| // 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 openscreen { |
| namespace cast { |
| |
| 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>( |
| 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 cast |
| } // namespace openscreen |