Update data reduction proxy statistics prefs less often on desktop

components/data_reduction_proxy/browser/data_reduction_proxy_statistics_prefs.h

+// Copyright 2014 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_DATA_REDUCTION_PROXY_BROWSER_DATA_REDUCTION_PROXY_STATISTICS_PREFS_H_
+#define COMPONENTS_DATA_REDUCTION_PROXY_BROWSER_DATA_REDUCTION_PROXY_STATISTICS_PREFS_H_
+
+#include <map>
+
+#include "base/containers/scoped_ptr_hash_map.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/time/time.h"
+#include "components/data_reduction_proxy/common/data_reduction_proxy_pref_names.h"
+
+class PrefService;
+
+namespace base {
+class ListValue;
+class SequencedTaskRunner;
+}
+
+namespace data_reduction_proxy {
+
+// Data reduction proxy delayed pref service reduces the number calls to pref
+// service by storing prefs in memory and writing to the given PrefService after
+// |delay| amount of time. If |delay| is zero, the delayed pref service writes
+// directly to the PrefService and does not store the prefs in memory. All
+// prefs must be stored and read on the UI thread.
+class DataReductionProxyStatisticsPrefs {
+public:
+  // Constructs a data reduction proxy delayed pref service object using
+  // |pref_service|. Writes prefs to |pref_service| after |delay|
+  // and stores them in |pref_map_| and |list_pref_map| between writes.
+  // If |delay| is zero, writes directly to the PrefService and does not store
+  // in the maps.
+  DataReductionProxyStatisticsPrefs(
+      PrefService* pref_service,
+      scoped_refptr<base::SequencedTaskRunner> task_runner,
+      const base::TimeDelta& delay);
+  ~DataReductionProxyStatisticsPrefs();
+
+  // Loads all data_reduction_proxy::prefs into the |pref_map_| and
+  // |list_pref_map_|.
+  void Init();
+
+  // Gets the int64 pref at |pref_path| from the |DataReductionProxyPrefMap|.
+  int64 GetInt64(const char* pref_path);
+
+  // Updates the pref value in the |DataReductionProxyPrefMap| map.
+  // The pref is later written to |pref service_|.
+  void SetInt64(const char* pref_path, int64 pref_value);
+
+  // Gets the pref list at |pref_path| from the |DataReductionProxyPrefMap|.
+  base::ListValue* GetList(const char* pref_path);
+
+  // Writes the prefs stored in |DataReductionProxyPrefMap| and
+  // |DataReductionProxyListPrefMap| to |pref_service|.
+  void WritePrefs();
+
+private:
+  typedef std::map<const char*, int64> DataReductionProxyPrefMap;
+  typedef base::ScopedPtrHashMap<const char*, base::ListValue>
+      DataReductionProxyListPrefMap;
+
+  // Gets the value of |pref| from the pref service and adds it to the
+  // |pref_map|.
+  void InitInt64Pref(const char* pref);
+
+  // Gets the value of |pref| from the pref service and adds it to the
+  // |list_pref_map|.
+  void InitListPref(const char* pref);
+
+  // Writes the stored prefs to |pref_service| and then posts another a delayed
+  // task to write prefs again in |kMinutesBetweenWrites|.
+  void DelayedWritePrefs();
+
+  // Copies the values at each index of |from_list| to the same index in
+  // |to_list|.
+  void TransferList(const base::ListValue& from_list,
+                    base::ListValue* to_list);
+
+  // Gets an int64, stored as a string, in a ListPref at the specified
+  // index.
+  int64 GetListPrefInt64Value(const base::ListValue& list_update, size_t index);
+
+  PrefService* pref_service_;
+  scoped_refptr<base::SequencedTaskRunner> task_runner_;
+  base::WeakPtrFactory<DataReductionProxyStatisticsPrefs> weak_factory_;
+  const base::TimeDelta delay_;
+  bool delayed_task_posted_;
+  DataReductionProxyPrefMap pref_map_;
+  DataReductionProxyListPrefMap list_pref_map_;
+
+  DISALLOW_COPY_AND_ASSIGN(DataReductionProxyStatisticsPrefs);
+};
+
+}  // namespace data_reduction_proxy
+
+#endif  // COMPONENTS_DATA_REDUCTION_PROXY_BROWSER_DATA_REDUCTION_PROXY_STATISTICS_PREFS_H_