OW_RandomNumber.cpp

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#include "OW_config.h"
#include "OW_RandomNumber.hpp"
#include "OW_Assertion.hpp"
#include "OW_ThreadOnce.hpp"
#include "OW_Mutex.hpp"
#include "OW_MutexLock.hpp"
#include <fstream>
#include <sys/types.h>

#ifdef OW_HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef OW_HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#include <stdlib.h>
#include <time.h>

namespace OW_NAMESPACE
{

namespace
{
OnceFlag guard;
unsigned int seed = 0;
}

RandomNumber::RandomNumber(Int32 lowVal, Int32 highVal)
: m_lowVal(lowVal), m_highVal(highVal)
{
   if (lowVal > highVal)
   {
      m_lowVal = highVal;
      m_highVal = lowVal;
   }
   callOnce(guard, &initRandomness);
}
   
void
RandomNumber::initRandomness()
{
#ifdef OW_WIN32
   time_t timeval = ::time(NULL);
   seed = timeval;
#else
   // use the time as part of the seed
   struct timeval tv;
   gettimeofday(&tv, 0);
   // try to get something from the kernel
   std::ifstream infile("/dev/urandom", std::ios::in);
   if (!infile)
   {
      infile.open("/dev/random", std::ios::in);
   }
   // don't initialize this, we may get random stack
   // junk in case infile isn't usable.
   unsigned int dev_rand_input;
   if (infile)
   {
      infile.read(reinterpret_cast<char*>(&dev_rand_input), sizeof(dev_rand_input));
      infile.close();
   }
   // Build the seed. Take into account our pid and uid.
   seed = dev_rand_input ^ (getpid() << 16) ^ getuid() ^ tv.tv_sec ^ tv.tv_usec;
#endif
#ifdef OW_HAVE_SRANDOM
   srandom(seed);
#else
   srand(seed);
#endif
}

void
RandomNumber::saveRandomState()
{
   // Do nothing. This function is so that RandomNumber has the same interface as CryptographicRandomNumber
}

namespace
{
Mutex g_guard;
}
Int32
RandomNumber::getNextNumber()
{
   MutexLock lock(g_guard);
#ifdef OW_HAVE_RANDOM
   return m_lowVal + (random() % (m_highVal - m_lowVal + 1));
#else
   return m_lowVal + (rand() % (m_highVal - m_lowVal + 1));
#endif
}

} // end namespace OW_NAMESPACE

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