sync/internal_api/change_reorder_buffer.h

   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 // Defines ChangeReorderBuffer, which can be used to sort a list of item
   6 // actions to achieve the ordering constraint required by the SyncObserver
   7 // interface of the SyncAPI.
   8
   9 #ifndef SYNC_INTERNAL_API_CHANGE_REORDER_BUFFER_H_
  10 #define SYNC_INTERNAL_API_CHANGE_REORDER_BUFFER_H_
  11
  12 #include <map>
  13 #include <vector>
  14
  15 #include "base/compiler_specific.h"
  16 #include "base/memory/linked_ptr.h"
  17 #include "sync/internal_api/public/change_record.h"
  18 #include "sync/protocol/sync.pb.h"
  19
  20 namespace syncer {
  21
  22 class BaseTransaction;
  23
  24 // ChangeReorderBuffer is a utility type which accepts an unordered set
  25 // of changes (via its Push methods), and yields an ImmutableChangeRecordList
  26 // (via the GetAllChangesInTreeOrder method) that are in the order that
  27 // the SyncObserver expects them to be. A buffer is initially empty.
  28 //
  29 // The ordering produced by ChangeReorderBuffer is as follows:
  30 //  (a) All Deleted items appear first.
  31 //  (b) For Updated and/or Added items, parents appear before their children.
  32 //
  33 // The sibling order is not necessarily preserved.
  34 class ChangeReorderBuffer {
  35  public:
  36   ChangeReorderBuffer();
  37   ~ChangeReorderBuffer();
  38
  39   // Insert an item, identified by the metahandle |id|, into the reorder buffer.
  40   // This item will appear in the output list as an ACTION_ADD ChangeRecord.
  41   void PushAddedItem(int64 id);
  42
  43   // Insert an item, identified by the metahandle |id|, into the reorder buffer.
  44   // This item will appear in the output list as an ACTION_DELETE ChangeRecord.
  45   void PushDeletedItem(int64 id);
  46
  47   // Insert an item, identified by the metahandle |id|, into the reorder buffer.
  48   // This item will appear in the output list as an ACTION_UPDATE ChangeRecord.
  49   void PushUpdatedItem(int64 id);
  50
  51   void SetExtraDataForId(int64 id, ExtraPasswordChangeRecordData* extra);
  52
  53   void SetSpecificsForId(int64 id, const sync_pb::EntitySpecifics& specifics);
  54
  55   // Reset the buffer, forgetting any pushed items, so that it can be used again
  56   // to reorder a new set of changes.
  57   void Clear();
  58
  59   bool IsEmpty() const;
  60
  61   // Output a reordered list of changes to |changes| using the items
  62   // that were pushed into the reorder buffer. |sync_trans| is used to
  63   // determine the ordering.  Returns true if successful, or false if
  64   // an error was encountered.
  65   bool GetAllChangesInTreeOrder(
  66       const BaseTransaction* sync_trans,
  67       ImmutableChangeRecordList* changes) WARN_UNUSED_RESULT;
  68
  69  private:
  70   class Traversal;
  71   typedef std::map<int64, ChangeRecord::Action> OperationMap;
  72   typedef std::map<int64, sync_pb::EntitySpecifics> SpecificsMap;
  73   typedef std::map<int64, linked_ptr<ExtraPasswordChangeRecordData> >
  74       ExtraDataMap;
  75
  76   // Stores the items that have been pushed into the buffer, and the type of
  77   // operation that was associated with them.
  78   OperationMap operations_;
  79
  80   // Stores entity-specific ChangeRecord data per-ID.
  81   SpecificsMap specifics_;
  82
  83   // Stores type-specific extra data per-ID.
  84   ExtraDataMap extra_data_;
  85
  86   DISALLOW_COPY_AND_ASSIGN(ChangeReorderBuffer);
  87 };
  88
  89 }  // namespace syncer
  90
  91 #endif  // SYNC_INTERNAL_API_CHANGE_REORDER_BUFFER_H_