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// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_BINDINGS_TRACE_WRAPPER_MEMBER_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_BINDINGS_TRACE_WRAPPER_MEMBER_H_
#include "third_party/blink/renderer/platform/bindings/script_wrappable_marking_visitor.h"
#include "third_party/blink/renderer/platform/heap/heap_allocator.h"
namespace blink {
template <typename T>
class Member;
// TraceWrapperMember is used for Member fields that should participate in
// wrapper tracing, i.e., strongly hold a ScriptWrappable alive. All
// TraceWrapperMember fields must be traced in the class' |Trace| method.
template <class T>
class TraceWrapperMember : public Member<T> {
DISALLOW_NEW();
public:
TraceWrapperMember() : Member<T>(nullptr) {}
TraceWrapperMember(T* raw) : Member<T>(raw) {
// We have to use a write barrier here because of in-place construction
// in containers, such as HeapVector::push_back.
ScriptWrappableMarkingVisitor::WriteBarrier(raw);
}
TraceWrapperMember(WTF::HashTableDeletedValueType x) : Member<T>(x) {}
TraceWrapperMember(const TraceWrapperMember& other) { *this = other; }
TraceWrapperMember& operator=(const TraceWrapperMember& other) {
Member<T>::operator=(other);
DCHECK_EQ(other.Get(), this->Get());
ScriptWrappableMarkingVisitor::WriteBarrier(this->Get());
return *this;
}
TraceWrapperMember& operator=(const Member<T>& other) {
Member<T>::operator=(other);
DCHECK_EQ(other.Get(), this->Get());
ScriptWrappableMarkingVisitor::WriteBarrier(this->Get());
return *this;
}
TraceWrapperMember& operator=(T* other) {
Member<T>::operator=(other);
DCHECK_EQ(other, this->Get());
ScriptWrappableMarkingVisitor::WriteBarrier(this->Get());
return *this;
}
TraceWrapperMember& operator=(std::nullptr_t) {
// No need for a write barrier when assigning nullptr.
Member<T>::operator=(nullptr);
return *this;
}
};
// Swaps two HeapVectors specialized for TraceWrapperMember. The custom swap
// function is required as TraceWrapperMember potentially requires emitting a
// write barrier.
template <typename T>
void swap(HeapVector<TraceWrapperMember<T>>& a,
HeapVector<TraceWrapperMember<T>>& b) {
// HeapVector<Member<T>> and HeapVector<TraceWrapperMember<T>> have the
// same size and semantics.
HeapVector<Member<T>>& a_ = reinterpret_cast<HeapVector<Member<T>>&>(a);
HeapVector<Member<T>>& b_ = reinterpret_cast<HeapVector<Member<T>>&>(b);
a_.swap(b_);
if (ThreadState::IsAnyWrapperTracing() &&
ThreadState::Current()->IsWrapperTracing()) {
// If incremental marking is enabled we need to emit the write barrier since
// the swap was performed on HeapVector<Member<T>>.
for (auto item : a) {
ScriptWrappableMarkingVisitor::WriteBarrier(item.Get());
}
for (auto item : b) {
ScriptWrappableMarkingVisitor::WriteBarrier(item.Get());
}
}
}
// HeapVectorBacking<TraceWrapperMember<T>> need to map to
// HeapVectorBacking<Member<T>> for performing the swap method below.
template <typename T, typename Traits>
struct GCInfoTrait<HeapVectorBacking<TraceWrapperMember<T>, Traits>>
: public GCInfoTrait<
HeapVectorBacking<Member<T>, WTF::VectorTraits<Member<T>>>> {};
// Swaps two HeapVectors, one containing TraceWrapperMember and one with
// regular Members. The custom swap function is required as TraceWrapperMember
// potentially requires emitting a write barrier.
template <typename T>
void swap(HeapVector<TraceWrapperMember<T>>& a, HeapVector<Member<T>>& b) {
// HeapVector<Member<T>> and HeapVector<TraceWrapperMember<T>> have the
// same size and semantics. This cast and swap assumes that GCInfo for both
// TraceWrapperMember and Member match in vector backings.
HeapVector<Member<T>>& a_ = reinterpret_cast<HeapVector<Member<T>>&>(a);
a_.swap(b);
if (ThreadState::IsAnyWrapperTracing() &&
ThreadState::Current()->IsWrapperTracing()) {
// If incremental marking is enabled we need to emit the write barrier since
// the swap was performed on HeapVector<Member<T>>.
for (auto item : a) {
ScriptWrappableMarkingVisitor::WriteBarrier(item.Get());
}
}
}
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_BINDINGS_TRACE_WRAPPER_MEMBER_H_
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