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//===-- RandomNumberGenerator.cpp - Implement RNG class -------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// This file implements deterministic random number generation (RNG).
// The current implementation is NOT cryptographically secure as it uses
// the C++11 <random> facilities.
#include "llvm/Support/RandomNumberGenerator.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#ifdef _WIN32
#include "llvm/Support/Windows/WindowsSupport.h"
#include "Unix/Unix.h"
using namespace llvm;
#define DEBUG_TYPE "rng"
static cl::opt<uint64_t> Seed("rng-seed", cl::value_desc("seed"), cl::Hidden,
cl::desc("Seed for the random number generator"),
RandomNumberGenerator::RandomNumberGenerator(StringRef Salt) {
LLVM_DEBUG(if (Seed == 0) dbgs()
<< "Warning! Using unseeded random number generator.\n");
// Combine seed and salts using std::seed_seq.
// Data: Seed-low, Seed-high, Salt
// Note: std::seed_seq can only store 32-bit values, even though we
// are using a 64-bit RNG. This isn't a problem since the Mersenne
// twister constructor copies these correctly into its initial state.
std::vector<uint32_t> Data;
Data.resize(2 + Salt.size());
Data[0] = Seed;
Data[1] = Seed >> 32;
llvm::copy(Salt, Data.begin() + 2);
std::seed_seq SeedSeq(Data.begin(), Data.end());
RandomNumberGenerator::result_type RandomNumberGenerator::operator()() {
return Generator();
// Get random vector of specified size
std::error_code llvm::getRandomBytes(void *Buffer, size_t Size) {
#ifdef _WIN32
if (CryptAcquireContext(&hProvider, 0, 0, PROV_RSA_FULL,
ScopedCryptContext ScopedHandle(hProvider);
if (CryptGenRandom(hProvider, Size, static_cast<BYTE *>(Buffer)))
return std::error_code();
return std::error_code(GetLastError(), std::system_category());
int Fd = open("/dev/urandom", O_RDONLY);
if (Fd != -1) {
std::error_code Ret;
ssize_t BytesRead = read(Fd, Buffer, Size);
if (BytesRead == -1)
Ret = std::error_code(errno, std::system_category());
else if (BytesRead != static_cast<ssize_t>(Size))
Ret = std::error_code(EIO, std::system_category());
if (close(Fd) == -1)
Ret = std::error_code(errno, std::system_category());
return Ret;
return std::error_code(errno, std::system_category());