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	truerand.c - 9base - revived minimalist port of Plan 9 userland to Unix
	git clone git://git.suckless.org/9base
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	truerand.c (662B)
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	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); …
	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 }