Move webrtc/{base => rtc_base}

webrtc/base/random.cc

-/*
- *  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.
- */
-#include "webrtc/base/random.h"
-
-#include <math.h>
-
-#include "webrtc/base/checks.h"
-
-namespace webrtc {
-
-Random::Random(uint64_t seed) {
-  RTC_DCHECK(seed != 0x0ull);
-  state_ = seed;
-}
-
-uint32_t Random::Rand(uint32_t t) {
-  // Casting the output to 32 bits will give an almost uniform number.
-  // Pr[x=0] = (2^32-1) / (2^64-1)
-  // Pr[x=k] = 2^32 / (2^64-1) for k!=0
-  // Uniform would be Pr[x=k] = 2^32 / 2^64 for all 32-bit integers k.
-  uint32_t x = NextOutput();
-  // If x / 2^32 is uniform on [0,1), then x / 2^32 * (t+1) is uniform on
-  // the interval [0,t+1), so the integer part is uniform on [0,t].
-  uint64_t result = x * (static_cast<uint64_t>(t) + 1);
-  result >>= 32;
-  return result;
-}
-
-uint32_t Random::Rand(uint32_t low, uint32_t high) {
-  RTC_DCHECK(low <= high);
-  return Rand(high - low) + low;
-}
-
-int32_t Random::Rand(int32_t low, int32_t high) {
-  RTC_DCHECK(low <= high);
-  // We rely on subtraction (and addition) to be the same for signed and
-  // unsigned numbers in two-complement representation. Thus, although
-  // high - low might be negative as an int, it is the correct difference
-  // when interpreted as an unsigned.
-  return Rand(high - low) + low;
-}
-
-template <>
-float Random::Rand<float>() {
-  double result = NextOutput() - 1;
-  result = result / 0xFFFFFFFFFFFFFFFEull;
-  return static_cast<float>(result);
-}
-
-template <>
-double Random::Rand<double>() {
-  double result = NextOutput() - 1;
-  result = result / 0xFFFFFFFFFFFFFFFEull;
-  return result;
-}
-
-template <>
-bool Random::Rand<bool>() {
-  return Rand(0, 1) == 1;
-}
-
-double Random::Gaussian(double mean, double standard_deviation) {
-  // Creating a Normal distribution variable from two independent uniform
-  // variables based on the Box-Muller transform, which is defined on the
-  // interval (0, 1]. Note that we rely on NextOutput to generate integers
-  // in the range [1, 2^64-1]. Normally this behavior is a bit frustrating,
-  // but here it is exactly what we need.
-  const double kPi = 3.14159265358979323846;
-  double u1 = static_cast<double>(NextOutput()) / 0xFFFFFFFFFFFFFFFFull;
-  double u2 = static_cast<double>(NextOutput()) / 0xFFFFFFFFFFFFFFFFull;
-  return mean + standard_deviation * sqrt(-2 * log(u1)) * cos(2 * kPi * u2);
-}
-
-double Random::Exponential(double lambda) {
-  double uniform = Rand<double>();
-  return -log(uniform) / lambda;
-}
-
-}  // namespace webrtc