base/supports_user_data.cc

// Copyright (c) 2012 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.

#include "base/supports_user_data.h"

namespace base {

std::unique_ptr<SupportsUserData::Data> SupportsUserData::Data::Clone() {
  return nullptr;
}

SupportsUserData::SupportsUserData() {
  // Harmless to construct on a different execution sequence to subsequent
  // usage.
  sequence_checker_.DetachFromSequence();
}

SupportsUserData::Data* SupportsUserData::GetUserData(const void* key) const {
  DCHECK(sequence_checker_.CalledOnValidSequence());
  // Avoid null keys; they are too vulnerable to collision.
  DCHECK(key);
  auto found = user_data_.find(key);
  if (found != user_data_.end())
    return found->second.get();
  return nullptr;
}

void SupportsUserData::SetUserData(const void* key,
                                   std::unique_ptr<Data> data) {
  DCHECK(sequence_checker_.CalledOnValidSequence());
  // Avoid null keys; they are too vulnerable to collision.
  DCHECK(key);
  if (data.get())
    user_data_[key] = std::move(data);
  else
    RemoveUserData(key);
}

void SupportsUserData::RemoveUserData(const void* key) {
  DCHECK(sequence_checker_.CalledOnValidSequence());
  user_data_.erase(key);
}

void SupportsUserData::DetachFromSequence() {
  sequence_checker_.DetachFromSequence();
}

void SupportsUserData::CloneDataFrom(const SupportsUserData& other) {
  for (const auto& data_pair : other.user_data_) {
    auto cloned_data = data_pair.second->Clone();
    if (cloned_data)
      SetUserData(data_pair.first, std::move(cloned_data));
  }
}

SupportsUserData::~SupportsUserData() {
  DCHECK(sequence_checker_.CalledOnValidSequence() || user_data_.empty());
  DataMap local_user_data;
  user_data_.swap(local_user_data);
  // Now this->user_data_ is empty, and any destructors called transitively from
  // the destruction of |local_user_data| will see it that way instead of
  // examining a being-destroyed object.
}

}  // namespace base