LLVM  4.0.0
RandomNumberGenerator.cpp
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1 //===-- RandomNumberGenerator.cpp - Implement RNG class -------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements deterministic random number generation (RNG).
11 // The current implementation is NOT cryptographically secure as it uses
12 // the C++11 <random> facilities.
13 //
14 //===----------------------------------------------------------------------===//
15 
18 #include "llvm/Support/Debug.h"
20 #ifdef LLVM_ON_WIN32
21 #include "Windows/WindowsSupport.h"
22 #else
23 #include "Unix/Unix.h"
24 #endif
25 
26 using namespace llvm;
27 
28 #define DEBUG_TYPE "rng"
29 
30 // Tracking BUG: 19665
31 // http://llvm.org/bugs/show_bug.cgi?id=19665
32 //
33 // Do not change to cl::opt<uint64_t> since this silently breaks argument parsing.
35 Seed("rng-seed", cl::value_desc("seed"),
36  cl::desc("Seed for the random number generator"), cl::init(0));
37 
38 RandomNumberGenerator::RandomNumberGenerator(StringRef Salt) {
39  DEBUG(
40  if (Seed == 0)
41  dbgs() << "Warning! Using unseeded random number generator.\n"
42  );
43 
44  // Combine seed and salts using std::seed_seq.
45  // Data: Seed-low, Seed-high, Salt
46  // Note: std::seed_seq can only store 32-bit values, even though we
47  // are using a 64-bit RNG. This isn't a problem since the Mersenne
48  // twister constructor copies these correctly into its initial state.
49  std::vector<uint32_t> Data;
50  Data.resize(2 + Salt.size());
51  Data[0] = Seed;
52  Data[1] = Seed >> 32;
53 
54  std::copy(Salt.begin(), Salt.end(), Data.begin() + 2);
55 
56  std::seed_seq SeedSeq(Data.begin(), Data.end());
57  Generator.seed(SeedSeq);
58 }
59 
61  return Generator();
62 }
63 
64 // Get random vector of specified size
65 std::error_code llvm::getRandomBytes(void *Buffer, size_t Size) {
66 #ifdef LLVM_ON_WIN32
67  HCRYPTPROV hProvider;
68  if (CryptAcquireContext(&hProvider, 0, 0, PROV_RSA_FULL,
69  CRYPT_VERIFYCONTEXT | CRYPT_SILENT)) {
71  if (CryptGenRandom(hProvider, Size, static_cast<BYTE *>(Buffer)))
72  return std::error_code();
73  }
74  return std::error_code(GetLastError(), std::system_category());
75 #else
76  int Fd = open("/dev/urandom", O_RDONLY);
77  if (Fd != -1) {
78  std::error_code Ret;
79  ssize_t BytesRead = read(Fd, Buffer, Size);
80  if (BytesRead == -1)
81  Ret = std::error_code(errno, std::system_category());
82  else if (BytesRead != static_cast<ssize_t>(Size))
83  Ret = std::error_code(EIO, std::system_category());
84  if (close(Fd) == -1)
85  Ret = std::error_code(errno, std::system_category());
86 
87  return Ret;
88  }
89  return std::error_code(errno, std::system_category());
90 #endif
91 }
static cl::opt< unsigned long long > Seed("rng-seed", cl::value_desc("seed"), cl::desc("Seed for the random number generator"), cl::init(0))
value_type read(const void *memory)
Read a value of a particular endianness from memory.
Definition: Endian.h:48
LLVM_NODISCARD LLVM_ATTRIBUTE_ALWAYS_INLINE size_t size() const
size - Get the string size.
Definition: StringRef.h:135
iterator begin() const
Definition: StringRef.h:103
initializer< Ty > init(const Ty &Val)
Definition: CommandLine.h:395
std::error_code getRandomBytes(void *Buffer, size_t Size)
raw_ostream & dbgs()
dbgs() - This returns a reference to a raw_ostream for debugging messages.
Definition: Debug.cpp:132
generator_type::result_type result_type
result_type operator()()
Returns a random number in the range [0, Max).
iterator end() const
Definition: StringRef.h:105
#define DEBUG(X)
Definition: Debug.h:100
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:47