1 //==- llvm/Support/RandomNumberGenerator.h - RNG for diversity ---*- C++ -*-==// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file defines an abstraction for deterministic random number 11 // generation (RNG). Note that the current implementation is not 12 // cryptographically secure as it uses the C++11 <random> facilities. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #ifndef LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_ 17 #define LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_ 18 19 #include "llvm/Support/Compiler.h" 20 #include "llvm/Support/DataTypes.h" // Needed for uint64_t on Windows. 21 #include <random> 22 #include <system_error> 23 24 namespace llvm { 25 class StringRef; 26 27 /// A random number generator. 28 /// 29 /// Instances of this class should not be shared across threads. The 30 /// seed should be set by passing the -rng-seed=<uint64> option. Use 31 /// Module::createRNG to create a new RNG instance for use with that 32 /// module. 33 class RandomNumberGenerator { 34 35 // 64-bit Mersenne Twister by Matsumoto and Nishimura, 2000 36 // http://en.cppreference.com/w/cpp/numeric/random/mersenne_twister_engine 37 // This RNG is deterministically portable across C++11 38 // implementations. 39 using generator_type = std::mt19937_64; 40 41 public: 42 using result_type = generator_type::result_type; 43 44 /// Returns a random number in the range [0, Max). 45 result_type operator()(); 46 47 static constexpr result_type min() { return generator_type::min(); } 48 static constexpr result_type max() { return generator_type::max(); } 49 50 private: 51 /// Seeds and salts the underlying RNG engine. 52 /// 53 /// This constructor should not be used directly. Instead use 54 /// Module::createRNG to create a new RNG salted with the Module ID. 55 RandomNumberGenerator(StringRef Salt); 56 57 generator_type Generator; 58 59 // Noncopyable. 60 RandomNumberGenerator(const RandomNumberGenerator &other) = delete; 61 RandomNumberGenerator &operator=(const RandomNumberGenerator &other) = delete; 62 63 friend class Module; 64 }; 65 66 // Get random vector of specified size 67 std::error_code getRandomBytes(void *Buffer, size_t Size); 68 } 69 70 #endif 71
