Initial implementation of a record-level bitcode fuzzer.

include/llvm/Bitcode/NaCl/NaClRandNumGen.h

+//===- NaClRandNumGen.h - random number generator ---------------*- 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 a random number generator API for 64-bit unsigned
+// values, and a corresponding default implementation.
+//
+// *** WARNING *** One should assume that random number generators are not
+// thread safe.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_BITCODE_NACL_NACLRANDNUMGEN_H
+#define LLVM_BITCODE_NACL_NACLRANDNUMGEN_H
+
+#include "llvm/ADT/StringRef.h"
+#include <random>
+
+namespace naclfuzz {
+
+/// Defines API for a random number generator to use with fuzzing.
+class RandomNumberGenerator {
+  RandomNumberGenerator(const RandomNumberGenerator&) = delete;
+  void operator=(const RandomNumberGenerator&) = delete;
+public:
+  virtual ~RandomNumberGenerator();
+  /// Returns a random number.
+  virtual uint64_t operator()() = 0;
+  // Returns a random value in [0..Limit)
+  uint64_t chooseInRange(uint64_t Limit) {
+    return (*this)() % Limit;
+  }
+protected:
+  RandomNumberGenerator() {}
+};
+
+/// Defines a random number generator based on C++ generator std::mt19937_64.
+class DefaultRandomNumberGenerator : public RandomNumberGenerator {
+  DefaultRandomNumberGenerator(const DefaultRandomNumberGenerator&) = delete;
+  void operator=(const DefaultRandomNumberGenerator&) = delete;
+public:
+  DefaultRandomNumberGenerator(llvm::StringRef Seed);
+  uint64_t operator()() final;
+  ~DefaultRandomNumberGenerator() final {}
+  // Resets random number seed by salting the seed of constructor with Salt.
+  void saltSeed(uint64_t Salt);
+private:
+  // 64-bit Mersenne Twister by Matsumoto and Nishimura, 2000
+  // http://en.cppreference.com/w/cpp/numeric/random/mersenne_twister_engine
+  // This RNG is deterministically portable across C++11
+  // implementations.
+  std::mt19937_64 Generator;
+  // Seed for the random number generator.
+  std::string Seed;
+};
+
+} // end of namespace naclfuzz
+
+#endif // LLVM_BITCODE_NACL_NACLRANDNUMGEN_H