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// Copyright 2020 the V8 project 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 INCLUDE_CPPGC_TRACE_TRAIT_H_
#define INCLUDE_CPPGC_TRACE_TRAIT_H_
#include <type_traits>
#include "cppgc/type-traits.h"
#include "v8config.h" // NOLINT(build/include_directory)
namespace cppgc {
class Visitor;
namespace internal {
// Implementation of the default TraceTrait handling GarbageCollected and
// GarbageCollectedMixin.
template <typename T,
bool =
IsGarbageCollectedMixinTypeV<typename std::remove_const<T>::type>>
struct TraceTraitImpl;
} // namespace internal
/**
* Callback for invoking tracing on a given object.
*
* \param visitor The visitor to dispatch to.
* \param object The object to invoke tracing on.
*/
using TraceCallback = void (*)(Visitor* visitor, const void* object);
/**
* Describes how to trace an object, i.e., how to visit all Oilpan-relevant
* fields of an object.
*/
struct TraceDescriptor {
/**
* Adjusted base pointer, i.e., the pointer to the class inheriting directly
* from GarbageCollected, of the object that is being traced.
*/
const void* base_object_payload;
/**
* Callback for tracing the object.
*/
TraceCallback callback;
};
namespace internal {
struct V8_EXPORT TraceTraitFromInnerAddressImpl {
static TraceDescriptor GetTraceDescriptor(const void* address);
};
} // namespace internal
/**
* Trait specifying how the garbage collector processes an object of type T.
*
* Advanced users may override handling by creating a specialization for their
* type.
*/
template <typename T>
struct TraceTrait {
static_assert(internal::IsTraceableV<T>, "T must have a Trace() method");
/**
* Accessor for retrieving a TraceDescriptor to process an object of type T.
*
* \param self The object to be processed.
* \returns a TraceDescriptor to process the object.
*/
static TraceDescriptor GetTraceDescriptor(const void* self) {
return internal::TraceTraitImpl<T>::GetTraceDescriptor(
static_cast<const T*>(self));
}
/**
* Function invoking the tracing for an object of type T.
*
* \param visitor The visitor to dispatch to.
* \param self The object to invoke tracing on.
*/
static void Trace(Visitor* visitor, const void* self) {
static_cast<const T*>(self)->Trace(visitor);
}
};
namespace internal {
template <typename T>
struct TraceTraitImpl<T, false> {
static TraceDescriptor GetTraceDescriptor(const void* self) {
return {self, TraceTrait<T>::Trace};
}
};
template <typename T>
struct TraceTraitImpl<T, true> {
static TraceDescriptor GetTraceDescriptor(const void* self) {
return internal::TraceTraitFromInnerAddressImpl::GetTraceDescriptor(self);
}
};
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_TRACE_TRAIT_H_
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