Add module for counting date-last-roll-call and persisting those counts

components/update_client/persisted_data.h

+// Copyright 2016 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 COMPONENTS_UPDATE_CLIENT_PERSISTED_DATA_H_
+#define COMPONENTS_UPDATE_CLIENT_PERSISTED_DATA_H_
+
+#include <string>
+#include <vector>
+
+#include "base/files/file_path.h"
+#include "base/files/important_file_writer.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "base/values.h"
+
+namespace base {
+
+class SequencedTaskRunner;
+class SingleThreadTaskRunner;
+
+}  // namespace base
+
+namespace update_client {
+
+// A PersistedData is a storer and provider of any per-component metadata
+// that outlives the browser process and isn't exposed outside of update_client.
+//
+// It implements an in-memory data structure that is initialized from disk upon
+// startup. Writes to the data structure are written to the disk.
+//
+// The public methods of this class should be called only on the thread that
+// initializes it.
+class PersistedData : public base::RefCountedThreadSafe<PersistedData> {
+ public:
+  // Constructs a provider that uses a file at the specified |path|. The
+  // |task_runner| will be used to serialize the data.
+  PersistedData(
+      const base::FilePath& path,
+      const scoped_refptr<base::SequencedTaskRunner>& task_runner);
+
+  // Returns the DateLastRollCall of the specified |id|. -2 indicates that there
+  // is no record of the app.
+  int DateLastRollCall(const std::string& id) const;
+
+  // Records the DateLastRollCall for the specified |ids|. |datenum| must be a
+  // non-negative integer: calls with a negative |datenum| are simply ignored.
+  // Calls to SetDateLastRollCall that occur prior to the persisted data store
+  // has been fully initialized are ignored.
+  void SetDateLastRollCall(const std::vector<std::string>& ids, int datenum);
+
+ private:
+  friend class base::RefCountedThreadSafe<PersistedData>;
+
+  ~PersistedData();
+
+  void Initialize(
+      const scoped_refptr<base::SingleThreadTaskRunner>& main_task_runner);
+  void LoadFromFile();
+  void Ready();
+
+  base::ThreadChecker thread_checker_;
+
+  const base::FilePath path_;
+  base::ImportantFileWriter file_writer_;
+  scoped_ptr<base::DictionaryValue> metadata_;
+  bool ready_;
+  const scoped_refptr<base::SequencedTaskRunner> task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(PersistedData);
+};
+
+}  // namespace update_client
+
+#endif  // COMPONENTS_UPDATE_CLIENT_PERSISTED_DATA_H_