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/*
* Copyright (C) 2011-2019 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 <wtf/DumbPtrTraits.h>
#include <wtf/FastMalloc.h>
#include <wtf/StdLibExtras.h>
#include <wtf/Vector.h>
// This implements a reference counted array for POD** values, which is optimized for:
// - An empty array only uses one word.
// - A copy of the array only uses one word (i.e. assignment means aliasing).
// - The vector can't grow beyond 2^32-1 elements.
// - In all other regards this has similar space usage to a Vector.
//
// ** This could be modified to support non-POD values quite easily. It just
// hasn't been, so far, because there has been no need. Moreover, even now,
// it's used for things that aren't quite POD according to the official
// defintion, such as JSC::Instruction.
namespace WTF {
template<typename T, typename PtrTraits = DumbPtrTraits<T>>
class RefCountedArray {
enum CommonCopyConstructorTag { CommonCopyConstructor };
public:
RefCountedArray() = default;
RefCountedArray(const RefCountedArray& other)
: RefCountedArray(CommonCopyConstructor, other)
{ }
template<typename OtherTraits>
RefCountedArray(const RefCountedArray<T, OtherTraits>& other)
: RefCountedArray(CommonCopyConstructor, other)
{ }
explicit RefCountedArray(size_t size)
{
if (!size) {
// NOTE: JSC's LowLevelInterpreter relies on this being nullptr when the size is zero.
PtrTraits::exchange(m_data, nullptr);
return;
}
T* data = (static_cast<Header*>(fastMalloc(Header::size() + sizeof(T) * size)))->payload();
m_data = data;
Header::fromPayload(data)->refCount = 1;
Header::fromPayload(data)->length = size;
ASSERT(Header::fromPayload(data)->length == size);
VectorTypeOperations<T>::initializeIfNonPOD(begin(), end());
}
template<typename OtherTraits = PtrTraits>
RefCountedArray<T, OtherTraits> clone() const
{
RefCountedArray<T, OtherTraits> result(size());
const T* data = this->data();
T* resultData = result.data();
for (unsigned i = size(); i--;)
resultData[i] = data[i];
return result;
}
template<size_t inlineCapacity, typename OverflowHandler>
explicit RefCountedArray(const Vector<T, inlineCapacity, OverflowHandler>& other)
{
if (other.isEmpty()) {
PtrTraits::exchange(m_data, nullptr);
return;
}
T* data = (static_cast<Header*>(fastMalloc(Header::size() + sizeof(T) * other.size())))->payload();
m_data = data;
Header::fromPayload(data)->refCount = 1;
Header::fromPayload(data)->length = other.size();
ASSERT(Header::fromPayload(data)->length == other.size());
VectorTypeOperations<T>::uninitializedCopy(other.begin(), other.end(), data);
}
template<typename OtherTraits = PtrTraits>
RefCountedArray& operator=(const RefCountedArray<T, OtherTraits>& other)
{
return assign<OtherTraits>(other);
}
RefCountedArray& operator=(const RefCountedArray& other)
{
return assign<PtrTraits>(other);
}
~RefCountedArray()
{
if (!m_data)
return;
T* data = this->data();
if (--Header::fromPayload(data)->refCount)
return;
VectorTypeOperations<T>::destruct(begin(), end());
fastFree(Header::fromPayload(data));
}
unsigned refCount() const
{
if (!m_data)
return 0;
return Header::fromPayload(data())->refCount;
}
size_t size() const
{
if (!m_data)
return 0;
return Header::fromPayload(data())->length;
}
size_t byteSize() const { return size() * sizeof(T); }
T* data() { return PtrTraits::unwrap(m_data); }
T* begin() { return data(); }
T* end()
{
if (!m_data)
return 0;
T* data = this->data();
return data + Header::fromPayload(data)->length;
}
const T* data() const { return const_cast<RefCountedArray*>(this)->data(); }
const T* begin() const { return const_cast<RefCountedArray*>(this)->begin(); }
const T* end() const { return const_cast<RefCountedArray*>(this)->end(); }
T& at(size_t i)
{
ASSERT_WITH_SECURITY_IMPLICATION(i < size());
return begin()[i];
}
const T& at(size_t i) const
{
ASSERT_WITH_SECURITY_IMPLICATION(i < size());
return begin()[i];
}
T& operator[](size_t i) { return at(i); }
const T& operator[](size_t i) const { return at(i); }
template<typename OtherTraits = PtrTraits>
bool operator==(const RefCountedArray<T, OtherTraits>& other) const
{
T* data = const_cast<T*>(this->data());
T* otherData = const_cast<T*>(other.data());
if (data == otherData)
return true;
if (!data || !otherData)
return false;
unsigned length = Header::fromPayload(data)->length;
if (length != Header::fromPayload(otherData)->length)
return false;
for (unsigned i = 0; i < length; ++i) {
if (data[i] != otherData[i])
return false;
}
return true;
}
bool operator==(const RefCountedArray& other) const { return this->operator==<PtrTraits>(other); }
private:
template<typename OtherTraits = PtrTraits>
RefCountedArray& assign(const RefCountedArray<T, OtherTraits>& other)
{
T* oldData = data();
T* otherData = const_cast<T*>(other.data());
if (otherData)
Header::fromPayload(otherData)->refCount++;
m_data = otherData;
if (!oldData)
return *this;
if (--Header::fromPayload(oldData)->refCount)
return *this;
VectorTypeOperations<T>::destruct(oldData, oldData + Header::fromPayload(oldData)->length);
fastFree(Header::fromPayload(oldData));
return *this;
}
struct Header {
unsigned refCount;
unsigned length;
static size_t size()
{
return (sizeof(Header) + 7) & ~7;
}
T* payload()
{
char* result = reinterpret_cast<char*>(this) + size();
ASSERT(!(bitwise_cast<uintptr_t>(result) & 7));
return reinterpret_cast_ptr<T*>(result);
}
static Header* fromPayload(T* payload)
{
return reinterpret_cast_ptr<Header*>(reinterpret_cast<char*>(payload) - size());
}
static const Header* fromPayload(const T* payload)
{
return fromPayload(const_cast<T*>(payload));
}
};
template<typename OtherTraits>
RefCountedArray(CommonCopyConstructorTag, const RefCountedArray<T, OtherTraits>& other)
: m_data(const_cast<T*>(other.data()))
{
if (m_data)
Header::fromPayload(data())->refCount++;
}
friend class JSC::LLIntOffsetsExtractor;
typename PtrTraits::StorageType m_data { nullptr };
};
} // namespace WTF
using WTF::RefCountedArray;