1// Copyright (c) 2012 The Chromium 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 I18N_PHONENUMBERS_BASE_MEMORY_SCOPED_PTR_H_
6#define I18N_PHONENUMBERS_BASE_MEMORY_SCOPED_PTR_H_
7
8#if defined(I18N_PHONENUMBERS_USE_BOOST)
9
10#include <boost/scoped_ptr.hpp>
11using boost::scoped_ptr;
12
13#else  // !I18N_PHONENUMBERS_USE_BOOST
14
15// This is an implementation designed to match the anticipated future TR2
16// implementation of the scoped_ptr class and scoped_ptr_malloc (deprecated).
17
18#include <assert.h>
19#include <stddef.h>
20#include <stdlib.h>
21
22#include <algorithm>  // For std::swap().
23
24#include "phonenumbers/base/basictypes.h"
25#include "phonenumbers/base/template_util.h"
26
27namespace i18n {
28namespace phonenumbers {
29
30// Function object which deletes its parameter, which must be a pointer.
31// If C is an array type, invokes 'delete[]' on the parameter; otherwise,
32// invokes 'delete'. The default deleter for scoped_ptr<T>.
33template <class T>
34struct DefaultDeleter {
35  DefaultDeleter() {}
36  template <typename U> DefaultDeleter(const DefaultDeleter<U>& other) {
37    // IMPLEMENTATION NOTE: C++11 20.7.1.1.2p2 only provides this constructor
38    // if U* is implicitly convertible to T* and U is not an array type.
39    //
40    // Correct implementation should use SFINAE to disable this
41    // constructor. However, since there are no other 1-argument constructors,
42    // using a COMPILE_ASSERT() based on is_convertible<> and requiring
43    // complete types is simpler and will cause compile failures for equivalent
44    // misuses.
45    //
46    // Note, the is_convertible<U*, T*> check also ensures that U is not an
47    // array. T is guaranteed to be a non-array, so any U* where U is an array
48    // cannot convert to T*.
49    enum { T_must_be_complete = sizeof(T) };
50    enum { U_must_be_complete = sizeof(U) };
51    COMPILE_ASSERT((is_convertible<U*, T*>::value),
52                   U_ptr_must_implicitly_convert_to_T_ptr);
53  }
54  inline void operator()(T* ptr) const {
55    enum { type_must_be_complete = sizeof(T) };
56    delete ptr;
57  }
58};
59
60// Specialization of DefaultDeleter for array types.
61template <class T>
62struct DefaultDeleter<T[]> {
63  inline void operator()(T* ptr) const {
64    enum { type_must_be_complete = sizeof(T) };
65    delete[] ptr;
66  }
67
68 private:
69  // Disable this operator for any U != T because it is undefined to execute
70  // an array delete when the static type of the array mismatches the dynamic
71  // type.
72  //
73  // References:
74  //   C++98 [expr.delete]p3
75  //   http://cplusplus.github.com/LWG/lwg-defects.html#938
76  template <typename U> void operator()(U* array) const;
77};
78
79template <class T, int n>
80struct DefaultDeleter<T[n]> {
81  // Never allow someone to declare something like scoped_ptr<int[10]>.
82  COMPILE_ASSERT(sizeof(T) == -1, do_not_use_array_with_size_as_type);
83};
84
85// Function object which invokes 'free' on its parameter, which must be
86// a pointer. Can be used to store malloc-allocated pointers in scoped_ptr:
87//
88// scoped_ptr<int, base::FreeDeleter> foo_ptr(
89//     static_cast<int*>(malloc(sizeof(int))));
90struct FreeDeleter {
91  inline void operator()(void* ptr) const {
92    free(ptr);
93  }
94};
95
96// Minimal implementation of the core logic of scoped_ptr, suitable for
97// reuse in both scoped_ptr and its specializations.
98template <class T, class D>
99class scoped_ptr_impl {
100 public:
101  explicit scoped_ptr_impl(T* p) : data_(p) { }
102
103  // Initializer for deleters that have data parameters.
104  scoped_ptr_impl(T* p, const D& d) : data_(p, d) {}
105
106  // Templated constructor that destructively takes the value from another
107  // scoped_ptr_impl.
108  template <typename U, typename V>
109  scoped_ptr_impl(scoped_ptr_impl<U, V>* other)
110      : data_(other->release(), other->get_deleter()) {
111    // We do not support move-only deleters.  We could modify our move
112    // emulation to have base::subtle::move() and base::subtle::forward()
113    // functions that are imperfect emulations of their C++11 equivalents,
114    // but until there's a requirement, just assume deleters are copyable.
115  }
116
117  template <typename U, typename V>
118  void TakeState(scoped_ptr_impl<U, V>* other) {
119    // See comment in templated constructor above regarding lack of support
120    // for move-only deleters.
121    reset(other->release());
122    get_deleter() = other->get_deleter();
123  }
124
125  ~scoped_ptr_impl() {
126    if (data_.ptr != NULL) {
127      // Not using get_deleter() saves one function call in non-optimized
128      // builds.
129      static_cast<D&>(data_)(data_.ptr);
130    }
131  }
132
133  void reset(T* p) {
134    // This is a self-reset, which is no longer allowed: http://crbug.com/162971
135    if (p != NULL && p == data_.ptr)
136      abort();
137
138    // Note that running data_.ptr = p can lead to undefined behavior if
139    // get_deleter()(get()) deletes this. In order to pevent this, reset()
140    // should update the stored pointer before deleting its old value.
141    //
142    // However, changing reset() to use that behavior may cause current code to
143    // break in unexpected ways. If the destruction of the owned object
144    // dereferences the scoped_ptr when it is destroyed by a call to reset(),
145    // then it will incorrectly dispatch calls to |p| rather than the original
146    // value of |data_.ptr|.
147    //
148    // During the transition period, set the stored pointer to NULL while
149    // deleting the object. Eventually, this safety check will be removed to
150    // prevent the scenario initially described from occuring and
151    // http://crbug.com/176091 can be closed.
152    T* old = data_.ptr;
153    data_.ptr = NULL;
154    if (old != NULL)
155      static_cast<D&>(data_)(old);
156    data_.ptr = p;
157  }
158
159  T* get() const { return data_.ptr; }
160
161  D& get_deleter() { return data_; }
162  const D& get_deleter() const { return data_; }
163
164  void swap(scoped_ptr_impl& p2) {
165    // Standard swap idiom: 'using std::swap' ensures that std::swap is
166    // present in the overload set, but we call swap unqualified so that
167    // any more-specific overloads can be used, if available.
168    using std::swap;
169    swap(static_cast<D&>(data_), static_cast<D&>(p2.data_));
170    swap(data_.ptr, p2.data_.ptr);
171  }
172
173  T* release() {
174    T* old_ptr = data_.ptr;
175    data_.ptr = NULL;
176    return old_ptr;
177  }
178
179 private:
180  // Needed to allow type-converting constructor.
181  template <typename U, typename V> friend class scoped_ptr_impl;
182
183  // Use the empty base class optimization to allow us to have a D
184  // member, while avoiding any space overhead for it when D is an
185  // empty class.  See e.g. http://www.cantrip.org/emptyopt.html for a good
186  // discussion of this technique.
187  struct Data : public D {
188    explicit Data(T* ptr_in) : ptr(ptr_in) {}
189    Data(T* ptr_in, const D& other) : D(other), ptr(ptr_in) {}
190    T* ptr;
191  };
192
193  Data data_;
194
195  DISALLOW_COPY_AND_ASSIGN(scoped_ptr_impl);
196};
197
198// A scoped_ptr<T> is like a T*, except that the destructor of scoped_ptr<T>
199// automatically deletes the pointer it holds (if any).
200// That is, scoped_ptr<T> owns the T object that it points to.
201// Like a T*, a scoped_ptr<T> may hold either NULL or a pointer to a T object.
202// Also like T*, scoped_ptr<T> is thread-compatible, and once you
203// dereference it, you get the thread safety guarantees of T.
204//
205// The size of scoped_ptr is small. On most compilers, when using the
206// DefaultDeleter, sizeof(scoped_ptr<T>) == sizeof(T*). Custom deleters will
207// increase the size proportional to whatever state they need to have. See
208// comments inside scoped_ptr_impl<> for details.
209//
210// Current implementation targets having a strict subset of  C++11's
211// unique_ptr<> features. Known deficiencies include not supporting move-only
212// deleteres, function pointers as deleters, and deleters with reference
213// types.
214template <class T, class D = DefaultDeleter<T> >
215class scoped_ptr {
216 public:
217  // The element and deleter types.
218  typedef T element_type;
219  typedef D deleter_type;
220
221  // Constructor.  Defaults to initializing with NULL.
222  scoped_ptr() : impl_(NULL) { }
223
224  // Constructor.  Takes ownership of p.
225  explicit scoped_ptr(element_type* p) : impl_(p) { }
226
227  // Constructor.  Allows initialization of a stateful deleter.
228  scoped_ptr(element_type* p, const D& d) : impl_(p, d) { }
229
230  // Constructor.  Allows construction from a scoped_ptr rvalue for a
231  // convertible type and deleter.
232  //
233  // IMPLEMENTATION NOTE: C++11 unique_ptr<> keeps this constructor distinct
234  // from the normal move constructor. By C++11 20.7.1.2.1.21, this constructor
235  // has different post-conditions if D is a reference type. Since this
236  // implementation does not support deleters with reference type,
237  // we do not need a separate move constructor allowing us to avoid one
238  // use of SFINAE. You only need to care about this if you modify the
239  // implementation of scoped_ptr.
240  template <typename U, typename V>
241  scoped_ptr(scoped_ptr<U, V> other) : impl_(&other.impl_) {
242    COMPILE_ASSERT(!is_array<U>::value, U_cannot_be_an_array);
243  }
244
245  // operator=.  Allows assignment from a scoped_ptr rvalue for a convertible
246  // type and deleter.
247  //
248  // IMPLEMENTATION NOTE: C++11 unique_ptr<> keeps this operator= distinct from
249  // the normal move assignment operator. By C++11 20.7.1.2.3.4, this templated
250  // form has different requirements on for move-only Deleters. Since this
251  // implementation does not support move-only Deleters, we do not need a
252  // separate move assignment operator allowing us to avoid one use of SFINAE.
253  // You only need to care about this if you modify the implementation of
254  // scoped_ptr.
255  template <typename U, typename V>
256  scoped_ptr& operator=(scoped_ptr<U, V> rhs) {
257    COMPILE_ASSERT(!is_array<U>::value, U_cannot_be_an_array);
258    impl_.TakeState(&rhs.impl_);
259    return *this;
260  }
261
262  // Reset.  Deletes the currently owned object, if any.
263  // Then takes ownership of a new object, if given.
264  void reset(element_type* p = NULL) { impl_.reset(p); }
265
266  // Accessors to get the owned object.
267  // operator* and operator-> will assert() if there is no current object.
268  element_type& operator*() const {
269    assert(impl_.get() != NULL);
270    return *impl_.get();
271  }
272  element_type* operator->() const  {
273    assert(impl_.get() != NULL);
274    return impl_.get();
275  }
276  element_type* get() const { return impl_.get(); }
277
278  // Access to the deleter.
279  deleter_type& get_deleter() { return impl_.get_deleter(); }
280  const deleter_type& get_deleter() const { return impl_.get_deleter(); }
281
282  // Allow scoped_ptr<element_type> to be used in boolean expressions, but not
283  // implicitly convertible to a real bool (which is dangerous).
284 private:
285  typedef scoped_ptr_impl<element_type, deleter_type> scoped_ptr::*Testable;
286
287 public:
288  operator Testable() const { return impl_.get() ? &scoped_ptr::impl_ : NULL; }
289
290  // Comparison operators.
291  // These return whether two scoped_ptr refer to the same object, not just to
292  // two different but equal objects.
293  bool operator==(const element_type* p) const { return impl_.get() == p; }
294  bool operator!=(const element_type* p) const { return impl_.get() != p; }
295
296  // Swap two scoped pointers.
297  void swap(scoped_ptr& p2) {
298    impl_.swap(p2.impl_);
299  }
300
301  // Release a pointer.
302  // The return value is the current pointer held by this object.
303  // If this object holds a NULL pointer, the return value is NULL.
304  // After this operation, this object will hold a NULL pointer,
305  // and will not own the object any more.
306  element_type* release() {
307    return impl_.release();
308  }
309
310 private:
311  // Needed to reach into |impl_| in the constructor.
312  template <typename U, typename V> friend class scoped_ptr;
313  scoped_ptr_impl<element_type, deleter_type> impl_;
314
315  // Forbid comparison of scoped_ptr types.  If U != T, it totally
316  // doesn't make sense, and if U == T, it still doesn't make sense
317  // because you should never have the same object owned by two different
318  // scoped_ptrs.
319  template <class U> bool operator==(scoped_ptr<U> const& p2) const;
320  template <class U> bool operator!=(scoped_ptr<U> const& p2) const;
321};
322
323template <class T, class D>
324class scoped_ptr<T[], D> {
325 public:
326  // The element and deleter types.
327  typedef T element_type;
328  typedef D deleter_type;
329
330  // Constructor.  Defaults to initializing with NULL.
331  scoped_ptr() : impl_(NULL) { }
332
333  // Constructor. Stores the given array. Note that the argument's type
334  // must exactly match T*. In particular:
335  // - it cannot be a pointer to a type derived from T, because it is
336  //   inherently unsafe in the general case to access an array through a
337  //   pointer whose dynamic type does not match its static type (eg., if
338  //   T and the derived types had different sizes access would be
339  //   incorrectly calculated). Deletion is also always undefined
340  //   (C++98 [expr.delete]p3). If you're doing this, fix your code.
341  // - it cannot be NULL, because NULL is an integral expression, not a
342  //   pointer to T. Use the no-argument version instead of explicitly
343  //   passing NULL.
344  // - it cannot be const-qualified differently from T per unique_ptr spec
345  //   (http://cplusplus.github.com/LWG/lwg-active.html#2118). Users wanting
346  //   to work around this may use implicit_cast<const T*>().
347  //   However, because of the first bullet in this comment, users MUST
348  //   NOT use implicit_cast<Base*>() to upcast the static type of the array.
349  explicit scoped_ptr(element_type* array) : impl_(array) { }
350
351  // Reset.  Deletes the currently owned array, if any.
352  // Then takes ownership of a new object, if given.
353  void reset(element_type* array = NULL) { impl_.reset(array); }
354
355  // Accessors to get the owned array.
356  element_type& operator[](size_t i) const {
357    assert(impl_.get() != NULL);
358    return impl_.get()[i];
359  }
360  element_type* get() const { return impl_.get(); }
361
362  // Access to the deleter.
363  deleter_type& get_deleter() { return impl_.get_deleter(); }
364  const deleter_type& get_deleter() const { return impl_.get_deleter(); }
365
366  // Allow scoped_ptr<element_type> to be used in boolean expressions, but not
367  // implicitly convertible to a real bool (which is dangerous).
368 private:
369  typedef scoped_ptr_impl<element_type, deleter_type> scoped_ptr::*Testable;
370
371 public:
372  operator Testable() const { return impl_.get() ? &scoped_ptr::impl_ : NULL; }
373
374  // Comparison operators.
375  // These return whether two scoped_ptr refer to the same object, not just to
376  // two different but equal objects.
377  bool operator==(element_type* array) const { return impl_.get() == array; }
378  bool operator!=(element_type* array) const { return impl_.get() != array; }
379
380  // Swap two scoped pointers.
381  void swap(scoped_ptr& p2) {
382    impl_.swap(p2.impl_);
383  }
384
385  // Release a pointer.
386  // The return value is the current pointer held by this object.
387  // If this object holds a NULL pointer, the return value is NULL.
388  // After this operation, this object will hold a NULL pointer,
389  // and will not own the object any more.
390  element_type* release() {
391    return impl_.release();
392  }
393
394 private:
395  // Force element_type to be a complete type.
396  enum { type_must_be_complete = sizeof(element_type) };
397
398  // Actually hold the data.
399  scoped_ptr_impl<element_type, deleter_type> impl_;
400
401  // Disable initialization from any type other than element_type*, by
402  // providing a constructor that matches such an initialization, but is
403  // private and has no definition. This is disabled because it is not safe to
404  // call delete[] on an array whose static type does not match its dynamic
405  // type.
406  template <typename U> explicit scoped_ptr(U* array);
407  explicit scoped_ptr(int disallow_construction_from_null);
408
409  // Disable reset() from any type other than element_type*, for the same
410  // reasons as the constructor above.
411  template <typename U> void reset(U* array);
412  void reset(int disallow_reset_from_null);
413
414  // Forbid comparison of scoped_ptr types.  If U != T, it totally
415  // doesn't make sense, and if U == T, it still doesn't make sense
416  // because you should never have the same object owned by two different
417  // scoped_ptrs.
418  template <class U> bool operator==(scoped_ptr<U> const& p2) const;
419  template <class U> bool operator!=(scoped_ptr<U> const& p2) const;
420};
421
422// Free functions
423template <class T, class D>
424void swap(scoped_ptr<T, D>& p1, scoped_ptr<T, D>& p2) {
425  p1.swap(p2);
426}
427
428template <class T, class D>
429bool operator==(T* p1, const scoped_ptr<T, D>& p2) {
430  return p1 == p2.get();
431}
432
433template <class T, class D>
434bool operator!=(T* p1, const scoped_ptr<T, D>& p2) {
435  return p1 != p2.get();
436}
437
438// A function to convert T* into scoped_ptr<T>
439// Doing e.g. make_scoped_ptr(new FooBarBaz<type>(arg)) is a shorter notation
440// for scoped_ptr<FooBarBaz<type> >(new FooBarBaz<type>(arg))
441template <typename T>
442scoped_ptr<T> make_scoped_ptr(T* ptr) {
443  return scoped_ptr<T>(ptr);
444}
445
446}  // namespace phonenumbers
447}  // namespace i18n
448
449#endif  // !I18N_PHONENUMBERS_USE_BOOST
450#endif  // I18N_PHONENUMBERS_BASE_MEMORY_SCOPED_PTR_H_
451