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