git.itanic.dy.fi Git - sdl-planets/blob - random.c

   1 #include <stdio.h>
   2 #include <sys/types.h>
   3 #include <sys/stat.h>
   4 #include <fcntl.h>
   5 #include <errno.h>
   6 #include <string.h>
   7 #include <unistd.h>
   8
   9 #include "random.h"
  10
  11 #define RAND_BUF_SIZE   1024
  12 #define RND_DEV         "/dev/urandom"
  13
  14 unsigned int get_random(void)
  15 {
  16         static int rndbuf[RAND_BUF_SIZE];
  17         static int index = RAND_BUF_SIZE;
  18         int fd, error, i = 0, ret;
  19
  20         if (index < RAND_BUF_SIZE)
  21                 return rndbuf[index++];
  22
  23         fd = open(RND_DEV, O_RDONLY);
  24         if (fd < 0) {
  25                 error = errno;
  26                 fprintf(stderr, "Error opening file %s: %s\n",
  27                         RND_DEV, strerror(error));
  28                 ret = error;
  29                 goto err;
  30         }
  31
  32         do {
  33                 ret = read(fd, rndbuf + i,
  34                           RAND_BUF_SIZE * (sizeof(rndbuf[0]) - i));
  35
  36                 if (ret <= 0) {
  37                         error = errno;
  38                         fprintf(stderr, "Error reading file %s: %s\n",
  39                                 RND_DEV, strerror(error));
  40                         ret = error;
  41                         goto err;
  42                 }
  43
  44                 i += ret;
  45         } while (i < RAND_BUF_SIZE * sizeof(rndbuf[0]));
  46         index = 0;
  47
  48         close(fd);
  49         return get_random();
  50
  51 err:
  52         close(fd);
  53         return ret;
  54 }
  55
  56 double get_random_double(void)
  57 {
  58         return get_random() / (double)((unsigned int)(-1));
  59 }