1 // Copyright 2009 The Chromium Authors
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 // This file contains the unit tests for the bit utilities.
6
7 #include "base/bits.h"
8
9 #include <stddef.h>
10
11 #include <limits>
12
13 #include "testing/gtest/include/gtest/gtest.h"
14
15 namespace base::bits {
16
TEST(BitsTest,Log2Floor)17 TEST(BitsTest, Log2Floor) {
18 EXPECT_EQ(-1, Log2Floor(0));
19 EXPECT_EQ(0, Log2Floor(1));
20 EXPECT_EQ(1, Log2Floor(2));
21 EXPECT_EQ(1, Log2Floor(3));
22 EXPECT_EQ(2, Log2Floor(4));
23 for (int i = 3; i < 31; ++i) {
24 unsigned int value = 1U << i;
25 EXPECT_EQ(i, Log2Floor(value));
26 EXPECT_EQ(i, Log2Floor(value + 1));
27 EXPECT_EQ(i, Log2Floor(value + 2));
28 EXPECT_EQ(i - 1, Log2Floor(value - 1));
29 EXPECT_EQ(i - 1, Log2Floor(value - 2));
30 }
31 EXPECT_EQ(31, Log2Floor(0xffffffffU));
32 }
33
TEST(BitsTest,Log2Ceiling)34 TEST(BitsTest, Log2Ceiling) {
35 EXPECT_EQ(-1, Log2Ceiling(0));
36 EXPECT_EQ(0, Log2Ceiling(1));
37 EXPECT_EQ(1, Log2Ceiling(2));
38 EXPECT_EQ(2, Log2Ceiling(3));
39 EXPECT_EQ(2, Log2Ceiling(4));
40 for (int i = 3; i < 31; ++i) {
41 unsigned int value = 1U << i;
42 EXPECT_EQ(i, Log2Ceiling(value));
43 EXPECT_EQ(i + 1, Log2Ceiling(value + 1));
44 EXPECT_EQ(i + 1, Log2Ceiling(value + 2));
45 EXPECT_EQ(i, Log2Ceiling(value - 1));
46 EXPECT_EQ(i, Log2Ceiling(value - 2));
47 }
48 EXPECT_EQ(32, Log2Ceiling(0xffffffffU));
49 }
50
TEST(BitsTest,AlignUp)51 TEST(BitsTest, AlignUp) {
52 static constexpr size_t kSizeTMax = std::numeric_limits<size_t>::max();
53 EXPECT_EQ(0u, AlignUp(0u, 4u));
54 EXPECT_EQ(4u, AlignUp(1u, 4u));
55 EXPECT_EQ(4096u, AlignUp(1u, 4096u));
56 EXPECT_EQ(4096u, AlignUp(4096u, 4096u));
57 EXPECT_EQ(4096u, AlignUp(4095u, 4096u));
58 EXPECT_EQ(8192u, AlignUp(4097u, 4096u));
59 EXPECT_EQ(kSizeTMax - 31, AlignUp(kSizeTMax - 62, size_t{32}));
60 EXPECT_EQ(kSizeTMax / 2 + 1, AlignUp(size_t{1}, kSizeTMax / 2 + 1));
61 }
62
TEST(BitsTest,AlignUpPointer)63 TEST(BitsTest, AlignUpPointer) {
64 static constexpr uintptr_t kUintPtrTMax =
65 std::numeric_limits<uintptr_t>::max();
66 EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
67 AlignUp(reinterpret_cast<uint8_t*>(0), 4));
68 EXPECT_EQ(reinterpret_cast<uint8_t*>(4),
69 AlignUp(reinterpret_cast<uint8_t*>(1), 4));
70 EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
71 AlignUp(reinterpret_cast<uint8_t*>(1), 4096));
72 EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
73 AlignUp(reinterpret_cast<uint8_t*>(4096), 4096));
74 EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
75 AlignUp(reinterpret_cast<uint8_t*>(4095), 4096));
76 EXPECT_EQ(reinterpret_cast<uint8_t*>(8192),
77 AlignUp(reinterpret_cast<uint8_t*>(4097), 4096));
78 EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 31),
79 AlignUp(reinterpret_cast<uint8_t*>(kUintPtrTMax - 62), 32));
80 EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax / 2 + 1),
81 AlignUp(reinterpret_cast<uint8_t*>(1), kUintPtrTMax / 2 + 1));
82 }
83
TEST(BitsTest,AlignDown)84 TEST(BitsTest, AlignDown) {
85 static constexpr size_t kSizeTMax = std::numeric_limits<size_t>::max();
86 EXPECT_EQ(0u, AlignDown(0u, 4u));
87 EXPECT_EQ(0u, AlignDown(1u, 4u));
88 EXPECT_EQ(0u, AlignDown(1u, 4096u));
89 EXPECT_EQ(4096u, AlignDown(4096u, 4096u));
90 EXPECT_EQ(0u, AlignDown(4095u, 4096u));
91 EXPECT_EQ(4096u, AlignDown(4097u, 4096u));
92 EXPECT_EQ(kSizeTMax - 63, AlignDown(kSizeTMax - 62, size_t{32}));
93 EXPECT_EQ(kSizeTMax - 31, AlignDown(kSizeTMax, size_t{32}));
94 EXPECT_EQ(0ul, AlignDown(size_t{1}, kSizeTMax / 2 + 1));
95 }
96
TEST(BitsTest,AlignDownPointer)97 TEST(BitsTest, AlignDownPointer) {
98 static constexpr uintptr_t kUintPtrTMax =
99 std::numeric_limits<uintptr_t>::max();
100 EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
101 AlignDown(reinterpret_cast<uint8_t*>(0), 4));
102 EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
103 AlignDown(reinterpret_cast<uint8_t*>(1), 4));
104 EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
105 AlignDown(reinterpret_cast<uint8_t*>(1), 4096));
106 EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
107 AlignDown(reinterpret_cast<uint8_t*>(4096), 4096));
108 EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
109 AlignDown(reinterpret_cast<uint8_t*>(4095), 4096));
110 EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
111 AlignDown(reinterpret_cast<uint8_t*>(4097), 4096));
112 EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 63),
113 AlignDown(reinterpret_cast<uint8_t*>(kUintPtrTMax - 62), 32));
114 EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 31),
115 AlignDown(reinterpret_cast<uint8_t*>(kUintPtrTMax), 32));
116 EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
117 AlignDown(reinterpret_cast<uint8_t*>(1), kUintPtrTMax / 2 + 1));
118 }
119
TEST(BitsTest,PowerOfTwoDeprecatedDoNotUse)120 TEST(BitsTest, PowerOfTwoDeprecatedDoNotUse) {
121 EXPECT_FALSE(IsPowerOfTwoDeprecatedDoNotUse(-1));
122 // Signed 64 bit cases.
123 for (uint32_t i = 2; i < 63; i++) {
124 const int64_t val = int64_t{1} << i;
125 EXPECT_FALSE(IsPowerOfTwoDeprecatedDoNotUse(val - 1));
126 EXPECT_TRUE(IsPowerOfTwoDeprecatedDoNotUse(val));
127 EXPECT_FALSE(IsPowerOfTwoDeprecatedDoNotUse(val + 1));
128 }
129 // Signed integers with only the last bit set are negative, not powers of two.
130 EXPECT_FALSE(IsPowerOfTwoDeprecatedDoNotUse(int64_t{1} << 63));
131 }
132
TEST(BitsTest,LeftMostBit)133 TEST(BitsTest, LeftMostBit) {
134 // Construction of a signed type from an unsigned one of the same width
135 // preserves all bits. Explicitly confirming this behavior here to illustrate
136 // correctness of reusing unsigned literals to test behavior of signed types.
137 // Using signed literals does not work with EXPECT_EQ.
138 static_assert(int64_t(0xFFFFFFFFFFFFFFFFu) == 0xFFFFFFFFFFFFFFFFl,
139 "Comparing signed with unsigned literals compares bits.");
140 static_assert((0xFFFFFFFFFFFFFFFFu ^ 0xFFFFFFFFFFFFFFFFl) == 0,
141 "Signed and unsigned literals have the same bits set");
142
143 uint64_t unsigned_long_long_value = 0x8000000000000000u;
144 EXPECT_EQ(LeftmostBit<uint64_t>(), unsigned_long_long_value);
145 EXPECT_EQ(LeftmostBit<int64_t>(), int64_t(unsigned_long_long_value));
146
147 uint32_t unsigned_long_value = 0x80000000u;
148 EXPECT_EQ(LeftmostBit<uint32_t>(), unsigned_long_value);
149 EXPECT_EQ(LeftmostBit<int32_t>(), int32_t(unsigned_long_value));
150
151 uint16_t unsigned_short_value = 0x8000u;
152 EXPECT_EQ(LeftmostBit<uint16_t>(), unsigned_short_value);
153 EXPECT_EQ(LeftmostBit<int16_t>(), int16_t(unsigned_short_value));
154
155 uint8_t unsigned_byte_value = 0x80u;
156 EXPECT_EQ(LeftmostBit<uint8_t>(), unsigned_byte_value);
157 EXPECT_EQ(LeftmostBit<int8_t>(), int8_t(unsigned_byte_value));
158 }
159
160 } // namespace base::bits
161