1 /* 2 * Copyright (c) 2015 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #ifndef WEBRTC_BASE_RANDOM_H_ 12 #define WEBRTC_BASE_RANDOM_H_ 13 14 #include <limits> 15 16 #include "webrtc/typedefs.h" 17 #include "webrtc/base/constructormagic.h" 18 #include "webrtc/base/checks.h" 19 20 namespace webrtc { 21 22 class Random { 23 public: 24 explicit Random(uint64_t seed); 25 26 // Return pseudo-random integer of the specified type. 27 // We need to limit the size to 32 bits to keep the output close to uniform. 28 template <typename T> 29 T Rand() { 30 static_assert(std::numeric_limits<T>::is_integer && 31 std::numeric_limits<T>::radix == 2 && 32 std::numeric_limits<T>::digits <= 32, 33 "Rand is only supported for built-in integer types that are " 34 "32 bits or smaller."); 35 return static_cast<T>(NextOutput()); 36 } 37 38 // Uniformly distributed pseudo-random number in the interval [0, t]. 39 uint32_t Rand(uint32_t t); 40 41 // Uniformly distributed pseudo-random number in the interval [low, high]. 42 uint32_t Rand(uint32_t low, uint32_t high); 43 44 // Uniformly distributed pseudo-random number in the interval [low, high]. 45 int32_t Rand(int32_t low, int32_t high); 46 47 // Normal Distribution. 48 double Gaussian(double mean, double standard_deviation); 49 50 // Exponential Distribution. 51 double Exponential(double lambda); 52 53 private: 54 // Outputs a nonzero 64-bit random number. 55 uint64_t NextOutput() { 56 state_ ^= state_ >> 12; 57 state_ ^= state_ << 25; 58 state_ ^= state_ >> 27; 59 RTC_DCHECK(state_ != 0x0ULL); 60 return state_ * 2685821657736338717ull; 61 } 62 63 uint64_t state_; 64 65 RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(Random); 66 }; 67 68 // Return pseudo-random number in the interval [0.0, 1.0). 69 template <> 70 float Random::Rand<float>(); 71 72 // Return pseudo-random number in the interval [0.0, 1.0). 73 template <> 74 double Random::Rand<double>(); 75 76 // Return pseudo-random boolean value. 77 template <> 78 bool Random::Rand<bool>(); 79 80 } // namespace webrtc 81 82 #endif // WEBRTC_BASE_RANDOM_H_ 83
