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1 /* | 1 /* |
2 * Copyright 2014 Google Inc. | 2 * Copyright 2014 Google Inc. |
3 * | 3 * |
4 * Use of this source code is governed by a BSD-style license that can be | 4 * Use of this source code is governed by a BSD-style license that can be |
5 * found in the LICENSE file. | 5 * found in the LICENSE file. |
6 */ | 6 */ |
7 | 7 |
8 #ifndef SkLazyPtr_DEFINED | 8 #ifndef SkLazyPtr_DEFINED |
9 #define SkLazyPtr_DEFINED | 9 #define SkLazyPtr_DEFINED |
10 | 10 |
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42 * You can think of SK_DECLARE_STATIC_LAZY_PTR as a cheaper specialization of | 42 * You can think of SK_DECLARE_STATIC_LAZY_PTR as a cheaper specialization of |
43 * SkOnce. There is no mutex or extra storage used past the pointer itself. | 43 * SkOnce. There is no mutex or extra storage used past the pointer itself. |
44 * | 44 * |
45 * We may call Create more than once, but all threads will see the same pointer | 45 * We may call Create more than once, but all threads will see the same pointer |
46 * returned from get(). Any extra calls to Create will be cleaned up. | 46 * returned from get(). Any extra calls to Create will be cleaned up. |
47 * | 47 * |
48 * These macros must be used in a global scope, not in function scope or as a c
lass member. | 48 * These macros must be used in a global scope, not in function scope or as a c
lass member. |
49 */ | 49 */ |
50 | 50 |
51 #define SK_DECLARE_STATIC_LAZY_PTR(T, name, ...) \ | 51 #define SK_DECLARE_STATIC_LAZY_PTR(T, name, ...) \ |
52 namespace {} static Private::SkLazyPtrBase<T, ##__VA_ARGS__> name | 52 namespace {} static Private::SkStaticLazyPtr<T, ##__VA_ARGS__> name |
53 | 53 |
54 #define SK_DECLARE_STATIC_LAZY_PTR_ARRAY(T, name, N, ...) \ | 54 #define SK_DECLARE_STATIC_LAZY_PTR_ARRAY(T, name, N, ...) \ |
55 namespace {} static Private::SkLazyPtrArray<T, N, ##__VA_ARGS__> name | 55 namespace {} static Private::SkStaticLazyPtrArray<T, N, ##__VA_ARGS__> name |
56 | 56 |
57 // namespace {} forces these macros to only be legal in global scopes. Chrome h
as thread-safety | 57 // namespace {} forces these macros to only be legal in global scopes. Chrome h
as thread-safety |
58 // problems with them in function-local statics because it uses -fno-threadsafe-
statics, and even | 58 // problems with them in function-local statics because it uses -fno-threadsafe-
statics, and even |
59 // in builds with threadsafe statics, those threadsafe statics are just unnecess
ary overhead. | 59 // in builds with threadsafe statics, those threadsafe statics are just unnecess
ary overhead. |
60 | 60 |
61 // Everything below here is private implementation details. Don't touch, don't
even look. | 61 // Everything below here is private implementation details. Don't touch, don't
even look. |
62 | 62 |
63 #include "SkDynamicAnnotations.h" | 63 #include "SkDynamicAnnotations.h" |
64 #include "SkThread.h" | 64 #include "SkThread.h" |
65 #include "SkThreadPriv.h" | 65 #include "SkThreadPriv.h" |
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95 // _through_ our atomically set pointer, there is a data dependency between our | 95 // _through_ our atomically set pointer, there is a data dependency between our |
96 // atomic and the guarded data, and so we only need writer-releases / | 96 // atomic and the guarded data, and so we only need writer-releases / |
97 // reader-consumes memory pairing rather than the more general write-releases / | 97 // reader-consumes memory pairing rather than the more general write-releases / |
98 // reader-acquires convention. | 98 // reader-acquires convention. |
99 // | 99 // |
100 // This is nice, because a sk_consume_load is free on all our platforms: x86, | 100 // This is nice, because a sk_consume_load is free on all our platforms: x86, |
101 // ARM, MIPS. In contrast, sk_acquire_load issues a memory barrier on non-x86. | 101 // ARM, MIPS. In contrast, sk_acquire_load issues a memory barrier on non-x86. |
102 | 102 |
103 // This has no constructor and must be zero-initalized (the macro above does thi
s). | 103 // This has no constructor and must be zero-initalized (the macro above does thi
s). |
104 template <typename T, T* (*Create)() = sk_new<T>, void (*Destroy)(T*) = sk_delet
e<T> > | 104 template <typename T, T* (*Create)() = sk_new<T>, void (*Destroy)(T*) = sk_delet
e<T> > |
105 class SkLazyPtrBase { | 105 class SkStaticLazyPtr { |
106 public: | 106 public: |
107 T* get() { | 107 T* get() { |
108 // If fPtr has already been filled, we need a consume barrier when loadi
ng it. | 108 // If fPtr has already been filled, we need a consume barrier when loadi
ng it. |
109 // If not, we need a release barrier when setting it. try_cas will do t
hat. | 109 // If not, we need a release barrier when setting it. try_cas will do t
hat. |
110 T* ptr = (T*)sk_consume_load(&fPtr); | 110 T* ptr = (T*)sk_consume_load(&fPtr); |
111 return ptr ? ptr : try_cas<T*, Destroy>(&fPtr, Create()); | 111 return ptr ? ptr : try_cas<T*, Destroy>(&fPtr, Create()); |
112 } | 112 } |
113 | 113 |
114 protected: | 114 private: |
115 void* fPtr; | 115 void* fPtr; |
116 }; | 116 }; |
117 | 117 |
118 template <typename T> T* sk_new_arg(int i) { return SkNEW_ARGS(T, (i)); } | 118 template <typename T> T* sk_new_arg(int i) { return SkNEW_ARGS(T, (i)); } |
119 | 119 |
120 // This has no constructor and must be zero-initalized (the macro above does thi
s). | 120 // This has no constructor and must be zero-initalized (the macro above does thi
s). |
121 template <typename T, int N, T* (*Create)(int) = sk_new_arg<T>, void (*Destroy)(
T*) = sk_delete<T> > | 121 template <typename T, int N, T* (*Create)(int) = sk_new_arg<T>, void (*Destroy)(
T*) = sk_delete<T> > |
122 class SkLazyPtrArray { | 122 class SkStaticLazyPtrArray { |
123 public: | 123 public: |
124 T* operator[](int i) { | 124 T* operator[](int i) { |
125 SkASSERT(i >= 0 && i < N); | 125 SkASSERT(i >= 0 && i < N); |
126 // If fPtr has already been filled, we need an consume barrier when load
ing it. | 126 // If fPtr has already been filled, we need an consume barrier when load
ing it. |
127 // If not, we need a release barrier when setting it. try_cas will do t
hat. | 127 // If not, we need a release barrier when setting it. try_cas will do t
hat. |
128 T* ptr = (T*)sk_consume_load(&fArray[i]); | 128 T* ptr = (T*)sk_consume_load(&fArray[i]); |
129 return ptr ? ptr : try_cas<T*, Destroy>(&fArray[i], Create(i)); | 129 return ptr ? ptr : try_cas<T*, Destroy>(&fArray[i], Create(i)); |
130 } | 130 } |
131 | 131 |
132 private: | 132 private: |
133 void* fArray[N]; | 133 void* fArray[N]; |
134 }; | 134 }; |
135 | 135 |
136 } // namespace Private | 136 } // namespace Private |
137 | 137 |
138 // This version is suitable for use as a class member. | 138 // This version is suitable for use as a class member. |
139 // It's the same as above except it has a constructor to zero itself and a destr
uctor to clean up. | 139 // It's much the same as above except: |
140 template <typename T, | 140 // - it has a constructor to zero itself; |
141 T* (*Create)() = Private::sk_new<T>, | 141 // - it has a destructor to clean up; |
142 void (*Destroy)(T*) = Private::sk_delete<T> > | 142 // - get() calls SkNew(T) to create the pointer; |
143 class SkLazyPtr : public Private::SkLazyPtrBase<T, Create, Destroy> { | 143 // - get(functor) calls functor to create the pointer. |
| 144 template <typename T, void (*Destroy)(T*) = Private::sk_delete<T> > |
| 145 class SkLazyPtr : SkNoncopyable { |
144 public: | 146 public: |
145 SkLazyPtr() { INHERITED::fPtr = NULL; } | 147 SkLazyPtr() : fPtr(NULL) {} |
146 ~SkLazyPtr() { if (INHERITED::fPtr) { Destroy((T*)INHERITED::fPtr); } } | 148 ~SkLazyPtr() { if (fPtr) { Destroy((T*)fPtr); } } |
| 149 |
| 150 T* get() { |
| 151 T* ptr = (T*)sk_consume_load(&fPtr); |
| 152 return ptr ? ptr : Private::try_cas<T*, Destroy>(&fPtr, SkNEW(T)); |
| 153 } |
| 154 |
| 155 template <typename Create> |
| 156 T* get(const Create& create) { |
| 157 T* ptr = (T*)sk_consume_load(&fPtr); |
| 158 return ptr ? ptr : Private::try_cas<T*, Destroy>(&fPtr, create()); |
| 159 } |
| 160 |
147 private: | 161 private: |
148 typedef Private::SkLazyPtrBase<T, Create, Destroy> INHERITED; | 162 void* fPtr; |
149 }; | 163 }; |
150 | 164 |
151 | 165 |
152 #endif//SkLazyPtr_DEFINED | 166 #endif//SkLazyPtr_DEFINED |
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