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// Copyright 2017 The Cobalt Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef COBALT_SCRIPT_TRACER_H_
#define COBALT_SCRIPT_TRACER_H_
#include <memory>
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "cobalt/script/sequence.h"
namespace cobalt {
namespace script {
class Tracer;
class Traceable {
public:
virtual ~Traceable() {}
// Trace all native |Traceable|s accessible by the |Traceable|. Any class
// that owns a |Traceable| must implement this interface and trace each of
// its |Traceable| members. Note that here, "owns" means is accessible from
// JavaScript, which means that weak and raw pointers must be traced in
// addition to |std::unique_ptr|s and |scoped_refptr|s. Consider, for
// example, a list IDL interface, with parent and child references. A C++
// implementation backed by |scoped__refptr| will be forced to demote the
// pointer from a child to a parent to a |base::WeakPtr| or raw pointer, in
// order to break the reference cycle. In JavaScript however, holding a
// reference to a child implies that the parent is still reachable, and
// should not be garbage collected.
virtual void TraceMembers(Tracer* tracer) = 0;
// Whether the |Traceable| is a |Wrappable| or not. This should never be
// implemented by any class other than |Traceable| and |Wrappable|.
virtual bool IsWrappable() const { return false; }
};
// Traverses |Traceable|s, while marking found JavaScript wrappers as
// reachable.
class Tracer {
public:
// Trace a |Traceable| by forwarding its wrapper (which is engine specific)
// to the engine's internal tracer, or manually tracing reachable
// |Traceable|s in the case where the wrapper did not exist.
virtual void Trace(Traceable* traceable) = 0;
void Trace(const Traceable& traceable) {
Trace(const_cast<Traceable*>(&traceable));
}
template <typename T>
void Trace(const scoped_refptr<T>& ptr) {
Trace(ptr.get());
}
template <typename T>
void Trace(const base::WeakPtr<T>& ptr) {
Trace(ptr.get());
}
template <typename T>
void Trace(const std::unique_ptr<T>& ptr) {
Trace(ptr.get());
}
// Trace the items of a container of |Traceable|s, such as |std::vector|.
template <typename T>
void TraceItems(const T& items) {
for (const auto& item : items) {
Trace(item);
}
}
// Trace the value part of a container of key value pairs, where the values
// are |Traceable|s, such as |std::map|.
template <typename T>
void TraceValues(const T& key_value_pairs) {
for (const auto& pair : key_value_pairs) {
Trace(pair.second);
}
}
// Note: If your new class wants to own a container of |Traceable|s that
// does not have an iteration helper function here, you should add one.
};
} // namespace script
} // namespace cobalt
#endif // COBALT_SCRIPT_TRACER_H_