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/* See LICENSE file for copyright and license details. */
#include "internals.h"
#include <fcntl.h>
#include <unistd.h>
#ifndef FAST_RANDOM_PATHNAME
# define FAST_RANDOM_PATHNAME "/dev/urandom"
#endif
#ifndef SECURE_RANDOM_PATHNAME
# define SECURE_RANDOM_PATHNAME "/dev/random"
#endif
static void
zrand_get_random_bits(z_t r, size_t bits, int fd)
{
size_t read_total = 0, n, chars = CEILING_BITS_TO_CHARS(bits);
ssize_t read_just;
zahl_char_t mask = 1;
char *buf;
ENSURE_SIZE(r, chars);
buf = (char *)(r->chars);
for (n = chars * sizeof(zahl_char_t); n;) {
read_just = read(fd, buf + read_total, n);
if (read_just < 0)
FAILURE(errno);
read_total += (size_t)read_just;
n -= (size_t)read_just;
}
bits = BITS_IN_LAST_CHAR(bits);
mask <<= bits;
mask -= 1;
r->chars[chars - 1] &= mask;
for (n = chars; n--;) {
if (r->chars[n]) {
r->used = n + 1;
SET_SIGNUM(r, 1);
return;
}
}
SET_SIGNUM(r, 0);
}
void
zrand(z_t r, enum zranddev dev, enum zranddist dist, z_t n)
{
const char *pathname = 0;
size_t bits;
int fd;
switch (dev) {
case FAST_RANDOM:
pathname = FAST_RANDOM_PATHNAME;
break;
case SECURE_RANDOM:
pathname = SECURE_RANDOM_PATHNAME;
break;
default:
abort();
}
if (zzero(n)) {
SET_SIGNUM(r, 0);
return;
}
fd = open(pathname, O_RDONLY);
if (fd < 0)
FAILURE(errno);
switch (dist) {
case QUASIUNIFORM:
if (zsignum(n) < 0)
FAILURE(EDOM); /* n must be non-negative. */
bits = zbits(n);
zrand_get_random_bits(r, bits, fd);
zadd(r, r, libzahl_const_1);
zmul(r, r, n);
zrsh(r, r, bits);
break;
case UNIFORM:
if (zsignum(n) < 0)
FAILURE(EDOM); /* n must be non-negative. */
bits = zbits(n);
do
zrand_get_random_bits(r, bits, fd);
while (zcmpmag(r, n) > 0);
break;
default:
abort();
}
close(fd);
}
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