base/bits_unittest.cc - chromium/src - Git at Google

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 // This file contains the unit tests for the bit utilities.

 #include "base/bits.h"
 #include "build/build_config.h"

 #include <stddef.h>

 #include <limits>

 #include "testing/gtest/include/gtest/gtest.h"

 namespace base {
 namespace bits {

 TEST(BitsTest, Log2Floor) {
   EXPECT_EQ(-1, Log2Floor(0));
   EXPECT_EQ(0, Log2Floor(1));
   EXPECT_EQ(1, Log2Floor(2));
   EXPECT_EQ(1, Log2Floor(3));
   EXPECT_EQ(2, Log2Floor(4));
   for (int i = 3; i < 31; ++i) {
     unsigned int value = 1U << i;
     EXPECT_EQ(i, Log2Floor(value));
     EXPECT_EQ(i, Log2Floor(value + 1));
     EXPECT_EQ(i, Log2Floor(value + 2));
     EXPECT_EQ(i - 1, Log2Floor(value - 1));
     EXPECT_EQ(i - 1, Log2Floor(value - 2));
   }
   EXPECT_EQ(31, Log2Floor(0xffffffffU));
 }

 TEST(BitsTest, Log2Ceiling) {
   EXPECT_EQ(-1, Log2Ceiling(0));
   EXPECT_EQ(0, Log2Ceiling(1));
   EXPECT_EQ(1, Log2Ceiling(2));
   EXPECT_EQ(2, Log2Ceiling(3));
   EXPECT_EQ(2, Log2Ceiling(4));
   for (int i = 3; i < 31; ++i) {
     unsigned int value = 1U << i;
     EXPECT_EQ(i, Log2Ceiling(value));
     EXPECT_EQ(i + 1, Log2Ceiling(value + 1));
     EXPECT_EQ(i + 1, Log2Ceiling(value + 2));
     EXPECT_EQ(i, Log2Ceiling(value - 1));
     EXPECT_EQ(i, Log2Ceiling(value - 2));
   }
   EXPECT_EQ(32, Log2Ceiling(0xffffffffU));
 }

 TEST(BitsTest, Align) {
   static constexpr size_t kSizeTMax = std::numeric_limits<size_t>::max();
   EXPECT_EQ(0ul, Align(0, 4));
   EXPECT_EQ(4ul, Align(1, 4));
   EXPECT_EQ(4096ul, Align(1, 4096));
   EXPECT_EQ(4096ul, Align(4096, 4096));
   EXPECT_EQ(4096ul, Align(4095, 4096));
   EXPECT_EQ(8192ul, Align(4097, 4096));
   EXPECT_EQ(kSizeTMax - 31, Align(kSizeTMax - 62, 32));
   EXPECT_EQ(kSizeTMax / 2 + 1, Align(1, kSizeTMax / 2 + 1));
 }

 TEST(BitsTest, AlignPointer) {
   static constexpr uintptr_t kUintPtrTMax =
       std::numeric_limits<uintptr_t>::max();
   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
             Align(reinterpret_cast<uint8_t*>(0), 4));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(4),
             Align(reinterpret_cast<uint8_t*>(1), 4));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
             Align(reinterpret_cast<uint8_t*>(1), 4096));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
             Align(reinterpret_cast<uint8_t*>(4096), 4096));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
             Align(reinterpret_cast<uint8_t*>(4095), 4096));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(8192),
             Align(reinterpret_cast<uint8_t*>(4097), 4096));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 31),
             Align(reinterpret_cast<uint8_t*>(kUintPtrTMax - 62), 32));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax / 2 + 1),
             Align(reinterpret_cast<uint8_t*>(1), kUintPtrTMax / 2 + 1));
 }

 TEST(BitsTest, AlignDown) {
   static constexpr size_t kSizeTMax = std::numeric_limits<size_t>::max();
   EXPECT_EQ(0ul, AlignDown(0, 4));
   EXPECT_EQ(0ul, AlignDown(1, 4));
   EXPECT_EQ(0ul, AlignDown(1, 4096));
   EXPECT_EQ(4096ul, AlignDown(4096, 4096));
   EXPECT_EQ(0ul, AlignDown(4095, 4096));
   EXPECT_EQ(4096ul, AlignDown(4097, 4096));
   EXPECT_EQ(kSizeTMax - 63, AlignDown(kSizeTMax - 62, 32));
   EXPECT_EQ(kSizeTMax - 31, AlignDown(kSizeTMax, 32));
   EXPECT_EQ(0ul, AlignDown(1, kSizeTMax / 2 + 1));
 }

 TEST(BitsTest, AlignDownPointer) {
   static constexpr uintptr_t kUintPtrTMax =
       std::numeric_limits<uintptr_t>::max();
   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
             AlignDown(reinterpret_cast<uint8_t*>(0), 4));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
             AlignDown(reinterpret_cast<uint8_t*>(1), 4));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
             AlignDown(reinterpret_cast<uint8_t*>(1), 4096));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
             AlignDown(reinterpret_cast<uint8_t*>(4096), 4096));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
             AlignDown(reinterpret_cast<uint8_t*>(4095), 4096));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
             AlignDown(reinterpret_cast<uint8_t*>(4097), 4096));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 63),
             AlignDown(reinterpret_cast<uint8_t*>(kUintPtrTMax - 62), 32));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 31),
             AlignDown(reinterpret_cast<uint8_t*>(kUintPtrTMax), 32));
   EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
             AlignDown(reinterpret_cast<uint8_t*>(1), kUintPtrTMax / 2 + 1));
 }

 TEST(BitsTest, CountLeadingZeroBits8) {
   EXPECT_EQ(8u, CountLeadingZeroBits(uint8_t{0}));
   EXPECT_EQ(7u, CountLeadingZeroBits(uint8_t{1}));
   for (uint8_t shift = 0; shift <= 7; shift++) {
     EXPECT_EQ(7u - shift,
               CountLeadingZeroBits(static_cast<uint8_t>(1 << shift)));
   }
   EXPECT_EQ(4u, CountLeadingZeroBits(uint8_t{0x0f}));
 }

 TEST(BitsTest, CountLeadingZeroBits16) {
   EXPECT_EQ(16u, CountLeadingZeroBits(uint16_t{0}));
   EXPECT_EQ(15u, CountLeadingZeroBits(uint16_t{1}));
   for (uint16_t shift = 0; shift <= 15; shift++) {
     EXPECT_EQ(15u - shift,
               CountLeadingZeroBits(static_cast<uint16_t>(1 << shift)));
   }
   EXPECT_EQ(4u, CountLeadingZeroBits(uint16_t{0x0f0f}));
 }

 TEST(BitsTest, CountLeadingZeroBits32) {
   EXPECT_EQ(32u, CountLeadingZeroBits(uint32_t{0}));
   EXPECT_EQ(31u, CountLeadingZeroBits(uint32_t{1}));
   for (uint32_t shift = 0; shift <= 31; shift++) {
     EXPECT_EQ(31u - shift, CountLeadingZeroBits(uint32_t{1} << shift));
   }
   EXPECT_EQ(4u, CountLeadingZeroBits(uint32_t{0x0f0f0f0f}));
 }

 TEST(BitsTest, CountTrailingeZeroBits8) {
   EXPECT_EQ(8u, CountTrailingZeroBits(uint8_t{0}));
   EXPECT_EQ(7u, CountTrailingZeroBits(uint8_t{128}));
   for (uint8_t shift = 0; shift <= 7; shift++) {
     EXPECT_EQ(shift, CountTrailingZeroBits(static_cast<uint8_t>(1 << shift)));
   }
   EXPECT_EQ(4u, CountTrailingZeroBits(uint8_t{0xf0}));
 }

 TEST(BitsTest, CountTrailingeZeroBits16) {
   EXPECT_EQ(16u, CountTrailingZeroBits(uint16_t{0}));
   EXPECT_EQ(15u, CountTrailingZeroBits(uint16_t{32768}));
   for (uint16_t shift = 0; shift <= 15; shift++) {
     EXPECT_EQ(shift, CountTrailingZeroBits(static_cast<uint16_t>(1 << shift)));
   }
   EXPECT_EQ(4u, CountTrailingZeroBits(uint16_t{0xf0f0}));
 }

 TEST(BitsTest, CountTrailingeZeroBits32) {
   EXPECT_EQ(32u, CountTrailingZeroBits(uint32_t{0}));
   EXPECT_EQ(31u, CountTrailingZeroBits(uint32_t{1} << 31));
   for (uint32_t shift = 0; shift <= 31; shift++) {
     EXPECT_EQ(shift, CountTrailingZeroBits(uint32_t{1} << shift));
   }
   EXPECT_EQ(4u, CountTrailingZeroBits(uint32_t{0xf0f0f0f0}));
 }

 TEST(BitsTest, CountLeadingZeroBits64) {
   EXPECT_EQ(64u, CountLeadingZeroBits(uint64_t{0}));
   EXPECT_EQ(63u, CountLeadingZeroBits(uint64_t{1}));
   for (uint64_t shift = 0; shift <= 63; shift++) {
     EXPECT_EQ(63u - shift, CountLeadingZeroBits(uint64_t{1} << shift));
   }
   EXPECT_EQ(4u, CountLeadingZeroBits(uint64_t{0x0f0f0f0f0f0f0f0f}));
 }

 TEST(BitsTest, CountTrailingeZeroBits64) {
   EXPECT_EQ(64u, CountTrailingZeroBits(uint64_t{0}));
   EXPECT_EQ(63u, CountTrailingZeroBits(uint64_t{1} << 63));
   for (uint64_t shift = 0; shift <= 31; shift++) {
     EXPECT_EQ(shift, CountTrailingZeroBits(uint64_t{1} << shift));
   }
   EXPECT_EQ(4u, CountTrailingZeroBits(uint64_t{0xf0f0f0f0f0f0f0f0}));
 }

 TEST(BitsTest, CountLeadingZeroBitsSizeT) {
 #if defined(ARCH_CPU_64_BITS)
   EXPECT_EQ(64u, CountLeadingZeroBitsSizeT(size_t{0}));
   EXPECT_EQ(63u, CountLeadingZeroBitsSizeT(size_t{1}));
   EXPECT_EQ(32u, CountLeadingZeroBitsSizeT(size_t{1} << 31));
   EXPECT_EQ(1u, CountLeadingZeroBitsSizeT(size_t{1} << 62));
   EXPECT_EQ(0u, CountLeadingZeroBitsSizeT(size_t{1} << 63));
 #else
   EXPECT_EQ(32u, CountLeadingZeroBitsSizeT(size_t{0}));
   EXPECT_EQ(31u, CountLeadingZeroBitsSizeT(size_t{1}));
   EXPECT_EQ(1u, CountLeadingZeroBitsSizeT(size_t{1} << 30));
   EXPECT_EQ(0u, CountLeadingZeroBitsSizeT(size_t{1} << 31));
 #endif  // ARCH_CPU_64_BITS
 }

 TEST(BitsTest, CountTrailingZeroBitsSizeT) {
 #if defined(ARCH_CPU_64_BITS)
   EXPECT_EQ(64u, CountTrailingZeroBitsSizeT(size_t{0}));
   EXPECT_EQ(63u, CountTrailingZeroBitsSizeT(size_t{1} << 63));
   EXPECT_EQ(31u, CountTrailingZeroBitsSizeT(size_t{1} << 31));
   EXPECT_EQ(1u, CountTrailingZeroBitsSizeT(size_t{2}));
   EXPECT_EQ(0u, CountTrailingZeroBitsSizeT(size_t{1}));
 #else
   EXPECT_EQ(32u, CountTrailingZeroBitsSizeT(size_t{0}));
   EXPECT_EQ(31u, CountTrailingZeroBitsSizeT(size_t{1} << 31));
   EXPECT_EQ(1u, CountTrailingZeroBitsSizeT(size_t{2}));
   EXPECT_EQ(0u, CountTrailingZeroBitsSizeT(size_t{1}));
 #endif  // ARCH_CPU_64_BITS
 }

 TEST(BitsTest, PowerOfTwo) {
   EXPECT_FALSE(IsPowerOfTwo(-1));
   EXPECT_FALSE(IsPowerOfTwo(0));
   EXPECT_TRUE(IsPowerOfTwo(1));
   EXPECT_TRUE(IsPowerOfTwo(2));
   // Unsigned 64 bit cases.
   for (uint32_t i = 2; i < 64; i++) {
     const uint64_t val = uint64_t{1} << i;
     EXPECT_FALSE(IsPowerOfTwo(val - 1));
     EXPECT_TRUE(IsPowerOfTwo(val));
     EXPECT_FALSE(IsPowerOfTwo(val + 1));
   }
   // Signed 64 bit cases.
   for (uint32_t i = 2; i < 63; i++) {
     const int64_t val = int64_t{1} << i;
     EXPECT_FALSE(IsPowerOfTwo(val - 1));
     EXPECT_TRUE(IsPowerOfTwo(val));
     EXPECT_FALSE(IsPowerOfTwo(val + 1));
   }
   // Signed integers with only the last bit set are negative, not powers of two.
   EXPECT_FALSE(IsPowerOfTwo(int64_t{1} << 63));
 }

 TEST(BitsTest, LeftMostBit) {
   // Construction of a signed type from an unsigned one of the same width
   // preserves all bits. Explicitily confirming this behavior here to illustrate
   // correctness of reusing unsigned literals to test behavior of signed types.
   // Using signed literals does not work with EXPECT_EQ.
   static_assert(int64_t(0xFFFFFFFFFFFFFFFFu) == 0xFFFFFFFFFFFFFFFFl,
                 "Comparing signed with unsigned literals compares bits.");
   static_assert((0xFFFFFFFFFFFFFFFFu ^ 0xFFFFFFFFFFFFFFFFl) == 0,
                 "Signed and unsigned literals have the same bits set");

   uint64_t unsigned_long_long_value = 0x8000000000000000u;
   EXPECT_EQ(LeftmostBit<uint64_t>(), unsigned_long_long_value);
   EXPECT_EQ(LeftmostBit<int64_t>(), int64_t(unsigned_long_long_value));

   uint32_t unsigned_long_value = 0x80000000u;
   EXPECT_EQ(LeftmostBit<uint32_t>(), unsigned_long_value);
   EXPECT_EQ(LeftmostBit<int32_t>(), int32_t(unsigned_long_value));

   uint16_t unsigned_short_value = 0x8000u;
   EXPECT_EQ(LeftmostBit<uint16_t>(), unsigned_short_value);
   EXPECT_EQ(LeftmostBit<int16_t>(), int16_t(unsigned_short_value));

   uint8_t unsigned_byte_value = 0x80u;
   EXPECT_EQ(LeftmostBit<uint8_t>(), unsigned_byte_value);
   EXPECT_EQ(LeftmostBit<int8_t>(), int8_t(unsigned_byte_value));
 }

 }  // namespace bits
 }  // namespace base
	// Copyright (c) 2009 The Chromium Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	// This file contains the unit tests for the bit utilities.

	#include "base/bits.h"
	#include "build/build_config.h"

	#include <stddef.h>

	#include <limits>

	#include "testing/gtest/include/gtest/gtest.h"

	namespace base {
	namespace bits {

	TEST(BitsTest, Log2Floor) {
	EXPECT_EQ(-1, Log2Floor(0));
	EXPECT_EQ(0, Log2Floor(1));
	EXPECT_EQ(1, Log2Floor(2));
	EXPECT_EQ(1, Log2Floor(3));
	EXPECT_EQ(2, Log2Floor(4));
	for (int i = 3; i < 31; ++i) {
	unsigned int value = 1U << i;
	EXPECT_EQ(i, Log2Floor(value));
	EXPECT_EQ(i, Log2Floor(value + 1));
	EXPECT_EQ(i, Log2Floor(value + 2));
	EXPECT_EQ(i - 1, Log2Floor(value - 1));
	EXPECT_EQ(i - 1, Log2Floor(value - 2));
	}
	EXPECT_EQ(31, Log2Floor(0xffffffffU));
	}

	TEST(BitsTest, Log2Ceiling) {
	EXPECT_EQ(-1, Log2Ceiling(0));
	EXPECT_EQ(0, Log2Ceiling(1));
	EXPECT_EQ(1, Log2Ceiling(2));
	EXPECT_EQ(2, Log2Ceiling(3));
	EXPECT_EQ(2, Log2Ceiling(4));
	for (int i = 3; i < 31; ++i) {
	unsigned int value = 1U << i;
	EXPECT_EQ(i, Log2Ceiling(value));
	EXPECT_EQ(i + 1, Log2Ceiling(value + 1));
	EXPECT_EQ(i + 1, Log2Ceiling(value + 2));
	EXPECT_EQ(i, Log2Ceiling(value - 1));
	EXPECT_EQ(i, Log2Ceiling(value - 2));
	}
	EXPECT_EQ(32, Log2Ceiling(0xffffffffU));
	}

	TEST(BitsTest, Align) {
	static constexpr size_t kSizeTMax = std::numeric_limits<size_t>::max();
	EXPECT_EQ(0ul, Align(0, 4));
	EXPECT_EQ(4ul, Align(1, 4));
	EXPECT_EQ(4096ul, Align(1, 4096));
	EXPECT_EQ(4096ul, Align(4096, 4096));
	EXPECT_EQ(4096ul, Align(4095, 4096));
	EXPECT_EQ(8192ul, Align(4097, 4096));
	EXPECT_EQ(kSizeTMax - 31, Align(kSizeTMax - 62, 32));
	EXPECT_EQ(kSizeTMax / 2 + 1, Align(1, kSizeTMax / 2 + 1));
	}

	TEST(BitsTest, AlignPointer) {
	static constexpr uintptr_t kUintPtrTMax =
	std::numeric_limits<uintptr_t>::max();
	EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
	Align(reinterpret_cast<uint8_t*>(0), 4));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(4),
	Align(reinterpret_cast<uint8_t*>(1), 4));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
	Align(reinterpret_cast<uint8_t*>(1), 4096));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
	Align(reinterpret_cast<uint8_t*>(4096), 4096));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
	Align(reinterpret_cast<uint8_t*>(4095), 4096));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(8192),
	Align(reinterpret_cast<uint8_t*>(4097), 4096));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 31),
	Align(reinterpret_cast<uint8_t*>(kUintPtrTMax - 62), 32));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax / 2 + 1),
	Align(reinterpret_cast<uint8_t*>(1), kUintPtrTMax / 2 + 1));
	}

	TEST(BitsTest, AlignDown) {
	static constexpr size_t kSizeTMax = std::numeric_limits<size_t>::max();
	EXPECT_EQ(0ul, AlignDown(0, 4));
	EXPECT_EQ(0ul, AlignDown(1, 4));
	EXPECT_EQ(0ul, AlignDown(1, 4096));
	EXPECT_EQ(4096ul, AlignDown(4096, 4096));
	EXPECT_EQ(0ul, AlignDown(4095, 4096));
	EXPECT_EQ(4096ul, AlignDown(4097, 4096));
	EXPECT_EQ(kSizeTMax - 63, AlignDown(kSizeTMax - 62, 32));
	EXPECT_EQ(kSizeTMax - 31, AlignDown(kSizeTMax, 32));
	EXPECT_EQ(0ul, AlignDown(1, kSizeTMax / 2 + 1));
	}

	TEST(BitsTest, AlignDownPointer) {
	static constexpr uintptr_t kUintPtrTMax =
	std::numeric_limits<uintptr_t>::max();
	EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
	AlignDown(reinterpret_cast<uint8_t*>(0), 4));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
	AlignDown(reinterpret_cast<uint8_t*>(1), 4));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
	AlignDown(reinterpret_cast<uint8_t*>(1), 4096));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
	AlignDown(reinterpret_cast<uint8_t*>(4096), 4096));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
	AlignDown(reinterpret_cast<uint8_t*>(4095), 4096));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(4096),
	AlignDown(reinterpret_cast<uint8_t*>(4097), 4096));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 63),
	AlignDown(reinterpret_cast<uint8_t*>(kUintPtrTMax - 62), 32));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(kUintPtrTMax - 31),
	AlignDown(reinterpret_cast<uint8_t*>(kUintPtrTMax), 32));
	EXPECT_EQ(reinterpret_cast<uint8_t*>(0),
	AlignDown(reinterpret_cast<uint8_t*>(1), kUintPtrTMax / 2 + 1));
	}

	TEST(BitsTest, CountLeadingZeroBits8) {
	EXPECT_EQ(8u, CountLeadingZeroBits(uint8_t{0}));
	EXPECT_EQ(7u, CountLeadingZeroBits(uint8_t{1}));
	for (uint8_t shift = 0; shift <= 7; shift++) {
	EXPECT_EQ(7u - shift,
	CountLeadingZeroBits(static_cast<uint8_t>(1 << shift)));
	}
	EXPECT_EQ(4u, CountLeadingZeroBits(uint8_t{0x0f}));
	}

	TEST(BitsTest, CountLeadingZeroBits16) {
	EXPECT_EQ(16u, CountLeadingZeroBits(uint16_t{0}));
	EXPECT_EQ(15u, CountLeadingZeroBits(uint16_t{1}));
	for (uint16_t shift = 0; shift <= 15; shift++) {
	EXPECT_EQ(15u - shift,
	CountLeadingZeroBits(static_cast<uint16_t>(1 << shift)));
	}
	EXPECT_EQ(4u, CountLeadingZeroBits(uint16_t{0x0f0f}));
	}

	TEST(BitsTest, CountLeadingZeroBits32) {
	EXPECT_EQ(32u, CountLeadingZeroBits(uint32_t{0}));
	EXPECT_EQ(31u, CountLeadingZeroBits(uint32_t{1}));
	for (uint32_t shift = 0; shift <= 31; shift++) {
	EXPECT_EQ(31u - shift, CountLeadingZeroBits(uint32_t{1} << shift));
	}
	EXPECT_EQ(4u, CountLeadingZeroBits(uint32_t{0x0f0f0f0f}));
	}

	TEST(BitsTest, CountTrailingeZeroBits8) {
	EXPECT_EQ(8u, CountTrailingZeroBits(uint8_t{0}));
	EXPECT_EQ(7u, CountTrailingZeroBits(uint8_t{128}));
	for (uint8_t shift = 0; shift <= 7; shift++) {
	EXPECT_EQ(shift, CountTrailingZeroBits(static_cast<uint8_t>(1 << shift)));
	}
	EXPECT_EQ(4u, CountTrailingZeroBits(uint8_t{0xf0}));
	}

	TEST(BitsTest, CountTrailingeZeroBits16) {
	EXPECT_EQ(16u, CountTrailingZeroBits(uint16_t{0}));
	EXPECT_EQ(15u, CountTrailingZeroBits(uint16_t{32768}));
	for (uint16_t shift = 0; shift <= 15; shift++) {
	EXPECT_EQ(shift, CountTrailingZeroBits(static_cast<uint16_t>(1 << shift)));
	}
	EXPECT_EQ(4u, CountTrailingZeroBits(uint16_t{0xf0f0}));
	}

	TEST(BitsTest, CountTrailingeZeroBits32) {
	EXPECT_EQ(32u, CountTrailingZeroBits(uint32_t{0}));
	EXPECT_EQ(31u, CountTrailingZeroBits(uint32_t{1} << 31));
	for (uint32_t shift = 0; shift <= 31; shift++) {
	EXPECT_EQ(shift, CountTrailingZeroBits(uint32_t{1} << shift));
	}
	EXPECT_EQ(4u, CountTrailingZeroBits(uint32_t{0xf0f0f0f0}));
	}

	TEST(BitsTest, CountLeadingZeroBits64) {
	EXPECT_EQ(64u, CountLeadingZeroBits(uint64_t{0}));
	EXPECT_EQ(63u, CountLeadingZeroBits(uint64_t{1}));
	for (uint64_t shift = 0; shift <= 63; shift++) {
	EXPECT_EQ(63u - shift, CountLeadingZeroBits(uint64_t{1} << shift));
	}
	EXPECT_EQ(4u, CountLeadingZeroBits(uint64_t{0x0f0f0f0f0f0f0f0f}));
	}

	TEST(BitsTest, CountTrailingeZeroBits64) {
	EXPECT_EQ(64u, CountTrailingZeroBits(uint64_t{0}));
	EXPECT_EQ(63u, CountTrailingZeroBits(uint64_t{1} << 63));
	for (uint64_t shift = 0; shift <= 31; shift++) {
	EXPECT_EQ(shift, CountTrailingZeroBits(uint64_t{1} << shift));
	}
	EXPECT_EQ(4u, CountTrailingZeroBits(uint64_t{0xf0f0f0f0f0f0f0f0}));
	}

	TEST(BitsTest, CountLeadingZeroBitsSizeT) {
	#if defined(ARCH_CPU_64_BITS)
	EXPECT_EQ(64u, CountLeadingZeroBitsSizeT(size_t{0}));
	EXPECT_EQ(63u, CountLeadingZeroBitsSizeT(size_t{1}));
	EXPECT_EQ(32u, CountLeadingZeroBitsSizeT(size_t{1} << 31));
	EXPECT_EQ(1u, CountLeadingZeroBitsSizeT(size_t{1} << 62));
	EXPECT_EQ(0u, CountLeadingZeroBitsSizeT(size_t{1} << 63));
	#else
	EXPECT_EQ(32u, CountLeadingZeroBitsSizeT(size_t{0}));
	EXPECT_EQ(31u, CountLeadingZeroBitsSizeT(size_t{1}));
	EXPECT_EQ(1u, CountLeadingZeroBitsSizeT(size_t{1} << 30));
	EXPECT_EQ(0u, CountLeadingZeroBitsSizeT(size_t{1} << 31));
	#endif // ARCH_CPU_64_BITS
	}

	TEST(BitsTest, CountTrailingZeroBitsSizeT) {
	#if defined(ARCH_CPU_64_BITS)
	EXPECT_EQ(64u, CountTrailingZeroBitsSizeT(size_t{0}));
	EXPECT_EQ(63u, CountTrailingZeroBitsSizeT(size_t{1} << 63));
	EXPECT_EQ(31u, CountTrailingZeroBitsSizeT(size_t{1} << 31));
	EXPECT_EQ(1u, CountTrailingZeroBitsSizeT(size_t{2}));
	EXPECT_EQ(0u, CountTrailingZeroBitsSizeT(size_t{1}));
	#else
	EXPECT_EQ(32u, CountTrailingZeroBitsSizeT(size_t{0}));
	EXPECT_EQ(31u, CountTrailingZeroBitsSizeT(size_t{1} << 31));
	EXPECT_EQ(1u, CountTrailingZeroBitsSizeT(size_t{2}));
	EXPECT_EQ(0u, CountTrailingZeroBitsSizeT(size_t{1}));
	#endif // ARCH_CPU_64_BITS
	}

	TEST(BitsTest, PowerOfTwo) {
	EXPECT_FALSE(IsPowerOfTwo(-1));
	EXPECT_FALSE(IsPowerOfTwo(0));
	EXPECT_TRUE(IsPowerOfTwo(1));
	EXPECT_TRUE(IsPowerOfTwo(2));
	// Unsigned 64 bit cases.
	for (uint32_t i = 2; i < 64; i++) {
	const uint64_t val = uint64_t{1} << i;
	EXPECT_FALSE(IsPowerOfTwo(val - 1));
	EXPECT_TRUE(IsPowerOfTwo(val));
	EXPECT_FALSE(IsPowerOfTwo(val + 1));
	}
	// Signed 64 bit cases.
	for (uint32_t i = 2; i < 63; i++) {
	const int64_t val = int64_t{1} << i;
	EXPECT_FALSE(IsPowerOfTwo(val - 1));
	EXPECT_TRUE(IsPowerOfTwo(val));
	EXPECT_FALSE(IsPowerOfTwo(val + 1));
	}
	// Signed integers with only the last bit set are negative, not powers of two.
	EXPECT_FALSE(IsPowerOfTwo(int64_t{1} << 63));
	}

	TEST(BitsTest, LeftMostBit) {
	// Construction of a signed type from an unsigned one of the same width
	// preserves all bits. Explicitily confirming this behavior here to illustrate
	// correctness of reusing unsigned literals to test behavior of signed types.
	// Using signed literals does not work with EXPECT_EQ.
	static_assert(int64_t(0xFFFFFFFFFFFFFFFFu) == 0xFFFFFFFFFFFFFFFFl,
	"Comparing signed with unsigned literals compares bits.");
	static_assert((0xFFFFFFFFFFFFFFFFu ^ 0xFFFFFFFFFFFFFFFFl) == 0,
	"Signed and unsigned literals have the same bits set");

	uint64_t unsigned_long_long_value = 0x8000000000000000u;
	EXPECT_EQ(LeftmostBit<uint64_t>(), unsigned_long_long_value);
	EXPECT_EQ(LeftmostBit<int64_t>(), int64_t(unsigned_long_long_value));

	uint32_t unsigned_long_value = 0x80000000u;
	EXPECT_EQ(LeftmostBit<uint32_t>(), unsigned_long_value);
	EXPECT_EQ(LeftmostBit<int32_t>(), int32_t(unsigned_long_value));

	uint16_t unsigned_short_value = 0x8000u;
	EXPECT_EQ(LeftmostBit<uint16_t>(), unsigned_short_value);
	EXPECT_EQ(LeftmostBit<int16_t>(), int16_t(unsigned_short_value));

	uint8_t unsigned_byte_value = 0x80u;
	EXPECT_EQ(LeftmostBit<uint8_t>(), unsigned_byte_value);
	EXPECT_EQ(LeftmostBit<int8_t>(), int8_t(unsigned_byte_value));
	}

	} // namespace bits
	} // namespace base