truerand.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 }