fbfcd56021
This CL is part I of IV (I broke down the 1280 files into 4 CLs). Review URL: https://codereview.appspot.com/6485054 git-svn-id: http://skia.googlecode.com/svn/trunk@5262 2bbb7eff-a529-9590-31e7-b0007b416f81
93 lines
2.1 KiB
C++
93 lines
2.1 KiB
C++
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/*
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* Copyright 2011 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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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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#include <new>
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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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if (src.isValid()) {
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fPtr = new (fStorage) T(*src->get());
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} else {
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fPtr = NULL;
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}
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}
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~SkTLazy() {
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if (this->isValid()) {
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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 (this->isValid()) {
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fPtr->~T();
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}
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fPtr = new (SkTCast<T*>(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 (this->isValid()) {
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*fPtr = src;
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} else {
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fPtr = new (SkTCast<T*>(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 true if a valid object has been initialized in the SkTLazy,
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* false otherwise.
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*/
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bool isValid() const { return NULL != fPtr; }
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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 { SkASSERT(this->isValid()); 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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