Jan Janssen
f996072fe0
The casting here isn't pretty, but at least it makes it obvious what is happening instead of implicit and it allows enabling -Wformat-signedness.
80 lines
2.4 KiB
C
80 lines
2.4 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <math.h>
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#include "hexdecoct.h"
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#include "log.h"
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#include "memory-util.h"
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#include "random-util.h"
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#include "terminal-util.h"
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#include "tests.h"
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TEST(random_bytes) {
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uint8_t buf[16] = {};
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for (size_t i = 1; i < sizeof buf; i++) {
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random_bytes(buf, i);
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if (i + 1 < sizeof buf)
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assert_se(buf[i] == 0);
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hexdump(stdout, buf, i);
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}
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}
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TEST(crypto_random_bytes) {
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uint8_t buf[16] = {};
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for (size_t i = 1; i < sizeof buf; i++) {
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assert_se(crypto_random_bytes(buf, i) == 0);
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if (i + 1 < sizeof buf)
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assert_se(buf[i] == 0);
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hexdump(stdout, buf, i);
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}
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}
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#define TOTAL 100000
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static void test_random_u64_range_one(unsigned mod) {
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log_info("/* %s(%u) */", __func__, mod);
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unsigned max = 0, count[mod];
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zero(count);
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for (unsigned i = 0; i < TOTAL; i++) {
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uint64_t x;
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x = random_u64_range(mod);
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count[x]++;
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max = MAX(max, count[x]);
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}
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/* Print histogram: vertical axis — value, horizontal axis — count.
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*
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* The expected value is always TOTAL/mod, because the distribution should be flat. The expected
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* variance is TOTAL×p×(1-p), where p==1/mod, and standard deviation the root of the variance.
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* Assert that the deviation from the expected value is less than 6 standard deviations.
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*/
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unsigned scale = 2 * max / (columns() < 20 ? 80 : columns() - 20);
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double exp = (double) TOTAL / mod;
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for (size_t i = 0; i < mod; i++) {
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double dev = (count[i] - exp) / sqrt(exp * (mod > 1 ? mod - 1 : 1) / mod);
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log_debug("%02zu: %5u (%+.3f)%*s",
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i, count[i], dev,
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(int) (count[i] / scale), "x");
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assert_se(fabs(dev) < 6); /* 6 sigma is excessive, but this check should be enough to
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* identify catastrophic failure while minimizing false
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* positives. */
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}
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}
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TEST(random_u64_range) {
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for (unsigned mod = 1; mod < 29; mod++)
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test_random_u64_range_one(mod);
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}
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DEFINE_TEST_MAIN(LOG_DEBUG);
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