#include <u.h> #include <libc.h> ulong truerand(void) { int i, n; uchar buf[sizeof(ulong)]; static int randfd = -1; static char *randfile; if(randfd < 0){ randfd = open(randfile="/dev/random", OREAD); /* OpenBSD lets you open /dev/random but not read it! */ if(randfd < 0 || read(randfd, buf, 1) != 1) randfd = open(randfile="/dev/srandom", OREAD); /* OpenBSD */ if(randfd < 0) sysfatal("can't open %s: %r", randfile); fcntl(randfd, F_SETFD, FD_CLOEXEC); } for(i=0; i<sizeof(buf); i += n) if((n = readn(randfd, buf+i, sizeof(buf)-i)) < 0) sysfatal("can't read %s: %r", randfile); return *((ulong*)buf); }