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
23namespace llvm {
24class 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.
32class 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
40public:
41 using result_type = generator_type::result_type;
42
43 /// Returns a random number in the range [0, Max).
44 LLVM_ABI result_type operator()();
45
46 static constexpr result_type min() { return generator_type::min(); }
47 static constexpr result_type max() { return generator_type::max(); }
48
49private:
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
66LLVM_ABI std::error_code getRandomBytes(void *Buffer, size_t Size);
67}
68
69#endif
70