net/disk_cache/simple/simple_index_file.h

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef NET_DISK_CACHE_SIMPLE_SIMPLE_INDEX_FILE_H_
   6 #define NET_DISK_CACHE_SIMPLE_SIMPLE_INDEX_FILE_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "base/containers/hash_tables.h"
  13 #include "base/files/file_path.h"
  14 #include "base/gtest_prod_util.h"
  15 #include "base/logging.h"
  16 #include "base/memory/scoped_ptr.h"
  17 #include "base/pickle.h"
  18 #include "base/port.h"
  19 #include "net/base/cache_type.h"
  20 #include "net/base/net_export.h"
  21 #include "net/disk_cache/simple/simple_index.h"
  22
  23 namespace base {
  24 class SingleThreadTaskRunner;
  25 class TaskRunner;
  26 }
  27
  28 namespace disk_cache {
  29
  30 const uint64 kSimpleIndexMagicNumber = GG_UINT64_C(0x656e74657220796f);
  31
  32 struct NET_EXPORT_PRIVATE SimpleIndexLoadResult {
  33   SimpleIndexLoadResult();
  34   ~SimpleIndexLoadResult();
  35   void Reset();
  36
  37   bool did_load;
  38   SimpleIndex::EntrySet entries;
  39   bool flush_required;
  40 };
  41
  42 // Simple Index File format is a pickle serialized data of IndexMetadata and
  43 // EntryMetadata objects. The file format is as follows: one instance of
  44 // serialized |IndexMetadata| followed serialized |EntryMetadata| entries
  45 // repeated |number_of_entries| amount of times. To know more about the format,
  46 // see SimpleIndexFile::Serialize() and SeeSimpleIndexFile::LoadFromDisk()
  47 // methods.
  48 //
  49 // The non-static methods must run on the IO thread. All the real
  50 // work is done in the static methods, which are run on the cache thread
  51 // or in worker threads. Synchronization between methods is the
  52 // responsibility of the caller.
  53 class NET_EXPORT_PRIVATE SimpleIndexFile {
  54  public:
  55   class NET_EXPORT_PRIVATE IndexMetadata {
  56    public:
  57     IndexMetadata();
  58     IndexMetadata(uint64 number_of_entries, uint64 cache_size);
  59
  60     void Serialize(Pickle* pickle) const;
  61     bool Deserialize(PickleIterator* it);
  62
  63     bool CheckIndexMetadata();
  64
  65     uint64 GetNumberOfEntries() { return number_of_entries_; }
  66
  67    private:
  68     FRIEND_TEST_ALL_PREFIXES(IndexMetadataTest, Basics);
  69     FRIEND_TEST_ALL_PREFIXES(IndexMetadataTest, Serialize);
  70
  71     uint64 magic_number_;
  72     uint32 version_;
  73     uint64 number_of_entries_;
  74     uint64 cache_size_;  // Total cache storage size in bytes.
  75   };
  76
  77   SimpleIndexFile(
  78       const scoped_refptr<base::SingleThreadTaskRunner>& cache_thread,
  79       const scoped_refptr<base::TaskRunner>& worker_pool,
  80       net::CacheType cache_type,
  81       const base::FilePath& cache_directory);
  82   virtual ~SimpleIndexFile();
  83
  84   // Get index entries based on current disk context.
  85   virtual void LoadIndexEntries(base::Time cache_last_modified,
  86                                 const base::Closure& callback,
  87                                 SimpleIndexLoadResult* out_result);
  88
  89   // Write the specified set of entries to disk.
  90   virtual void WriteToDisk(const SimpleIndex::EntrySet& entry_set,
  91                            uint64 cache_size,
  92                            const base::TimeTicks& start,
  93                            bool app_on_background);
  94
  95  private:
  96   friend class WrappedSimpleIndexFile;
  97
  98   // Used for cache directory traversal.
  99   typedef base::Callback<void (const base::FilePath&)> EntryFileCallback;
 100
 101   // When loading the entries from disk, add this many extra hash buckets to
 102   // prevent reallocation on the IO thread when merging in new live entries.
 103   static const int kExtraSizeForMerge = 512;
 104
 105   // Synchronous (IO performing) implementation of LoadIndexEntries.
 106   static void SyncLoadIndexEntries(net::CacheType cache_type,
 107                                    base::Time cache_last_modified,
 108                                    const base::FilePath& cache_directory,
 109                                    const base::FilePath& index_file_path,
 110                                    SimpleIndexLoadResult* out_result);
 111
 112   // Load the index file from disk returning an EntrySet.
 113   static void SyncLoadFromDisk(const base::FilePath& index_filename,
 114                                base::Time* out_last_cache_seen_by_index,
 115                                SimpleIndexLoadResult* out_result);
 116
 117   // Returns a scoped_ptr for a newly allocated Pickle containing the serialized
 118   // data to be written to a file. Note: the pickle is not in a consistent state
 119   // immediately after calling this menthod, one needs to call
 120   // SerializeFinalData to make it ready to write to a file.
 121   static scoped_ptr<Pickle> Serialize(
 122       const SimpleIndexFile::IndexMetadata& index_metadata,
 123       const SimpleIndex::EntrySet& entries);
 124
 125   // Appends cache modification time data to the serialized format. This is
 126   // performed on a thread accessing the disk. It is not combined with the main
 127   // serialization path to avoid extra thread hops or copying the pickle to the
 128   // worker thread.
 129   static bool SerializeFinalData(base::Time cache_modified, Pickle* pickle);
 130
 131   // Given the contents of an index file |data| of length |data_len|, returns
 132   // the corresponding EntrySet. Returns NULL on error.
 133   static void Deserialize(const char* data, int data_len,
 134                           base::Time* out_cache_last_modified,
 135                           SimpleIndexLoadResult* out_result);
 136
 137   // Implemented either in simple_index_file_posix.cc or
 138   // simple_index_file_win.cc. base::FileEnumerator turned out to be very
 139   // expensive in terms of memory usage therefore it's used only on non-POSIX
 140   // environments for convenience (for now). Returns whether the traversal
 141   // succeeded.
 142   static bool TraverseCacheDirectory(
 143       const base::FilePath& cache_path,
 144       const EntryFileCallback& entry_file_callback);
 145
 146   // Writes the index file to disk atomically.
 147   static void SyncWriteToDisk(net::CacheType cache_type,
 148                               const base::FilePath& cache_directory,
 149                               const base::FilePath& index_filename,
 150                               const base::FilePath& temp_index_filename,
 151                               scoped_ptr<Pickle> pickle,
 152                               const base::TimeTicks& start_time,
 153                               bool app_on_background);
 154
 155   // Scan the index directory for entries, returning an EntrySet of all entries
 156   // found.
 157   static void SyncRestoreFromDisk(const base::FilePath& cache_directory,
 158                                   const base::FilePath& index_file_path,
 159                                   SimpleIndexLoadResult* out_result);
 160
 161   // Determines if an index file is stale relative to the time of last
 162   // modification of the cache directory. Obsolete, used only for a histogram to
 163   // compare with the new method.
 164   // TODO(pasko): remove this method after getting enough data.
 165   static bool LegacyIsIndexFileStale(base::Time cache_last_modified,
 166                                      const base::FilePath& index_file_path);
 167
 168   struct PickleHeader : public Pickle::Header {
 169     uint32 crc;
 170   };
 171
 172   const scoped_refptr<base::SingleThreadTaskRunner> cache_thread_;
 173   const scoped_refptr<base::TaskRunner> worker_pool_;
 174   const net::CacheType cache_type_;
 175   const base::FilePath cache_directory_;
 176   const base::FilePath index_file_;
 177   const base::FilePath temp_index_file_;
 178
 179   static const char kIndexDirectory[];
 180   static const char kIndexFileName[];
 181   static const char kTempIndexFileName[];
 182
 183   DISALLOW_COPY_AND_ASSIGN(SimpleIndexFile);
 184 };
 185
 186
 187 }  // namespace disk_cache
 188
 189 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_INDEX_FILE_H_