change_reorder_buffer.h revision 7d4cd473f85ac64c3747c96c277f9e506a0d2246 
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
20namespace syncer {
21
22class 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.
34class 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_
92