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