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