components/search_provider_logos/logo_cache.h

   1 // Copyright 2014 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 COMPONENTS_SEARCH_PROVIDER_LOGOS_LOGO_CACHE_H_
   6 #define COMPONENTS_SEARCH_PROVIDER_LOGOS_LOGO_CACHE_H_
   7
   8 #include <string>
   9
  10 #include "base/callback.h"
  11 #include "base/files/file_path.h"
  12 #include "base/gtest_prod_util.h"
  13 #include "base/memory/ref_counted.h"
  14 #include "base/memory/ref_counted_memory.h"
  15 #include "base/memory/scoped_ptr.h"
  16 #include "base/threading/thread_checker.h"
  17 #include "components/search_provider_logos/logo_common.h"
  18
  19 namespace search_provider_logos {
  20
  21 // A file-based cache for the search provider's logo. This allows clients to
  22 // store and retrieve a logo (of type EncodedLogo) and its associated metadata
  23 // (of type LogoMetadata). Metadata can be updated independently from the logo
  24 // to handle cases where, e.g. the expiration date changes, but the logo stays
  25 // the same. If corruption is detected in the metadata or logo, the cache will
  26 // be cleared.
  27 //
  28 // Note: this class must only be used on a single thread. All methods are
  29 // are blocking, so this should not be used on the UI thread.
  30 //
  31 // The logo and its metadata are stored in files, so they persist even when
  32 // Chrome is closed. Once loaded from disk, the metadata is kept in memory to
  33 // enable quick retrieval. The logo is not kept around in memory because of its
  34 // size.
  35 class LogoCache {
  36  public:
  37   // Constructs a logo cache that stores data in |cache_directory|.
  38   // |cache_directory| will be created if it does not already exist.
  39   explicit LogoCache(const base::FilePath& cache_directory);
  40   virtual ~LogoCache();
  41
  42   // Updates the metadata for the cached logo.
  43   virtual void UpdateCachedLogoMetadata(const LogoMetadata& metadata);
  44
  45   // Returns metadata for the cached logo, or NULL if logo is cached.
  46   virtual const LogoMetadata* GetCachedLogoMetadata();
  47
  48   // Sets the cached logo and metadata. |logo| may be NULL, in which case the
  49   // cached logo and metadata will be cleared.
  50   virtual void SetCachedLogo(const EncodedLogo* logo);
  51
  52   // Returns the cached logo, or NULL if no logo is cached or the cached logo is
  53   // corrupt.
  54   virtual scoped_ptr<EncodedLogo> GetCachedLogo();
  55
  56  private:
  57   FRIEND_TEST_ALL_PREFIXES(LogoCacheSerializationTest, SerializeMetadata);
  58   FRIEND_TEST_ALL_PREFIXES(LogoCacheSerializationTest,
  59                            DeserializeCorruptMetadata);
  60   FRIEND_TEST_ALL_PREFIXES(LogoCacheTest, StoreAndRetrieveMetadata);
  61   FRIEND_TEST_ALL_PREFIXES(LogoCacheTest, RetrieveCorruptMetadata);
  62   FRIEND_TEST_ALL_PREFIXES(LogoCacheTest, RetrieveCorruptLogo);
  63
  64   // Converts string |str| to a LogoMetadata object and returns it. Returns NULL
  65   // if |str| cannot be converted.
  66   static scoped_ptr<LogoMetadata> LogoMetadataFromString(
  67       const std::string& str, int* logo_num_bytes);
  68
  69   // Converts |metadata| to a string and stores it in |str|.
  70   static void LogoMetadataToString(const LogoMetadata& metadata,
  71                                    int logo_num_bytes,
  72                                    std::string* str);
  73
  74   // Returns the path where the cached logo will be saved.
  75   base::FilePath GetLogoPath();
  76
  77   // Returns the path where the metadata for the cached logo will be saved.
  78   base::FilePath GetMetadataPath();
  79
  80   // Updates the in-memory metadata.
  81   void UpdateMetadata(scoped_ptr<LogoMetadata> metadata);
  82
  83   // If the cached logo's metadata isn't available in memory (i.e.
  84   // |metadata_is_valid_| is false), reads it from disk and stores it in
  85   // |metadata_|. If no logo is cached, |metadata_| will be updated to NULL.
  86   void ReadMetadataIfNeeded();
  87
  88   // Writes the metadata for the cached logo to disk.
  89   void WriteMetadata();
  90
  91   // Writes |metadata_| to the cached metadata file and |encoded_image| to the
  92   // cached logo file.
  93   void WriteLogo(scoped_refptr<base::RefCountedMemory> encoded_image);
  94
  95   // Deletes all the cache files.
  96   void DeleteLogoAndMetadata();
  97
  98   // Tries to create the cache directory if it does not already exist. Returns
  99   // whether the cache directory exists.
 100   bool EnsureCacheDirectoryExists();
 101
 102   // The directory in which the cached logo and metadata will be saved.
 103   base::FilePath cache_directory_;
 104
 105   // The metadata describing the cached logo, or NULL if no logo is cached. This
 106   // value is meaningful iff |metadata_is_valid_| is true; otherwise, the
 107   // metadata must be read from file and |metadata_| will be NULL.
 108   // Note: Once read from file, metadata will be stored in memory indefinitely.
 109   scoped_ptr<LogoMetadata> metadata_;
 110   bool metadata_is_valid_;
 111
 112   // The number of bytes in the logo file, as recorded in the metadata file.
 113   // Valid iff |metadata_is_valid_|. This is used to verify that the logo file
 114   // is complete and corresponds to the current metadata file.
 115   int logo_num_bytes_;
 116
 117   // Ensure LogoCache is only used on a single thread.
 118   base::ThreadChecker thread_checker_;
 119
 120   DISALLOW_COPY_AND_ASSIGN(LogoCache);
 121 };
 122
 123 }  // namespace search_provider_logos
 124
 125 #endif  // COMPONENTS_SEARCH_PROVIDER_LOGOS_LOGO_CACHE_H_