Write the Simple Cache Index file to disk once in a while

net/disk_cache/simple/simple_index.h

 // Copyright (c) 2013 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 NET_DISK_CACHE_SIMPLE_SIMPLE_INDEX_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_INDEX_H_
 
 #include <map>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/hash_tables.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "base/time.h"
+#include "base/timer.h"
 #include "net/base/net_export.h"
 
 class Pickle;
 class PickleIterator;
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace disk_cache {
@@ skipping 67 matching lines @@
 
   // TODO(felipeg): This way we are storing the hash_key twice, as the
   // hash_map::key and as a member of EntryMetadata. We could save space if we
   // use a hash_set.
   typedef base::hash_map<uint64, EntryMetadata> EntrySet;
 
   static void InsertInEntrySet(const EntryMetadata& entry_metadata,
                                EntrySet* entry_set);
 
  private:
-  typedef base::Callback<void(scoped_ptr<EntrySet>)> IndexCompletionCallback;
+  typedef base::Callback<void(scoped_ptr<EntrySet>, bool force_index_flush)>
+      IndexCompletionCallback;
+
+  void PostponeWritingToDisk();
 
   static void LoadFromDisk(
       const base::FilePath& index_filename,
       base::SingleThreadTaskRunner* io_thread,
       const IndexCompletionCallback& completion_callback);
 
   // Enumerates all entries' files on disk and regenerates the index.
   static scoped_ptr<SimpleIndex::EntrySet> RestoreFromDisk(
       const base::FilePath& index_filename);
 
   static void WriteToDiskInternal(const base::FilePath& index_filename,
                                   scoped_ptr<Pickle> pickle);
 
   // Must run on IO Thread.
-  void MergeInitializingSet(scoped_ptr<EntrySet> index_file_entries);
+  void MergeInitializingSet(scoped_ptr<EntrySet> index_file_entries,
+                            bool force_index_flush);
 
   EntrySet entries_set_;
   uint64 cache_size_;  // Total cache storage size in bytes.
 
   // This stores all the hash_key of entries that are removed during
   // initialization.
   base::hash_set<uint64> removed_entries_;
   bool initialized_;
 
   base::FilePath index_filename_;
 
   scoped_refptr<base::SingleThreadTaskRunner> cache_thread_;
   scoped_refptr<base::SingleThreadTaskRunner> io_thread_;
 
   // All nonstatic SimpleEntryImpl methods should always be called on the IO
   // thread, in all cases. |io_thread_checker_| documents and enforces this.
   base::ThreadChecker io_thread_checker_;
+
+  // Timestamp of the last time we wrote the index to disk.
+  // PostponeWritingToDisk() may give up postponing and allow the write if it
+  // has been a while since last time we wrote.
+  base::Time last_write_to_disk_;
+  base::OneShotTimer<SimpleIndex> write_to_disk_timer_;
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_INDEX_H_