| // Copyright (c) 2016 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| // unique_ptr-style pointer that stores values that may be from an arena. Takes |
| // up the same storage as the platform's native pointer type. Takes ownership |
| // of the value it's constructed with; if holding a value in an arena, and the |
| // type has a non-trivial destructor, the arena must outlive the |
| // QuicArenaScopedPtr. Does not support array overloads. |
| |
| #ifndef NET_THIRD_PARTY_QUIC_CORE_QUIC_ARENA_SCOPED_PTR_H_ |
| #define NET_THIRD_PARTY_QUIC_CORE_QUIC_ARENA_SCOPED_PTR_H_ |
| |
| #include <cstdint> // for uintptr_t |
| |
| #include "base/macros.h" |
| #include "net/third_party/quic/platform/api/quic_aligned.h" |
| #include "net/third_party/quic/platform/api/quic_logging.h" |
| |
| namespace quic { |
| |
| template <typename T> |
| class QuicArenaScopedPtr { |
| static_assert(QUIC_ALIGN_OF(T*) > 1, |
| "QuicArenaScopedPtr can only store objects that are aligned to " |
| "greater than 1 byte."); |
| |
| public: |
| // Constructs an empty QuicArenaScopedPtr. |
| QuicArenaScopedPtr(); |
| |
| // Constructs a QuicArenaScopedPtr referencing the heap-allocated memory |
| // provided. |
| explicit QuicArenaScopedPtr(T* value); |
| |
| template <typename U> |
| QuicArenaScopedPtr(QuicArenaScopedPtr<U>&& other); // NOLINT |
| template <typename U> |
| QuicArenaScopedPtr& operator=(QuicArenaScopedPtr<U>&& other); |
| ~QuicArenaScopedPtr(); |
| |
| // Returns a pointer to the value. |
| T* get() const; |
| |
| // Returns a reference to the value. |
| T& operator*() const; |
| |
| // Returns a pointer to the value. |
| T* operator->() const; |
| |
| // Swaps the value of this pointer with |other|. |
| void swap(QuicArenaScopedPtr& other); |
| |
| // Resets the held value to |value|. |
| void reset(T* value = nullptr); |
| |
| // Returns true if |this| came from an arena. Primarily exposed for testing |
| // and assertions. |
| bool is_from_arena(); |
| |
| private: |
| // Friends with other derived types of QuicArenaScopedPtr, to support the |
| // derived-types case. |
| template <typename U> |
| friend class QuicArenaScopedPtr; |
| // Also befriend all known arenas, only to prevent misuse. |
| template <uint32_t ArenaSize> |
| friend class QuicOneBlockArena; |
| |
| // Tag to denote that a QuicArenaScopedPtr is being explicitly created by an |
| // arena. |
| enum class ConstructFrom { kHeap, kArena }; |
| |
| // Constructs a QuicArenaScopedPtr with the given representation. |
| QuicArenaScopedPtr(void* value, ConstructFrom from); |
| QuicArenaScopedPtr(const QuicArenaScopedPtr&) = delete; |
| QuicArenaScopedPtr& operator=(const QuicArenaScopedPtr&) = delete; |
| |
| // Low-order bits of value_ that determine if the pointer came from an arena. |
| static const uintptr_t kFromArenaMask = 0x1; |
| |
| // Every platform we care about has at least 4B aligned integers, so store the |
| // is_from_arena bit in the least significant bit. |
| void* value_; |
| }; |
| |
| template <typename T> |
| bool operator==(const QuicArenaScopedPtr<T>& left, |
| const QuicArenaScopedPtr<T>& right) { |
| return left.get() == right.get(); |
| } |
| |
| template <typename T> |
| bool operator!=(const QuicArenaScopedPtr<T>& left, |
| const QuicArenaScopedPtr<T>& right) { |
| return left.get() != right.get(); |
| } |
| |
| template <typename T> |
| bool operator==(std::nullptr_t, const QuicArenaScopedPtr<T>& right) { |
| return nullptr == right.get(); |
| } |
| |
| template <typename T> |
| bool operator!=(std::nullptr_t, const QuicArenaScopedPtr<T>& right) { |
| return nullptr != right.get(); |
| } |
| |
| template <typename T> |
| bool operator==(const QuicArenaScopedPtr<T>& left, std::nullptr_t) { |
| return left.get() == nullptr; |
| } |
| |
| template <typename T> |
| bool operator!=(const QuicArenaScopedPtr<T>& left, std::nullptr_t) { |
| return left.get() != nullptr; |
| } |
| |
| template <typename T> |
| QuicArenaScopedPtr<T>::QuicArenaScopedPtr() : value_(nullptr) {} |
| |
| template <typename T> |
| QuicArenaScopedPtr<T>::QuicArenaScopedPtr(T* value) |
| : QuicArenaScopedPtr(value, ConstructFrom::kHeap) {} |
| |
| template <typename T> |
| template <typename U> |
| QuicArenaScopedPtr<T>::QuicArenaScopedPtr(QuicArenaScopedPtr<U>&& other) |
| : value_(other.value_) { |
| static_assert( |
| std::is_base_of<T, U>::value || std::is_same<T, U>::value, |
| "Cannot construct QuicArenaScopedPtr; type is not derived or same."); |
| other.value_ = nullptr; |
| } |
| |
| template <typename T> |
| template <typename U> |
| QuicArenaScopedPtr<T>& QuicArenaScopedPtr<T>::operator=( |
| QuicArenaScopedPtr<U>&& other) { |
| static_assert( |
| std::is_base_of<T, U>::value || std::is_same<T, U>::value, |
| "Cannot assign QuicArenaScopedPtr; type is not derived or same."); |
| swap(other); |
| return *this; |
| } |
| |
| template <typename T> |
| QuicArenaScopedPtr<T>::~QuicArenaScopedPtr() { |
| reset(); |
| } |
| |
| template <typename T> |
| T* QuicArenaScopedPtr<T>::get() const { |
| return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(value_) & |
| ~kFromArenaMask); |
| } |
| |
| template <typename T> |
| T& QuicArenaScopedPtr<T>::operator*() const { |
| return *get(); |
| } |
| |
| template <typename T> |
| T* QuicArenaScopedPtr<T>::operator->() const { |
| return get(); |
| } |
| |
| template <typename T> |
| void QuicArenaScopedPtr<T>::swap(QuicArenaScopedPtr& other) { |
| using std::swap; |
| swap(value_, other.value_); |
| } |
| |
| template <typename T> |
| bool QuicArenaScopedPtr<T>::is_from_arena() { |
| return (reinterpret_cast<uintptr_t>(value_) & kFromArenaMask) != 0; |
| } |
| |
| template <typename T> |
| void QuicArenaScopedPtr<T>::reset(T* value) { |
| if (value_ != nullptr) { |
| if (is_from_arena()) { |
| // Manually invoke the destructor. |
| get()->~T(); |
| } else { |
| delete get(); |
| } |
| } |
| DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(value) & kFromArenaMask); |
| value_ = value; |
| } |
| |
| template <typename T> |
| QuicArenaScopedPtr<T>::QuicArenaScopedPtr(void* value, ConstructFrom from_arena) |
| : value_(value) { |
| DCHECK_EQ(0u, reinterpret_cast<uintptr_t>(value_) & kFromArenaMask); |
| switch (from_arena) { |
| case ConstructFrom::kHeap: |
| break; |
| case ConstructFrom::kArena: |
| value_ = reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(value_) | |
| QuicArenaScopedPtr<T>::kFromArenaMask); |
| break; |
| } |
| } |
| |
| } // namespace quic |
| |
| #endif // NET_THIRD_PARTY_QUIC_CORE_QUIC_ARENA_SCOPED_PTR_H_ |