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// Copyright 2016 PDFium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CORE_FXCRT_MAYBE_OWNED_H_
#define CORE_FXCRT_MAYBE_OWNED_H_
#include <algorithm>
#include <memory>
#include <utility>
#include "core/fxcrt/fx_memory.h"
#include "core/fxcrt/fx_system.h"
#include "core/fxcrt/unowned_ptr.h"
namespace fxcrt {
// A template that can hold either owned or unowned references, and cleans up
// appropriately. Possibly the most pernicious anti-pattern imaginable, but
// it crops up throughout the codebase due to a desire to avoid copying-in
// objects or data.
template <typename T, typename D = std::default_delete<T>>
class MaybeOwned {
public:
MaybeOwned() : m_pObj(nullptr) {}
explicit MaybeOwned(T* ptr) : m_pObj(ptr) {}
explicit MaybeOwned(std::unique_ptr<T, D> ptr)
: m_pOwnedObj(std::move(ptr)), m_pObj(m_pOwnedObj.get()) {}
MaybeOwned(const MaybeOwned& that) = delete;
MaybeOwned(MaybeOwned&& that) noexcept
: m_pOwnedObj(that.m_pOwnedObj.release()), m_pObj(that.m_pObj) {
that.m_pObj = nullptr;
}
void Reset(std::unique_ptr<T, D> ptr) {
m_pObj = ptr.get();
m_pOwnedObj = std::move(ptr);
}
void Reset(T* ptr = nullptr) {
m_pObj = ptr;
m_pOwnedObj.reset();
}
// Helpful for untangling a collection of intertwined MaybeOwned<>.
void ResetIfUnowned() {
if (!IsOwned())
Reset();
}
T* Get() const { return m_pObj.Get(); }
bool IsOwned() const { return !!m_pOwnedObj; }
// Downgrades to unowned, caller takes ownership.
std::unique_ptr<T, D> Release() {
ASSERT(IsOwned());
return std::move(m_pOwnedObj);
}
// Downgrades to empty, caller takes ownership.
std::unique_ptr<T, D> ReleaseAndClear() {
ASSERT(IsOwned());
m_pObj = nullptr;
return std::move(m_pOwnedObj);
}
MaybeOwned& operator=(const MaybeOwned& that) = delete;
MaybeOwned& operator=(MaybeOwned&& that) {
m_pObj = that.m_pObj;
m_pOwnedObj = std::move(that.m_pOwnedObj);
that.m_pObj = nullptr;
return *this;
}
MaybeOwned& operator=(T* ptr) {
Reset(ptr);
return *this;
}
MaybeOwned& operator=(std::unique_ptr<T, D> ptr) {
Reset(std::move(ptr));
return *this;
}
bool operator==(const MaybeOwned& that) const { return Get() == that.Get(); }
bool operator==(const std::unique_ptr<T, D>& ptr) const {
return Get() == ptr.get();
}
bool operator==(T* ptr) const { return Get() == ptr; }
bool operator!=(const MaybeOwned& that) const { return !(*this == that); }
bool operator!=(const std::unique_ptr<T, D> ptr) const {
return !(*this == ptr);
}
bool operator!=(T* ptr) const { return !(*this == ptr); }
explicit operator bool() const { return !!m_pObj; }
T& operator*() const { return *m_pObj; }
T* operator->() const { return m_pObj.Get(); }
private:
std::unique_ptr<T, D> m_pOwnedObj;
UnownedPtr<T> m_pObj;
};
} // namespace fxcrt
using fxcrt::MaybeOwned;
#endif // CORE_FXCRT_MAYBE_OWNED_H_
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