Dynamic policy refresh support for the Mac.

chrome/browser/policy/file_based_policy_provider.h

+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_POLICY_FILE_BASED_POLICY_PROVIDER_H_
+#define CHROME_BROWSER_POLICY_FILE_BASED_POLICY_PROVIDER_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/file_path.h"
+#include "base/lock.h"
+#include "base/ref_counted.h"
+#include "base/scoped_ptr.h"
+#include "base/time.h"
+#include "base/weak_ptr.h"
+#include "chrome/browser/file_path_watcher.h"
+#include "chrome/browser/policy/configuration_policy_provider.h"
+
+class CancelableTask;
+class DictionaryValue;
+class MessageLoop;
+
+namespace policy {
+
+class FileBasedPolicyLoader;
+class FileBasedPolicyWatcher;
+
+// File based policy provider that coordinates watching and reloading policy
+// information from the configuration path. Actual logic for loading policy
+// information is handled by a delegate passed at construction time.
+class FileBasedPolicyProvider
+    : public ConfigurationPolicyProvider,
+      public base::SupportsWeakPtr<FileBasedPolicyProvider> {
+ public:
+  // Delegate interface for actual policy loading from the system.
+  class Delegate {
+   public:
+    virtual ~Delegate();
+
+    // Loads the policy information. Ownership of the return value is
+    // transferred to the caller.
+    virtual DictionaryValue* Load() = 0;
+
+    // Gets the last modification timestamp for the policy information from the
+    // filesystem. Returns base::Time() if the information is not present, in
+    // which case Load() should return an empty dictionary.
+    virtual base::Time GetLastModification() = 0;
+
+    const FilePath& config_file_path() { return config_file_path_; }
+
+   protected:
+    explicit Delegate(const FilePath& config_file_path);
+
+   private:
+    // The path at which we look for configuration files.
+    const FilePath config_file_path_;
+
+    DISALLOW_COPY_AND_ASSIGN(Delegate);
+  };
+
+  // Assumes ownership of |delegate|.
+  FileBasedPolicyProvider(const PolicyDefinitionList* policy_list,
+                          Delegate* delegate);
+  virtual ~FileBasedPolicyProvider();
+
+  // ConfigurationPolicyProvider implementation.
+  virtual bool Provide(ConfigurationPolicyStore* store);
+
+ private:
+  // Decodes the value tree and writes the configuration to the given |store|.
+  void DecodePolicyValueTree(DictionaryValue* policies,
+                             ConfigurationPolicyStore* store);
+
+  // Watches for changes to the configuration directory.
+  scoped_refptr<FileBasedPolicyWatcher> watcher_;
+
+  // The loader object we use internally.
+  scoped_refptr<FileBasedPolicyLoader> loader_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileBasedPolicyProvider);
+};
+
+// FilePathWatcher delegate implementation that handles change notifications for
+// the configuration file or directory. It keeps the authorative version of the
+// currently effective policy dictionary and updates it as appropriate. The
+// actual loading logic is handled by a delegate.
+class FileBasedPolicyLoader : public FilePathWatcher::Delegate {
+ public:
+  // Creates a new loader that'll load its data from |config_file_path|.
+  // Assumes ownership of |delegate|, which  provides the actual loading logic.
+  // The parameters |settle_interval_seconds| and |reload_interval_minutes|
+  // specify the time to wait before reading the file contents after a change
+  // and the period for checking |config_file_path| for changes, respectively.
+  FileBasedPolicyLoader(base::WeakPtr<ConfigurationPolicyProvider> provider,
+                        FileBasedPolicyProvider::Delegate* delegate,
+                        int settle_interval_seconds,
+                        int reload_interval_minutes);
+
+  // Stops any pending reload tasks.
+  void Stop();
+
+  // Reloads the policies and sends out a notification, if appropriate. Must be
+  // called on the file thread.
+  void Reload();
+
+  // Gets the current dictionary value object. Ownership of the returned value
+  // is transferred to the caller.
+  DictionaryValue* GetPolicy();
+
+  const FilePath& config_file_path() { return delegate_->config_file_path(); }
+
+  // FilePathWatcher::Delegate implementation:
+  void OnFilePathChanged(const FilePath& path);
+  void OnError();
+
+ private:
+  // FileBasedPolicyLoader objects should only be deleted by
+  // RefCountedThreadSafe.
+  friend class base::RefCountedThreadSafe<FileBasedPolicyLoader>;
+  virtual ~FileBasedPolicyLoader();
+
+  // Checks whether reading policy information  is safe to do. If not, returns
+  // false and the delay until it is considered safe to reload in |delay|.
+  bool IsSafeToReloadPolicy(const base::Time& now, base::TimeDelta* delay);
+
+  // Schedules a reload task to run when |delay| expires. Must be called on the
+  // file thread.
+  void ScheduleReloadTask(const base::TimeDelta& delay);
+
+  // Notifies the policy provider to send out a policy changed notification.
+  // Must be called on |origin_loop_|.
+  void NotifyPolicyChanged();
+
+  // Invoked from the reload task on the file thread.
+  void ReloadFromTask();
+
+  // The delegate.
+  scoped_ptr<FileBasedPolicyProvider::Delegate> delegate_;
+
+  // The provider this loader is associated with. Access only on the thread that
+  // called the constructor. See |origin_loop_| below.
+  base::WeakPtr<ConfigurationPolicyProvider> provider_;
+
+  // The message loop on which this object was constructed and |provider_|
+  // received on. Recorded so we can call back into the non thread safe provider
+  // to fire the notification.
+  MessageLoop* origin_loop_;
+
+  // Records last known modification timestamp of |config_file_path_|.
+  base::Time last_modification_file_;
+
+  // The wall clock time at which the last modification timestamp was recorded.
+  // It's better to not assume the file notification time and the wall clock
+  // times come from the same source, just in case there is some non-local
+  // filesystem involved.
+  base::Time last_modification_clock_;
+
+  // Protects |policy_|.
+  Lock lock_;
+
+  // The current policy definition.
+  scoped_ptr<DictionaryValue> policy_;
+
+  // The reload task. Access only on the file thread. Holds a reference to the
+  // currently posted task, so we can cancel and repost it if necessary.
+  CancelableTask* reload_task_;
+
+  // Settle and reload intervals.
+  const int settle_interval_seconds_;
+  const int reload_interval_minutes_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileBasedPolicyLoader);
+};
+
+// Wraps a FilePathWatcher for the configuration path and takes care of
+// initializing the watcher object on the file thread.
+class FileBasedPolicyWatcher
+    : public base::RefCountedThreadSafe<FileBasedPolicyWatcher> {
+ public:
+  FileBasedPolicyWatcher();
+
+  // Runs initialization. This is in a separate method since we need to post a
+  // task (which cannot be done from the constructor).
+  void Init(FileBasedPolicyLoader* loader);
+
+ private:
+  // FileBasedPolicyWatcher objects should only be deleted by
+  // RefCountedThreadSafe.
+  friend class base::RefCountedThreadSafe<FileBasedPolicyWatcher>;
+  virtual ~FileBasedPolicyWatcher();
+
+  // Actually sets up the watch with the FilePathWatcher code.
+  void InitWatcher(const scoped_refptr<FileBasedPolicyLoader>& loader);
+
+  // Wrapped watcher that takes care of the actual watching.
+  FilePathWatcher watcher_;
+
+  DISALLOW_COPY_AND_ASSIGN(FileBasedPolicyWatcher);
+};
+
+}  // namespace policy
+
+#endif  // CHROME_BROWSER_POLICY_FILE_BASED_POLICY_PROVIDER_H_