base/bits_unittest.cc

// 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 <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) {
  const 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, CLZWorks) {
  EXPECT_EQ(32u, CountLeadingZeroBits32(0u));
  EXPECT_EQ(31u, CountLeadingZeroBits32(1u));
  EXPECT_EQ(1u, CountLeadingZeroBits32(1u << 30));
  EXPECT_EQ(0u, CountLeadingZeroBits32(1u << 31));

#if defined(ARCH_CPU_64_BITS)
  EXPECT_EQ(64u, CountLeadingZeroBitsSizeT(0ull));
  EXPECT_EQ(63u, CountLeadingZeroBitsSizeT(1ull));
  EXPECT_EQ(32u, CountLeadingZeroBitsSizeT(1ull << 31));
  EXPECT_EQ(1u, CountLeadingZeroBitsSizeT(1ull << 62));
  EXPECT_EQ(0u, CountLeadingZeroBitsSizeT(1ull << 63));
#else
  EXPECT_EQ(32u, CountLeadingZeroBitsSizeT(0u));
  EXPECT_EQ(31u, CountLeadingZeroBitsSizeT(1u));
  EXPECT_EQ(1u, CountLeadingZeroBitsSizeT(1u << 30));
  EXPECT_EQ(0u, CountLeadingZeroBitsSizeT(1u << 31));
#endif
}

}  // namespace bits
}  // namespace base