name : v8-handle-base.h // Copyright 2023 the V8 project 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 INCLUDE_V8_HANDLE_BASE_H_ #define INCLUDE_V8_HANDLE_BASE_H_ #include "v8-internal.h" // NOLINT(build/include_directory) namespace v8::api_internal { template <bool check_statically_enabled> class StackAllocated { public: V8_INLINE StackAllocated() = default; protected: struct no_checking_tag {}; static constexpr no_checking_tag do_not_check{}; V8_INLINE explicit StackAllocated(no_checking_tag) {} V8_INLINE explicit StackAllocated(const StackAllocated& other, no_checking_tag) {} V8_INLINE void VerifyOnStack() const {} }; template <> class V8_TRIVIAL_ABI StackAllocated<true> : public StackAllocated<false> { public: V8_INLINE StackAllocated() { VerifyOnStack(); } #if V8_HAS_ATTRIBUTE_TRIVIAL_ABI // In this case, StackAllocated becomes not trivially copyable. V8_INLINE StackAllocated(const StackAllocated& other) { VerifyOnStack(); } StackAllocated& operator=(const StackAllocated&) = default; #endif protected: V8_INLINE explicit StackAllocated(no_checking_tag tag) : StackAllocated<false>(tag) {} V8_INLINE explicit StackAllocated(const StackAllocated& other, no_checking_tag tag) : StackAllocated<false>(other, tag) {} V8_EXPORT void VerifyOnStack() const; }; /** * A base class for abstract handles containing indirect pointers. * These are useful regardless of whether direct local support is enabled. */ class IndirectHandleBase { public: // Returns true if the handle is empty. V8_INLINE bool IsEmpty() const { return location_ == nullptr; } // Sets the handle to be empty. IsEmpty() will then return true. V8_INLINE void Clear() { location_ = nullptr; } protected: friend class internal::ValueHelper; friend class internal::HandleHelper; V8_INLINE IndirectHandleBase() = default; V8_INLINE IndirectHandleBase(const IndirectHandleBase& other) = default; V8_INLINE IndirectHandleBase& operator=(const IndirectHandleBase& that) = default; V8_INLINE explicit IndirectHandleBase(internal::Address* location) : location_(location) {} // Returns the address of the actual heap object (tagged). // This method must be called only if the handle is not empty, otherwise it // will crash. V8_INLINE internal::Address ptr() const { return *location_; } // Returns a reference to the slot (indirect pointer). V8_INLINE internal::Address* const& slot() const { return location_; } V8_INLINE internal::Address*& slot() { return location_; } // Returns the handler's "value" (direct or indirect pointer, depending on // whether direct local support is enabled). template <typename T, bool check_null = false> V8_INLINE T* value() const { return internal::ValueHelper::SlotAsValue<T, check_null>(slot()); } private: internal::Address* location_ = nullptr; }; #ifdef V8_ENABLE_DIRECT_LOCAL /** * A base class for abstract handles containing direct pointers. * These are only possible when conservative stack scanning is enabled. */ class DirectHandleBase { public: // Returns true if the handle is empty. V8_INLINE bool IsEmpty() const { return ptr_ == internal::ValueHelper::kEmpty; } // Sets the handle to be empty. IsEmpty() will then return true. V8_INLINE void Clear() { ptr_ = internal::ValueHelper::kEmpty; } protected: friend class internal::ValueHelper; friend class internal::HandleHelper; V8_INLINE DirectHandleBase() = default; V8_INLINE DirectHandleBase(const DirectHandleBase& other) = default; V8_INLINE DirectHandleBase& operator=(const DirectHandleBase& that) = default; V8_INLINE explicit DirectHandleBase(internal::Address ptr) : ptr_(ptr) {} // Returns the address of the referenced object. V8_INLINE internal::Address ptr() const { return ptr_; } // Returns the handler's "value" (direct pointer, as direct local support // is guaranteed to be enabled here). template <typename T, bool check_null = false> V8_INLINE T* value() const { return reinterpret_cast<T*>(ptr_); } private: internal::Address ptr_ = internal::ValueHelper::kEmpty; }; #endif // V8_ENABLE_DIRECT_LOCAL } // namespace v8::api_internal #endif // INCLUDE_V8_HANDLE_BASE_H_