/src/mozilla-central/dom/media/MediaChannelStatistics.h
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1 | | /* vim:set ts=2 sw=2 sts=2 et cindent: */ |
2 | | /* This Source Code Form is subject to the terms of the Mozilla Public |
3 | | * License, v. 2.0. If a copy of the MPL was not distributed with this |
4 | | * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ |
5 | | |
6 | | #if !defined(MediaChannelStatistics_h_) |
7 | | #define MediaChannelStatistics_h_ |
8 | | |
9 | | #include "mozilla/TimeStamp.h" |
10 | | |
11 | | namespace mozilla { |
12 | | |
13 | | // Number of bytes we have accumulated before we assume the connection download |
14 | | // rate can be reliably calculated. 57 Segments at IW=3 allows slow start to |
15 | | // reach a CWND of 30 (See bug 831998) |
16 | | static const int64_t RELIABLE_DATA_THRESHOLD = 57 * 1460; |
17 | | |
18 | | /** |
19 | | * This class is useful for estimating rates of data passing through |
20 | | * some channel. The idea is that activity on the channel "starts" |
21 | | * and "stops" over time. At certain times data passes through the |
22 | | * channel (usually while the channel is active; data passing through |
23 | | * an inactive channel is ignored). The GetRate() function computes |
24 | | * an estimate of the "current rate" of the channel, which is some |
25 | | * kind of average of the data passing through over the time the |
26 | | * channel is active. |
27 | | * |
28 | | * All methods take "now" as a parameter so the user of this class can |
29 | | * control the timeline used. |
30 | | */ |
31 | | class MediaChannelStatistics { |
32 | | public: |
33 | 0 | MediaChannelStatistics() = default; |
34 | | MediaChannelStatistics(const MediaChannelStatistics&) = default; |
35 | | MediaChannelStatistics& operator=(const MediaChannelStatistics&) = default; |
36 | | |
37 | 0 | void Reset() { |
38 | 0 | mLastStartTime = TimeStamp(); |
39 | 0 | mAccumulatedTime = TimeDuration(0); |
40 | 0 | mAccumulatedBytes = 0; |
41 | 0 | mIsStarted = false; |
42 | 0 | } |
43 | 0 | void Start() { |
44 | 0 | if (mIsStarted) |
45 | 0 | return; |
46 | 0 | mLastStartTime = TimeStamp::Now(); |
47 | 0 | mIsStarted = true; |
48 | 0 | } |
49 | 0 | void Stop() { |
50 | 0 | if (!mIsStarted) |
51 | 0 | return; |
52 | 0 | mAccumulatedTime += TimeStamp::Now() - mLastStartTime; |
53 | 0 | mIsStarted = false; |
54 | 0 | } |
55 | 0 | void AddBytes(int64_t aBytes) { |
56 | 0 | if (!mIsStarted) { |
57 | 0 | // ignore this data, it may be related to seeking or some other |
58 | 0 | // operation we don't care about |
59 | 0 | return; |
60 | 0 | } |
61 | 0 | mAccumulatedBytes += aBytes; |
62 | 0 | } |
63 | | double GetRateAtLastStop(bool* aReliable) const |
64 | 0 | { |
65 | 0 | double seconds = mAccumulatedTime.ToSeconds(); |
66 | 0 | *aReliable = (seconds >= 1.0) || |
67 | 0 | (mAccumulatedBytes >= RELIABLE_DATA_THRESHOLD); |
68 | 0 | if (seconds <= 0.0) |
69 | 0 | return 0.0; |
70 | 0 | return static_cast<double>(mAccumulatedBytes)/seconds; |
71 | 0 | } |
72 | | double GetRate(bool* aReliable) const |
73 | 0 | { |
74 | 0 | TimeDuration time = mAccumulatedTime; |
75 | 0 | if (mIsStarted) { |
76 | 0 | time += TimeStamp::Now() - mLastStartTime; |
77 | 0 | } |
78 | 0 | double seconds = time.ToSeconds(); |
79 | 0 | *aReliable = (seconds >= 3.0) || |
80 | 0 | (mAccumulatedBytes >= RELIABLE_DATA_THRESHOLD); |
81 | 0 | if (seconds <= 0.0) |
82 | 0 | return 0.0; |
83 | 0 | return static_cast<double>(mAccumulatedBytes)/seconds; |
84 | 0 | } |
85 | | private: |
86 | | int64_t mAccumulatedBytes = 0; |
87 | | TimeDuration mAccumulatedTime; |
88 | | TimeStamp mLastStartTime; |
89 | | bool mIsStarted = false; |
90 | | }; |
91 | | |
92 | | } // namespace mozilla |
93 | | |
94 | | #endif // MediaChannelStatistics_h_ |