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      1 // Copyright (c) 2012 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_SYNC_GLUE_CHANGE_PROCESSOR_H_
      6 #define CHROME_BROWSER_SYNC_GLUE_CHANGE_PROCESSOR_H_
      7 
      8 #include "chrome/browser/sync/glue/data_type_error_handler.h"
      9 #include "chrome/browser/sync/glue/sync_backend_host.h"
     10 #include "sync/internal_api/public/change_record.h"
     11 
     12 class Profile;
     13 
     14 namespace syncer {
     15 class UnrecoverableErrorHandler;
     16 }  // namespace syncer
     17 
     18 namespace browser_sync {
     19 
     20 class ModelAssociator;
     21 
     22 // An interface used to apply changes from the sync model to the browser's
     23 // native model.  This does not currently distinguish between model data types.
     24 class ChangeProcessor {
     25  public:
     26   explicit ChangeProcessor(DataTypeErrorHandler* error_handler);
     27   virtual ~ChangeProcessor();
     28 
     29   // Call when the processor should accept changes from either provided model
     30   // and apply them to the other.  Both the chrome model and sync_api are
     31   // expected to be initialized and loaded.  You must have set a valid
     32   // ModelAssociator and UnrecoverableErrorHandler before using this method, and
     33   // the two models should be associated w.r.t the ModelAssociator provided.
     34   // Subclasses can extract their associated chrome model from |profile| in
     35   // |StartImpl|.
     36   void Start(Profile* profile, syncer::UserShare* share_handle);
     37 
     38   // Changes have been applied to the backend model and are ready to be
     39   // applied to the frontend model. See syncapi.h for detailed instructions on
     40   // how to interpret and process |changes|.
     41   virtual void ApplyChangesFromSyncModel(
     42       const syncer::BaseTransaction* trans,
     43       int64 model_version,
     44       const syncer::ImmutableChangeRecordList& changes) = 0;
     45 
     46   // The changes found in ApplyChangesFromSyncModel may be too slow to be
     47   // performed while holding a [Read/Write]Transaction lock or may interact
     48   // with another thread, which might itself be waiting on the transaction lock,
     49   // putting us at risk of deadlock.
     50   // This function is called once the transactional lock is released and it is
     51   // safe to perform inter-thread or slow I/O operations. Note that not all
     52   // datatypes need this, so we provide an empty default version.
     53   virtual void CommitChangesFromSyncModel();
     54 
     55   // This ensures that startobserving gets called after stopobserving even
     56   // if there is an early return in the function.
     57   template <class T>
     58   class ScopedStopObserving {
     59    public:
     60     explicit ScopedStopObserving(T* processor)
     61         : processor_(processor) {
     62       processor_->StopObserving();
     63     }
     64     ~ScopedStopObserving() {
     65       processor_->StartObserving();
     66     }
     67 
     68    private:
     69     ScopedStopObserving() {}
     70     T* processor_;
     71   };
     72 
     73  protected:
     74   // These methods are invoked by Start() and Stop() to do
     75   // implementation-specific work.
     76   virtual void StartImpl(Profile* profile) = 0;
     77 
     78   DataTypeErrorHandler* error_handler() const;
     79   virtual syncer::UserShare* share_handle() const;
     80 
     81  private:
     82   DataTypeErrorHandler* error_handler_;  // Guaranteed to outlive us.
     83 
     84   // The sync model we are processing changes from.
     85   syncer::UserShare* share_handle_;
     86 
     87   DISALLOW_COPY_AND_ASSIGN(ChangeProcessor);
     88 };
     89 
     90 }  // namespace browser_sync
     91 
     92 #endif  // CHROME_BROWSER_SYNC_GLUE_CHANGE_PROCESSOR_H_
     93