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Side by Side Diff: include/core/SkTLazy.h

Issue 1283183003: Use forwarding with SkTLazy::init. (Closed) Base URL: https://skia.googlesource.com/skia.git@master
Patch Set: Add && in deducing context. Created 5 years, 4 months ago
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1
2 /* 1 /*
3 * Copyright 2011 Google Inc. 2 * Copyright 2011 Google Inc.
4 * 3 *
5 * 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
6 * found in the LICENSE file. 5 * found in the LICENSE file.
7 */ 6 */
8 7
9
10
11 #ifndef SkTLazy_DEFINED 8 #ifndef SkTLazy_DEFINED
12 #define SkTLazy_DEFINED 9 #define SkTLazy_DEFINED
13 10
11 #include "SkTemplates.h"
14 #include "SkTypes.h" 12 #include "SkTypes.h"
15 #include <new> 13 #include <new>
16 14
17 template <typename T> class SkTLazy;
18 template <typename T> void* operator new(size_t, SkTLazy<T>* lazy);
19
20 /** 15 /**
21 * Efficient way to defer allocating/initializing a class until it is needed 16 * Efficient way to defer allocating/initializing a class until it is needed
22 * (if ever). 17 * (if ever).
23 */ 18 */
24 template <typename T> class SkTLazy { 19 template <typename T> class SkTLazy {
25 public: 20 public:
26 SkTLazy() : fPtr(NULL) {} 21 SkTLazy() : fPtr(NULL) {}
27 22
28 explicit SkTLazy(const T* src) : fPtr(NULL) { 23 explicit SkTLazy(const T* src) : fPtr(NULL) {
29 if (src) { 24 if (src) {
30 fPtr = new (fStorage) T(*src); 25 fPtr = new (fStorage.get()) T(*src);
31 } 26 }
32 } 27 }
33 28
34 SkTLazy(const SkTLazy<T>& src) : fPtr(NULL) { 29 SkTLazy(const SkTLazy<T>& src) : fPtr(NULL) {
35 if (src.isValid()) { 30 if (src.isValid()) {
36 fPtr = new (fStorage) T(*src->get()); 31 fPtr = new (fStorage.get()) T(*src->get());
37 } else { 32 } else {
38 fPtr = NULL; 33 fPtr = NULL;
39 } 34 }
40 } 35 }
41 36
42 ~SkTLazy() { 37 ~SkTLazy() {
43 if (this->isValid()) { 38 if (this->isValid()) {
44 fPtr->~T(); 39 fPtr->~T();
45 } 40 }
46 } 41 }
47 42
48 /** 43 /**
49 * Return a pointer to a default-initialized instance of the class. If a 44 * Return a pointer to an instance of the class initialized with 'args'.
50 * previous instance had been initialized (either from init() or set()) it 45 * If a previous instance had been initialized (either from init() or
51 * will first be destroyed, so that a freshly initialized instance is 46 * set()) it will first be destroyed, so that a freshly initialized
52 * always returned. 47 * instance is always returned.
53 */ 48 */
54 T* init() { 49 template <typename... Args> T* init(Args&&... args) {
55 if (this->isValid()) { 50 if (this->isValid()) {
56 fPtr->~T(); 51 fPtr->~T();
57 } 52 }
58 fPtr = new (SkTCast<T*>(fStorage)) T; 53 fPtr = new (SkTCast<T*>(fStorage.get())) T(skstd::forward<Args>(args)... );
59 return fPtr; 54 return fPtr;
60 } 55 }
61 56
62 /** 57 /**
63 * Copy src into this, and return a pointer to a copy of it. Note this 58 * Copy src into this, and return a pointer to a copy of it. Note this
64 * will always return the same pointer, so if it is called on a lazy that 59 * will always return the same pointer, so if it is called on a lazy that
65 * has already been initialized, then this will copy over the previous 60 * has already been initialized, then this will copy over the previous
66 * contents. 61 * contents.
67 */ 62 */
68 T* set(const T& src) { 63 T* set(const T& src) {
69 if (this->isValid()) { 64 if (this->isValid()) {
70 *fPtr = src; 65 *fPtr = src;
71 } else { 66 } else {
72 fPtr = new (SkTCast<T*>(fStorage)) T(src); 67 fPtr = new (SkTCast<T*>(fStorage.get())) T(src);
73 } 68 }
74 return fPtr; 69 return fPtr;
75 } 70 }
76 71
77 /** 72 /**
78 * Destroy the lazy object (if it was created via init() or set()) 73 * Destroy the lazy object (if it was created via init() or set())
79 */ 74 */
80 void reset() { 75 void reset() {
81 if (this->isValid()) { 76 if (this->isValid()) {
82 fPtr->~T(); 77 fPtr->~T();
(...skipping 13 matching lines...) Expand all
96 */ 91 */
97 T* get() const { SkASSERT(this->isValid()); return fPtr; } 92 T* get() const { SkASSERT(this->isValid()); return fPtr; }
98 93
99 /** 94 /**
100 * Like above but doesn't assert if object isn't initialized (in which case 95 * Like above but doesn't assert if object isn't initialized (in which case
101 * NULL is returned). 96 * NULL is returned).
102 */ 97 */
103 T* getMaybeNull() const { return fPtr; } 98 T* getMaybeNull() const { return fPtr; }
104 99
105 private: 100 private:
106 friend void* operator new<T>(size_t, SkTLazy* lazy); 101 T* fPtr; // NULL or fStorage
107 102 SkAlignedSTStorage<1, T> fStorage;
108 T* fPtr; // NULL or fStorage
109 char fStorage[sizeof(T)];
110 }; 103 };
111 104
112 // Use the below macro (SkNEW_IN_TLAZY) rather than calling this directly
113 template <typename T> void* operator new(size_t, SkTLazy<T>* lazy) {
114 SkASSERT(!lazy->isValid());
115 lazy->fPtr = reinterpret_cast<T*>(lazy->fStorage);
116 return lazy->fPtr;
117 }
118
119 // Skia doesn't use C++ exceptions but it may be compiled with them enabled. Hav ing an op delete
120 // to match the op new silences warnings about missing op delete when a construc tor throws an
121 // exception.
122 template <typename T> void operator delete(void*, SkTLazy<T>*) { SK_CRASH(); }
123
124 // Use this to construct a T inside an SkTLazy using a non-default constructor.
125 #define SkNEW_IN_TLAZY(tlazy_ptr, type_name, args) (new (tlazy_ptr) type_name ar gs)
126
127 /** 105 /**
128 * A helper built on top of SkTLazy to do copy-on-first-write. The object is ini tialized 106 * A helper built on top of SkTLazy to do copy-on-first-write. The object is ini tialized
129 * with a const pointer but provides a non-const pointer accessor. The first tim e the 107 * with a const pointer but provides a non-const pointer accessor. The first tim e the
130 * accessor is called (if ever) the object is cloned. 108 * accessor is called (if ever) the object is cloned.
131 * 109 *
132 * In the following example at most one copy of constThing is made: 110 * In the following example at most one copy of constThing is made:
133 * 111 *
134 * SkTCopyOnFirstWrite<Thing> thing(&constThing); 112 * SkTCopyOnFirstWrite<Thing> thing(&constThing);
135 * ... 113 * ...
136 * function_that_takes_a_const_thing_ptr(thing); // constThing is passed 114 * function_that_takes_a_const_thing_ptr(thing); // constThing is passed
(...skipping 46 matching lines...) Expand 10 before | Expand all | Expand 10 after
183 operator const T*() const { return fObj; } 161 operator const T*() const { return fObj; }
184 162
185 const T& operator *() const { return *fObj; } 163 const T& operator *() const { return *fObj; }
186 164
187 private: 165 private:
188 const T* fObj; 166 const T* fObj;
189 SkTLazy<T> fLazy; 167 SkTLazy<T> fLazy;
190 }; 168 };
191 169
192 #endif 170 #endif
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