ui/gfx/sequential_id_generator.h

   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
  14 namespace 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.
  18 class 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  private:
  43   typedef base::hash_map<uint32, uint32> IDMap;
  44
  45   uint32 GetNextAvailableID();
  46
  47   void UpdateNextAvailableIDAfterRelease(uint32 id);
  48
  49   IDMap number_to_id_;
  50   IDMap id_to_number_;
  51
  52   uint32 min_id_;
  53   uint32 min_available_id_;
  54
  55   DISALLOW_COPY_AND_ASSIGN(SequentialIDGenerator);
  56 };
  57
  58 }  // namespace ui
  59
  60 #endif  // UI_GFX_SEQUENTIAL_ID_GENERATOR_H_