1 //==- llvm/Support/RandomNumberGenerator.h - RNG for diversity ---*- C++ -*-==// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file defines an abstraction for deterministic random number 10 // generation (RNG). Note that the current implementation is not 11 // cryptographically secure as it uses the C++11 <random> facilities. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_ 16 #define LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_ 17 18 #include "llvm/Support/Compiler.h" 19 #include "llvm/Support/DataTypes.h" // Needed for uint64_t on Windows. 20 #include <random> 21 #include <system_error> 22 23 namespace llvm { 24 class StringRef; 25 26 /// A random number generator. 27 /// 28 /// Instances of this class should not be shared across threads. The 29 /// seed should be set by passing the -rng-seed=<uint64> option. Use 30 /// Module::createRNG to create a new RNG instance for use with that 31 /// module. 32 class RandomNumberGenerator { 33 34 // 64-bit Mersenne Twister by Matsumoto and Nishimura, 2000 35 // http://en.cppreference.com/w/cpp/numeric/random/mersenne_twister_engine 36 // This RNG is deterministically portable across C++11 37 // implementations. 38 using generator_type = std::mt19937_64; 39 40 public: 41 using result_type = generator_type::result_type; 42 43 /// Returns a random number in the range [0, Max). 44 result_type operator()(); 45 min()46 static constexpr result_type min() { return generator_type::min(); } max()47 static constexpr result_type max() { return generator_type::max(); } 48 49 private: 50 /// Seeds and salts the underlying RNG engine. 51 /// 52 /// This constructor should not be used directly. Instead use 53 /// Module::createRNG to create a new RNG salted with the Module ID. 54 RandomNumberGenerator(StringRef Salt); 55 56 generator_type Generator; 57 58 // Noncopyable. 59 RandomNumberGenerator(const RandomNumberGenerator &other) = delete; 60 RandomNumberGenerator &operator=(const RandomNumberGenerator &other) = delete; 61 62 friend class Module; 63 }; 64 65 // Get random vector of specified size 66 std::error_code getRandomBytes(void *Buffer, size_t Size); 67 } 68 69 #endif 70