name : v8-array-buffer.h // Copyright 2021 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_ARRAY_BUFFER_H_ #define INCLUDE_V8_ARRAY_BUFFER_H_ #include <stddef.h> #include <memory> #include "v8-local-handle.h" // NOLINT(build/include_directory) #include "v8-object.h" // NOLINT(build/include_directory) #include "v8config.h" // NOLINT(build/include_directory) namespace v8 { class SharedArrayBuffer; #ifndef V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT // The number of required internal fields can be defined by embedder. #define V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT 2 #endif enum class ArrayBufferCreationMode { kInternalized, kExternalized }; /** * A wrapper around the backing store (i.e. the raw memory) of an array buffer. * See a document linked in http://crbug.com/v8/9908 for more information. * * The allocation and destruction of backing stores is generally managed by * V8. Clients should always use standard C++ memory ownership types (i.e. * std::unique_ptr and std::shared_ptr) to manage lifetimes of backing stores * properly, since V8 internal objects may alias backing stores. * * This object does not keep the underlying |ArrayBuffer::Allocator| alive by * default. Use Isolate::CreateParams::array_buffer_allocator_shared when * creating the Isolate to make it hold a reference to the allocator itself. */ class V8_EXPORT BackingStore : public v8::internal::BackingStoreBase { public: ~BackingStore(); /** * Return a pointer to the beginning of the memory block for this backing * store. The pointer is only valid as long as this backing store object * lives. */ void* Data() const; /** * The length (in bytes) of this backing store. */ size_t ByteLength() const; /** * The maximum length (in bytes) that this backing store may grow to. * * If this backing store was created for a resizable ArrayBuffer or a growable * SharedArrayBuffer, it is >= ByteLength(). Otherwise it is == * ByteLength(). */ size_t MaxByteLength() const; /** * Indicates whether the backing store was created for an ArrayBuffer or * a SharedArrayBuffer. */ bool IsShared() const; /** * Indicates whether the backing store was created for a resizable ArrayBuffer * or a growable SharedArrayBuffer, and thus may be resized by user JavaScript * code. */ bool IsResizableByUserJavaScript() const; /** * Prevent implicit instantiation of operator delete with size_t argument. * The size_t argument would be incorrect because ptr points to the * internal BackingStore object. */ void operator delete(void* ptr) { ::operator delete(ptr); } /** * Wrapper around ArrayBuffer::Allocator::Reallocate that preserves IsShared. * Assumes that the backing_store was allocated by the ArrayBuffer allocator * of the given isolate. */ static std::unique_ptr<BackingStore> Reallocate( v8::Isolate* isolate, std::unique_ptr<BackingStore> backing_store, size_t byte_length); /** * This callback is used only if the memory block for a BackingStore cannot be * allocated with an ArrayBuffer::Allocator. In such cases the destructor of * the BackingStore invokes the callback to free the memory block. */ using DeleterCallback = void (*)(void* data, size_t length, void* deleter_data); /** * If the memory block of a BackingStore is static or is managed manually, * then this empty deleter along with nullptr deleter_data can be passed to * ArrayBuffer::NewBackingStore to indicate that. * * The manually managed case should be used with caution and only when it * is guaranteed that the memory block freeing happens after detaching its * ArrayBuffer. */ static void EmptyDeleter(void* data, size_t length, void* deleter_data); private: /** * See [Shared]ArrayBuffer::GetBackingStore and * [Shared]ArrayBuffer::NewBackingStore. */ BackingStore(); }; #if !defined(V8_IMMINENT_DEPRECATION_WARNINGS) // Use v8::BackingStore::DeleterCallback instead. using BackingStoreDeleterCallback = void (*)(void* data, size_t length, void* deleter_data); #endif /** * An instance of the built-in ArrayBuffer constructor (ES6 draft 15.13.5). */ class V8_EXPORT ArrayBuffer : public Object { public: /** * A thread-safe allocator that V8 uses to allocate |ArrayBuffer|'s memory. * The allocator is a global V8 setting. It has to be set via * Isolate::CreateParams. * * Memory allocated through this allocator by V8 is accounted for as external * memory by V8. Note that V8 keeps track of the memory for all internalized * |ArrayBuffer|s. Responsibility for tracking external memory (using * Isolate::AdjustAmountOfExternalAllocatedMemory) is handed over to the * embedder upon externalization and taken over upon internalization (creating * an internalized buffer from an existing buffer). * * Note that it is unsafe to call back into V8 from any of the allocator * functions. */ class V8_EXPORT Allocator { public: virtual ~Allocator() = default; /** * Allocate |length| bytes. Return nullptr if allocation is not successful. * Memory should be initialized to zeroes. */ virtual void* Allocate(size_t length) = 0; /** * Allocate |length| bytes. Return nullptr if allocation is not successful. * Memory does not have to be initialized. */ virtual void* AllocateUninitialized(size_t length) = 0; /** * Free the memory block of size |length|, pointed to by |data|. * That memory is guaranteed to be previously allocated by |Allocate|. */ virtual void Free(void* data, size_t length) = 0; /** * Reallocate the memory block of size |old_length| to a memory block of * size |new_length| by expanding, contracting, or copying the existing * memory block. If |new_length| > |old_length|, then the new part of * the memory must be initialized to zeros. Return nullptr if reallocation * is not successful. * * The caller guarantees that the memory block was previously allocated * using Allocate or AllocateUninitialized. * * The default implementation allocates a new block and copies data. */ virtual void* Reallocate(void* data, size_t old_length, size_t new_length); /** * ArrayBuffer allocation mode. kNormal is a malloc/free style allocation, * while kReservation is for larger allocations with the ability to set * access permissions. */ enum class AllocationMode { kNormal, kReservation }; /** * Convenience allocator. * * When the sandbox is enabled, this allocator will allocate its backing * memory inside the sandbox. Otherwise, it will rely on malloc/free. * * Caller takes ownership, i.e. the returned object needs to be freed using * |delete allocator| once it is no longer in use. */ static Allocator* NewDefaultAllocator(); }; /** * Data length in bytes. */ size_t ByteLength() const; /** * Maximum length in bytes. */ size_t MaxByteLength() const; /** * Create a new ArrayBuffer. Allocate |byte_length| bytes. * Allocated memory will be owned by a created ArrayBuffer and * will be deallocated when it is garbage-collected, * unless the object is externalized. */ static Local<ArrayBuffer> New(Isolate* isolate, size_t byte_length); /** * Create a new ArrayBuffer with an existing backing store. * The created array keeps a reference to the backing store until the array * is garbage collected. Note that the IsExternal bit does not affect this * reference from the array to the backing store. * * In future IsExternal bit will be removed. Until then the bit is set as * follows. If the backing store does not own the underlying buffer, then * the array is created in externalized state. Otherwise, the array is created * in internalized state. In the latter case the array can be transitioned * to the externalized state using Externalize(backing_store). */ static Local<ArrayBuffer> New(Isolate* isolate, std::shared_ptr<BackingStore> backing_store); /** * Returns a new standalone BackingStore that is allocated using the array * buffer allocator of the isolate. The result can be later passed to * ArrayBuffer::New. * * If the allocator returns nullptr, then the function may cause GCs in the * given isolate and re-try the allocation. If GCs do not help, then the * function will crash with an out-of-memory error. */ static std::unique_ptr<BackingStore> NewBackingStore(Isolate* isolate, size_t byte_length); /** * Returns a new standalone BackingStore that takes over the ownership of * the given buffer. The destructor of the BackingStore invokes the given * deleter callback. * * The result can be later passed to ArrayBuffer::New. The raw pointer * to the buffer must not be passed again to any V8 API function. */ static std::unique_ptr<BackingStore> NewBackingStore( void* data, size_t byte_length, v8::BackingStore::DeleterCallback deleter, void* deleter_data); /** * Returns a new resizable standalone BackingStore that is allocated using the * array buffer allocator of the isolate. The result can be later passed to * ArrayBuffer::New. * * |byte_length| must be <= |max_byte_length|. * * This function is usable without an isolate. Unlike |NewBackingStore| calls * with an isolate, GCs cannot be triggered, and there are no * retries. Allocation failure will cause the function to crash with an * out-of-memory error. */ static std::unique_ptr<BackingStore> NewResizableBackingStore( size_t byte_length, size_t max_byte_length); /** * Returns true if this ArrayBuffer may be detached. */ bool IsDetachable() const; /** * Returns true if this ArrayBuffer has been detached. */ bool WasDetached() const; /** * Detaches this ArrayBuffer and all its views (typed arrays). * Detaching sets the byte length of the buffer and all typed arrays to zero, * preventing JavaScript from ever accessing underlying backing store. * ArrayBuffer should have been externalized and must be detachable. */ V8_DEPRECATE_SOON( "Use the version which takes a key parameter (passing a null handle is " "ok).") void Detach(); /** * Detaches this ArrayBuffer and all its views (typed arrays). * Detaching sets the byte length of the buffer and all typed arrays to zero, * preventing JavaScript from ever accessing underlying backing store. * ArrayBuffer should have been externalized and must be detachable. Returns * Nothing if the key didn't pass the [[ArrayBufferDetachKey]] check, * Just(true) otherwise. */ V8_WARN_UNUSED_RESULT Maybe<bool> Detach(v8::Local<v8::Value> key); /** * Sets the ArrayBufferDetachKey. */ void SetDetachKey(v8::Local<v8::Value> key); /** * Get a shared pointer to the backing store of this array buffer. This * pointer coordinates the lifetime management of the internal storage * with any live ArrayBuffers on the heap, even across isolates. The embedder * should not attempt to manage lifetime of the storage through other means. * * The returned shared pointer will not be empty, even if the ArrayBuffer has * been detached. Use |WasDetached| to tell if it has been detached instead. */ std::shared_ptr<BackingStore> GetBackingStore(); /** * More efficient shortcut for * GetBackingStore()->IsResizableByUserJavaScript(). */ bool IsResizableByUserJavaScript() const; /** * More efficient shortcut for GetBackingStore()->Data(). The returned pointer * is valid as long as the ArrayBuffer is alive. */ void* Data() const; V8_INLINE static ArrayBuffer* Cast(Value* value) { #ifdef V8_ENABLE_CHECKS CheckCast(value); #endif return static_cast<ArrayBuffer*>(value); } static const int kInternalFieldCount = V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT; static const int kEmbedderFieldCount = V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT; private: ArrayBuffer(); static void CheckCast(Value* obj); }; #ifndef V8_ARRAY_BUFFER_VIEW_INTERNAL_FIELD_COUNT // The number of required internal fields can be defined by embedder. #define V8_ARRAY_BUFFER_VIEW_INTERNAL_FIELD_COUNT 2 #endif /** * A base class for an instance of one of "views" over ArrayBuffer, * including TypedArrays and DataView (ES6 draft 15.13). */ class V8_EXPORT ArrayBufferView : public Object { public: /** * Returns underlying ArrayBuffer. */ Local<ArrayBuffer> Buffer(); /** * Byte offset in |Buffer|. */ size_t ByteOffset(); /** * Size of a view in bytes. */ size_t ByteLength(); /** * Copy the contents of the ArrayBufferView's buffer to an embedder defined * memory without additional overhead that calling ArrayBufferView::Buffer * might incur. * * Will write at most min(|byte_length|, ByteLength) bytes starting at * ByteOffset of the underlying buffer to the memory starting at |dest|. * Returns the number of bytes actually written. */ size_t CopyContents(void* dest, size_t byte_length); /** * Returns true if ArrayBufferView's backing ArrayBuffer has already been * allocated. */ bool HasBuffer() const; V8_INLINE static ArrayBufferView* Cast(Value* value) { #ifdef V8_ENABLE_CHECKS CheckCast(value); #endif return static_cast<ArrayBufferView*>(value); } static const int kInternalFieldCount = V8_ARRAY_BUFFER_VIEW_INTERNAL_FIELD_COUNT; static const int kEmbedderFieldCount = V8_ARRAY_BUFFER_VIEW_INTERNAL_FIELD_COUNT; private: ArrayBufferView(); static void CheckCast(Value* obj); }; /** * An instance of DataView constructor (ES6 draft 15.13.7). */ class V8_EXPORT DataView : public ArrayBufferView { public: static Local<DataView> New(Local<ArrayBuffer> array_buffer, size_t byte_offset, size_t length); static Local<DataView> New(Local<SharedArrayBuffer> shared_array_buffer, size_t byte_offset, size_t length); V8_INLINE static DataView* Cast(Value* value) { #ifdef V8_ENABLE_CHECKS CheckCast(value); #endif return static_cast<DataView*>(value); } private: DataView(); static void CheckCast(Value* obj); }; /** * An instance of the built-in SharedArrayBuffer constructor. */ class V8_EXPORT SharedArrayBuffer : public Object { public: /** * Data length in bytes. */ size_t ByteLength() const; /** * Maximum length in bytes. */ size_t MaxByteLength() const; /** * Create a new SharedArrayBuffer. Allocate |byte_length| bytes. * Allocated memory will be owned by a created SharedArrayBuffer and * will be deallocated when it is garbage-collected, * unless the object is externalized. */ static Local<SharedArrayBuffer> New(Isolate* isolate, size_t byte_length); /** * Create a new SharedArrayBuffer with an existing backing store. * The created array keeps a reference to the backing store until the array * is garbage collected. Note that the IsExternal bit does not affect this * reference from the array to the backing store. * * In future IsExternal bit will be removed. Until then the bit is set as * follows. If the backing store does not own the underlying buffer, then * the array is created in externalized state. Otherwise, the array is created * in internalized state. In the latter case the array can be transitioned * to the externalized state using Externalize(backing_store). */ static Local<SharedArrayBuffer> New( Isolate* isolate, std::shared_ptr<BackingStore> backing_store); /** * Returns a new standalone BackingStore that is allocated using the array * buffer allocator of the isolate. The result can be later passed to * SharedArrayBuffer::New. * * If the allocator returns nullptr, then the function may cause GCs in the * given isolate and re-try the allocation. If GCs do not help, then the * function will crash with an out-of-memory error. */ static std::unique_ptr<BackingStore> NewBackingStore(Isolate* isolate, size_t byte_length); /** * Returns a new standalone BackingStore that takes over the ownership of * the given buffer. The destructor of the BackingStore invokes the given * deleter callback. * * The result can be later passed to SharedArrayBuffer::New. The raw pointer * to the buffer must not be passed again to any V8 functions. */ static std::unique_ptr<BackingStore> NewBackingStore( void* data, size_t byte_length, v8::BackingStore::DeleterCallback deleter, void* deleter_data); /** * Get a shared pointer to the backing store of this array buffer. This * pointer coordinates the lifetime management of the internal storage * with any live ArrayBuffers on the heap, even across isolates. The embedder * should not attempt to manage lifetime of the storage through other means. */ std::shared_ptr<BackingStore> GetBackingStore(); /** * More efficient shortcut for GetBackingStore()->Data(). The returned pointer * is valid as long as the ArrayBuffer is alive. */ void* Data() const; V8_INLINE static SharedArrayBuffer* Cast(Value* value) { #ifdef V8_ENABLE_CHECKS CheckCast(value); #endif return static_cast<SharedArrayBuffer*>(value); } static const int kInternalFieldCount = V8_ARRAY_BUFFER_INTERNAL_FIELD_COUNT; private: SharedArrayBuffer(); static void CheckCast(Value* obj); }; } // namespace v8 #endif // INCLUDE_V8_ARRAY_BUFFER_H_