base/bits_unittest.cc

   1 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
   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 #include "build/build_config.h"
   9
  10 #include <stddef.h>
  11
  12 #include <limits>
  13
  14 #include "testing/gtest/include/gtest/gtest.h"
  15
  16 namespace base {
  17 namespace bits {
  18
  19 TEST(BitsTest, Log2Floor) {
  20   EXPECT_EQ(-1, Log2Floor(0));
  21   EXPECT_EQ(0, Log2Floor(1));
  22   EXPECT_EQ(1, Log2Floor(2));
  23   EXPECT_EQ(1, Log2Floor(3));
  24   EXPECT_EQ(2, Log2Floor(4));
  25   for (int i = 3; i < 31; ++i) {
  26     unsigned int value = 1U << i;
  27     EXPECT_EQ(i, Log2Floor(value));
  28     EXPECT_EQ(i, Log2Floor(value + 1));
  29     EXPECT_EQ(i, Log2Floor(value + 2));
  30     EXPECT_EQ(i - 1, Log2Floor(value - 1));
  31     EXPECT_EQ(i - 1, Log2Floor(value - 2));
  32   }
  33   EXPECT_EQ(31, Log2Floor(0xffffffffU));
  34 }
  35
  36 TEST(BitsTest, Log2Ceiling) {
  37   EXPECT_EQ(-1, Log2Ceiling(0));
  38   EXPECT_EQ(0, Log2Ceiling(1));
  39   EXPECT_EQ(1, Log2Ceiling(2));
  40   EXPECT_EQ(2, Log2Ceiling(3));
  41   EXPECT_EQ(2, Log2Ceiling(4));
  42   for (int i = 3; i < 31; ++i) {
  43     unsigned int value = 1U << i;
  44     EXPECT_EQ(i, Log2Ceiling(value));
  45     EXPECT_EQ(i + 1, Log2Ceiling(value + 1));
  46     EXPECT_EQ(i + 1, Log2Ceiling(value + 2));
  47     EXPECT_EQ(i, Log2Ceiling(value - 1));
  48     EXPECT_EQ(i, Log2Ceiling(value - 2));
  49   }
  50   EXPECT_EQ(32, Log2Ceiling(0xffffffffU));
  51 }
  52
  53 TEST(BitsTest, Align) {
  54   static constexpr size_t kSizeTMax = std::numeric_limits<size_t>::max();
  55   EXPECT_EQ(0ul, Align(0, 4));
  56   EXPECT_EQ(4ul, Align(1, 4));
  57   EXPECT_EQ(4096ul, Align(1, 4096));
  58   EXPECT_EQ(4096ul, Align(4096, 4096));
  59   EXPECT_EQ(4096ul, Align(4095, 4096));
  60   EXPECT_EQ(8192ul, Align(4097, 4096));
  61   EXPECT_EQ(kSizeTMax - 31, Align(kSizeTMax - 62, 32));
  62   EXPECT_EQ(kSizeTMax / 2 + 1, Align(1, kSizeTMax / 2 + 1));
  63 }
  64
  65 TEST(BitsTest, AlignDown) {
  66   static constexpr size_t kSizeTMax = std::numeric_limits<size_t>::max();
  67   EXPECT_EQ(0ul, AlignDown(0, 4));
  68   EXPECT_EQ(0ul, AlignDown(1, 4));
  69   EXPECT_EQ(0ul, AlignDown(1, 4096));
  70   EXPECT_EQ(4096ul, AlignDown(4096, 4096));
  71   EXPECT_EQ(0ul, AlignDown(4095, 4096));
  72   EXPECT_EQ(4096ul, AlignDown(4097, 4096));
  73   EXPECT_EQ(kSizeTMax - 63, AlignDown(kSizeTMax - 62, 32));
  74   EXPECT_EQ(kSizeTMax - 31, AlignDown(kSizeTMax, 32));
  75   EXPECT_EQ(0ul, AlignDown(1, kSizeTMax / 2 + 1));
  76 }
  77
  78 TEST(BitsTest, CountLeadingZeroBits8) {
  79   EXPECT_EQ(8u, CountLeadingZeroBits(uint8_t{0}));
  80   EXPECT_EQ(7u, CountLeadingZeroBits(uint8_t{1}));
  81   for (uint8_t shift = 0; shift <= 7; shift++) {
  82     EXPECT_EQ(7u - shift,
  83               CountLeadingZeroBits(static_cast<uint8_t>(1 << shift)));
  84   }
  85   EXPECT_EQ(4u, CountLeadingZeroBits(uint8_t{0x0f}));
  86 }
  87
  88 TEST(BitsTest, CountLeadingZeroBits16) {
  89   EXPECT_EQ(16u, CountLeadingZeroBits(uint16_t{0}));
  90   EXPECT_EQ(15u, CountLeadingZeroBits(uint16_t{1}));
  91   for (uint16_t shift = 0; shift <= 15; shift++) {
  92     EXPECT_EQ(15u - shift,
  93               CountLeadingZeroBits(static_cast<uint16_t>(1 << shift)));
  94   }
  95   EXPECT_EQ(4u, CountLeadingZeroBits(uint16_t{0x0f0f}));
  96 }
  97
  98 TEST(BitsTest, CountLeadingZeroBits32) {
  99   EXPECT_EQ(32u, CountLeadingZeroBits(uint32_t{0}));
 100   EXPECT_EQ(31u, CountLeadingZeroBits(uint32_t{1}));
 101   for (uint32_t shift = 0; shift <= 31; shift++) {
 102     EXPECT_EQ(31u - shift, CountLeadingZeroBits(uint32_t{1} << shift));
 103   }
 104   EXPECT_EQ(4u, CountLeadingZeroBits(uint32_t{0x0f0f0f0f}));
 105 }
 106
 107 TEST(BitsTest, CountTrailingeZeroBits8) {
 108   EXPECT_EQ(8u, CountTrailingZeroBits(uint8_t{0}));
 109   EXPECT_EQ(7u, CountTrailingZeroBits(uint8_t{128}));
 110   for (uint8_t shift = 0; shift <= 7; shift++) {
 111     EXPECT_EQ(shift, CountTrailingZeroBits(static_cast<uint8_t>(1 << shift)));
 112   }
 113   EXPECT_EQ(4u, CountTrailingZeroBits(uint8_t{0xf0}));
 114 }
 115
 116 TEST(BitsTest, CountTrailingeZeroBits16) {
 117   EXPECT_EQ(16u, CountTrailingZeroBits(uint16_t{0}));
 118   EXPECT_EQ(15u, CountTrailingZeroBits(uint16_t{32768}));
 119   for (uint16_t shift = 0; shift <= 15; shift++) {
 120     EXPECT_EQ(shift, CountTrailingZeroBits(static_cast<uint16_t>(1 << shift)));
 121   }
 122   EXPECT_EQ(4u, CountTrailingZeroBits(uint16_t{0xf0f0}));
 123 }
 124
 125 TEST(BitsTest, CountTrailingeZeroBits32) {
 126   EXPECT_EQ(32u, CountTrailingZeroBits(uint32_t{0}));
 127   EXPECT_EQ(31u, CountTrailingZeroBits(uint32_t{1} << 31));
 128   for (uint32_t shift = 0; shift <= 31; shift++) {
 129     EXPECT_EQ(shift, CountTrailingZeroBits(uint32_t{1} << shift));
 130   }
 131   EXPECT_EQ(4u, CountTrailingZeroBits(uint32_t{0xf0f0f0f0}));
 132 }
 133
 134 TEST(BitsTest, CountLeadingZeroBits64) {
 135   EXPECT_EQ(64u, CountLeadingZeroBits(uint64_t{0}));
 136   EXPECT_EQ(63u, CountLeadingZeroBits(uint64_t{1}));
 137   for (uint64_t shift = 0; shift <= 63; shift++) {
 138     EXPECT_EQ(63u - shift, CountLeadingZeroBits(uint64_t{1} << shift));
 139   }
 140   EXPECT_EQ(4u, CountLeadingZeroBits(uint64_t{0x0f0f0f0f0f0f0f0f}));
 141 }
 142
 143 TEST(BitsTest, CountTrailingeZeroBits64) {
 144   EXPECT_EQ(64u, CountTrailingZeroBits(uint64_t{0}));
 145   EXPECT_EQ(63u, CountTrailingZeroBits(uint64_t{1} << 63));
 146   for (uint64_t shift = 0; shift <= 31; shift++) {
 147     EXPECT_EQ(shift, CountTrailingZeroBits(uint64_t{1} << shift));
 148   }
 149   EXPECT_EQ(4u, CountTrailingZeroBits(uint64_t{0xf0f0f0f0f0f0f0f0}));
 150 }
 151
 152 TEST(BitsTest, CountLeadingZeroBitsSizeT) {
 153 #if defined(ARCH_CPU_64_BITS)
 154   EXPECT_EQ(64u, CountLeadingZeroBitsSizeT(size_t{0}));
 155   EXPECT_EQ(63u, CountLeadingZeroBitsSizeT(size_t{1}));
 156   EXPECT_EQ(32u, CountLeadingZeroBitsSizeT(size_t{1} << 31));
 157   EXPECT_EQ(1u, CountLeadingZeroBitsSizeT(size_t{1} << 62));
 158   EXPECT_EQ(0u, CountLeadingZeroBitsSizeT(size_t{1} << 63));
 159 #else
 160   EXPECT_EQ(32u, CountLeadingZeroBitsSizeT(size_t{0}));
 161   EXPECT_EQ(31u, CountLeadingZeroBitsSizeT(size_t{1}));
 162   EXPECT_EQ(1u, CountLeadingZeroBitsSizeT(size_t{1} << 30));
 163   EXPECT_EQ(0u, CountLeadingZeroBitsSizeT(size_t{1} << 31));
 164 #endif  // ARCH_CPU_64_BITS
 165 }
 166
 167 TEST(BitsTest, CountTrailingZeroBitsSizeT) {
 168 #if defined(ARCH_CPU_64_BITS)
 169   EXPECT_EQ(64u, CountTrailingZeroBitsSizeT(size_t{0}));
 170   EXPECT_EQ(63u, CountTrailingZeroBitsSizeT(size_t{1} << 63));
 171   EXPECT_EQ(31u, CountTrailingZeroBitsSizeT(size_t{1} << 31));
 172   EXPECT_EQ(1u, CountTrailingZeroBitsSizeT(size_t{2}));
 173   EXPECT_EQ(0u, CountTrailingZeroBitsSizeT(size_t{1}));
 174 #else
 175   EXPECT_EQ(32u, CountTrailingZeroBitsSizeT(size_t{0}));
 176   EXPECT_EQ(31u, CountTrailingZeroBitsSizeT(size_t{1} << 31));
 177   EXPECT_EQ(1u, CountTrailingZeroBitsSizeT(size_t{2}));
 178   EXPECT_EQ(0u, CountTrailingZeroBitsSizeT(size_t{1}));
 179 #endif  // ARCH_CPU_64_BITS
 180 }
 181
 182 TEST(BitsTest, PowerOfTwo) {
 183   EXPECT_FALSE(IsPowerOfTwo(-1));
 184   EXPECT_FALSE(IsPowerOfTwo(0));
 185   EXPECT_TRUE(IsPowerOfTwo(1));
 186   EXPECT_TRUE(IsPowerOfTwo(2));
 187   // Unsigned 64 bit cases.
 188   for (uint32_t i = 2; i < 64; i++) {
 189     const uint64_t val = uint64_t{1} << i;
 190     EXPECT_FALSE(IsPowerOfTwo(val - 1));
 191     EXPECT_TRUE(IsPowerOfTwo(val));
 192     EXPECT_FALSE(IsPowerOfTwo(val + 1));
 193   }
 194   // Signed 64 bit cases.
 195   for (uint32_t i = 2; i < 63; i++) {
 196     const int64_t val = int64_t{1} << i;
 197     EXPECT_FALSE(IsPowerOfTwo(val - 1));
 198     EXPECT_TRUE(IsPowerOfTwo(val));
 199     EXPECT_FALSE(IsPowerOfTwo(val + 1));
 200   }
 201   // Signed integers with only the last bit set are negative, not powers of two.
 202   EXPECT_FALSE(IsPowerOfTwo(int64_t{1} << 63));
 203 }
 204
 205 }  // namespace bits
 206 }  // namespace base