third_party/blink/renderer/platform/instance_counters.h

/*
* Copyright (C) 2012 Google Inc. All rights reserved.
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* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
*     * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*     * 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.
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* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_INSTANCE_COUNTERS_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_INSTANCE_COUNTERS_H_

#include <atomic>
#include "third_party/blink/renderer/platform/platform_export.h"
#include "third_party/blink/renderer/platform/wtf/allocator.h"
#include "third_party/blink/renderer/platform/wtf/wtf.h"

namespace blink {

#define INSTANCE_COUNTERS_LIST(V)  \
  V(AudioHandler)                  \
  V(Document)                      \
  V(Frame)                         \
  V(JSEventListener)               \
  V(LayoutObject)                  \
  V(MediaKeySession)               \
  V(MediaKeys)                     \
  V(Node)                          \
  V(Resource)                      \
  V(ScriptPromise)                 \
  V(ContextLifecycleStateObserver) \
  V(V8PerContextData)              \
  V(WorkerGlobalScope)             \
  V(UACSSResource)                 \
  V(RTCPeerConnection)             \
  V(ResourceFetcher)               \
  V(AdSubframe)                    \
  V(DetachedScriptState)

// Atomic counters of the number of instances of objects that exist.
//
// Note that while these operations are atomic, they do not imply that other
// changes to memory are visible to the accessing thread. As a result, this
// is primarily useful where either other synchronization exists (e.g. the
// objects are only used on one thread), or an inconsistent answer is
// acceptable.
class InstanceCounters {
  STATIC_ONLY(InstanceCounters);

 public:
  enum CounterType {
#define DECLARE_INSTANCE_COUNTER(name) k##name##Counter,
    INSTANCE_COUNTERS_LIST(DECLARE_INSTANCE_COUNTER)
#undef DECLARE_INSTANCE_COUNTER
        kCounterTypeLength
  };

  static inline void IncrementCounter(CounterType type) {
    // There are lots of nodes created. Atomic barriers or locks
    // should be avoided for the sake of performance. See crbug.com/641019
    if (type == kNodeCounter) {
      DCHECK(IsMainThread());
      ++counters_[kNodeCounter];
    } else {
      counters_[type].fetch_add(1, std::memory_order_relaxed);
    }
  }

  static inline void DecrementCounter(CounterType type) {
    if (type == kNodeCounter) {
      DCHECK(IsMainThread());
      --counters_[kNodeCounter];
    } else {
      counters_[type].fetch_sub(1, std::memory_order_relaxed);
    }
  }

  PLATFORM_EXPORT static int CounterValue(CounterType);

 private:
  PLATFORM_EXPORT static std::atomic_int counters_[];
  PLATFORM_EXPORT static int node_counter_;
};

}  // namespace blink

#endif  // !defined(InstanceCounters_h)