| //==- llvm/Support/RandomNumberGenerator.h - RNG for diversity ---*- C++ -*-==// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines an abstraction for random number generation (RNG). |
| // Note that the current implementation is not cryptographically secure |
| // as it uses the C++11 <random> facilities. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_ |
| #define LLVM_SUPPORT_RANDOMNUMBERGENERATOR_H_ |
| |
| #include "llvm/ADT/StringRef.h" |
| #include "llvm/Support/Compiler.h" |
| #include "llvm/Support/DataTypes.h" // Needed for uint64_t on Windows. |
| #include <random> |
| |
| namespace llvm { |
| |
| /// A random number generator. |
| /// Instances of this class should not be shared across threads. |
| class RandomNumberGenerator { |
| public: |
| /// Seeds and salts the underlying RNG engine. The salt of type StringRef |
| /// is passed into the constructor. The seed can be set on the command |
| /// line via -rng-seed=<uint64>. |
| /// The reason for the salt is to ensure different random streams even if |
| /// the same seed is used for multiple invocations of the compiler. |
| /// A good salt value should add additional entropy and be constant across |
| /// different machines (i.e., no paths) to allow for reproducible builds. |
| /// An instance of this class can be retrieved from the current Module. |
| /// \see Module::getRNG |
| RandomNumberGenerator(StringRef Salt); |
| |
| /// Returns a random number in the range [0, Max). |
| uint64_t next(uint64_t Max); |
| |
| private: |
| // 64-bit Mersenne Twister by Matsumoto and Nishimura, 2000 |
| // http://en.cppreference.com/w/cpp/numeric/random/mersenne_twister_engine |
| std::mt19937_64 Generator; |
| |
| // Noncopyable. |
| RandomNumberGenerator(const RandomNumberGenerator &other) |
| LLVM_DELETED_FUNCTION; |
| RandomNumberGenerator & |
| operator=(const RandomNumberGenerator &other) LLVM_DELETED_FUNCTION; |
| }; |
| } |
| |
| #endif |