compiler-rt/lib/fuzzer/FuzzerRandom.h

   1 //===- FuzzerRandom.h - Internal header for the Fuzzer ----------*- 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 // fuzzer::Random
   9 //===----------------------------------------------------------------------===//
  10
  11 #ifndef LLVM_FUZZER_RANDOM_H
  12 #define LLVM_FUZZER_RANDOM_H
  13
  14 #include <random>
  15
  16 namespace fuzzer {
  17 class Random : public std::minstd_rand {
  18  public:
  19   Random(unsigned int seed) : std::minstd_rand(seed) {}
  20   result_type operator()() { return this->std::minstd_rand::operator()(); }
  21   template <typename T>
  22   typename std::enable_if<std::is_integral<T>::value, T>::type Rand() {
  23     return static_cast<T>(this->operator()());
  24   }
  25   size_t RandBool() { return this->operator()() % 2; }
  26   size_t SkewTowardsLast(size_t n) {
  27     size_t T = this->operator()(n * n);
  28     size_t Res = static_cast<size_t>(sqrt(T));
  29     return Res;
  30   }
  31   template <typename T>
  32   typename std::enable_if<std::is_integral<T>::value, T>::type operator()(T n) {
  33     return n ? Rand<T>() % n : 0;
  34   }
  35   template <typename T>
  36   typename std::enable_if<std::is_integral<T>::value, T>::type
  37   operator()(T From, T To) {
  38     assert(From < To);
  39     auto RangeSize = static_cast<unsigned long long>(To) -
  40                      static_cast<unsigned long long>(From) + 1;
  41     return static_cast<T>(this->operator()(RangeSize) + From);
  42   }
  43 };
  44
  45 }  // namespace fuzzer
  46
  47 #endif  // LLVM_FUZZER_RANDOM_H