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// Copyright 2020 The Chromium Authors
// 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_ACTIVE_SCRIPT_WRAPPABLE_MANAGER_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_BINDINGS_ACTIVE_SCRIPT_WRAPPABLE_MANAGER_H_
#include <cstddef>
#include <utility>
#include "third_party/blink/renderer/platform/bindings/active_script_wrappable_base.h"
#include "third_party/blink/renderer/platform/bindings/name_client.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_vector.h"
#include "third_party/blink/renderer/platform/heap/garbage_collected.h"
#include "third_party/blink/renderer/platform/heap/member.h"
#include "third_party/blink/renderer/platform/platform_export.h"
namespace blink {
// ActiveScriptWrappableManager (ASWM) is integrated into the garbage collector
// and keeps ActiveScriptWrappable alive as long as they have
// HasPendingActivity() returning true and are attached to a live
// ExecutionContext.
//
// ASWM integrates with the GC through prologue and weakness callbacks which are
// not allowed to allocate.
class PLATFORM_EXPORT ActiveScriptWrappableManager final
: public GarbageCollected<ActiveScriptWrappableManager>,
public NameClient {
public:
enum class RecomputeMode { kOpportunistic, kRequired };
// Adds an ActiveScriptWrappable to the set that is managed by
// ActiveScriptWrappableManager.
void Add(ActiveScriptWrappableBase* wrappable) {
// The following calls may allocate and trigger GC. |wrappable| is kept
// alive as it is a parameter to this function.
//
// Shrink capacity here to avoid allocation in
// RecomputeActiveScriptWrappables and
// CleanupInactiveAndClearActiveScriptWrappables.
active_script_wrappables_.ShrinkToReasonableCapacity();
active_script_wrappables_.push_back(std::make_pair(wrappable, nullptr));
}
// Recomputes the current set of active ScriptWrappable objects that should be
// kept alive by the manager because there's some activity pending.
//
// If called with RecomputeMode::kOpportunistic, recomputation may be skipped.
//
// Called during GC prologue. Not allowed to allocate.
void RecomputeActiveScriptWrappables(RecomputeMode);
void Trace(Visitor* visitor) const;
// NameClient implementation.
const char* NameInHeapSnapshot() const final { return "Pending activities"; }
private:
// Called during weakness processing. Not allowed to allocate. The next Add()
// call ensures reasonable capacities.
//
// Does not allocate.
void CleanupInactiveAndClearActiveScriptWrappables(const LivenessBroker&);
// We use a single HeapVector to always have storage for the strong Member<>
// reference available. The alternative is keeping separate data structures
// and synchronize their capacities in Add(). We use UntracedMember<> as a
// weak references that is cleared in
// CleanupInactiveAndClearActiveScriptWrappables. WeakMember would require
// using a HeapHashSet which is slower to iterate. In addition, we already
// require a custom callback for clearing out the Member<> reference, so we
// can clear the UntracedMember<> there as well.
HeapVector<std::pair<UntracedMember<const ActiveScriptWrappableBase>,
Member<const ActiveScriptWrappableBase>>>
active_script_wrappables_;
// Count how often ASWs have been recomputed in the current GC cycle.
size_t recomputed_cnt_ = 0;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_BINDINGS_ACTIVE_SCRIPT_WRAPPABLE_MANAGER_H_
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