1 //==- llvm/Support/RandomNumberGenerator.h - RNG for diversity ---*- C++ -*-==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
14 //===----------------------------------------------------------------------===//
16 #ifndef LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_
17 #define LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_
19 #include "llvm/Support/Compiler.h"
20 #include "llvm/Support/DataTypes.h" // Needed for uint64_t on Windows.
22 #include <system_error>
27 /// A random number generator.
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
33 class RandomNumberGenerator {
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
39 using generator_type = std::mt19937_64;
42 using result_type = generator_type::result_type;
44 /// Returns a random number in the range [0, Max).
45 result_type operator()();
47 static constexpr result_type min() { return generator_type::min(); }
48 static constexpr result_type max() { return generator_type::max(); }
51 /// Seeds and salts the underlying RNG engine.
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);
57 generator_type Generator;
60 RandomNumberGenerator(const RandomNumberGenerator &other) = delete;
61 RandomNumberGenerator &operator=(const RandomNumberGenerator &other) = delete;
66 // Get random vector of specified size
67 std::error_code getRandomBytes(void *Buffer, size_t Size);