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staticData.h
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1 //
2 // Copyright 2016 Pixar
3 //
4 // Licensed under the Apache License, Version 2.0 (the "Apache License")
5 // with the following modification; you may not use this file except in
6 // compliance with the Apache License and the following modification to it:
7 // Section 6. Trademarks. is deleted and replaced with:
8 //
9 // 6. Trademarks. This License does not grant permission to use the trade
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11 // and its affiliates, except as required to comply with Section 4(c) of
12 // the License and to reproduce the content of the NOTICE file.
13 //
14 // You may obtain a copy of the Apache License at
15 //
16 // http://www.apache.org/licenses/LICENSE-2.0
17 //
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19 // distributed under the Apache License with the above modification is
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22 // language governing permissions and limitations under the Apache License.
23 //
24 #ifndef TF_STATICDATA_H
25 #define TF_STATICDATA_H
26 
29 
30 #include "pxr/pxr.h"
31 #include "pxr/base/arch/hints.h"
32 #include "pxr/base/tf/preprocessorUtils.h"
33 #include "pxr/base/tf/preprocessorUtilsLite.h"
34 
35 #include <atomic>
36 
37 PXR_NAMESPACE_OPEN_SCOPE
38 
107 template <class T>
108 struct Tf_StaticDataDefaultFactory {
109  static T *New() { return new T; }
110 };
111 
112 template <class T, class Factory = Tf_StaticDataDefaultFactory<T> >
114 public:
117  inline T* operator-> () const { return Get(); }
118 
121  inline T& operator* () const { return *Get(); }
122 
125  inline T* Get() const {
126  T *p = _data;
127  return ARCH_LIKELY(p) ? p : _TryToCreateData();
128  }
129 
132  inline bool IsInitialized() const { return _data.load() != nullptr; }
133 
134 private:
135  T *_TryToCreateData() const {
136  // Allocate an instance.
137  T *tmp = Factory::New();
138 
139  // Try to atomically set the pointer from null to tmp.
140  T *n = nullptr;
141  if (ARCH_LIKELY(_data.compare_exchange_strong(n, tmp)))
142  return tmp;
143 
144  // Another thread won the initialization race.
145  delete tmp;
146  return _data;
147  }
148 
149  mutable std::atomic<T *> _data;
150 };
151 
186 #define TF_MAKE_STATIC_DATA(Type, Name) \
187  static void TF_PP_CAT(Name,_Tf_StaticDataFactoryImpl)( \
188  TF_PP_EAT_PARENS(Type) *); \
189  namespace { \
190  struct TF_PP_CAT(Name,_Tf_StaticDataFactory) { \
191  static TF_PP_EAT_PARENS(Type) *New() { \
192  auto *p = new TF_PP_EAT_PARENS(Type); \
193  TF_PP_CAT(Name,_Tf_StaticDataFactoryImpl)(p); \
194  return p; \
195  } \
196  }; \
197  } \
198  static TfStaticData< \
199  TF_PP_EAT_PARENS(Type), TF_PP_CAT(Name,_Tf_StaticDataFactory)> Name; \
200  static void TF_PP_CAT(Name,_Tf_StaticDataFactoryImpl)( \
201  TF_PP_EAT_PARENS(Type) *Name)
202 
203 PXR_NAMESPACE_CLOSE_SCOPE
204 
205 #endif
bool IsInitialized() const
Return true if the underlying data object is created and initialized.
Definition: staticData.h:132
T * operator->() const
Return a pointer to the underlying data object.
Definition: staticData.h:117
Create or return a previously created object instance of global data.
Definition: staticData.h:113
T * Get() const
Return a pointer to the underlying object, creating and initializing it if necessary.
Definition: staticData.h:125
T & operator*() const
Member lookup.
Definition: staticData.h:121