1// Copyright (c) 2013 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 UI_GFX_SEQUENTIAL_ID_GENERATOR_H_
6#define UI_GFX_SEQUENTIAL_ID_GENERATOR_H_
7
8#include <map>
9
10#include "base/basictypes.h"
11#include "base/containers/hash_tables.h"
12#include "ui/gfx/gfx_export.h"
13
14namespace ui {
15
16// This is used to generate a series of sequential ID numbers in a way that a
17// new ID is always the lowest possible ID in the sequence.
18class GFX_EXPORT SequentialIDGenerator {
19 public:
20   // Creates a new generator with the specified lower bound for the IDs.
21  explicit SequentialIDGenerator(uint32 min_id);
22  ~SequentialIDGenerator();
23
24  // Generates a unique ID to represent |number|. The generated ID is the
25  // smallest available ID greater than or equal to the |min_id| specified
26  // during creation of the generator.
27  uint32 GetGeneratedID(uint32 number);
28
29  // Checks to see if the generator currently has a unique ID generated for
30  // |number|.
31  bool HasGeneratedIDFor(uint32 number) const;
32
33  // Removes the generated ID |id| from the internal mapping. Since the ID is
34  // no longer mapped to any number, subsequent calls to |GetGeneratedID()| can
35  // use this ID.
36  void ReleaseGeneratedID(uint32 id);
37
38  // Removes the ID previously generated for |number| by calling
39  // |GetGeneratedID()|.
40  void ReleaseNumber(uint32 number);
41
42  void ResetForTest();
43
44 private:
45  typedef base::hash_map<uint32, uint32> IDMap;
46
47  uint32 GetNextAvailableID();
48
49  void UpdateNextAvailableIDAfterRelease(uint32 id);
50
51  IDMap number_to_id_;
52  IDMap id_to_number_;
53
54  const uint32 min_id_;
55  uint32 min_available_id_;
56
57  DISALLOW_COPY_AND_ASSIGN(SequentialIDGenerator);
58};
59
60}  // namespace ui
61
62#endif  // UI_GFX_SEQUENTIAL_ID_GENERATOR_H_
63