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staticInterface.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
10// names, trademarks, service marks, or product names of the Licensor
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//
18// Unless required by applicable law or agreed to in writing, software
19// distributed under the Apache License with the above modification is
20// distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
21// KIND, either express or implied. See the Apache License for the specific
22// language governing permissions and limitations under the Apache License.
23//
24#ifndef PXR_BASE_PLUG_STATIC_INTERFACE_H
25#define PXR_BASE_PLUG_STATIC_INTERFACE_H
26
28
29#include "pxr/pxr.h"
30#include "pxr/base/plug/api.h"
31
32#include <atomic>
33#include <type_traits>
34#include <typeinfo>
35
36PXR_NAMESPACE_OPEN_SCOPE
37
38// Base class for common stuff.
39class Plug_StaticInterfaceBase {
40public:
44 bool IsInitialized() const
45 {
46 return _initialized;
47 }
48
49#if !defined(doxygen)
50 typedef void* Plug_StaticInterfaceBase::*UnspecifiedBoolType;
51#endif
52
53protected:
54 PLUG_API
55 void _LoadAndInstantiate(const std::type_info& type) const;
56
57protected:
58 // POD types only!
59 mutable std::atomic<bool> _initialized;
60 mutable void* _ptr;
61};
62
159template <class Interface>
160class PlugStaticInterface : private Plug_StaticInterfaceBase {
161public:
162 static_assert(std::is_abstract<Interface>::value,
163 "Interface type must be abstract.");
164
166
167 using Plug_StaticInterfaceBase::IsInitialized;
168
171 operator UnspecifiedBoolType() const
172 {
173 return _GetPtr() ? &This::_ptr : nullptr;
174 }
175
178 bool operator!() const
179 {
180 return !*this;
181 }
182
185 Interface* Get() const
186 {
187 return _GetPtr();
188 }
189
192 Interface* operator->() const
193 {
194 return _GetPtr();
195 }
196
200 Interface& operator*() const
201 {
202 return *_GetPtr();
203 }
204
205private:
206 Interface* _GetPtr() const
207 {
208 if (!_initialized) {
209 _LoadAndInstantiate(typeid(Interface));
210 }
211
212 // XXX: We must assume _ptr has the right type since we have
213 // no common base class to dynamic_cast<> from.
214 return static_cast<Interface*>(_ptr);
215 }
216};
217
218PXR_NAMESPACE_CLOSE_SCOPE
219
220#endif // PXR_BASE_PLUG_STATIC_INTERFACE_H
Provides access to an interface into a plugin.
Interface * Get() const
Returns the interface pointer, loading the plugin if necessary.
bool operator!() const
Load and instantiate then return false if the interface is valid, true otherwise.
Interface & operator*() const
Returns the interface pointer as a reference, loading the plugin if necessary.
Interface * operator->() const
Returns the interface pointer, loading the plugin if necessary.