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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 "SkAtomics.h" | 11 #include "SkAtomics.h" |
| 12 #include "SkUniquePtr.h" |
12 | 13 |
13 template <typename T> class SkStaticOnce; | 14 template <typename T> class SkBaseOncePtr; |
14 | 15 |
15 // Use this to create a global static pointer that's intialized exactly once whe
n you call get(). | 16 // Use this to create a global static pointer that's intialized exactly once whe
n you call get(). |
16 #define SK_DECLARE_STATIC_ONCE_PTR(type, name) namespace {} static SkStaticOnce<
type> name | 17 #define SK_DECLARE_STATIC_ONCE_PTR(type, name) namespace {} static SkBaseOncePtr
<type> name |
17 | 18 |
18 // Use this for a local or member pointer that's initialized exactly once when y
ou call get(). | 19 // Use this for a local or member pointer that's initialized exactly once when y
ou call get(). |
19 template <typename T> | 20 template <typename T, typename Delete = skstd::default_delete<T>> |
20 class SkOncePtr : SkNoncopyable { | 21 class SkOncePtr : SkNoncopyable { |
21 public: | 22 public: |
22 SkOncePtr() { sk_bzero(this, sizeof(*this)); } | 23 SkOncePtr() { sk_bzero(this, sizeof(*this)); } |
23 | 24 ~SkOncePtr() { |
24 // SkOncePtr does not have a destructor and does not clean up the pointer.
But you may, e.g. | 25 if (T* ptr = (T*)*this) { |
25 // delete (T*)fOncePtr; | 26 Delete()(ptr); |
26 // SkSafeUnref((T*)fOncePtr); | 27 } |
27 // etc. | 28 } |
28 | 29 |
29 template <typename F> | 30 template <typename F> |
30 T* get(const F& f) const { | 31 T* get(const F& f) const { |
31 return fOnce.get(f); | 32 return fOnce.get(f); |
32 } | 33 } |
33 | 34 |
34 operator T*() const { | 35 operator T*() const { |
35 return (T*)fOnce; | 36 return (T*)fOnce; |
36 } | 37 } |
37 | 38 |
38 private: | 39 private: |
39 SkStaticOnce<T> fOnce; | 40 SkBaseOncePtr<T> fOnce; |
40 }; | 41 }; |
41 | 42 |
42 /* TODO(mtklein): in next CL | 43 /* TODO(mtklein): in next CL |
43 typedef SkStaticOnce<void> SkOnceFlag; | 44 typedef SkBaseOncePtr<void> SkOnceFlag; |
44 #define SK_DECLARE_STATIC_ONCE(name) namespace {} static SkOnceFlag name | 45 #define SK_DECLARE_STATIC_ONCE(name) namespace {} static SkOnceFlag name |
45 | 46 |
46 template <typename F> | 47 template <typename F> |
47 inline void SkOnce(SkOnceFlag* once, const F& f) { | 48 inline void SkOnce(SkOnceFlag* once, const F& f) { |
48 once->get([&]{ f(); return (void*)2; }); | 49 once->get([&]{ f(); return (void*)2; }); |
49 } | 50 } |
50 */ | 51 */ |
51 | 52 |
52 // Implementation details below here! No peeking! | 53 // Implementation details below here! No peeking! |
53 | 54 |
54 template <typename T> | 55 template <typename T> |
55 class SkStaticOnce { | 56 class SkBaseOncePtr { |
56 public: | 57 public: |
57 template <typename F> | 58 template <typename F> |
58 T* get(const F& f) const { | 59 T* get(const F& f) const { |
59 uintptr_t state = fState.load(sk_memory_order_acquire); | 60 uintptr_t state = fState.load(sk_memory_order_acquire); |
60 if (state < 2) { | 61 if (state < 2) { |
61 if (state == 0) { | 62 if (state == 0) { |
62 // It looks like no one has tried to create our pointer yet. | 63 // It looks like no one has tried to create our pointer yet. |
63 // We try to claim that task by atomically swapping our state fr
om '0' to '1'. | 64 // We try to claim that task by atomically swapping our state fr
om '0' to '1'. |
64 if (fState.compare_exchange(&state, 1, sk_memory_order_relaxed, | 65 if (fState.compare_exchange(&state, 1, sk_memory_order_relaxed, |
65 sk_memory_order_relaxed))
{ | 66 sk_memory_order_relaxed))
{ |
(...skipping 27 matching lines...) Expand all Loading... |
93 } | 94 } |
94 | 95 |
95 private: | 96 private: |
96 // fState == 0 --> we have not created our ptr yet | 97 // fState == 0 --> we have not created our ptr yet |
97 // fState == 1 --> someone is in the middle of creating our ptr | 98 // fState == 1 --> someone is in the middle of creating our ptr |
98 // else --> (T*)fState is our ptr | 99 // else --> (T*)fState is our ptr |
99 mutable SkAtomic<uintptr_t> fState; | 100 mutable SkAtomic<uintptr_t> fState; |
100 }; | 101 }; |
101 | 102 |
102 #endif//SkOncePtr_DEFINED | 103 #endif//SkOncePtr_DEFINED |
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