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Side by Side Diff: base/memory/manual_constructor.h

Issue 2932053002: Use C++11 alignment primitives (Closed)
Patch Set: Fix merge Created 3 years, 6 months ago
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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 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 2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file. 3 // found in the LICENSE file.
4 4
5 // ManualConstructor statically-allocates space in which to store some 5 // ManualConstructor statically-allocates space in which to store some
6 // object, but does not initialize it. You can then call the constructor 6 // object, but does not initialize it. You can then call the constructor
7 // and destructor for the object yourself as you see fit. This is useful 7 // and destructor for the object yourself as you see fit. This is useful
8 // for memory management optimizations, where you want to initialize and 8 // for memory management optimizations, where you want to initialize and
9 // destroy an object multiple times but only allocate it once. 9 // destroy an object multiple times but only allocate it once.
10 // 10 //
(...skipping 16 matching lines...) Expand all
27 class ManualConstructor { 27 class ManualConstructor {
28 public: 28 public:
29 // No constructor or destructor because one of the most useful uses of 29 // No constructor or destructor because one of the most useful uses of
30 // this class is as part of a union, and members of a union cannot have 30 // this class is as part of a union, and members of a union cannot have
31 // constructors or destructors. And, anyway, the whole point of this 31 // constructors or destructors. And, anyway, the whole point of this
32 // class is to bypass these. 32 // class is to bypass these.
33 33
34 // Support users creating arrays of ManualConstructor<>s. This ensures that 34 // Support users creating arrays of ManualConstructor<>s. This ensures that
35 // the array itself has the correct alignment. 35 // the array itself has the correct alignment.
36 static void* operator new[](size_t size) { 36 static void* operator new[](size_t size) {
37 return AlignedAlloc(size, ALIGNOF(Type)); 37 return AlignedAlloc(size, alignof(Type));
38 } 38 }
39 static void operator delete[](void* mem) { 39 static void operator delete[](void* mem) {
40 AlignedFree(mem); 40 AlignedFree(mem);
41 } 41 }
42 42
43 inline Type* get() { 43 inline Type* get() { return reinterpret_cast<Type*>(space_); }
44 return space_.template data_as<Type>();
45 }
46 inline const Type* get() const { 44 inline const Type* get() const {
47 return space_.template data_as<Type>(); 45 return reinterpret_cast<const Type*>(space_);
48 } 46 }
49 47
50 inline Type* operator->() { return get(); } 48 inline Type* operator->() { return get(); }
51 inline const Type* operator->() const { return get(); } 49 inline const Type* operator->() const { return get(); }
52 50
53 inline Type& operator*() { return *get(); } 51 inline Type& operator*() { return *get(); }
54 inline const Type& operator*() const { return *get(); } 52 inline const Type& operator*() const { return *get(); }
55 53
56 template <typename... Ts> 54 template <typename... Ts>
57 inline void Init(Ts&&... params) { 55 inline void Init(Ts&&... params) {
58 new(space_.void_data()) Type(std::forward<Ts>(params)...); 56 new (space_) Type(std::forward<Ts>(params)...);
59 } 57 }
60 58
61 inline void InitFromMove(ManualConstructor<Type>&& o) { 59 inline void InitFromMove(ManualConstructor<Type>&& o) {
62 Init(std::move(*o)); 60 Init(std::move(*o));
63 } 61 }
64 62
65 inline void Destroy() { 63 inline void Destroy() {
66 get()->~Type(); 64 get()->~Type();
67 } 65 }
68 66
69 private: 67 private:
70 AlignedMemory<sizeof(Type), ALIGNOF(Type)> space_; 68 alignas(Type) char space_[sizeof(Type)];
71 }; 69 };
72 70
73 } // namespace base 71 } // namespace base
74 72
75 #endif // BASE_MEMORY_MANUAL_CONSTRUCTOR_H_ 73 #endif // BASE_MEMORY_MANUAL_CONSTRUCTOR_H_
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