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

 /*
  * Copyright (C) 2012-2018 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 "IndexingHeader.h"
 #include "IndexingType.h"
 #include "PropertyStorage.h"
 #include <wtf/Gigacage.h>
 #include <wtf/Noncopyable.h>

 namespace JSC {

 class VM;
 class CopyVisitor;
 class GCDeferralContext;
 struct ArrayStorage;

 template <typename T>
 struct ContiguousData {
     ContiguousData() = default;
     ContiguousData(T* data, size_t length)
         : m_data(data)
 #if ASSERT_ENABLED
         , m_length(length)
 #endif
     {
         UNUSED_PARAM(length);
     }

     struct Data {
         Data(T& location, IndexingType indexingMode)
             : m_data(location)
 #if ASSERT_ENABLED
             , m_isWritable(!isCopyOnWrite(indexingMode))
 #endif
         {
             UNUSED_PARAM(indexingMode);
         }

         explicit operator bool() const { return !!m_data.get(); }

         const T& operator=(const T& value)
         {
             ASSERT(m_isWritable);
             m_data = value;
             return value;
         }

         operator const T&() const { return m_data; }

         // WriteBarrier forwarded methods.

         void set(VM& vm, const JSCell* owner, const JSValue& value)
         {
             ASSERT(m_isWritable);
             m_data.set(vm, owner, value);
         }

         void setWithoutWriteBarrier(const JSValue& value)
         {
             ASSERT(m_isWritable);
             m_data.setWithoutWriteBarrier(value);
         }

         void setStartingValue(JSValue value)
         {
             m_data.setStartingValue(value);
         }

         void clear()
         {
             ASSERT(m_isWritable);
             m_data.clear();
         }

         JSValue get() const
         {
             return m_data.get();
         }


         T& m_data;
 #if ASSERT_ENABLED
         bool m_isWritable;
 #endif
     };

     const Data at(const JSCell* owner, size_t index) const;
     Data at(const JSCell* owner, size_t index);

     T& atUnsafe(size_t index) { ASSERT(index < m_length); return m_data[index]; }

     T* data() const { return m_data; }
 #if ASSERT_ENABLED
     size_t length() const { return m_length; }
 #endif

 private:
     T* m_data { nullptr };
 #if ASSERT_ENABLED
     size_t m_length { 0 };
 #endif
 };

 using ContiguousDoubles = ContiguousData<double>;
 using ContiguousJSValues = ContiguousData<WriteBarrier<Unknown>>;
 using ConstContiguousDoubles = ContiguousData<const double>;
 using ConstContiguousJSValues = ContiguousData<const WriteBarrier<Unknown>>;

 class Butterfly {
     WTF_MAKE_NONCOPYABLE(Butterfly);
 private:
     Butterfly() { } // Not instantiable.
 public:

     static size_t totalSize(size_t preCapacity, size_t propertyCapacity, bool hasIndexingHeader, size_t indexingPayloadSizeInBytes)
     {
         ASSERT(indexingPayloadSizeInBytes ? hasIndexingHeader : true);
         ASSERT(sizeof(EncodedJSValue) == sizeof(IndexingHeader));
         return (preCapacity + propertyCapacity) * sizeof(EncodedJSValue) + (hasIndexingHeader ? sizeof(IndexingHeader) : 0) + indexingPayloadSizeInBytes;
     }

     static Butterfly* fromBase(void* base, size_t preCapacity, size_t propertyCapacity)
     {
         return reinterpret_cast<Butterfly*>(static_cast<EncodedJSValue*>(base) + preCapacity + propertyCapacity + 1);
     }

     ALWAYS_INLINE static unsigned availableContiguousVectorLength(size_t propertyCapacity, unsigned vectorLength);
     static unsigned availableContiguousVectorLength(Structure*, unsigned vectorLength);

     ALWAYS_INLINE static unsigned optimalContiguousVectorLength(size_t propertyCapacity, unsigned vectorLength);
     static unsigned optimalContiguousVectorLength(Structure*, unsigned vectorLength);

     // This method is here not just because it's handy, but to remind you that
     // the whole point of butterflies is to do evil pointer arithmetic.
     static Butterfly* fromPointer(char* ptr)
     {
         return reinterpret_cast<Butterfly*>(ptr);
     }

     char* pointer() { return reinterpret_cast<char*>(this); }

     static ptrdiff_t offsetOfIndexingHeader() { return IndexingHeader::offsetOfIndexingHeader(); }
     static ptrdiff_t offsetOfArrayBuffer() { return offsetOfIndexingHeader() + IndexingHeader::offsetOfArrayBuffer(); }
     static ptrdiff_t offsetOfPublicLength() { return offsetOfIndexingHeader() + IndexingHeader::offsetOfPublicLength(); }
     static ptrdiff_t offsetOfVectorLength() { return offsetOfIndexingHeader() + IndexingHeader::offsetOfVectorLength(); }

     static Butterfly* tryCreateUninitialized(VM&, JSObject* intendedOwner, size_t preCapacity, size_t propertyCapacity, bool hasIndexingHeader, size_t indexingPayloadSizeInBytes, GCDeferralContext* = nullptr);
     static Butterfly* createUninitialized(VM&, JSObject* intendedOwner, size_t preCapacity, size_t propertyCapacity, bool hasIndexingHeader, size_t indexingPayloadSizeInBytes);

     static Butterfly* tryCreate(VM& vm, JSObject*, size_t preCapacity, size_t propertyCapacity, bool hasIndexingHeader, const IndexingHeader& indexingHeader, size_t indexingPayloadSizeInBytes);
     static Butterfly* create(VM&, JSObject* intendedOwner, size_t preCapacity, size_t propertyCapacity, bool hasIndexingHeader, const IndexingHeader&, size_t indexingPayloadSizeInBytes);
     static Butterfly* create(VM&, JSObject* intendedOwner, Structure*);

     IndexingHeader* indexingHeader() { return IndexingHeader::from(this); }
     const IndexingHeader* indexingHeader() const { return IndexingHeader::from(this); }
     PropertyStorage propertyStorage() { return indexingHeader()->propertyStorage(); }
     ConstPropertyStorage propertyStorage() const { return indexingHeader()->propertyStorage(); }

     uint32_t publicLength() const { return indexingHeader()->publicLength(); }
     uint32_t vectorLength() const { return indexingHeader()->vectorLength(); }
     void setPublicLength(uint32_t value) { indexingHeader()->setPublicLength(value); }
     void setVectorLength(uint32_t value) { indexingHeader()->setVectorLength(value); }

     template<typename T>
     T* indexingPayload() { return reinterpret_cast_ptr<T*>(this); }
     ArrayStorage* arrayStorage() { return indexingPayload<ArrayStorage>(); }
     ContiguousJSValues contiguousInt32() { return ContiguousJSValues(indexingPayload<WriteBarrier<Unknown>>(), vectorLength()); }
     ContiguousDoubles contiguousDouble() { return ContiguousDoubles(indexingPayload<double>(), vectorLength()); }
     ContiguousJSValues contiguous() { return ContiguousJSValues(indexingPayload<WriteBarrier<Unknown>>(), vectorLength()); }

     template<typename T>
     const T* indexingPayload() const { return reinterpret_cast_ptr<const T*>(this); }
     const ArrayStorage* arrayStorage() const { return indexingPayload<ArrayStorage>(); }
     ConstContiguousJSValues contiguousInt32() const { return ConstContiguousJSValues(indexingPayload<WriteBarrier<Unknown>>(), vectorLength()); }
     ConstContiguousDoubles contiguousDouble() const { return ConstContiguousDoubles(indexingPayload<double>(), vectorLength()); }
     ConstContiguousJSValues contiguous() const { return ConstContiguousJSValues(indexingPayload<WriteBarrier<Unknown>>(), vectorLength()); }

     static Butterfly* fromContiguous(WriteBarrier<Unknown>* contiguous)
     {
         return reinterpret_cast<Butterfly*>(contiguous);
     }
     static Butterfly* fromContiguous(double* contiguous)
     {
         return reinterpret_cast<Butterfly*>(contiguous);
     }

     static ptrdiff_t offsetOfPropertyStorage() { return -static_cast<ptrdiff_t>(sizeof(IndexingHeader)); }
     static int indexOfPropertyStorage()
     {
         ASSERT(sizeof(IndexingHeader) == sizeof(EncodedJSValue));
         return -1;
     }

     void* base(size_t preCapacity, size_t propertyCapacity) { return propertyStorage() - propertyCapacity - preCapacity; }
     void* base(Structure*);

     static Butterfly* createOrGrowArrayRight(
         Butterfly*, VM&, JSObject* intendedOwner, Structure* oldStructure,
         size_t propertyCapacity, bool hadIndexingHeader,
         size_t oldIndexingPayloadSizeInBytes, size_t newIndexingPayloadSizeInBytes);

     // The butterfly reallocation methods perform the reallocation itself but do not change any
     // of the meta-data to reflect that the reallocation occurred. Note that this set of
     // methods is not exhaustive and is not intended to encapsulate all possible allocation
     // modes of butterflies - there are code paths that allocate butterflies by calling
     // directly into Heap::tryAllocateStorage.
     static Butterfly* createOrGrowPropertyStorage(Butterfly*, VM&, JSObject* intendedOwner, Structure*, size_t oldPropertyCapacity, size_t newPropertyCapacity);
     Butterfly* growArrayRight(VM&, JSObject* intendedOwner, Structure* oldStructure, size_t propertyCapacity, bool hadIndexingHeader, size_t oldIndexingPayloadSizeInBytes, size_t newIndexingPayloadSizeInBytes); // Assumes that preCapacity is zero, and asserts as much.
     Butterfly* growArrayRight(VM&, JSObject* intendedOwner, Structure*, size_t newIndexingPayloadSizeInBytes);

     Butterfly* reallocArrayRightIfPossible(VM&, GCDeferralContext&, JSObject* intendedOwner, Structure* oldStructure, size_t propertyCapacity, bool hadIndexingHeader, size_t oldIndexingPayloadSizeInBytes, size_t newIndexingPayloadSizeInBytes); // Assumes that preCapacity is zero, and asserts as much.

     Butterfly* resizeArray(VM&, JSObject* intendedOwner, size_t propertyCapacity, bool oldHasIndexingHeader, size_t oldIndexingPayloadSizeInBytes, size_t newPreCapacity, bool newHasIndexingHeader, size_t newIndexingPayloadSizeInBytes);
     Butterfly* resizeArray(VM&, JSObject* intendedOwner, Structure*, size_t newPreCapacity, size_t newIndexingPayloadSizeInBytes); // Assumes that you're not changing whether or not the object has an indexing header.
     Butterfly* unshift(Structure*, size_t numberOfSlots);
     Butterfly* shift(Structure*, size_t numberOfSlots);
 };

 } // namespace JSC
	/*
	* Copyright (C) 2012-2018 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 "IndexingHeader.h"
	#include "IndexingType.h"
	#include "PropertyStorage.h"
	#include <wtf/Gigacage.h>
	#include <wtf/Noncopyable.h>

	namespace JSC {

	class VM;
	class CopyVisitor;
	class GCDeferralContext;
	struct ArrayStorage;

	template <typename T>
	struct ContiguousData {
	ContiguousData() = default;
	ContiguousData(T* data, size_t length)
	: m_data(data)
	#if ASSERT_ENABLED
	, m_length(length)
	#endif
	{
	UNUSED_PARAM(length);
	}

	struct Data {
	Data(T& location, IndexingType indexingMode)
	: m_data(location)
	#if ASSERT_ENABLED
	, m_isWritable(!isCopyOnWrite(indexingMode))
	#endif
	{
	UNUSED_PARAM(indexingMode);
	}

	explicit operator bool() const { return !!m_data.get(); }

	const T& operator=(const T& value)
	{
	ASSERT(m_isWritable);
	m_data = value;
	return value;
	}

	operator const T&() const { return m_data; }

	// WriteBarrier forwarded methods.

	void set(VM& vm, const JSCell* owner, const JSValue& value)
	{
	ASSERT(m_isWritable);
	m_data.set(vm, owner, value);
	}

	void setWithoutWriteBarrier(const JSValue& value)
	{
	ASSERT(m_isWritable);
	m_data.setWithoutWriteBarrier(value);
	}

	void setStartingValue(JSValue value)
	{
	m_data.setStartingValue(value);
	}

	void clear()
	{
	ASSERT(m_isWritable);
	m_data.clear();
	}

	JSValue get() const
	{
	return m_data.get();
	}


	T& m_data;
	#if ASSERT_ENABLED
	bool m_isWritable;
	#endif
	};

	const Data at(const JSCell* owner, size_t index) const;
	Data at(const JSCell* owner, size_t index);

	T& atUnsafe(size_t index) { ASSERT(index < m_length); return m_data[index]; }

	T* data() const { return m_data; }
	#if ASSERT_ENABLED
	size_t length() const { return m_length; }
	#endif

	private:
	T* m_data { nullptr };
	#if ASSERT_ENABLED
	size_t m_length { 0 };
	#endif
	};

	using ContiguousDoubles = ContiguousData<double>;
	using ContiguousJSValues = ContiguousData<WriteBarrier<Unknown>>;
	using ConstContiguousDoubles = ContiguousData<const double>;
	using ConstContiguousJSValues = ContiguousData<const WriteBarrier<Unknown>>;

	class Butterfly {
	WTF_MAKE_NONCOPYABLE(Butterfly);
	private:
	Butterfly() { } // Not instantiable.
	public:

	static size_t totalSize(size_t preCapacity, size_t propertyCapacity, bool hasIndexingHeader, size_t indexingPayloadSizeInBytes)
	{
	ASSERT(indexingPayloadSizeInBytes ? hasIndexingHeader : true);
	ASSERT(sizeof(EncodedJSValue) == sizeof(IndexingHeader));
	return (preCapacity + propertyCapacity) * sizeof(EncodedJSValue) + (hasIndexingHeader ? sizeof(IndexingHeader) : 0) + indexingPayloadSizeInBytes;
	}

	static Butterfly* fromBase(void* base, size_t preCapacity, size_t propertyCapacity)
	{
	return reinterpret_cast<Butterfly>(static_cast<EncodedJSValue>(base) + preCapacity + propertyCapacity + 1);
	}

	ALWAYS_INLINE static unsigned availableContiguousVectorLength(size_t propertyCapacity, unsigned vectorLength);
	static unsigned availableContiguousVectorLength(Structure*, unsigned vectorLength);

	ALWAYS_INLINE static unsigned optimalContiguousVectorLength(size_t propertyCapacity, unsigned vectorLength);
	static unsigned optimalContiguousVectorLength(Structure*, unsigned vectorLength);

	// This method is here not just because it's handy, but to remind you that
	// the whole point of butterflies is to do evil pointer arithmetic.
	static Butterfly* fromPointer(char* ptr)
	{
	return reinterpret_cast<Butterfly*>(ptr);
	}

	char* pointer() { return reinterpret_cast<char*>(this); }

	static ptrdiff_t offsetOfIndexingHeader() { return IndexingHeader::offsetOfIndexingHeader(); }
	static ptrdiff_t offsetOfArrayBuffer() { return offsetOfIndexingHeader() + IndexingHeader::offsetOfArrayBuffer(); }
	static ptrdiff_t offsetOfPublicLength() { return offsetOfIndexingHeader() + IndexingHeader::offsetOfPublicLength(); }
	static ptrdiff_t offsetOfVectorLength() { return offsetOfIndexingHeader() + IndexingHeader::offsetOfVectorLength(); }

	static Butterfly* tryCreateUninitialized(VM&, JSObject* intendedOwner, size_t preCapacity, size_t propertyCapacity, bool hasIndexingHeader, size_t indexingPayloadSizeInBytes, GCDeferralContext* = nullptr);
	static Butterfly* createUninitialized(VM&, JSObject* intendedOwner, size_t preCapacity, size_t propertyCapacity, bool hasIndexingHeader, size_t indexingPayloadSizeInBytes);

	static Butterfly* tryCreate(VM& vm, JSObject*, size_t preCapacity, size_t propertyCapacity, bool hasIndexingHeader, const IndexingHeader& indexingHeader, size_t indexingPayloadSizeInBytes);
	static Butterfly* create(VM&, JSObject* intendedOwner, size_t preCapacity, size_t propertyCapacity, bool hasIndexingHeader, const IndexingHeader&, size_t indexingPayloadSizeInBytes);
	static Butterfly* create(VM&, JSObject* intendedOwner, Structure*);

	IndexingHeader* indexingHeader() { return IndexingHeader::from(this); }
	const IndexingHeader* indexingHeader() const { return IndexingHeader::from(this); }
	PropertyStorage propertyStorage() { return indexingHeader()->propertyStorage(); }
	ConstPropertyStorage propertyStorage() const { return indexingHeader()->propertyStorage(); }

	uint32_t publicLength() const { return indexingHeader()->publicLength(); }
	uint32_t vectorLength() const { return indexingHeader()->vectorLength(); }
	void setPublicLength(uint32_t value) { indexingHeader()->setPublicLength(value); }
	void setVectorLength(uint32_t value) { indexingHeader()->setVectorLength(value); }

	template<typename T>
	T* indexingPayload() { return reinterpret_cast_ptr<T*>(this); }
	ArrayStorage* arrayStorage() { return indexingPayload<ArrayStorage>(); }
	ContiguousJSValues contiguousInt32() { return ContiguousJSValues(indexingPayload<WriteBarrier<Unknown>>(), vectorLength()); }
	ContiguousDoubles contiguousDouble() { return ContiguousDoubles(indexingPayload<double>(), vectorLength()); }
	ContiguousJSValues contiguous() { return ContiguousJSValues(indexingPayload<WriteBarrier<Unknown>>(), vectorLength()); }

	template<typename T>
	const T* indexingPayload() const { return reinterpret_cast_ptr<const T*>(this); }
	const ArrayStorage* arrayStorage() const { return indexingPayload<ArrayStorage>(); }
	ConstContiguousJSValues contiguousInt32() const { return ConstContiguousJSValues(indexingPayload<WriteBarrier<Unknown>>(), vectorLength()); }
	ConstContiguousDoubles contiguousDouble() const { return ConstContiguousDoubles(indexingPayload<double>(), vectorLength()); }
	ConstContiguousJSValues contiguous() const { return ConstContiguousJSValues(indexingPayload<WriteBarrier<Unknown>>(), vectorLength()); }

	static Butterfly* fromContiguous(WriteBarrier<Unknown>* contiguous)
	{
	return reinterpret_cast<Butterfly*>(contiguous);
	}
	static Butterfly* fromContiguous(double* contiguous)
	{
	return reinterpret_cast<Butterfly*>(contiguous);
	}

	static ptrdiff_t offsetOfPropertyStorage() { return -static_cast<ptrdiff_t>(sizeof(IndexingHeader)); }
	static int indexOfPropertyStorage()
	{
	ASSERT(sizeof(IndexingHeader) == sizeof(EncodedJSValue));
	return -1;
	}

	void* base(size_t preCapacity, size_t propertyCapacity) { return propertyStorage() - propertyCapacity - preCapacity; }
	void* base(Structure*);

	static Butterfly* createOrGrowArrayRight(
	Butterfly, VM&, JSObject intendedOwner, Structure* oldStructure,
	size_t propertyCapacity, bool hadIndexingHeader,
	size_t oldIndexingPayloadSizeInBytes, size_t newIndexingPayloadSizeInBytes);

	// The butterfly reallocation methods perform the reallocation itself but do not change any
	// of the meta-data to reflect that the reallocation occurred. Note that this set of
	// methods is not exhaustive and is not intended to encapsulate all possible allocation
	// modes of butterflies - there are code paths that allocate butterflies by calling
	// directly into Heap::tryAllocateStorage.
	static Butterfly* createOrGrowPropertyStorage(Butterfly, VM&, JSObject intendedOwner, Structure*, size_t oldPropertyCapacity, size_t newPropertyCapacity);
	Butterfly* growArrayRight(VM&, JSObject* intendedOwner, Structure* oldStructure, size_t propertyCapacity, bool hadIndexingHeader, size_t oldIndexingPayloadSizeInBytes, size_t newIndexingPayloadSizeInBytes); // Assumes that preCapacity is zero, and asserts as much.
	Butterfly* growArrayRight(VM&, JSObject* intendedOwner, Structure*, size_t newIndexingPayloadSizeInBytes);

	Butterfly* reallocArrayRightIfPossible(VM&, GCDeferralContext&, JSObject* intendedOwner, Structure* oldStructure, size_t propertyCapacity, bool hadIndexingHeader, size_t oldIndexingPayloadSizeInBytes, size_t newIndexingPayloadSizeInBytes); // Assumes that preCapacity is zero, and asserts as much.

	Butterfly* resizeArray(VM&, JSObject* intendedOwner, size_t propertyCapacity, bool oldHasIndexingHeader, size_t oldIndexingPayloadSizeInBytes, size_t newPreCapacity, bool newHasIndexingHeader, size_t newIndexingPayloadSizeInBytes);
	Butterfly* resizeArray(VM&, JSObject* intendedOwner, Structure*, size_t newPreCapacity, size_t newIndexingPayloadSizeInBytes); // Assumes that you're not changing whether or not the object has an indexing header.
	Butterfly* unshift(Structure*, size_t numberOfSlots);
	Butterfly* shift(Structure*, size_t numberOfSlots);
	};

	} // namespace JSC