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chromium / chromium / src / f3b599b9922b753585ed5bc6be9fe40dbea60ad0 / . / base / rand_util_unittest.cc
blob: 11a118a944b057c2c0ac60cec3b0d58fe1b2d993 [file] [log] [blame]
abarth@chromium.org29548d82011-04-29 21:03:54[diff] [blame]1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
mark@chromium.org05f9b682008-09-29 22:18:01[diff] [blame]2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "base/rand_util.h"
6
avi9b6f42932015-12-26 22:15:14[diff] [blame]7#include <stddef.h>
8#include <stdint.h>
9
dilmah@chromium.org0173b962011-08-24 19:58:36[diff] [blame]10#include <algorithm>
mark@chromium.org05f9b682008-09-29 22:18:01[diff] [blame]11#include <limits>
dcheng093de9b2016-04-04 21:25:51[diff] [blame]12#include <memory>
mark@chromium.org05f9b682008-09-29 22:18:01[diff] [blame]13
dalecurtis@chromium.orgc910c5a2014-01-23 02:14:28[diff] [blame]14#include "base/logging.h"
dalecurtis@chromium.orgc910c5a2014-01-23 02:14:28[diff] [blame]15#include "base/time/time.h"
mark@chromium.org05f9b682008-09-29 22:18:01[diff] [blame]16#include "testing/gtest/include/gtest/gtest.h"
17
18namespace {
19
20const int kIntMin = std::numeric_limits<int>::min();
21const int kIntMax = std::numeric_limits<int>::max();
22
23} // namespace
24
Nico Weber0a3852a72015-10-29 20:42:58[diff] [blame]25TEST(RandUtilTest, RandInt) {
mark@chromium.org05f9b682008-09-29 22:18:01[diff] [blame]26 EXPECT_EQ(base::RandInt(0, 0), 0);
27 EXPECT_EQ(base::RandInt(kIntMin, kIntMin), kIntMin);
28 EXPECT_EQ(base::RandInt(kIntMax, kIntMax), kIntMax);
Nico Weber0a3852a72015-10-29 20:42:58[diff] [blame]29
30 // Check that the DCHECKS in RandInt() don't fire due to internal overflow.
31 // There was a 50% chance of that happening, so calling it 40 times means
32 // the chances of this passing by accident are tiny (9e-13).
33 for (int i = 0; i < 40; ++i)
34 base::RandInt(kIntMin, kIntMax);
mark@chromium.org05f9b682008-09-29 22:18:01[diff] [blame]35}
mark@chromium.org94a0f312008-09-30 14:26:33[diff] [blame]36
37TEST(RandUtilTest, RandDouble) {
abarth@chromium.org29548d82011-04-29 21:03:54[diff] [blame]38 // Force 64-bit precision, making sure we're not in a 80-bit FPU register.
39 volatile double number = base::RandDouble();
40 EXPECT_GT(1.0, number);
41 EXPECT_LE(0.0, number);
42}
43
qsr@google.com51a01812011-05-05 08:46:11[diff] [blame]44TEST(RandUtilTest, RandBytes) {
dilmah@chromium.org0173b962011-08-24 19:58:36[diff] [blame]45 const size_t buffer_size = 50;
qsr@google.com51a01812011-05-05 08:46:11[diff] [blame]46 char buffer[buffer_size];
47 memset(buffer, 0, buffer_size);
48 base::RandBytes(buffer, buffer_size);
dilmah@chromium.org0173b962011-08-24 19:58:36[diff] [blame]49 std::sort(buffer, buffer + buffer_size);
50 // Probability of occurrence of less than 25 unique bytes in 50 random bytes
51 // is below 10^-25.
52 EXPECT_GT(std::unique(buffer, buffer + buffer_size) - buffer, 25);
qsr@google.com51a01812011-05-05 08:46:11[diff] [blame]53}
54
Sergey Ulanovfdc62f8e2017-08-01 19:51:00[diff] [blame]55// Verify that calling base::RandBytes with an empty buffer doesn't fail.
56TEST(RandUtilTest, RandBytes0) {
57 base::RandBytes(nullptr, 0);
58}
59
abarth@chromium.org29548d82011-04-29 21:03:54[diff] [blame]60TEST(RandUtilTest, RandBytesAsString) {
pkasting@chromium.orgfdce4782011-11-29 20:06:18[diff] [blame]61 std::string random_string = base::RandBytesAsString(1);
62 EXPECT_EQ(1U, random_string.size());
abarth@chromium.org29548d82011-04-29 21:03:54[diff] [blame]63 random_string = base::RandBytesAsString(145);
64 EXPECT_EQ(145U, random_string.size());
65 char accumulator = 0;
66 for (size_t i = 0; i < random_string.size(); ++i)
67 accumulator |= random_string[i];
68 // In theory this test can fail, but it won't before the universe dies of
69 // heat death.
70 EXPECT_NE(0, accumulator);
mark@chromium.org94a0f312008-09-30 14:26:33[diff] [blame]71}
isherman@chromium.orga74dcae2010-08-30 21:07:05[diff] [blame]72
73// Make sure that it is still appropriate to use RandGenerator in conjunction
74// with std::random_shuffle().
75TEST(RandUtilTest, RandGeneratorForRandomShuffle) {
76 EXPECT_EQ(base::RandGenerator(1), 0U);
77 EXPECT_LE(std::numeric_limits<ptrdiff_t>::max(),
avi9b6f42932015-12-26 22:15:14[diff] [blame]78 std::numeric_limits<int64_t>::max());
isherman@chromium.orga74dcae2010-08-30 21:07:05[diff] [blame]79}
joi@chromium.orgaf2e192b2011-05-30 17:39:09[diff] [blame]80
81TEST(RandUtilTest, RandGeneratorIsUniform) {
82 // Verify that RandGenerator has a uniform distribution. This is a
83 // regression test that consistently failed when RandGenerator was
84 // implemented this way:
85 //
86 // return base::RandUint64() % max;
87 //
88 // A degenerate case for such an implementation is e.g. a top of
89 // range that is 2/3rds of the way to MAX_UINT64, in which case the
90 // bottom half of the range would be twice as likely to occur as the
91 // top half. A bit of calculus care of jar@ shows that the largest
92 // measurable delta is when the top of the range is 3/4ths of the
93 // way, so that's what we use in the test.
avi9b6f42932015-12-26 22:15:14[diff] [blame]94 const uint64_t kTopOfRange =
95 (std::numeric_limits<uint64_t>::max() / 4ULL) * 3ULL;
96 const uint64_t kExpectedAverage = kTopOfRange / 2ULL;
97 const uint64_t kAllowedVariance = kExpectedAverage / 50ULL; // +/- 2%
joi@chromium.orgaf2e192b2011-05-30 17:39:09[diff] [blame]98 const int kMinAttempts = 1000;
99 const int kMaxAttempts = 1000000;
100
101 double cumulative_average = 0.0;
102 int count = 0;
103 while (count < kMaxAttempts) {
avi9b6f42932015-12-26 22:15:14[diff] [blame]104 uint64_t value = base::RandGenerator(kTopOfRange);
joi@chromium.orgaf2e192b2011-05-30 17:39:09[diff] [blame]105 cumulative_average = (count * cumulative_average + value) / (count + 1);
106
107 // Don't quit too quickly for things to start converging, or we may have
108 // a false positive.
109 if (count > kMinAttempts &&
110 kExpectedAverage - kAllowedVariance < cumulative_average &&
111 cumulative_average < kExpectedAverage + kAllowedVariance) {
112 break;
113 }
114
115 ++count;
116 }
117
118 ASSERT_LT(count, kMaxAttempts) << "Expected average was " <<
119 kExpectedAverage << ", average ended at " << cumulative_average;
120}
121
122TEST(RandUtilTest, RandUint64ProducesBothValuesOfAllBits) {
123 // This tests to see that our underlying random generator is good
124 // enough, for some value of good enough.
avi9b6f42932015-12-26 22:15:14[diff] [blame]125 uint64_t kAllZeros = 0ULL;
126 uint64_t kAllOnes = ~kAllZeros;
127 uint64_t found_ones = kAllZeros;
128 uint64_t found_zeros = kAllOnes;
joi@chromium.orgaf2e192b2011-05-30 17:39:09[diff] [blame]129
130 for (size_t i = 0; i < 1000; ++i) {
avi9b6f42932015-12-26 22:15:14[diff] [blame]131 uint64_t value = base::RandUint64();
joi@chromium.orgaf2e192b2011-05-30 17:39:09[diff] [blame]132 found_ones |= value;
133 found_zeros &= value;
134
135 if (found_zeros == kAllZeros && found_ones == kAllOnes)
136 return;
137 }
138
139 FAIL() << "Didn't achieve all bit values in maximum number of tries.";
140}
dalecurtis@chromium.orgc910c5a2014-01-23 02:14:28[diff] [blame]141
Scott Graham4ffd63b2017-06-01 18:03:33[diff] [blame]142TEST(RandUtilTest, RandBytesLonger) {
143 // Fuchsia can only retrieve 256 bytes of entropy at a time, so make sure we
144 // handle longer requests than that.
145 std::string random_string0 = base::RandBytesAsString(255);
146 EXPECT_EQ(255u, random_string0.size());
147 std::string random_string1 = base::RandBytesAsString(1023);
148 EXPECT_EQ(1023u, random_string1.size());
149 std::string random_string2 = base::RandBytesAsString(4097);
150 EXPECT_EQ(4097u, random_string2.size());
151}
152
dalecurtis@chromium.orgc910c5a2014-01-23 02:14:28[diff] [blame]153// Benchmark test for RandBytes(). Disabled since it's intentionally slow and
154// does not test anything that isn't already tested by the existing RandBytes()
155// tests.
156TEST(RandUtilTest, DISABLED_RandBytesPerf) {
157 // Benchmark the performance of |kTestIterations| of RandBytes() using a
158 // buffer size of |kTestBufferSize|.
159 const int kTestIterations = 10;
160 const size_t kTestBufferSize = 1 * 1024 * 1024;
161
dcheng093de9b2016-04-04 21:25:51[diff] [blame]162 std::unique_ptr<uint8_t[]> buffer(new uint8_t[kTestBufferSize]);
charliea3be839702015-01-26 17:35:41[diff] [blame]163 const base::TimeTicks now = base::TimeTicks::Now();
dalecurtis@chromium.orgc910c5a2014-01-23 02:14:28[diff] [blame]164 for (int i = 0; i < kTestIterations; ++i)
165 base::RandBytes(buffer.get(), kTestBufferSize);
charliea3be839702015-01-26 17:35:41[diff] [blame]166 const base::TimeTicks end = base::TimeTicks::Now();
dalecurtis@chromium.orgc910c5a2014-01-23 02:14:28[diff] [blame]167
168 LOG(INFO) << "RandBytes(" << kTestBufferSize << ") took: "
169 << (end - now).InMicroseconds() << "µs";
170}