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/*
* Copyright 2011 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkTLazy_DEFINED
#define SkTLazy_DEFINED
#include "SkTypes.h"
#include <new>
/**
* 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) {
if (src.isValid()) {
fPtr = new (fStorage) T(*src->get());
} else {
fPtr = NULL;
}
}
~SkTLazy() {
if (this->isValid()) {
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 (this->isValid()) {
fPtr->~T();
}
fPtr = new (SkTCast<T*>(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 (this->isValid()) {
*fPtr = src;
} else {
fPtr = new (SkTCast<T*>(fStorage)) T(src);
}
return fPtr;
}
/**
* Returns true if a valid object has been initialized in the SkTLazy,
* false otherwise.
*/
bool isValid() const { return NULL != fPtr; }
/**
* Returns either NULL, or a copy of the object that was passed to
* set() or the constructor.
*/
T* get() const { SkASSERT(this->isValid()); return fPtr; }
private:
T* fPtr; // NULL or fStorage
char fStorage[sizeof(T)];
};
#endif
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