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, AlignUp) {
  54   static constexpr size_t kSizeTMax = std::numeric_limits<size_t>::max();
  55   EXPECT_EQ(0ul, AlignUp(0, 4));
  56   EXPECT_EQ(4ul, AlignUp(1, 4));
  57   EXPECT_EQ(4096ul, AlignUp(1, 4096));
  58   EXPECT_EQ(4096ul, AlignUp(4096, 4096));
  59   EXPECT_EQ(4096ul, AlignUp(4095, 4096));
  60   EXPECT_EQ(8192ul, AlignUp(4097, 4096));
  61   EXPECT_EQ(kSizeTMax - 31, AlignUp(kSizeTMax - 62, 32));
  62   EXPECT_EQ(kSizeTMax / 2 + 1, AlignUp(1, kSizeTMax / 2 + 1));
  63 }
  64
  65 TEST(BitsTest, AlignUpPointer) {
  66   static constexpr uintptr_t kUintPtrTMax =
  67       std::numeric_limits<uintptr_t>::max();
  68   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
  69             AlignUp(reinterpret_cast<uint8_t*>(0), 4));
  70   EXPECT_EQ(reinterpret_cast<uint8_t*>(4),
  71             AlignUp(reinterpret_cast<uint8_t*>(1), 4));
  72   EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
  73             AlignUp(reinterpret_cast<uint8_t*>(1), 4096));
  74   EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
  75             AlignUp(reinterpret_cast<uint8_t*>(4096), 4096));
  76   EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
  77             AlignUp(reinterpret_cast<uint8_t*>(4095), 4096));
  78   EXPECT_EQ(reinterpret_cast<uint8_t*>(8192),
  79             AlignUp(reinterpret_cast<uint8_t*>(4097), 4096));
  80   EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 31),
  81             AlignUp(reinterpret_cast<uint8_t*>(kUintPtrTMax - 62), 32));
  82   EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax / 2 + 1),
  83             AlignUp(reinterpret_cast<uint8_t*>(1), kUintPtrTMax / 2 + 1));
  84 }
  85
  86 TEST(BitsTest, AlignDown) {
  87   static constexpr size_t kSizeTMax = std::numeric_limits<size_t>::max();
  88   EXPECT_EQ(0ul, AlignDown(0, 4));
  89   EXPECT_EQ(0ul, AlignDown(1, 4));
  90   EXPECT_EQ(0ul, AlignDown(1, 4096));
  91   EXPECT_EQ(4096ul, AlignDown(4096, 4096));
  92   EXPECT_EQ(0ul, AlignDown(4095, 4096));
  93   EXPECT_EQ(4096ul, AlignDown(4097, 4096));
  94   EXPECT_EQ(kSizeTMax - 63, AlignDown(kSizeTMax - 62, 32));
  95   EXPECT_EQ(kSizeTMax - 31, AlignDown(kSizeTMax, 32));
  96   EXPECT_EQ(0ul, AlignDown(1, kSizeTMax / 2 + 1));
  97 }
  98
  99 TEST(BitsTest, AlignDownPointer) {
 100   static constexpr uintptr_t kUintPtrTMax =
 101       std::numeric_limits<uintptr_t>::max();
 102   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
 103             AlignDown(reinterpret_cast<uint8_t*>(0), 4));
 104   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
 105             AlignDown(reinterpret_cast<uint8_t*>(1), 4));
 106   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
 107             AlignDown(reinterpret_cast<uint8_t*>(1), 4096));
 108   EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
 109             AlignDown(reinterpret_cast<uint8_t*>(4096), 4096));
 110   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
 111             AlignDown(reinterpret_cast<uint8_t*>(4095), 4096));
 112   EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
 113             AlignDown(reinterpret_cast<uint8_t*>(4097), 4096));
 114   EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 63),
 115             AlignDown(reinterpret_cast<uint8_t*>(kUintPtrTMax - 62), 32));
 116   EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 31),
 117             AlignDown(reinterpret_cast<uint8_t*>(kUintPtrTMax), 32));
 118   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
 119             AlignDown(reinterpret_cast<uint8_t*>(1), kUintPtrTMax / 2 + 1));
 120 }
 121
 122 TEST(BitsTest, CountLeadingZeroBits8) {
 123   EXPECT_EQ(8u, CountLeadingZeroBits(uint8_t{0}));
 124   EXPECT_EQ(7u, CountLeadingZeroBits(uint8_t{1}));
 125   for (uint8_t shift = 0; shift <= 7; shift++) {
 126     EXPECT_EQ(7u - shift,
 127               CountLeadingZeroBits(static_cast<uint8_t>(1 << shift)));
 128   }
 129   EXPECT_EQ(4u, CountLeadingZeroBits(uint8_t{0x0f}));
 130 }
 131
 132 TEST(BitsTest, CountLeadingZeroBits16) {
 133   EXPECT_EQ(16u, CountLeadingZeroBits(uint16_t{0}));
 134   EXPECT_EQ(15u, CountLeadingZeroBits(uint16_t{1}));
 135   for (uint16_t shift = 0; shift <= 15; shift++) {
 136     EXPECT_EQ(15u - shift,
 137               CountLeadingZeroBits(static_cast<uint16_t>(1 << shift)));
 138   }
 139   EXPECT_EQ(4u, CountLeadingZeroBits(uint16_t{0x0f0f}));
 140 }
 141
 142 TEST(BitsTest, CountLeadingZeroBits32) {
 143   EXPECT_EQ(32u, CountLeadingZeroBits(uint32_t{0}));
 144   EXPECT_EQ(31u, CountLeadingZeroBits(uint32_t{1}));
 145   for (uint32_t shift = 0; shift <= 31; shift++) {
 146     EXPECT_EQ(31u - shift, CountLeadingZeroBits(uint32_t{1} << shift));
 147   }
 148   EXPECT_EQ(4u, CountLeadingZeroBits(uint32_t{0x0f0f0f0f}));
 149 }
 150
 151 TEST(BitsTest, CountTrailingeZeroBits8) {
 152   EXPECT_EQ(8u, CountTrailingZeroBits(uint8_t{0}));
 153   EXPECT_EQ(7u, CountTrailingZeroBits(uint8_t{128}));
 154   for (uint8_t shift = 0; shift <= 7; shift++) {
 155     EXPECT_EQ(shift, CountTrailingZeroBits(static_cast<uint8_t>(1 << shift)));
 156   }
 157   EXPECT_EQ(4u, CountTrailingZeroBits(uint8_t{0xf0}));
 158 }
 159
 160 TEST(BitsTest, CountTrailingeZeroBits16) {
 161   EXPECT_EQ(16u, CountTrailingZeroBits(uint16_t{0}));
 162   EXPECT_EQ(15u, CountTrailingZeroBits(uint16_t{32768}));
 163   for (uint16_t shift = 0; shift <= 15; shift++) {
 164     EXPECT_EQ(shift, CountTrailingZeroBits(static_cast<uint16_t>(1 << shift)));
 165   }
 166   EXPECT_EQ(4u, CountTrailingZeroBits(uint16_t{0xf0f0}));
 167 }
 168
 169 TEST(BitsTest, CountTrailingeZeroBits32) {
 170   EXPECT_EQ(32u, CountTrailingZeroBits(uint32_t{0}));
 171   EXPECT_EQ(31u, CountTrailingZeroBits(uint32_t{1} << 31));
 172   for (uint32_t shift = 0; shift <= 31; shift++) {
 173     EXPECT_EQ(shift, CountTrailingZeroBits(uint32_t{1} << shift));
 174   }
 175   EXPECT_EQ(4u, CountTrailingZeroBits(uint32_t{0xf0f0f0f0}));
 176 }
 177
 178 TEST(BitsTest, CountLeadingZeroBits64) {
 179   EXPECT_EQ(64u, CountLeadingZeroBits(uint64_t{0}));
 180   EXPECT_EQ(63u, CountLeadingZeroBits(uint64_t{1}));
 181   for (uint64_t shift = 0; shift <= 63; shift++) {
 182     EXPECT_EQ(63u - shift, CountLeadingZeroBits(uint64_t{1} << shift));
 183   }
 184   EXPECT_EQ(4u, CountLeadingZeroBits(uint64_t{0x0f0f0f0f0f0f0f0f}));
 185 }
 186
 187 TEST(BitsTest, CountTrailingeZeroBits64) {
 188   EXPECT_EQ(64u, CountTrailingZeroBits(uint64_t{0}));
 189   EXPECT_EQ(63u, CountTrailingZeroBits(uint64_t{1} << 63));
 190   for (uint64_t shift = 0; shift <= 31; shift++) {
 191     EXPECT_EQ(shift, CountTrailingZeroBits(uint64_t{1} << shift));
 192   }
 193   EXPECT_EQ(4u, CountTrailingZeroBits(uint64_t{0xf0f0f0f0f0f0f0f0}));
 194 }
 195
 196 TEST(BitsTest, CountLeadingZeroBitsSizeT) {
 197 #if defined(ARCH_CPU_64_BITS)
 198   EXPECT_EQ(64u, CountLeadingZeroBitsSizeT(size_t{0}));
 199   EXPECT_EQ(63u, CountLeadingZeroBitsSizeT(size_t{1}));
 200   EXPECT_EQ(32u, CountLeadingZeroBitsSizeT(size_t{1} << 31));
 201   EXPECT_EQ(1u, CountLeadingZeroBitsSizeT(size_t{1} << 62));
 202   EXPECT_EQ(0u, CountLeadingZeroBitsSizeT(size_t{1} << 63));
 203 #else
 204   EXPECT_EQ(32u, CountLeadingZeroBitsSizeT(size_t{0}));
 205   EXPECT_EQ(31u, CountLeadingZeroBitsSizeT(size_t{1}));
 206   EXPECT_EQ(1u, CountLeadingZeroBitsSizeT(size_t{1} << 30));
 207   EXPECT_EQ(0u, CountLeadingZeroBitsSizeT(size_t{1} << 31));
 208 #endif  // ARCH_CPU_64_BITS
 209 }
 210
 211 TEST(BitsTest, CountTrailingZeroBitsSizeT) {
 212 #if defined(ARCH_CPU_64_BITS)
 213   EXPECT_EQ(64u, CountTrailingZeroBitsSizeT(size_t{0}));
 214   EXPECT_EQ(63u, CountTrailingZeroBitsSizeT(size_t{1} << 63));
 215   EXPECT_EQ(31u, CountTrailingZeroBitsSizeT(size_t{1} << 31));
 216   EXPECT_EQ(1u, CountTrailingZeroBitsSizeT(size_t{2}));
 217   EXPECT_EQ(0u, CountTrailingZeroBitsSizeT(size_t{1}));
 218 #else
 219   EXPECT_EQ(32u, CountTrailingZeroBitsSizeT(size_t{0}));
 220   EXPECT_EQ(31u, CountTrailingZeroBitsSizeT(size_t{1} << 31));
 221   EXPECT_EQ(1u, CountTrailingZeroBitsSizeT(size_t{2}));
 222   EXPECT_EQ(0u, CountTrailingZeroBitsSizeT(size_t{1}));
 223 #endif  // ARCH_CPU_64_BITS
 224 }
 225
 226 TEST(BitsTest, PowerOfTwo) {
 227   EXPECT_FALSE(IsPowerOfTwo(-1));
 228   EXPECT_FALSE(IsPowerOfTwo(0));
 229   EXPECT_TRUE(IsPowerOfTwo(1));
 230   EXPECT_TRUE(IsPowerOfTwo(2));
 231   // Unsigned 64 bit cases.
 232   for (uint32_t i = 2; i < 64; i++) {
 233     const uint64_t val = uint64_t{1} << i;
 234     EXPECT_FALSE(IsPowerOfTwo(val - 1));
 235     EXPECT_TRUE(IsPowerOfTwo(val));
 236     EXPECT_FALSE(IsPowerOfTwo(val + 1));
 237   }
 238   // Signed 64 bit cases.
 239   for (uint32_t i = 2; i < 63; i++) {
 240     const int64_t val = int64_t{1} << i;
 241     EXPECT_FALSE(IsPowerOfTwo(val - 1));
 242     EXPECT_TRUE(IsPowerOfTwo(val));
 243     EXPECT_FALSE(IsPowerOfTwo(val + 1));
 244   }
 245   // Signed integers with only the last bit set are negative, not powers of two.
 246   EXPECT_FALSE(IsPowerOfTwo(int64_t{1} << 63));
 247 }
 248
 249 TEST(BitsTest, LeftMostBit) {
 250   // Construction of a signed type from an unsigned one of the same width
 251   // preserves all bits. Explicitily confirming this behavior here to illustrate
 252   // correctness of reusing unsigned literals to test behavior of signed types.
 253   // Using signed literals does not work with EXPECT_EQ.
 254   static_assert(int64_t(0xFFFFFFFFFFFFFFFFu) == 0xFFFFFFFFFFFFFFFFl,
 255                 "Comparing signed with unsigned literals compares bits.");
 256   static_assert((0xFFFFFFFFFFFFFFFFu ^ 0xFFFFFFFFFFFFFFFFl) == 0,
 257                 "Signed and unsigned literals have the same bits set");
 258
 259   uint64_t unsigned_long_long_value = 0x8000000000000000u;
 260   EXPECT_EQ(LeftmostBit<uint64_t>(), unsigned_long_long_value);
 261   EXPECT_EQ(LeftmostBit<int64_t>(), int64_t(unsigned_long_long_value));
 262
 263   uint32_t unsigned_long_value = 0x80000000u;
 264   EXPECT_EQ(LeftmostBit<uint32_t>(), unsigned_long_value);
 265   EXPECT_EQ(LeftmostBit<int32_t>(), int32_t(unsigned_long_value));
 266
 267   uint16_t unsigned_short_value = 0x8000u;
 268   EXPECT_EQ(LeftmostBit<uint16_t>(), unsigned_short_value);
 269   EXPECT_EQ(LeftmostBit<int16_t>(), int16_t(unsigned_short_value));
 270
 271   uint8_t unsigned_byte_value = 0x80u;
 272   EXPECT_EQ(LeftmostBit<uint8_t>(), unsigned_byte_value);
 273   EXPECT_EQ(LeftmostBit<int8_t>(), int8_t(unsigned_byte_value));
 274 }
 275
 276 }  // namespace bits
 277 }  // namespace base