Rewrote the PRNG using an xorshift* algorithm and moved the files from test/ to base/.

webrtc/test/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/test/random.h"
-
-#include <math.h>
-
-#include "webrtc/base/checks.h"
-
-namespace webrtc {
-
-namespace test {
-
-Random::Random(uint32_t seed) : a_(0x531FDB97 ^ seed), b_(0x6420ECA8 + seed) {
-}
-
-uint32_t Random::Rand(uint32_t t) {
-  // If b / 2^32 is uniform on [0,1), then b / 2^32 * (t+1) is uniform on
-  // the interval [0,t+1), so the integer part is uniform on [0,t].
-  uint64_t result = b_ * (static_cast<uint64_t>(t) + 1);
-  result >>= 32;
-  a_ ^= b_;
-  b_ += a_;
-  return result;
-}
-
-uint32_t Random::Rand(uint32_t low, uint32_t high) {
-  RTC_DCHECK(low <= high);
-  return Rand(high - low) + low;
-}
-
-template <>
-float Random::Rand<float>() {
-  const double kScale = 1.0f / (static_cast<uint64_t>(1) << 32);
-  double result = kScale * b_;
-  a_ ^= b_;
-  b_ += a_;
-  return static_cast<float>(result);
-}
-
-template <>
-bool Random::Rand<bool>() {
-  return Rand(0, 1) == 1;
-}
-
-int Random::Gaussian(int mean, int 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], hence the mask+add below.
-  const double kPi = 3.14159265358979323846;
-  const double kScale = 1.0 / 0x80000000ul;
-  double u1 = kScale * ((a_ & 0x7ffffffful) + 1);
-  double u2 = kScale * ((b_ & 0x7ffffffful) + 1);
-  a_ ^= b_;
-  b_ += a_;
-  return static_cast<int>(
-      mean + standard_deviation * sqrt(-2 * log(u1)) * cos(2 * kPi * u2));
-}
-
-int Random::Exponential(float lambda) {
-  float uniform = Rand<float>();
-  return static_cast<int>(-log(uniform) / lambda);
-}
-}  // namespace test
-}  // namespace webrtc