blob: d3f2446906ebfa5e88438b840b6e30c0bbad9df1 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
|
// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "cast/streaming/ssrc.h"
#include <random>
#include "platform/api/time.h"
namespace cast {
namespace streaming {
namespace {
// These ranges are arbitrary, but have been used for several years (in prior
// implementations of Cast Streaming).
constexpr int kHigherPriorityMin = 1;
constexpr int kHigherPriorityMax = 50000;
constexpr int kNormalPriorityMin = 50001;
constexpr int kNormalPriorityMax = 100000;
} // namespace
Ssrc GenerateSsrc(bool higher_priority) {
// Use a statically-allocated generator, instantiated upon first use, and
// seeded with the current time tick count. This generator was chosen because
// it is light-weight and does not need to produce unguessable (nor
// crypto-secure) values.
static std::minstd_rand generator(static_cast<std::minstd_rand::result_type>(
openscreen::platform::Clock::now().time_since_epoch().count()));
std::uniform_int_distribution<int> distribution(
higher_priority ? kHigherPriorityMin : kNormalPriorityMin,
higher_priority ? kHigherPriorityMax : kNormalPriorityMax);
return static_cast<Ssrc>(distribution(generator));
}
int ComparePriority(Ssrc ssrc_a, Ssrc ssrc_b) {
return static_cast<int>(ssrc_a) - static_cast<int>(ssrc_b);
}
} // namespace streaming
} // namespace cast
|
