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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
commit | 26a029d407be480d791972afb5975cf62c9360a6 (patch) | |
tree | f435a8308119effd964b339f76abb83a57c29483 /third_party/libwebrtc/rtc_base/random.h | |
parent | Initial commit. (diff) | |
download | firefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz firefox-26a029d407be480d791972afb5975cf62c9360a6.zip |
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'third_party/libwebrtc/rtc_base/random.h')
-rw-r--r-- | third_party/libwebrtc/rtc_base/random.h | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/third_party/libwebrtc/rtc_base/random.h b/third_party/libwebrtc/rtc_base/random.h new file mode 100644 index 0000000000..b3b9fd1608 --- /dev/null +++ b/third_party/libwebrtc/rtc_base/random.h @@ -0,0 +1,96 @@ +/* + * Copyright (c) 2015 The WebRTC project authors. All Rights Reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree. An additional intellectual property rights grant can be found + * in the file PATENTS. All contributing project authors may + * be found in the AUTHORS file in the root of the source tree. + */ + +#ifndef RTC_BASE_RANDOM_H_ +#define RTC_BASE_RANDOM_H_ + +#include <stdint.h> + +#include <limits> + +#include "rtc_base/checks.h" + +namespace webrtc { + +class Random { + public: + // TODO(tommi): Change this so that the seed can be initialized internally, + // e.g. by offering two ways of constructing or offer a static method that + // returns a seed that's suitable for initialization. + // The problem now is that callers are calling clock_->TimeInMicroseconds() + // which calls TickTime::Now().Ticks(), which can return a very low value on + // Mac and can result in a seed of 0 after conversion to microseconds. + // Besides the quality of the random seed being poor, this also requires + // the client to take on extra dependencies to generate a seed. + // If we go for a static seed generator in Random, we can use something from + // webrtc/rtc_base and make sure that it works the same way across platforms. + // See also discussion here: https://codereview.webrtc.org/1623543002/ + explicit Random(uint64_t seed); + + Random() = delete; + Random(const Random&) = delete; + Random& operator=(const Random&) = delete; + + // Return pseudo-random integer of the specified type. + // We need to limit the size to 32 bits to keep the output close to uniform. + template <typename T> + T Rand() { + static_assert(std::numeric_limits<T>::is_integer && + std::numeric_limits<T>::radix == 2 && + std::numeric_limits<T>::digits <= 32, + "Rand is only supported for built-in integer types that are " + "32 bits or smaller."); + return static_cast<T>(NextOutput()); + } + + // Uniformly distributed pseudo-random number in the interval [0, t]. + uint32_t Rand(uint32_t t); + + // Uniformly distributed pseudo-random number in the interval [low, high]. + uint32_t Rand(uint32_t low, uint32_t high); + + // Uniformly distributed pseudo-random number in the interval [low, high]. + int32_t Rand(int32_t low, int32_t high); + + // Normal Distribution. + double Gaussian(double mean, double standard_deviation); + + // Exponential Distribution. + double Exponential(double lambda); + + private: + // Outputs a nonzero 64-bit random number using Xorshift algorithm. + // https://en.wikipedia.org/wiki/Xorshift + uint64_t NextOutput() { + state_ ^= state_ >> 12; + state_ ^= state_ << 25; + state_ ^= state_ >> 27; + RTC_DCHECK(state_ != 0x0ULL); + return state_ * 2685821657736338717ull; + } + + uint64_t state_; +}; + +// Return pseudo-random number in the interval [0.0, 1.0). +template <> +float Random::Rand<float>(); + +// Return pseudo-random number in the interval [0.0, 1.0). +template <> +double Random::Rand<double>(); + +// Return pseudo-random boolean value. +template <> +bool Random::Rand<bool>(); + +} // namespace webrtc + +#endif // RTC_BASE_RANDOM_H_ |