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/*
* Copyright (C) 2008-2021 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.
*/
#include "config.h"
#include "StructureChain.h"
#include "JSCInlines.h"
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace JSC {
const ClassInfo StructureChain::s_info = { "StructureChain"_s, nullptr, nullptr, nullptr, CREATE_METHOD_TABLE(StructureChain) };
StructureChain::StructureChain(VM& vm, Structure* structure, StructureID* vector)
: Base(vm, structure)
, m_vector(vector, WriteBarrierEarlyInit)
{
}
StructureChain* StructureChain::create(VM& vm, JSObject* head)
{
// FIXME: Make StructureChain::create fail for large chain. Caching large chain is not so profitable.
// By making the size <= UINT16_MAX, we can store length in a high bits of auxiliary pointer.
// https://bugs.webkit.org/show_bug.cgi?id=200290
size_t size = 0;
for (JSObject* current = head; current; current = current->structure()->storedPrototypeObject(current))
++size;
++size; // Sentinel nullptr.
size_t bytes = Checked<size_t>(size) * sizeof(StructureID);
void* vector = vm.auxiliarySpace().allocate(vm, bytes, nullptr, AllocationFailureMode::Assert);
static_assert(!StructureID().bits(), "Make sure the value we're going to memcpy below matches the default StructureID");
memset(vector, 0, bytes);
StructureChain* chain = new (NotNull, allocateCell<StructureChain>(vm)) StructureChain(vm, vm.structureChainStructure.get(), static_cast<StructureID*>(vector));
chain->finishCreation(vm, head);
return chain;
}
void StructureChain::finishCreation(VM& vm, JSObject* head)
{
Base::finishCreation(vm);
size_t i = 0;
for (JSObject* current = head; current; current = current->structure()->storedPrototypeObject(current)) {
Structure* structure = current->structure();
m_vector.get()[i++] = structure->id();
vm.writeBarrier(this);
}
}
template<typename Visitor>
void StructureChain::visitChildrenImpl(JSCell* cell, Visitor& visitor)
{
StructureChain* thisObject = jsCast<StructureChain*>(cell);
ASSERT_GC_OBJECT_INHERITS(thisObject, info());
Base::visitChildren(thisObject, visitor);
visitor.markAuxiliary(thisObject->m_vector.get());
for (auto* current = thisObject->m_vector.get(); *current; ++current) {
StructureID structureID = *current;
Structure* structure = structureID.decode();
visitor.appendUnbarriered(structure);
}
}
DEFINE_VISIT_CHILDREN(StructureChain);
} // namespace JSC
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
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