Source/JavaScriptCore/runtime/JSArrayBufferView.h - WebKit - Git at Google

 /*
  * Copyright (C) 2013-2019 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #pragma once

 #include "AuxiliaryBarrier.h"
 #include "JSObject.h"
 #include <wtf/TaggedArrayStoragePtr.h>

 namespace JSC {

 class LLIntOffsetsExtractor;

 // This class serves two purposes:
 //
 // 1) It provides those parts of JSGenericTypedArrayView that don't depend
 //    on template parameters.
 //
 // 2) It represents the DOM/WebCore-visible "JSArrayBufferView" type, which
 //    C++ code uses when it wants to pass around a view of an array buffer
 //    without concern for the actual type of the view.
 //
 // These two roles are quite different. (1) is just a matter of optimizing
 // compile and link times by having as much code and data as possible not
 // be subject to template specialization. (2) is *almost* a matter of
 // semantics; indeed at the very least it is a matter of obeying a contract
 // that we have with WebCore right now.
 //
 // One convenient thing that saves us from too much crazy is that
 // ArrayBufferView is not instantiable.

 // Typed array views have different modes depending on how big they are and
 // whether the user has done anything that requires a separate backing
 // buffer or the DOM-specified neutering capabilities.
 enum TypedArrayMode : uint32_t {
     // Small and fast typed array. B is unused, V points to a vector
     // allocated in copied space, and M = FastTypedArray. V's liveness is
     // determined entirely by the view's liveness.
     FastTypedArray,

     // A large typed array that still attempts not to waste too much
     // memory. B is initialized to point to a slot that could hold a
     // buffer pointer, V points to a vector allocated using fastCalloc(),
     // and M = OversizeTypedArray. V's liveness is determined entirely by
     // the view's liveness, and the view will add a finalizer to delete V.
     OversizeTypedArray,

     // A typed array that was used in some crazy way. B's IndexingHeader
     // is hijacked to contain a reference to the native array buffer. The
     // native typed array view points back to the JS view. V points to a
     // vector allocated using who-knows-what, and M = WastefulTypedArray.
     // The view does not own the vector.
     WastefulTypedArray,

     // A data view. B is unused, V points to a vector allocated using who-
     // knows-what, and M = DataViewMode. The view does not own the vector.
     // There is an extra field (in JSDataView) that points to the
     // ArrayBuffer.
     DataViewMode
 };

 inline bool hasArrayBuffer(TypedArrayMode mode)
 {
     return mode >= WastefulTypedArray;
 }

 // When WebCore uses a JSArrayBufferView, it expects to be able to get the native
 // ArrayBuffer and little else. This requires slowing down and wasting memory,
 // and then accessing things via the Butterfly. When JS uses a JSArrayBufferView
 // it is always via the usual methods in the MethodTable, so this class's
 // implementation of those has no need to even exist - we could at any time sink
 // code into JSGenericTypedArrayView if it was convenient.

 class JSArrayBufferView : public JSNonFinalObject {
 public:
     using Base = JSNonFinalObject;

     template<typename, SubspaceAccess>
     static void subspaceFor(VM&)
     {
         RELEASE_ASSERT_NOT_REACHED();
     }

     static constexpr unsigned fastSizeLimit = 1000;
     using VectorPtr = CagedBarrierPtr<Gigacage::Primitive, void, tagCagedPtr>;

     static size_t sizeOf(uint32_t length, uint32_t elementSize)
     {
         return (static_cast<size_t>(length) * elementSize + sizeof(EncodedJSValue) - 1)
             & ~(sizeof(EncodedJSValue) - 1);
     }

     static size_t allocationSize(Checked<size_t> inlineCapacity)
     {
         ASSERT_UNUSED(inlineCapacity, !inlineCapacity);
         return sizeof(JSArrayBufferView);
     }

 protected:
     class ConstructionContext {
         WTF_MAKE_NONCOPYABLE(ConstructionContext);

     public:
         enum InitializationMode { ZeroFill, DontInitialize };

         JS_EXPORT_PRIVATE ConstructionContext(VM&, Structure*, uint32_t length, uint32_t elementSize, InitializationMode = ZeroFill);

         // This is only for constructing fast typed arrays. It's used by the JIT's slow path.
         ConstructionContext(Structure*, uint32_t length, void* vector);

         JS_EXPORT_PRIVATE ConstructionContext(
             VM&, Structure*, RefPtr<ArrayBuffer>&&,
             unsigned byteOffset, unsigned length);

         enum DataViewTag { DataView };
         ConstructionContext(
             Structure*, RefPtr<ArrayBuffer>&&,
             unsigned byteOffset, unsigned length, DataViewTag);

         bool operator!() const { return !m_structure; }

         Structure* structure() const { return m_structure; }
         void* vector() const { return m_vector.getMayBeNull(m_length); }
         uint32_t length() const { return m_length; }
         TypedArrayMode mode() const { return m_mode; }
         Butterfly* butterfly() const { return m_butterfly; }

     private:
         Structure* m_structure;
         using VectorType = CagedPtr<Gigacage::Primitive, void, tagCagedPtr>;
         VectorType m_vector;
         uint32_t m_length;
         TypedArrayMode m_mode;
         Butterfly* m_butterfly;
     };

     JS_EXPORT_PRIVATE JSArrayBufferView(VM&, ConstructionContext&);
     JS_EXPORT_PRIVATE void finishCreation(VM&);

     static bool put(JSCell*, JSGlobalObject*, PropertyName, JSValue, PutPropertySlot&);

     static void visitChildren(JSCell*, SlotVisitor&);

 public:
     TypedArrayMode mode() const { return m_mode; }
     bool hasArrayBuffer() const { return JSC::hasArrayBuffer(mode()); }

     bool isShared();
     JS_EXPORT_PRIVATE ArrayBuffer* unsharedBuffer();
     inline ArrayBuffer* possiblySharedBuffer();
     JSArrayBuffer* unsharedJSBuffer(JSGlobalObject* globalObject);
     JSArrayBuffer* possiblySharedJSBuffer(JSGlobalObject* globalObject);
     RefPtr<ArrayBufferView> unsharedImpl();
     JS_EXPORT_PRIVATE RefPtr<ArrayBufferView> possiblySharedImpl();
     bool isNeutered() { return hasArrayBuffer() && !hasVector(); }
     void neuter();

     bool hasVector() const { return !!m_vector; }
     void* vector() const { return m_vector.getMayBeNull(length()); }

     inline unsigned byteOffset();
     inline Optional<unsigned> byteOffsetConcurrently();

     unsigned length() const { return m_length; }

     DECLARE_EXPORT_INFO;

     static ptrdiff_t offsetOfVector() { return OBJECT_OFFSETOF(JSArrayBufferView, m_vector); }
     static ptrdiff_t offsetOfLength() { return OBJECT_OFFSETOF(JSArrayBufferView, m_length); }
     static ptrdiff_t offsetOfMode() { return OBJECT_OFFSETOF(JSArrayBufferView, m_mode); }

     static RefPtr<ArrayBufferView> toWrapped(VM&, JSValue);

 private:
     enum Requester { Mutator, ConcurrentThread };
     template<Requester, typename ResultType> ResultType byteOffsetImpl();
     template<Requester> ArrayBuffer* possiblySharedBufferImpl();

     JS_EXPORT_PRIVATE ArrayBuffer* slowDownAndWasteMemory();
     static void finalize(JSCell*);

 protected:
     friend class LLIntOffsetsExtractor;

     ArrayBuffer* existingBufferInButterfly();

     static String toStringName(const JSObject*, JSGlobalObject*);

     VectorPtr m_vector;
     uint32_t m_length;
     TypedArrayMode m_mode;
 };

 } // namespace JSC

 namespace WTF {

 JS_EXPORT_PRIVATE void printInternal(PrintStream&, JSC::TypedArrayMode);

 } // namespace WTF
	/*
	* Copyright (C) 2013-2019 Apple Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
	* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#pragma once

	#include "AuxiliaryBarrier.h"
	#include "JSObject.h"
	#include <wtf/TaggedArrayStoragePtr.h>

	namespace JSC {

	class LLIntOffsetsExtractor;

	// This class serves two purposes:
	//
	// 1) It provides those parts of JSGenericTypedArrayView that don't depend
	// on template parameters.
	//
	// 2) It represents the DOM/WebCore-visible "JSArrayBufferView" type, which
	// C++ code uses when it wants to pass around a view of an array buffer
	// without concern for the actual type of the view.
	//
	// These two roles are quite different. (1) is just a matter of optimizing
	// compile and link times by having as much code and data as possible not
	// be subject to template specialization. (2) is almost a matter of
	// semantics; indeed at the very least it is a matter of obeying a contract
	// that we have with WebCore right now.
	//
	// One convenient thing that saves us from too much crazy is that
	// ArrayBufferView is not instantiable.

	// Typed array views have different modes depending on how big they are and
	// whether the user has done anything that requires a separate backing
	// buffer or the DOM-specified neutering capabilities.
	enum TypedArrayMode : uint32_t {
	// Small and fast typed array. B is unused, V points to a vector
	// allocated in copied space, and M = FastTypedArray. V's liveness is
	// determined entirely by the view's liveness.
	FastTypedArray,

	// A large typed array that still attempts not to waste too much
	// memory. B is initialized to point to a slot that could hold a
	// buffer pointer, V points to a vector allocated using fastCalloc(),
	// and M = OversizeTypedArray. V's liveness is determined entirely by
	// the view's liveness, and the view will add a finalizer to delete V.
	OversizeTypedArray,

	// A typed array that was used in some crazy way. B's IndexingHeader
	// is hijacked to contain a reference to the native array buffer. The
	// native typed array view points back to the JS view. V points to a
	// vector allocated using who-knows-what, and M = WastefulTypedArray.
	// The view does not own the vector.
	WastefulTypedArray,

	// A data view. B is unused, V points to a vector allocated using who-
	// knows-what, and M = DataViewMode. The view does not own the vector.
	// There is an extra field (in JSDataView) that points to the
	// ArrayBuffer.
	DataViewMode
	};

	inline bool hasArrayBuffer(TypedArrayMode mode)
	{
	return mode >= WastefulTypedArray;
	}

	// When WebCore uses a JSArrayBufferView, it expects to be able to get the native
	// ArrayBuffer and little else. This requires slowing down and wasting memory,
	// and then accessing things via the Butterfly. When JS uses a JSArrayBufferView
	// it is always via the usual methods in the MethodTable, so this class's
	// implementation of those has no need to even exist - we could at any time sink
	// code into JSGenericTypedArrayView if it was convenient.

	class JSArrayBufferView : public JSNonFinalObject {
	public:
	using Base = JSNonFinalObject;

	template<typename, SubspaceAccess>
	static void subspaceFor(VM&)
	{
	RELEASE_ASSERT_NOT_REACHED();
	}

	static constexpr unsigned fastSizeLimit = 1000;
	using VectorPtr = CagedBarrierPtr<Gigacage::Primitive, void, tagCagedPtr>;

	static size_t sizeOf(uint32_t length, uint32_t elementSize)
	{
	return (static_cast<size_t>(length) * elementSize + sizeof(EncodedJSValue) - 1)
	& ~(sizeof(EncodedJSValue) - 1);
	}

	static size_t allocationSize(Checked<size_t> inlineCapacity)
	{
	ASSERT_UNUSED(inlineCapacity, !inlineCapacity);
	return sizeof(JSArrayBufferView);
	}

	protected:
	class ConstructionContext {
	WTF_MAKE_NONCOPYABLE(ConstructionContext);

	public:
	enum InitializationMode { ZeroFill, DontInitialize };

	JS_EXPORT_PRIVATE ConstructionContext(VM&, Structure*, uint32_t length, uint32_t elementSize, InitializationMode = ZeroFill);

	// This is only for constructing fast typed arrays. It's used by the JIT's slow path.
	ConstructionContext(Structure, uint32_t length, void vector);

	JS_EXPORT_PRIVATE ConstructionContext(
	VM&, Structure*, RefPtr<ArrayBuffer>&&,
	unsigned byteOffset, unsigned length);

	enum DataViewTag { DataView };
	ConstructionContext(
	Structure*, RefPtr<ArrayBuffer>&&,
	unsigned byteOffset, unsigned length, DataViewTag);

	bool operator!() const { return !m_structure; }

	Structure* structure() const { return m_structure; }
	void* vector() const { return m_vector.getMayBeNull(m_length); }
	uint32_t length() const { return m_length; }
	TypedArrayMode mode() const { return m_mode; }
	Butterfly* butterfly() const { return m_butterfly; }

	private:
	Structure* m_structure;
	using VectorType = CagedPtr<Gigacage::Primitive, void, tagCagedPtr>;
	VectorType m_vector;
	uint32_t m_length;
	TypedArrayMode m_mode;
	Butterfly* m_butterfly;
	};

	JS_EXPORT_PRIVATE JSArrayBufferView(VM&, ConstructionContext&);
	JS_EXPORT_PRIVATE void finishCreation(VM&);

	static bool put(JSCell, JSGlobalObject, PropertyName, JSValue, PutPropertySlot&);

	static void visitChildren(JSCell*, SlotVisitor&);

	public:
	TypedArrayMode mode() const { return m_mode; }
	bool hasArrayBuffer() const { return JSC::hasArrayBuffer(mode()); }

	bool isShared();
	JS_EXPORT_PRIVATE ArrayBuffer* unsharedBuffer();
	inline ArrayBuffer* possiblySharedBuffer();
	JSArrayBuffer* unsharedJSBuffer(JSGlobalObject* globalObject);
	JSArrayBuffer* possiblySharedJSBuffer(JSGlobalObject* globalObject);
	RefPtr<ArrayBufferView> unsharedImpl();
	JS_EXPORT_PRIVATE RefPtr<ArrayBufferView> possiblySharedImpl();
	bool isNeutered() { return hasArrayBuffer() && !hasVector(); }
	void neuter();

	bool hasVector() const { return !!m_vector; }
	void* vector() const { return m_vector.getMayBeNull(length()); }

	inline unsigned byteOffset();
	inline Optional<unsigned> byteOffsetConcurrently();

	unsigned length() const { return m_length; }

	DECLARE_EXPORT_INFO;

	static ptrdiff_t offsetOfVector() { return OBJECT_OFFSETOF(JSArrayBufferView, m_vector); }
	static ptrdiff_t offsetOfLength() { return OBJECT_OFFSETOF(JSArrayBufferView, m_length); }
	static ptrdiff_t offsetOfMode() { return OBJECT_OFFSETOF(JSArrayBufferView, m_mode); }

	static RefPtr<ArrayBufferView> toWrapped(VM&, JSValue);

	private:
	enum Requester { Mutator, ConcurrentThread };
	template<Requester, typename ResultType> ResultType byteOffsetImpl();
	template<Requester> ArrayBuffer* possiblySharedBufferImpl();

	JS_EXPORT_PRIVATE ArrayBuffer* slowDownAndWasteMemory();
	static void finalize(JSCell*);

	protected:
	friend class LLIntOffsetsExtractor;

	ArrayBuffer* existingBufferInButterfly();

	static String toStringName(const JSObject, JSGlobalObject);

	VectorPtr m_vector;
	uint32_t m_length;
	TypedArrayMode m_mode;
	};

	} // namespace JSC

	namespace WTF {

	JS_EXPORT_PRIVATE void printInternal(PrintStream&, JSC::TypedArrayMode);

	} // namespace WTF