Disk cache: Reference CL for the implementation of file format version 3.

net/disk_cache/stats.h

 // 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.
 
 #ifndef NET_DISK_CACHE_STATS_H_
 #define NET_DISK_CACHE_STATS_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
+#include "net/disk_cache/addr.h"
 #include "net/disk_cache/stats_histogram.h"
 
 namespace base {
 class HistogramSamples;
 }  // namespace base
 
 namespace disk_cache {
 
-class BackendImpl;
-
 typedef std::vector<std::pair<std::string, std::string> > StatsItems;
 
 // This class stores cache-specific usage information, for tunning purposes.
 class Stats {
  public:
   static const int kDataSizesLength = 28;
   enum Counters {
     MIN_COUNTER = 0,
     OPEN_MISS = MIN_COUNTER,
     OPEN_HIT,
     CREATE_MISS,
     CREATE_HIT,
     RESURRECT_HIT,
     CREATE_ERROR,
     TRIM_ENTRY,
     DOOM_ENTRY,
     DOOM_CACHE,
     INVALID_ENTRY,
     OPEN_ENTRIES,  // Average number of open entries.
     MAX_ENTRIES,  // Maximum number of open entries.
     TIMER,
     READ_DATA,
     WRITE_DATA,
     OPEN_RANKINGS,  // An entry has to be read just to modify rankings.
     GET_RANKINGS,  // We got the ranking info without reading the whole entry.
     FATAL_ERROR,
     LAST_REPORT,  // Time of the last time we sent a report.
     LAST_REPORT_TIMER,  // Timer count of the last time we sent a report.
     DOOM_RECENT,  // The cache was partially cleared.
-    GAJS_EVICTED,  // ga.js was evicted from the cache.
+    UNUSED,  // Was: ga.js was evicted from the cache.
     MAX_COUNTER
   };
 
   Stats();
   ~Stats();
 
-  bool Init(BackendImpl* backend, uint32* storage_addr);
+  // Initializes this object with |data| from disk.
+  bool Init(void* data, int num_bytes, Addr address);
+
+  // Generates a size distribution histogram.
+  void InitSizeHistogram();
+
+  // Returns the number of bytes needed to store the stats on disk.
+  int StorageSize();
 
   // Tracks changes to the stoage space used by an entry.
   void ModifyStorageStats(int32 old_size, int32 new_size);
 
   // Tracks general events.
   void OnEvent(Counters an_event);
   void SetCounter(Counters counter, int64 value);
   int64 GetCounter(Counters counter) const;
 
   void GetItems(StatsItems* items);
   int GetHitRatio() const;
   int GetResurrectRatio() const;
   void ResetRatios();
 
   // Returns the lower bound of the space used by entries bigger than 512 KB.
   int GetLargeEntriesSize();
 
-  // Saves the stats to disk.
-  void Store();
+  // Writes the stats into |data|, to be stored at the given cache address.
+  // Returns the number of bytes copied.
+  int SerializeStats(void* data, int num_bytes, Addr* address);
 
   // Support for StatsHistograms. Together, these methods allow StatsHistograms
   // to take a snapshot of the data_sizes_ as the histogram data.
   int GetBucketRange(size_t i) const;
   void Snapshot(base::HistogramSamples* samples) const;
 
  private:
   int GetStatsBucket(int32 size);
   int GetRatio(Counters hit, Counters miss) const;
 
-  BackendImpl* backend_;
-  uint32 storage_addr_;
+  Addr storage_addr_;
   int data_sizes_[kDataSizesLength];
   int64 counters_[MAX_COUNTER];
   StatsHistogram* size_histogram_;
 
   DISALLOW_COPY_AND_ASSIGN(Stats);
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_STATS_H_