#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <sys/rnd.h>

#define _PATH_URANDOM	"/dev/urandom"

int
main(void)
{
  rndpoolstat_t rs;
  int fd, result;
  long gCriticalEntropyThreshold, gMaxEntropy;
  u_int32_t entropy;

  fd = open(_PATH_URANDOM, O_RDONLY, 0644);
  if (fd < 0) {
    fprintf(stderr, "Could not open %s: %s\n", _PATH_URANDOM, strerror(errno));
    exit(1);
  }

  if (ioctl(fd, RNDGETPOOLSTAT, &rs) < 0) {
    fprintf(stderr, "RNDGETPOOLSTAT failed: %s\n", strerror(errno));
    exit(1);
  }

  result = ioctl( fd, RNDGETENTCNT, &entropy );
  if( result == -1 ) {
    fprintf(stderr, "Call to ioctl() failed.  Exiting.\n");
    exit(1);
  }


  close(fd);

  gMaxEntropy = rs.maxentropy;
  gCriticalEntropyThreshold = rs.threshold;
  if (gCriticalEntropyThreshold < 2 * SHA1_DIGEST_LENGTH) {
    gCriticalEntropyThreshold = 2 * SHA1_DIGEST_LENGTH;
  }

  printf("Entropy threshold: %ld; available: %ld\n", gCriticalEntropyThreshold, (long)entropy);
  return 0;
}