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

   1 // random -*- C++ -*-
   2
   3 // Copyright (C) 2012 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 #include <random>
  26
  27 #if defined __i386__ || defined __x86_64__
  28 # include <cpuid.h>
  29 #endif
  30
  31
  32 namespace std _GLIBCXX_VISIBILITY(default)
  33 {
  34
  35   namespace
  36   {
  37     static unsigned long
  38     _M_strtoul(const std::string& __str)
  39     {
  40       unsigned long __ret = 5489UL;
  41       if (__str != "mt19937")
  42         {
  43           const char* __nptr = __str.c_str();
  44           char* __endptr;
  45           __ret = std::strtoul(__nptr, &__endptr, 0);
  46           if (*__nptr == '\0' || *__endptr != '\0')
  47             std::__throw_runtime_error(__N("random_device::_M_strtoul"
  48                                            "(const std::string&)"));
  49         }
  50       return __ret;
  51     }
  52
  53 #if defined __i386__ || defined __x86_64__
  54     unsigned int
  55     __attribute__ ((target("rdrnd")))
  56     __x86_rdrand(void)
  57     {
  58       unsigned int retries = 100;
  59       unsigned int val;
  60
  61       while (__builtin_ia32_rdrand32_step(&val) == 0)
  62         if (--retries == 0)
  63           std::__throw_runtime_error(__N("random_device::__x86_rdrand(void)"));
  64
  65       return val;
  66     }
  67 #endif
  68   }
  69
  70
  71   void
  72   random_device::_M_init(const std::string& token)
  73   {
  74     const char *fname = token.c_str();
  75
  76     if (token == "default")
  77       {
  78 #if defined __i386__ || defined __x86_64__
  79         unsigned int eax, ebx, ecx, edx;
  80         __cpuid(0, eax, ebx, ecx, edx);
  81         // Check for "GenuineIntel"
  82         if (ebx == 0x756e6547 && ecx == 0x6c65746e && edx == 0x49656e69)
  83           {
  84             __cpuid(1, eax, ebx, ecx, edx);
  85             if (ecx & bit_RDRND)
  86               {
  87                 _M_file = nullptr;
  88                 return;
  89               }
  90           }
  91 #endif
  92
  93         fname = "/dev/urandom";
  94       }
  95     else if (token != "/dev/urandom" && token != "/dev/random")
  96     fail:
  97       std::__throw_runtime_error(__N("random_device::"
  98                                      "random_device(const std::string&)"));
  99
 100     _M_file = std::fopen(fname, "rb");
 101     if (! _M_file)
 102       goto fail;
 103   }
 104
 105   void
 106   random_device::_M_init_pretr1(const std::string& token)
 107
 108   {
 109     _M_mt.seed(_M_strtoul(token));
 110   }
 111
 112   void
 113   random_device::_M_fini()
 114   {
 115     if (_M_file)
 116       std::fclose(_M_file);
 117   }
 118
 119   random_device::result_type
 120   random_device::_M_getval()
 121   {
 122 #if (defined __i386__ || defined __x86_64__)
 123     if (! _M_file)
 124       return __x86_rdrand();
 125 #endif
 126
 127     result_type __ret;
 128     std::fread(reinterpret_cast<void*>(&__ret), sizeof(result_type),
 129                1, _M_file);
 130     return __ret;
 131   }
 132
 133   random_device::result_type
 134   random_device::_M_getval_pretr1()
 135   {
 136     return _M_mt();
 137   }
 138
 139   template class mersenne_twister_engine<
 140     uint_fast32_t,
 141     32, 624, 397, 31,
 142     0x9908b0dfUL, 11,
 143     0xffffffffUL, 7,
 144     0x9d2c5680UL, 15,
 145     0xefc60000UL, 18, 1812433253UL>;
 146
 147 }