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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <math.h>
#include "hexdecoct.h"
#include "log.h"
#include "memory-util.h"
#include "random-util.h"
#include "terminal-util.h"
#include "tests.h"
TEST(random_bytes) {
uint8_t buf[16] = {};
for (size_t i = 1; i < sizeof buf; i++) {
random_bytes(buf, i);
if (i + 1 < sizeof buf)
assert_se(buf[i] == 0);
hexdump(stdout, buf, i);
}
}
TEST(crypto_random_bytes) {
uint8_t buf[16] = {};
for (size_t i = 1; i < sizeof buf; i++) {
assert_se(crypto_random_bytes(buf, i) == 0);
if (i + 1 < sizeof buf)
assert_se(buf[i] == 0);
hexdump(stdout, buf, i);
}
}
#define TOTAL 100000
static void test_random_u64_range_one(unsigned mod) {
log_info("/* %s(%u) */", __func__, mod);
unsigned max = 0, count[mod];
zero(count);
for (unsigned i = 0; i < TOTAL; i++) {
uint64_t x;
x = random_u64_range(mod);
count[x]++;
max = MAX(max, count[x]);
}
/* Print histogram: vertical axis — value, horizontal axis — count.
*
* The expected value is always TOTAL/mod, because the distribution should be flat. The expected
* variance is TOTAL×p×(1-p), where p==1/mod, and standard deviation the root of the variance.
* Assert that the deviation from the expected value is less than 6 standard deviations.
*/
unsigned scale = 2 * max / (columns() < 20 ? 80 : columns() - 20);
double exp = (double) TOTAL / mod;
for (size_t i = 0; i < mod; i++) {
double dev = (count[i] - exp) / sqrt(exp * (mod > 1 ? mod - 1 : 1) / mod);
log_debug("%02zu: %5u (%+.3f)%*s",
i, count[i], dev,
(int) (count[i] / scale), "x");
assert_se(fabs(dev) < 6); /* 6 sigma is excessive, but this check should be enough to
* identify catastrophic failure while minimizing false
* positives. */
}
}
TEST(random_u64_range) {
for (unsigned mod = 1; mod < 29; mod++)
test_random_u64_range_one(mod);
}
DEFINE_TEST_MAIN(LOG_DEBUG);
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