| /* |
| Copyright 2011 Google Inc. |
| |
| Licensed under the Apache License, Version 2.0 (the "License"); |
| you may not use this file except in compliance with the License. |
| You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, |
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| See the License for the specific language governing permissions and |
| limitations under the License. |
| */ |
| |
| |
| #ifndef SkTLazy_DEFINED |
| #define SkTLazy_DEFINED |
| |
| #include "SkTypes.h" |
| |
| /** |
| * Efficient way to defer allocating/initializing a class until it is needed |
| * (if ever). |
| */ |
| template <typename T> class SkTLazy { |
| public: |
| SkTLazy() : fPtr(NULL) {} |
| |
| explicit SkTLazy(const T* src) : fPtr(NULL) { |
| if (src) { |
| fPtr = new (fStorage) T(*src); |
| } |
| } |
| |
| SkTLazy(const SkTLazy<T>& src) : fPtr(NULL) { |
| const T* ptr = src.get(); |
| if (ptr) { |
| fPtr = new (fStorage) T(*ptr); |
| } |
| } |
| |
| ~SkTLazy() { |
| if (fPtr) { |
| fPtr->~T(); |
| } |
| } |
| |
| /** |
| * Return a pointer to a default-initialized instance of the class. If a |
| * previous instance had been initialzied (either from init() or set()) it |
| * will first be destroyed, so that a freshly initialized instance is |
| * always returned. |
| */ |
| T* init() { |
| if (fPtr) { |
| fPtr->~T(); |
| } |
| fPtr = new (fStorage) T; |
| return fPtr; |
| } |
| |
| /** |
| * Copy src into this, and return a pointer to a copy of it. Note this |
| * will always return the same pointer, so if it is called on a lazy that |
| * has already been initialized, then this will copy over the previous |
| * contents. |
| */ |
| T* set(const T& src) { |
| if (fPtr) { |
| *fPtr = src; |
| } else { |
| fPtr = new (fStorage) T(src); |
| } |
| return fPtr; |
| } |
| |
| /** |
| * Returns either NULL, or a copy of the object that was passed to |
| * set() or the constructor. |
| */ |
| T* get() const { return fPtr; } |
| |
| private: |
| T* fPtr; // NULL or fStorage |
| char fStorage[sizeof(T)]; |
| }; |
| |
| #endif |
| |