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1 /* | 1 /* |
2 * Copyright 2015 Google Inc. | 2 * Copyright 2015 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 SkOncePtr_DEFINED | 8 #ifndef SkOncePtr_DEFINED |
9 #define SkOncePtr_DEFINED | 9 #define SkOncePtr_DEFINED |
10 | 10 |
11 #include "../private/SkAtomics.h" | 11 #include "../private/SkAtomics.h" |
12 #include <memory> | 12 #include <memory> |
13 | 13 |
14 template <typename T> class SkBaseOncePtr; | |
15 | |
16 // Use this to create a global static pointer that's intialized exactly once whe
n you call get(). | 14 // Use this to create a global static pointer that's intialized exactly once whe
n you call get(). |
17 #define SK_DECLARE_STATIC_ONCE_PTR(type, name) namespace {} static SkBaseOncePtr
<type> name; | 15 #define SK_DECLARE_STATIC_ONCE_PTR(type, name) namespace {} static SkBaseOncePtr
<type> name; |
18 | 16 |
19 // Use this for a local or member pointer that's initialized exactly once when y
ou call get(). | |
20 template <typename T, typename Delete = std::default_delete<T>> | |
21 class SkOncePtr : SkNoncopyable { | |
22 public: | |
23 SkOncePtr() { sk_bzero(this, sizeof(*this)); } | |
24 ~SkOncePtr() { | |
25 if (T* ptr = (T*)*this) { | |
26 Delete()(ptr); | |
27 } | |
28 } | |
29 | |
30 template <typename F> | |
31 T* get(const F& f) const { | |
32 return fOnce.get(f); | |
33 } | |
34 | |
35 operator T*() const { | |
36 return (T*)fOnce; | |
37 } | |
38 | |
39 private: | |
40 SkBaseOncePtr<T> fOnce; | |
41 }; | |
42 | |
43 // If you ask for SkOncePtr<T[]>, we'll clean up with delete[] by default. | |
44 template <typename T> | |
45 class SkOncePtr<T[]> : public SkOncePtr<T, std::default_delete<T[]>> {}; | |
46 | |
47 /* TODO(mtklein): in next CL | |
48 typedef SkBaseOncePtr<void> SkOnceFlag; | |
49 #define SK_DECLARE_STATIC_ONCE(name) namespace {} static SkOnceFlag name | |
50 | |
51 template <typename F> | |
52 inline void SkOnce(SkOnceFlag* once, const F& f) { | |
53 once->get([&]{ f(); return (void*)2; }); | |
54 } | |
55 */ | |
56 | |
57 // Implementation details below here! No peeking! | |
58 | |
59 template <typename T> | 17 template <typename T> |
60 class SkBaseOncePtr { | 18 class SkBaseOncePtr { |
61 public: | 19 public: |
62 template <typename F> | 20 template <typename F> |
63 T* get(const F& f) const { | 21 T* get(const F& f) const { |
64 uintptr_t state = sk_atomic_load(&fState, sk_memory_order_acquire); | 22 uintptr_t state = sk_atomic_load(&fState, sk_memory_order_acquire); |
65 if (state < 2) { | 23 if (state < 2) { |
66 if (state == 0) { | 24 if (state == 0) { |
67 // It looks like no one has tried to create our pointer yet. | 25 // It looks like no one has tried to create our pointer yet. |
68 // We try to claim that task by atomically swapping our state fr
om '0' to '1'. | 26 // We try to claim that task by atomically swapping our state fr
om '0' to '1'. |
(...skipping 29 matching lines...) Expand all Loading... |
98 // TODO: If state == 1 spin until it's not? | 56 // TODO: If state == 1 spin until it's not? |
99 } | 57 } |
100 | 58 |
101 // fState == 0 --> we have not created our ptr yet | 59 // fState == 0 --> we have not created our ptr yet |
102 // fState == 1 --> someone is in the middle of creating our ptr | 60 // fState == 1 --> someone is in the middle of creating our ptr |
103 // else --> (T*)fState is our ptr | 61 // else --> (T*)fState is our ptr |
104 mutable uintptr_t fState; | 62 mutable uintptr_t fState; |
105 }; | 63 }; |
106 | 64 |
107 #endif//SkOncePtr_DEFINED | 65 #endif//SkOncePtr_DEFINED |
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