include/llvm/Support/RandomNumberGenerator.h

   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
  46   static constexpr result_type min() { return generator_type::min(); }
  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