chrome/profiling/backtrace_storage.h

// Copyright 2017 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 CHROME_PROFILING_BACKTRACE_STORAGE_H_
#define CHROME_PROFILING_BACKTRACE_STORAGE_H_

#include <unordered_set>
#include <vector>

#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "base/synchronization/lock.h"
#include "chrome/profiling/backtrace.h"

namespace profiling {

// Backtraces are stored effectively as atoms, and this class is the backing
// store for the atoms. When you insert a backtrace, it will get de-duped with
// existing ones, one refcount added, and returned. When you're done with a
// backtrace, call Free() which will release the refcount. This may or may not
// release the underlying Backtrace itself, depending on whether other refs are
// held.
//
// This class is threadsafe.
class BacktraceStorage {
 public:
  BacktraceStorage();
  ~BacktraceStorage();

  // Adds the given backtrace to the storage and returns a key to it. If a
  // matching backtrace already exists, a key to the existing one will be
  // returned.
  //
  // The returned key will have a reference count associated with it, call
  // Free when the key is no longer needed.
  const Backtrace* Insert(std::vector<Address>&& bt);

  // Frees one reference to a backtrace.
  void Free(const Backtrace* bt);
  void Free(const std::vector<const Backtrace*>& bts);

 private:
  using Container = std::unordered_set<Backtrace>;

  mutable base::Lock lock_;

  // List of live backtraces for de-duping. Protected by the lock_.
  Container backtraces_;
};

}  // namespace profiling

#endif  // CHROME_PROFILING_BACKTRACE_STORAGE_H_