a plain pointer.
35  T& operator[](size_t i) {
36    return p_[i];
37  }
38
39  // You can use [n] to index as if it was a plain pointer.
40  const T& operator[](size_t i) const {
41    return p_[i];
42  }
43
44  // We don't have implicit conversion to a T* since that hinders migration:
45  // You would not be able to change a method from returning a T* to
46  // returning an SmartArrayPointer<T> and then get errors wherever it is used.
47
48
49  // If you want to take out the plain pointer and don't want it automatically
50  // deleted then call Detach().  Afterwards, the smart pointer is empty
51  // (NULL).
52  T* Detach() {
53    T* temp = p_;
54    p_ = NULL;
55    return temp;
56  }
57
58  void Reset(T* new_value) {
59    DCHECK(p_ == NULL || p_ != new_value);
60    if (p_) Deallocator::Delete(p_);
61    p_ = new_value;
62  }
63
64  // Assignment requires an empty (NULL) SmartArrayPointer as the receiver. Like
65  // the copy constructor it removes the pointer in the original to avoid
66  // double freeing.
67  SmartPointerBase<Deallocator, T>& operator=(
68      const SmartPointerBase<Deallocator, T>& rhs) {
69    DCHECK(is_empty());
70    T* tmp = rhs.p_;  // swap to handle self-assignment
71    const_cast<SmartPointerBase<Deallocator, T>&>(rhs).p_ = NULL;
72    p_ = tmp;
73    return *this;
74  }
75
76  bool is_empty() const { return p_ == NULL; }
77
78 protected:
79  // When the destructor of the scoped pointer is executed the plain pointer
80  // is deleted using DeleteArray.  This implies that you must allocate with
81  // NewArray.
82  ~SmartPointerBase() { if (p_) Deallocator::Delete(p_); }
83
84 private:
85  T* p_;
86};
87
88// A 'scoped array pointer' that calls DeleteArray on its pointer when the
89// destructor is called.
90
91template<typename T>
92struct ArrayDeallocator {
93  static void Delete(T* array) {
94    DeleteArray(array);
95  }
96};
97
98
99template<typename T>
100class SmartArrayPointer: public SmartPointerBase<ArrayDeallocator<T>, T> {
101 public:
102  SmartArrayPointer() { }
103  explicit SmartArrayPointer(T* ptr)
104      : SmartPointerBase<ArrayDeallocator<T>, T>(ptr) { }
105  SmartArrayPointer(const SmartArrayPointer<T>& rhs)
106      : SmartPointerBase<ArrayDeallocator<T>, T>(rhs) { }
107};
108
109
110template<typename T>
111struct ObjectDeallocator {
112  static void Delete(T* object) {
113    delete object;
114  }
115};
116
117
118template<typename T>
119class SmartPointer: public SmartPointerBase<ObjectDeallocator<T>, T> {
120 public:
121  SmartPointer() { }
122  explicit SmartPointer(T* ptr)
123      : SmartPointerBase<ObjectDeallocator<T>, T>(ptr) { }
124  SmartPointer(const SmartPointer<T>& rhs)
125      : SmartPointerBase<ObjectDeallocator<T>, T>(rhs) { }
126};
127
128} }  // namespace v8::internal
129
130#endif  // V8_SMART_POINTERS_H_
131