components/policy/core/common/external_data_fetcher.h

   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 COMPONENTS_POLICY_CORE_COMMON_EXTERNAL_DATA_FETCHER_H_
   6 #define COMPONENTS_POLICY_CORE_COMMON_EXTERNAL_DATA_FETCHER_H_
   7
   8 #include <string>
   9
  10 #include "base/callback_forward.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/memory/weak_ptr.h"
  13 #include "components/policy/policy_export.h"
  14
  15 namespace policy {
  16
  17 class ExternalDataManager;
  18
  19 // A helper that encapsulates the parameters required to retrieve the external
  20 // data for a policy.
  21 class POLICY_EXPORT ExternalDataFetcher {
  22  public:
  23   typedef base::Callback<void(scoped_ptr<std::string>)> FetchCallback;
  24
  25   // This instance's Fetch() method will instruct the |manager| to retrieve the
  26   // external data referenced by the given |policy|.
  27   ExternalDataFetcher(base::WeakPtr<ExternalDataManager> manager,
  28                       const std::string& policy);
  29   ExternalDataFetcher(const ExternalDataFetcher& other);
  30
  31   ~ExternalDataFetcher();
  32
  33   static bool Equals(const ExternalDataFetcher* first,
  34                      const ExternalDataFetcher* second);
  35
  36   // Retrieves the external data referenced by |policy_| and invokes |callback|
  37   // with the result. If |policy_| does not reference any external data, the
  38   // |callback| is invoked with a NULL pointer. Otherwise, the |callback| is
  39   // invoked with the referenced data once it has been successfully retrieved.
  40   // If retrieval is temporarily impossible (e.g. no network connectivity), the
  41   // |callback| will be invoked when the temporary hindrance is resolved. If
  42   // retrieval is permanently impossible (e.g. |policy_| references data that
  43   // does not exist on the server), the |callback| will never be invoked.
  44   void Fetch(const FetchCallback& callback) const;
  45
  46  private:
  47   base::WeakPtr<ExternalDataManager> manager_;
  48   const std::string policy_;
  49 };
  50
  51 }  // namespace policy
  52
  53 #endif  // COMPONENTS_POLICY_CORE_COMMON_EXTERNAL_DATA_FETCHER_H_