1// Copyright 2014 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 MEDIA_BASE_TEXT_RANGES_H_
6#define MEDIA_BASE_TEXT_RANGES_H_
7
8#include <map>
9
10#include "base/macros.h"
11#include "base/time/time.h"
12#include "media/base/media_export.h"
13
14namespace media {
15
16// Helper class used by the TextRenderer to filter out text cues that
17// have already been passed downstream.
18class MEDIA_EXPORT TextRanges {
19 public:
20  TextRanges();
21  ~TextRanges();
22
23  // Reset the current range pointer, such that we bind to a new range
24  // (either one that exists already, or one that is freshly-created)
25  // during the next AddCue().
26  void Reset();
27
28  // Given a cue with starting timestamp |start_time|, add its start
29  // time to the time ranges. (Note that following a Reset(), cue
30  // times are assumed to be monotonically increasing.) If this time
31  // has already been added to the time ranges, then AddCue() returns
32  // false and clients should not push the cue downstream. Otherwise,
33  // the time is added to the time ranges and AddCue() returns true,
34  // meaning that the cue should be pushed downstream.
35  bool AddCue(base::TimeDelta start_time);
36
37  // Returns a count of the number of time ranges, intended for use by
38  // the unit test module to vet proper time range merge behavior.
39  size_t RangeCountForTesting() const;
40
41 private:
42  // Describes a range of times for cues that have already been
43  // pushed downstream.
44  class Range {
45   public:
46    // Initialize last_time count.
47    void ResetCount(base::TimeDelta start_time);
48
49    // Set last_time and associated counts.
50    void SetLastTime(base::TimeDelta last_time);
51
52    // Adjust time range state to mark the cue as having been seen,
53    // returning true if we have not seen |start_time| already and
54    // false otherwise.
55    bool AddCue(base::TimeDelta start_time);
56
57    // Returns the value of the last time in the range.
58    base::TimeDelta last_time() const;
59
60   private:
61    // The last timestamp of this range.
62    base::TimeDelta last_time_;
63
64    // The number of cues we have detected so far, for this range,
65    // whose timestamp matches last_time.
66    int max_count_;
67
68    // The number of cues we have seen since the most recent Reset(),
69    // whose timestamp matches last_time.
70    int count_;
71  };
72
73  typedef std::map<base::TimeDelta, Range> RangeMap;
74
75  // NewRange() is used to create a new time range when AddCue() is
76  // called immediately following a Reset(), and no existing time
77  // range contains the indicated |start_time| of the cue.
78  void NewRange(base::TimeDelta start_time);
79
80  // Coalesce curr_range with the range that immediately follows.
81  void Merge(Range& curr_range, const RangeMap::iterator& next_range_itr);
82
83  // The collection of time ranges, each of which is bounded
84  // (inclusive) by the key and Range::last_time.
85  RangeMap range_map_;
86
87  // The time range to which we bind following a Reset().
88  RangeMap::iterator curr_range_itr_;
89
90  DISALLOW_COPY_AND_ASSIGN(TextRanges);
91};
92
93}  // namespace media
94
95#endif  // MEDIA_BASE_TEXT_RANGES_H_
96