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      1 // Copyright (c) 2011 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_POLICY_FILE_BASED_POLICY_LOADER_H_
      6 #define CHROME_BROWSER_POLICY_FILE_BASED_POLICY_LOADER_H_
      7 #pragma once
      8 
      9 #include "base/files/file_path_watcher.h"
     10 #include "chrome/browser/policy/asynchronous_policy_loader.h"
     11 #include "chrome/browser/policy/file_based_policy_provider.h"
     12 
     13 namespace policy {
     14 
     15 // A customized asynchronous policy loader that handles loading policy from a
     16 // file using a FilePathWatcher. The loader creates a fallback task to load
     17 // policy periodically in case the watcher fails and retries policy loads when
     18 // the watched file is in flux.
     19 class FileBasedPolicyLoader : public AsynchronousPolicyLoader {
     20  public:
     21   FileBasedPolicyLoader(
     22       FileBasedPolicyProvider::ProviderDelegate* provider_delegate);
     23 
     24   // AsynchronousPolicyLoader overrides:
     25   virtual void Reload();
     26 
     27   void OnFilePathChanged(const FilePath& path);
     28   void OnFilePathError(const FilePath& path);
     29 
     30  protected:
     31   // FileBasedPolicyLoader objects should only be deleted by
     32   // RefCountedThreadSafe.
     33   friend class base::RefCountedThreadSafe<AsynchronousPolicyLoader>;
     34   virtual ~FileBasedPolicyLoader();
     35 
     36   const FilePath& config_file_path() { return config_file_path_; }
     37 
     38   // AsynchronousPolicyLoader overrides:
     39 
     40   // Creates the file path watcher and configures it to watch
     41   // |config_file_path_|.  Must be called on the file thread.
     42   virtual void InitOnFileThread();
     43   virtual void StopOnFileThread();
     44 
     45  private:
     46   // Checks whether policy information is safe to read. If not, returns false
     47   // and then delays until it is considered safe to reload in |delay|.
     48   // Must be called on the file thread.
     49   bool IsSafeToReloadPolicy(const base::Time& now, base::TimeDelta* delay);
     50 
     51   // The path at which we look for configuration files.
     52   const FilePath config_file_path_;
     53 
     54   // Managed with a scoped_ptr rather than being declared as an inline member to
     55   // decouple the watcher's life cycle from the loader's. This decoupling makes
     56   // it possible to destroy the watcher before the loader's destructor is called
     57   // (e.g. during Stop), since |watcher_| internally holds a reference to the
     58   // loader and keeps it alive.
     59   scoped_ptr<base::files::FilePathWatcher> watcher_;
     60 
     61   // Settle interval.
     62   const base::TimeDelta settle_interval_;
     63 
     64   // Records last known modification timestamp of |config_file_path_|.
     65   base::Time last_modification_file_;
     66 
     67   // The wall clock time at which the last modification timestamp was
     68   // recorded.  It's better to not assume the file notification time and the
     69   // wall clock times come from the same source, just in case there is some
     70   // non-local filesystem involved.
     71   base::Time last_modification_clock_;
     72 
     73   DISALLOW_COPY_AND_ASSIGN(FileBasedPolicyLoader);
     74 };
     75 
     76 }  // namespace policy
     77 
     78 #endif  // CHROME_BROWSER_POLICY_FILE_BASED_POLICY_LOADER_H_
     79