RandomNumberGenerator.cpp revision cd81d94322a39503e4a3e87b6ee03d4fcb3465fb
125b3c049e70834cf33790a28643ab058b507b35cBen Cheng//===-- RandomNumberGenerator.cpp - Implement RNG class -------------------===// 225b3c049e70834cf33790a28643ab058b507b35cBen Cheng// 325b3c049e70834cf33790a28643ab058b507b35cBen Cheng// The LLVM Compiler Infrastructure 425b3c049e70834cf33790a28643ab058b507b35cBen Cheng// 525b3c049e70834cf33790a28643ab058b507b35cBen Cheng// This file is distributed under the University of Illinois Open Source 625b3c049e70834cf33790a28643ab058b507b35cBen Cheng// License. See LICENSE.TXT for details. 725b3c049e70834cf33790a28643ab058b507b35cBen Cheng// 825b3c049e70834cf33790a28643ab058b507b35cBen Cheng//===----------------------------------------------------------------------===// 925b3c049e70834cf33790a28643ab058b507b35cBen Cheng// 1025b3c049e70834cf33790a28643ab058b507b35cBen Cheng// This file implements random number generation (RNG). 1125b3c049e70834cf33790a28643ab058b507b35cBen Cheng// The current implementation is NOT cryptographically secure as it uses 1225b3c049e70834cf33790a28643ab058b507b35cBen Cheng// the C++11 <random> facilities. 1325b3c049e70834cf33790a28643ab058b507b35cBen Cheng// 1425b3c049e70834cf33790a28643ab058b507b35cBen Cheng//===----------------------------------------------------------------------===// 1525b3c049e70834cf33790a28643ab058b507b35cBen Cheng 1625b3c049e70834cf33790a28643ab058b507b35cBen Cheng#define DEBUG_TYPE "rng" 1725b3c049e70834cf33790a28643ab058b507b35cBen Cheng#include "llvm/Support/RandomNumberGenerator.h" 1825b3c049e70834cf33790a28643ab058b507b35cBen Cheng#include "llvm/Support/CommandLine.h" 1925b3c049e70834cf33790a28643ab058b507b35cBen Cheng#include "llvm/Support/Debug.h" 2025b3c049e70834cf33790a28643ab058b507b35cBen Cheng 2125b3c049e70834cf33790a28643ab058b507b35cBen Chengusing namespace llvm; 2225b3c049e70834cf33790a28643ab058b507b35cBen Cheng 2325b3c049e70834cf33790a28643ab058b507b35cBen Cheng// Tracking BUG: 19665 2425b3c049e70834cf33790a28643ab058b507b35cBen Cheng// http://llvm.org/bugs/show_bug.cgi?id=19665 2525b3c049e70834cf33790a28643ab058b507b35cBen Cheng// 2625b3c049e70834cf33790a28643ab058b507b35cBen Cheng// Do not change to cl::opt<uint64_t> since this silently breaks argument parsing. 2725b3c049e70834cf33790a28643ab058b507b35cBen Chengstatic cl::opt<unsigned long long> 2825b3c049e70834cf33790a28643ab058b507b35cBen ChengSeed("rng-seed", cl::value_desc("seed"), 2925b3c049e70834cf33790a28643ab058b507b35cBen Cheng cl::desc("Seed for the random number generator"), cl::init(0)); 3025b3c049e70834cf33790a28643ab058b507b35cBen Cheng 3125b3c049e70834cf33790a28643ab058b507b35cBen ChengRandomNumberGenerator::RandomNumberGenerator(StringRef Salt) { 3225b3c049e70834cf33790a28643ab058b507b35cBen Cheng DEBUG( 3325b3c049e70834cf33790a28643ab058b507b35cBen Cheng if (Seed == 0) 3425b3c049e70834cf33790a28643ab058b507b35cBen Cheng errs() << "Warning! Using unseeded random number generator.\n" 3525b3c049e70834cf33790a28643ab058b507b35cBen Cheng ); 3625b3c049e70834cf33790a28643ab058b507b35cBen Cheng 37 // Combine seed and salt using std::seed_seq. 38 // Entropy: Seed-low, Seed-high, Salt... 39 std::vector<uint32_t> Data; 40 Data.reserve(2 + Salt.size()/4 + 1); 41 Data.push_back(Seed); 42 Data.push_back(Seed >> 32); 43 44 uint32_t Pack = 0; 45 for (size_t I = 0; I < Salt.size(); ++I) { 46 Pack <<= 8; 47 Pack += Salt[I]; 48 49 if (I%4 == 3) 50 Data.push_back(Pack); 51 } 52 Data.push_back(Pack); 53 54 std::seed_seq SeedSeq(Data.begin(), Data.end()); 55 Generator.seed(SeedSeq); 56} 57 58uint64_t RandomNumberGenerator::next(uint64_t Max) { 59 std::uniform_int_distribution<uint64_t> distribution(0, Max - 1); 60 return distribution(Generator); 61} 62