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1 // Protocol Buffers - Google's data interchange format
2 // Copyright 2008 Google Inc.  All rights reserved.
3 // https://developers.google.com/protocol-buffers/
4 //
5 // Redistribution and use in source and binary forms, with or without
6 // modification, are permitted provided that the following conditions are
7 // met:
8 //
9 //     * Redistributions of source code must retain the above copyright
10 // notice, this list of conditions and the following disclaimer.
11 //     * Redistributions in binary form must reproduce the above
12 // copyright notice, this list of conditions and the following disclaimer
13 // in the documentation and/or other materials provided with the
14 // distribution.
15 //     * Neither the name of Google Inc. nor the names of its
16 // contributors may be used to endorse or promote products derived from
17 // this software without specific prior written permission.
18 //
19 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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30 
31 #ifndef GOOGLE_PROTOBUF_STUBS_SCOPED_PTR_H_
32 #define GOOGLE_PROTOBUF_STUBS_SCOPED_PTR_H_
33 
34 #include <google/protobuf/stubs/port.h>
35 
36 namespace google {
37 namespace protobuf {
38 
39 // ===================================================================
40 // from google3/base/scoped_ptr.h
41 
42 namespace internal {
43 
44 //  This is an implementation designed to match the anticipated future TR2
45 //  implementation of the scoped_ptr class, and its closely-related brethren,
46 //  scoped_array, scoped_ptr_malloc, and make_scoped_ptr.
47 
48 template <class C> class scoped_ptr;
49 template <class C> class scoped_array;
50 
51 // A scoped_ptr<T> is like a T*, except that the destructor of scoped_ptr<T>
52 // automatically deletes the pointer it holds (if any).
53 // That is, scoped_ptr<T> owns the T object that it points to.
54 // Like a T*, a scoped_ptr<T> may hold either NULL or a pointer to a T object.
55 //
56 // The size of a scoped_ptr is small:
57 // sizeof(scoped_ptr<C>) == sizeof(C*)
58 template <class C>
59 class scoped_ptr {
60  public:
61 
62   // The element type
63   typedef C element_type;
64 
65   // Constructor.  Defaults to initializing with NULL.
66   // There is no way to create an uninitialized scoped_ptr.
67   // The input parameter must be allocated with new.
ptr_(p)68   explicit scoped_ptr(C* p = NULL) : ptr_(p) { }
69 
70   // Destructor.  If there is a C object, delete it.
71   // We don't need to test ptr_ == NULL because C++ does that for us.
~scoped_ptr()72   ~scoped_ptr() {
73     enum { type_must_be_complete = sizeof(C) };
74     delete ptr_;
75   }
76 
77   // Reset.  Deletes the current owned object, if any.
78   // Then takes ownership of a new object, if given.
79   // this->reset(this->get()) works.
80   void reset(C* p = NULL) {
81     if (p != ptr_) {
82       enum { type_must_be_complete = sizeof(C) };
83       delete ptr_;
84       ptr_ = p;
85     }
86   }
87 
88   // Accessors to get the owned object.
89   // operator* and operator-> will assert() if there is no current object.
90   C& operator*() const {
91     assert(ptr_ != NULL);
92     return *ptr_;
93   }
94   C* operator->() const  {
95     assert(ptr_ != NULL);
96     return ptr_;
97   }
get()98   C* get() const { return ptr_; }
99 
100   // Comparison operators.
101   // These return whether two scoped_ptr refer to the same object, not just to
102   // two different but equal objects.
103   bool operator==(C* p) const { return ptr_ == p; }
104   bool operator!=(C* p) const { return ptr_ != p; }
105 
106   // Swap two scoped pointers.
swap(scoped_ptr & p2)107   void swap(scoped_ptr& p2) {
108     C* tmp = ptr_;
109     ptr_ = p2.ptr_;
110     p2.ptr_ = tmp;
111   }
112 
113   // Release a pointer.
114   // The return value is the current pointer held by this object.
115   // If this object holds a NULL pointer, the return value is NULL.
116   // After this operation, this object will hold a NULL pointer,
117   // and will not own the object any more.
release()118   C* release() {
119     C* retVal = ptr_;
120     ptr_ = NULL;
121     return retVal;
122   }
123 
124  private:
125   C* ptr_;
126 
127   // Forbid comparison of scoped_ptr types.  If C2 != C, it totally doesn't
128   // make sense, and if C2 == C, it still doesn't make sense because you should
129   // never have the same object owned by two different scoped_ptrs.
130   template <class C2> bool operator==(scoped_ptr<C2> const& p2) const;
131   template <class C2> bool operator!=(scoped_ptr<C2> const& p2) const;
132 
133   // Disallow evil constructors
134   scoped_ptr(const scoped_ptr&);
135   void operator=(const scoped_ptr&);
136 };
137 
138 // scoped_array<C> is like scoped_ptr<C>, except that the caller must allocate
139 // with new [] and the destructor deletes objects with delete [].
140 //
141 // As with scoped_ptr<C>, a scoped_array<C> either points to an object
142 // or is NULL.  A scoped_array<C> owns the object that it points to.
143 //
144 // Size: sizeof(scoped_array<C>) == sizeof(C*)
145 template <class C>
146 class scoped_array {
147  public:
148 
149   // The element type
150   typedef C element_type;
151 
152   // Constructor.  Defaults to initializing with NULL.
153   // There is no way to create an uninitialized scoped_array.
154   // The input parameter must be allocated with new [].
array_(p)155   explicit scoped_array(C* p = NULL) : array_(p) { }
156 
157   // Destructor.  If there is a C object, delete it.
158   // We don't need to test ptr_ == NULL because C++ does that for us.
~scoped_array()159   ~scoped_array() {
160     enum { type_must_be_complete = sizeof(C) };
161     delete[] array_;
162   }
163 
164   // Reset.  Deletes the current owned object, if any.
165   // Then takes ownership of a new object, if given.
166   // this->reset(this->get()) works.
167   void reset(C* p = NULL) {
168     if (p != array_) {
169       enum { type_must_be_complete = sizeof(C) };
170       delete[] array_;
171       array_ = p;
172     }
173   }
174 
175   // Get one element of the current object.
176   // Will assert() if there is no current object, or index i is negative.
177   C& operator[](std::ptrdiff_t i) const {
178     assert(i >= 0);
179     assert(array_ != NULL);
180     return array_[i];
181   }
182 
183   // Get a pointer to the zeroth element of the current object.
184   // If there is no current object, return NULL.
get()185   C* get() const {
186     return array_;
187   }
188 
189   // Comparison operators.
190   // These return whether two scoped_array refer to the same object, not just to
191   // two different but equal objects.
192   bool operator==(C* p) const { return array_ == p; }
193   bool operator!=(C* p) const { return array_ != p; }
194 
195   // Swap two scoped arrays.
swap(scoped_array & p2)196   void swap(scoped_array& p2) {
197     C* tmp = array_;
198     array_ = p2.array_;
199     p2.array_ = tmp;
200   }
201 
202   // Release an array.
203   // The return value is the current pointer held by this object.
204   // If this object holds a NULL pointer, the return value is NULL.
205   // After this operation, this object will hold a NULL pointer,
206   // and will not own the object any more.
release()207   C* release() {
208     C* retVal = array_;
209     array_ = NULL;
210     return retVal;
211   }
212 
213  private:
214   C* array_;
215 
216   // Forbid comparison of different scoped_array types.
217   template <class C2> bool operator==(scoped_array<C2> const& p2) const;
218   template <class C2> bool operator!=(scoped_array<C2> const& p2) const;
219 
220   // Disallow evil constructors
221   scoped_array(const scoped_array&);
222   void operator=(const scoped_array&);
223 };
224 
225 }  // namespace internal
226 
227 // We made these internal so that they would show up as such in the docs,
228 // but we don't want to stick "internal::" in front of them everywhere.
229 using internal::scoped_ptr;
230 using internal::scoped_array;
231 
232 
233 }  // namespace protobuf
234 }  // namespace google
235 
236 #endif  // GOOGLE_PROTOBUF_STUBS_SCOPED_PTR_H_
237