ttruerand.c - plan9port - [fork] Plan 9 from user space
  HTML git clone git://src.adamsgaard.dk/plan9port
   DIR Log
   DIR Files
   DIR Refs
   DIR README
   DIR LICENSE
       ---
       ttruerand.c (662B)
       ---
            1 #include <u.h>
            2 #include <libc.h>
            3 
            4 ulong
            5 truerand(void)
            6 {
            7         int i, n;
            8         uchar buf[sizeof(ulong)];
            9         ulong x;
           10         static int randfd = -1;
           11         static char *randfile;
           12 
           13         if(randfd < 0){
           14                 randfd = open(randfile="/dev/random", OREAD);
           15                 /* OpenBSD lets you open /dev/random but not read it! */
           16                 if(randfd < 0 || read(randfd, buf, 1) != 1)
           17                         randfd = open(randfile="/dev/srandom", OREAD);        /* OpenBSD */
           18                 if(randfd < 0)
           19                         sysfatal("can't open %s: %r", randfile);
           20                 fcntl(randfd, F_SETFD, FD_CLOEXEC);
           21         }
           22         for(i=0; i<sizeof(buf); i += n)
           23                 if((n = readn(randfd, buf+i, sizeof(buf)-i)) < 0)
           24                         sysfatal("can't read %s: %r", randfile);
           25         memmove(&x, buf, sizeof x);
           26         return x;
           27 }