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 #include "media/base/text_ranges.h"
6
7 #include "base/check_op.h"
8
9 namespace media {
10
TextRanges()11 TextRanges::TextRanges() {
12 Reset();
13 }
14
15 TextRanges::~TextRanges() = default;
16
Reset()17 void TextRanges::Reset() {
18 curr_range_itr_ = range_map_.end();
19 }
20
AddCue(base::TimeDelta start_time)21 bool TextRanges::AddCue(base::TimeDelta start_time) {
22 typedef RangeMap::iterator Itr;
23
24 if (curr_range_itr_ == range_map_.end()) {
25 // There is no active time range, so this is the first AddCue()
26 // attempt that follows a Reset().
27
28 if (range_map_.empty()) {
29 NewRange(start_time);
30 return true;
31 }
32
33 if (start_time < range_map_.begin()->first) {
34 NewRange(start_time);
35 return true;
36 }
37
38 const Itr itr = --Itr(range_map_.upper_bound(start_time));
39 DCHECK(start_time >= itr->first);
40
41 Range& range = itr->second;
42
43 if (start_time > range.last_time()) {
44 NewRange(start_time);
45 return true;
46 }
47
48 range.ResetCount(start_time);
49 curr_range_itr_ = itr;
50 return false;
51 }
52
53 DCHECK(start_time >= curr_range_itr_->first);
54
55 Range& curr_range = curr_range_itr_->second;
56
57 if (start_time <= curr_range.last_time())
58 return curr_range.AddCue(start_time);
59
60 const Itr next_range_itr = ++Itr(curr_range_itr_);
61
62 if (next_range_itr != range_map_.end()) {
63 DCHECK(next_range_itr->first > curr_range.last_time());
64 DCHECK(start_time <= next_range_itr->first);
65
66 if (start_time == next_range_itr->first) {
67 // We have walked off the current range, and onto the next one.
68 // There is now no ambiguity about where the current time range
69 // ends, and so we coalesce the current and next ranges.
70
71 Merge(curr_range, next_range_itr);
72 return false;
73 }
74 }
75
76 // Either |curr_range| is the last range in the map, or there is a
77 // next range beyond |curr_range|, but its start time is ahead of
78 // this cue's start time. In either case, this cue becomes the new
79 // last_time for |curr_range|. Eventually we will see a cue whose
80 // time matches the start time of the next range, in which case we
81 // coalesce the current and next ranges.
82
83 curr_range.SetLastTime(start_time);
84 return true;
85 }
86
RangeCountForTesting() const87 size_t TextRanges::RangeCountForTesting() const {
88 return range_map_.size();
89 }
90
NewRange(base::TimeDelta start_time)91 void TextRanges::NewRange(base::TimeDelta start_time) {
92 Range range;
93 range.SetLastTime(start_time);
94
95 std::pair<RangeMap::iterator, bool> result =
96 range_map_.insert(std::make_pair(start_time, range));
97 DCHECK(result.second);
98
99 curr_range_itr_ = result.first;
100 }
101
Merge(Range & curr_range,const RangeMap::iterator & next_range_itr)102 void TextRanges::Merge(
103 Range& curr_range,
104 const RangeMap::iterator& next_range_itr) {
105 curr_range = next_range_itr->second;
106 curr_range.ResetCount(next_range_itr->first);
107 range_map_.erase(next_range_itr);
108 }
109
ResetCount(base::TimeDelta start_time)110 void TextRanges::Range::ResetCount(base::TimeDelta start_time) {
111 count_ = (start_time < last_time_) ? 0 : 1;
112 }
113
SetLastTime(base::TimeDelta last_time)114 void TextRanges::Range::SetLastTime(base::TimeDelta last_time) {
115 last_time_ = last_time;
116 count_ = 1;
117 max_count_ = 1;
118 }
119
AddCue(base::TimeDelta start_time)120 bool TextRanges::Range::AddCue(base::TimeDelta start_time) {
121 if (start_time < last_time_) {
122 DCHECK_EQ(count_, 0);
123 return false;
124 }
125
126 DCHECK(start_time == last_time_);
127
128 ++count_;
129 if (count_ <= max_count_)
130 return false;
131
132 ++max_count_;
133 return true;
134 }
135
last_time() const136 base::TimeDelta TextRanges::Range::last_time() const {
137 return last_time_;
138 }
139
140 } // namespace media
141