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      1 // Copyright 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 CHROME_BROWSER_CHROMEOS_POLICY_CLOUD_EXTERNAL_DATA_STORE_H_
      6 #define CHROME_BROWSER_CHROMEOS_POLICY_CLOUD_EXTERNAL_DATA_STORE_H_
      7 
      8 #include <string>
      9 
     10 #include "base/basictypes.h"
     11 #include "base/memory/ref_counted.h"
     12 #include "components/policy/core/common/cloud/cloud_external_data_manager.h"
     13 
     14 namespace base {
     15 class SequencedTaskRunner;
     16 }
     17 
     18 namespace policy {
     19 
     20 class ResourceCache;
     21 
     22 // Stores external data referenced by policies. Data is keyed by (policy, hash),
     23 // the name of the policy referencing it and its SHA1 hash. Outdated entries are
     24 // removed by calling Prune() with the list of (policy, hash) entries that are
     25 // to be kept. Instances of this class may be created on any thread and may
     26 // share the same cache, however:
     27 // * After creation, the cache and all stores using it must always be accessed
     28 //   via the same |task_runner| only.
     29 // * Stores sharing a cache must use different cache_keys to avoid namespace
     30 //   overlaps.
     31 // * The cache must outlive all stores using it.
     32 class CloudExternalDataStore {
     33  public:
     34   CloudExternalDataStore(const std::string& cache_key,
     35                          scoped_refptr<base::SequencedTaskRunner> task_runner,
     36                          ResourceCache* cache);
     37   ~CloudExternalDataStore();
     38 
     39   // Removes all entries from the store whose (policy, hash) pair is not found
     40   // in |metadata|.
     41   void Prune(const CloudExternalDataManager::Metadata& metadata);
     42 
     43   // Stores |data| under (policy, hash). Returns true if the store succeeded.
     44   bool Store(const std::string& policy,
     45              const std::string& hash,
     46              const std::string& data);
     47 
     48   // Loads the entry at (policy, hash) into |data|, verifies that it does not
     49   // exceed |max_size| and matches the expected |hash|, then returns true.
     50   // Returns false if no entry is found at (policy, hash), there is a problem
     51   // during the load, the entry exceeds |max_size| or does not match |hash|.
     52   bool Load(const std::string& policy,
     53             const std::string& hash,
     54             size_t max_size,
     55             std::string* data);
     56 
     57  private:
     58   std::string cache_key_;
     59 
     60   // Task runner that |this| runs on.
     61   scoped_refptr<base::SequencedTaskRunner> task_runner_;
     62 
     63   ResourceCache* cache_;  // Not owned.
     64 
     65   DISALLOW_COPY_AND_ASSIGN(CloudExternalDataStore);
     66 };
     67 
     68 }  // namespace policy
     69 
     70 #endif  // CHROME_BROWSER_CHROMEOS_POLICY_CLOUD_EXTERNAL_DATA_STORE_H_
     71