Line data    Source code

       1              : /** \file randomSeed.hpp
       2              :  * \author Jared R. Males
       3              :  * \brief Defines a random number seed generator
       4              :  * \ingroup gen_math_files
       5              :  *
       6              :  */
       7              : 
       8              : //***********************************************************************//
       9              : // Copyright 2015, 2016, 2017, 2020 Jared R. Males (jaredmales@gmail.com)
      10              : //
      11              : // This file is part of mxlib.
      12              : //
      13              : // mxlib is free software: you can redistribute it and/or modify
      14              : // it under the terms of the GNU General Public License as published by
      15              : // the Free Software Foundation, either version 3 of the License, or
      16              : // (at your option) any later version.
      17              : //
      18              : // mxlib is distributed in the hope that it will be useful,
      19              : // but WITHOUT ANY WARRANTY; without even the implied warranty of
      20              : // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      21              : // GNU General Public License for more details.
      22              : //
      23              : // You should have received a copy of the GNU General Public License
      24              : // along with mxlib.  If not, see <http://www.gnu.org/licenses/>.
      25              : //***********************************************************************//
      26              : 
      27              : #ifndef mx_math_randomSeed_hpp
      28              : #define mx_math_randomSeed_hpp
      29              : 
      30              : #include <unistd.h>
      31              : #include <fcntl.h>
      32              : 
      33              : #include "../mxlib.hpp"
      34              : 
      35              : namespace mx
      36              : {
      37              : namespace math
      38              : {
      39              : 
      40              : /// Get a value to use as a random seed
      41              : /** On Linux systems, uses /dev/urandom to populate the value with sizeof(intT) bytes.
      42              :  * Otherwise, uses time(0) to get time since the epoch.
      43              :  *
      44              :  * \returns 0 on success.
      45              :  * \returns -1 on error.
      46              :  *
      47              :  * \tparam intT is the integer type of seeval.
      48              :  *
      49              :  * \ingroup random
      50              :  *
      51              :  */
      52              : template <typename intT>
      53            9 : int randomSeed( intT &seedval /**< [out] will be populated with the seed.*/ )
      54              : {
      55              : #ifdef __linux__
      56              : 
      57              :     int fd;
      58              : 
      59            9 :     errno = 0;
      60            9 :     fd = open( "/dev/urandom", O_RDONLY );
      61              : 
      62            9 :     if( fd < 0 )
      63              :     {
      64            0 :         internal::mxlib_error_report(errno2error_t(errno), "error opening /dev/urandom" );
      65              : 
      66            0 :         return -1;
      67              :     }
      68              : 
      69            9 :     seedval = 0;
      70              : 
      71            9 :     errno = 0;
      72            9 :     int rv = ::read( fd, &seedval, sizeof( intT ) );
      73              : 
      74            9 :     if( rv < 0 )
      75              :     {
      76            0 :         internal::mxlib_error_report(errno2error_t(errno), "Error on read from /dev/urandom." );
      77            0 :         close( fd );
      78            0 :         return -1;
      79              :     }
      80              : 
      81            9 :     close( fd );
      82              : 
      83            9 :     int sz = sizeof( intT );
      84              : 
      85            9 :     if( rv < sz )
      86              :     {
      87            0 :         internal::mxlib_error_report(error_t::filererr, "Read from /dev/urandom did not return enough bytes" );
      88              : 
      89            0 :         return -1;
      90              :     }
      91              : 
      92            9 :     return 0;
      93              : 
      94              : #endif //__linux__
      95              : 
      96              :     seedval = time( 0 );
      97              : 
      98              :     return 0;
      99              : }
     100              : 
     101              : } // namespace math
     102              : } // namespace mx
     103              : 
     104              : #endif // mx_math_randomSeed_hpp