libstdc++-v3/src/c++11/random.cc

   1 // random -*- C++ -*-
   2
   3 // Copyright (C) 2012-2017 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 #define _GLIBCXX_USE_CXX11_ABI 1
  26 #include <random>
  27
  28 #ifdef  _GLIBCXX_USE_C99_STDINT_TR1
  29
  30 #if defined __i386__ || defined __x86_64__
  31 # include <cpuid.h>
  32 #endif
  33
  34 #include <cerrno>
  35 #include <cstdio>
  36
  37 #ifdef _GLIBCXX_HAVE_UNISTD_H
  38 # include <unistd.h>
  39 #endif
  40
  41 #ifdef _GLIBCXX_HAVE_SYS_IOCTL_H
  42 # include <sys/ioctl.h>
  43 #endif
  44
  45 #ifdef _GLIBCXX_HAVE_LINUX_RANDOM_H
  46 # include <linux/random.h>
  47 #endif
  48
  49 namespace std _GLIBCXX_VISIBILITY(default)
  50 {
  51   namespace
  52   {
  53     static unsigned long
  54     _M_strtoul(const std::string& __str)
  55     {
  56       unsigned long __ret = 5489UL;
  57       if (__str != "mt19937")
  58         {
  59           const char* __nptr = __str.c_str();
  60           char* __endptr;
  61           __ret = std::strtoul(__nptr, &__endptr, 0);
  62           if (*__nptr == '\0' || *__endptr != '\0')
  63             std::__throw_runtime_error(__N("random_device::_M_strtoul"
  64                                            "(const std::string&)"));
  65         }
  66       return __ret;
  67     }
  68
  69 #if (defined __i386__ || defined __x86_64__) && defined _GLIBCXX_X86_RDRAND
  70     unsigned int
  71     __attribute__ ((target("rdrnd")))
  72     __x86_rdrand(void)
  73     {
  74       unsigned int retries = 100;
  75       unsigned int val;
  76
  77       while (__builtin_ia32_rdrand32_step(&val) == 0)
  78         if (--retries == 0)
  79           std::__throw_runtime_error(__N("random_device::__x86_rdrand(void)"));
  80
  81       return val;
  82     }
  83 #endif
  84   }
  85
  86   void
  87   random_device::_M_init(const std::string& token)
  88   {
  89     const char *fname = token.c_str();
  90
  91     if (token == "default")
  92       {
  93 #if (defined __i386__ || defined __x86_64__) && defined _GLIBCXX_X86_RDRAND
  94         unsigned int eax, ebx, ecx, edx;
  95         // Check availability of cpuid and, for now at least, also the
  96         // CPU signature for Intel's
  97         if (__get_cpuid_max(0, &ebx) > 0 && ebx == signature_INTEL_ebx)
  98           {
  99             __cpuid(1, eax, ebx, ecx, edx);
 100             if (ecx & bit_RDRND)
 101               {
 102                 _M_file = nullptr;
 103                 return;
 104               }
 105           }
 106 #endif
 107
 108         fname = "/dev/urandom";
 109       }
 110     else if (token != "/dev/urandom" && token != "/dev/random")
 111     fail:
 112       std::__throw_runtime_error(__N("random_device::"
 113                                      "random_device(const std::string&)"));
 114
 115     _M_file = static_cast<void*>(std::fopen(fname, "rb"));
 116     if (!_M_file)
 117       goto fail;
 118   }
 119
 120   void
 121   random_device::_M_init_pretr1(const std::string& token)
 122   {
 123     _M_mt.seed(_M_strtoul(token));
 124   }
 125
 126   void
 127   random_device::_M_fini()
 128   {
 129     if (_M_file)
 130       std::fclose(static_cast<FILE*>(_M_file));
 131   }
 132
 133   random_device::result_type
 134   random_device::_M_getval()
 135   {
 136 #if (defined __i386__ || defined __x86_64__) && defined _GLIBCXX_X86_RDRAND
 137     if (!_M_file)
 138       return __x86_rdrand();
 139 #endif
 140
 141     result_type __ret;
 142     void* p = &__ret;
 143     size_t n = sizeof(result_type);
 144 #ifdef _GLIBCXX_HAVE_UNISTD_H
 145     do
 146       {
 147         const int e = read(fileno(static_cast<FILE*>(_M_file)), p, n);
 148         if (e > 0)
 149           {
 150             n -= e;
 151             p = static_cast<char*>(p) + e;
 152           }
 153         else if (e != -1 || errno != EINTR)
 154           __throw_runtime_error(__N("random_device could not be read"));
 155       }
 156     while (n > 0);
 157 #else
 158     const size_t e = std::fread(p, n, 1, static_cast<FILE*>(_M_file));
 159     if (e != 1)
 160       __throw_runtime_error(__N("random_device could not be read"));
 161 #endif
 162
 163     return __ret;
 164   }
 165
 166   random_device::result_type
 167   random_device::_M_getval_pretr1()
 168   {
 169     return _M_mt();
 170   }
 171
 172   double
 173   random_device::_M_getentropy() const noexcept
 174   {
 175 #if defined _GLIBCXX_HAVE_SYS_IOCTL_H && defined RNDGETENTCNT
 176     if (!_M_file)
 177       return 0.0;
 178
 179     const int fd = fileno(static_cast<FILE*>(_M_file));
 180     if (fd < 0)
 181       return 0.0;
 182
 183     int ent;
 184     if (ioctl(fd, RNDGETENTCNT, &ent) < 0)
 185       return 0.0;
 186
 187     if (ent < 0)
 188       return 0.0;
 189
 190     const int max = sizeof(result_type) * __CHAR_BIT__;
 191     if (ent > max)
 192       ent = max;
 193
 194     return static_cast<double>(ent);
 195 #else
 196     return 0.0;
 197 #endif
 198   }
 199
 200   template class mersenne_twister_engine<
 201     uint_fast32_t,
 202     32, 624, 397, 31,
 203     0x9908b0dfUL, 11,
 204     0xffffffffUL, 7,
 205     0x9d2c5680UL, 15,
 206     0xefc60000UL, 18, 1812433253UL>;
 207 }
 208 #endif