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 }