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Diffstat (limited to 'absl/numeric/bits_test.cc')
| -rw-r--r-- | absl/numeric/bits_test.cc | 573 |
1 files changed, 573 insertions, 0 deletions
diff --git a/absl/numeric/bits_test.cc b/absl/numeric/bits_test.cc new file mode 100644 index 00000000..7c942aae --- /dev/null +++ b/absl/numeric/bits_test.cc @@ -0,0 +1,573 @@ +// Copyright 2020 The Abseil Authors +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// https://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +#include "absl/numeric/bits.h" + +#include <limits> + +#include "gmock/gmock.h" +#include "gtest/gtest.h" +#include "absl/random/random.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN +namespace { + +TEST(Rotate, Left) { + static_assert(rotl(uint8_t{0x12}, 0) == uint8_t{0x12}, ""); + static_assert(rotl(uint16_t{0x1234}, 0) == uint16_t{0x1234}, ""); + static_assert(rotl(uint32_t{0x12345678UL}, 0) == uint32_t{0x12345678UL}, ""); + static_assert(rotl(uint64_t{0x12345678ABCDEF01ULL}, 0) == + uint64_t{0x12345678ABCDEF01ULL}, + ""); + + EXPECT_EQ(rotl(uint8_t{0x12}, 0), uint8_t{0x12}); + EXPECT_EQ(rotl(uint16_t{0x1234}, 0), uint16_t{0x1234}); + EXPECT_EQ(rotl(uint32_t{0x12345678UL}, 0), uint32_t{0x12345678UL}); + EXPECT_EQ(rotl(uint64_t{0x12345678ABCDEF01ULL}, 0), + uint64_t{0x12345678ABCDEF01ULL}); + + EXPECT_EQ(rotl(uint8_t{0x12}, 8), uint8_t{0x12}); + EXPECT_EQ(rotl(uint16_t{0x1234}, 16), uint16_t{0x1234}); + EXPECT_EQ(rotl(uint32_t{0x12345678UL}, 32), uint32_t{0x12345678UL}); + EXPECT_EQ(rotl(uint64_t{0x12345678ABCDEF01ULL}, 64), + uint64_t{0x12345678ABCDEF01ULL}); + + EXPECT_EQ(rotl(uint8_t{0x12}, -8), uint8_t{0x12}); + EXPECT_EQ(rotl(uint16_t{0x1234}, -16), uint16_t{0x1234}); + EXPECT_EQ(rotl(uint32_t{0x12345678UL}, -32), uint32_t{0x12345678UL}); + EXPECT_EQ(rotl(uint64_t{0x12345678ABCDEF01ULL}, -64), + uint64_t{0x12345678ABCDEF01ULL}); + + EXPECT_EQ(rotl(uint8_t{0x12}, 4), uint8_t{0x21}); + EXPECT_EQ(rotl(uint16_t{0x1234}, 4), uint16_t{0x2341}); + EXPECT_EQ(rotl(uint32_t{0x12345678UL}, 4), uint32_t{0x23456781UL}); + EXPECT_EQ(rotl(uint64_t{0x12345678ABCDEF01ULL}, 4), + uint64_t{0x2345678ABCDEF011ULL}); + + EXPECT_EQ(rotl(uint8_t{0x12}, -4), uint8_t{0x21}); + EXPECT_EQ(rotl(uint16_t{0x1234}, -4), uint16_t{0x4123}); + EXPECT_EQ(rotl(uint32_t{0x12345678UL}, -4), uint32_t{0x81234567UL}); + EXPECT_EQ(rotl(uint64_t{0x12345678ABCDEF01ULL}, -4), + uint64_t{0x112345678ABCDEF0ULL}); +} + +TEST(Rotate, Right) { + static_assert(rotr(uint8_t{0x12}, 0) == uint8_t{0x12}, ""); + static_assert(rotr(uint16_t{0x1234}, 0) == uint16_t{0x1234}, ""); + static_assert(rotr(uint32_t{0x12345678UL}, 0) == uint32_t{0x12345678UL}, ""); + static_assert(rotr(uint64_t{0x12345678ABCDEF01ULL}, 0) == + uint64_t{0x12345678ABCDEF01ULL}, + ""); + + EXPECT_EQ(rotr(uint8_t{0x12}, 0), uint8_t{0x12}); + EXPECT_EQ(rotr(uint16_t{0x1234}, 0), uint16_t{0x1234}); + EXPECT_EQ(rotr(uint32_t{0x12345678UL}, 0), uint32_t{0x12345678UL}); + EXPECT_EQ(rotr(uint64_t{0x12345678ABCDEF01ULL}, 0), + uint64_t{0x12345678ABCDEF01ULL}); + + EXPECT_EQ(rotr(uint8_t{0x12}, 8), uint8_t{0x12}); + EXPECT_EQ(rotr(uint16_t{0x1234}, 16), uint16_t{0x1234}); + EXPECT_EQ(rotr(uint32_t{0x12345678UL}, 32), uint32_t{0x12345678UL}); + EXPECT_EQ(rotr(uint64_t{0x12345678ABCDEF01ULL}, 64), + uint64_t{0x12345678ABCDEF01ULL}); + + EXPECT_EQ(rotr(uint8_t{0x12}, -8), uint8_t{0x12}); + EXPECT_EQ(rotr(uint16_t{0x1234}, -16), uint16_t{0x1234}); + EXPECT_EQ(rotr(uint32_t{0x12345678UL}, -32), uint32_t{0x12345678UL}); + EXPECT_EQ(rotr(uint64_t{0x12345678ABCDEF01ULL}, -64), + uint64_t{0x12345678ABCDEF01ULL}); + + EXPECT_EQ(rotr(uint8_t{0x12}, 4), uint8_t{0x21}); + EXPECT_EQ(rotr(uint16_t{0x1234}, 4), uint16_t{0x4123}); + EXPECT_EQ(rotr(uint32_t{0x12345678UL}, 4), uint32_t{0x81234567UL}); + EXPECT_EQ(rotr(uint64_t{0x12345678ABCDEF01ULL}, 4), + uint64_t{0x112345678ABCDEF0ULL}); + + EXPECT_EQ(rotr(uint8_t{0x12}, -4), uint8_t{0x21}); + EXPECT_EQ(rotr(uint16_t{0x1234}, -4), uint16_t{0x2341}); + EXPECT_EQ(rotr(uint32_t{0x12345678UL}, -4), uint32_t{0x23456781UL}); + EXPECT_EQ(rotr(uint64_t{0x12345678ABCDEF01ULL}, -4), + uint64_t{0x2345678ABCDEF011ULL}); +} + +TEST(Rotate, Symmetry) { + // rotr(x, s) is equivalent to rotl(x, -s) + absl::BitGen rng; + constexpr int kTrials = 100; + + for (int i = 0; i < kTrials; ++i) { + uint8_t value = absl::Uniform(rng, std::numeric_limits<uint8_t>::min(), + std::numeric_limits<uint8_t>::max()); + int shift = absl::Uniform(rng, -2 * std::numeric_limits<uint8_t>::digits, + 2 * std::numeric_limits<uint8_t>::digits); + + EXPECT_EQ(rotl(value, shift), rotr(value, -shift)); + } + + for (int i = 0; i < kTrials; ++i) { + uint16_t value = absl::Uniform(rng, std::numeric_limits<uint16_t>::min(), + std::numeric_limits<uint16_t>::max()); + int shift = absl::Uniform(rng, -2 * std::numeric_limits<uint16_t>::digits, + 2 * std::numeric_limits<uint16_t>::digits); + + EXPECT_EQ(rotl(value, shift), rotr(value, -shift)); + } + + for (int i = 0; i < kTrials; ++i) { + uint32_t value = absl::Uniform(rng, std::numeric_limits<uint32_t>::min(), + std::numeric_limits<uint32_t>::max()); + int shift = absl::Uniform(rng, -2 * std::numeric_limits<uint32_t>::digits, + 2 * std::numeric_limits<uint32_t>::digits); + + EXPECT_EQ(rotl(value, shift), rotr(value, -shift)); + } + + for (int i = 0; i < kTrials; ++i) { + uint64_t value = absl::Uniform(rng, std::numeric_limits<uint64_t>::min(), + std::numeric_limits<uint64_t>::max()); + int shift = absl::Uniform(rng, -2 * std::numeric_limits<uint64_t>::digits, + 2 * std::numeric_limits<uint64_t>::digits); + + EXPECT_EQ(rotl(value, shift), rotr(value, -shift)); + } +} + +TEST(Counting, LeadingZeroes) { +#if ABSL_INTERNAL_HAS_CONSTEXPR_CLZ + static_assert(countl_zero(uint8_t{}) == 8, ""); + static_assert(countl_zero(static_cast<uint8_t>(-1)) == 0, ""); + static_assert(countl_zero(uint16_t{}) == 16, ""); + static_assert(countl_zero(static_cast<uint16_t>(-1)) == 0, ""); + static_assert(countl_zero(uint32_t{}) == 32, ""); + static_assert(countl_zero(~uint32_t{}) == 0, ""); + static_assert(countl_zero(uint64_t{}) == 64, ""); + static_assert(countl_zero(~uint64_t{}) == 0, ""); +#endif + + EXPECT_EQ(countl_zero(uint8_t{}), 8); + EXPECT_EQ(countl_zero(static_cast<uint8_t>(-1)), 0); + EXPECT_EQ(countl_zero(uint16_t{}), 16); + EXPECT_EQ(countl_zero(static_cast<uint16_t>(-1)), 0); + EXPECT_EQ(countl_zero(uint32_t{}), 32); + EXPECT_EQ(countl_zero(~uint32_t{}), 0); + EXPECT_EQ(countl_zero(uint64_t{}), 64); + EXPECT_EQ(countl_zero(~uint64_t{}), 0); + + for (int i = 0; i < 8; i++) { + EXPECT_EQ(countl_zero(static_cast<uint8_t>(1u << i)), 7 - i); + } + + for (int i = 0; i < 16; i++) { + EXPECT_EQ(countl_zero(static_cast<uint16_t>(1u << i)), 15 - i); + } + + for (int i = 0; i < 32; i++) { + EXPECT_EQ(countl_zero(uint32_t{1} << i), 31 - i); + } + + for (int i = 0; i < 64; i++) { + EXPECT_EQ(countl_zero(uint64_t{1} << i), 63 - i); + } +} + +TEST(Counting, LeadingOnes) { +#if ABSL_INTERNAL_HAS_CONSTEXPR_CLZ + static_assert(countl_one(uint8_t{}) == 0, ""); + static_assert(countl_one(static_cast<uint8_t>(-1)) == 8, ""); + static_assert(countl_one(uint16_t{}) == 0, ""); + static_assert(countl_one(static_cast<uint16_t>(-1)) == 16, ""); + static_assert(countl_one(uint32_t{}) == 0, ""); + static_assert(countl_one(~uint32_t{}) == 32, ""); + static_assert(countl_one(uint64_t{}) == 0, ""); + static_assert(countl_one(~uint64_t{}) == 64, ""); +#endif + + EXPECT_EQ(countl_one(uint8_t{}), 0); + EXPECT_EQ(countl_one(static_cast<uint8_t>(-1)), 8); + EXPECT_EQ(countl_one(uint16_t{}), 0); + EXPECT_EQ(countl_one(static_cast<uint16_t>(-1)), 16); + EXPECT_EQ(countl_one(uint32_t{}), 0); + EXPECT_EQ(countl_one(~uint32_t{}), 32); + EXPECT_EQ(countl_one(uint64_t{}), 0); + EXPECT_EQ(countl_one(~uint64_t{}), 64); +} + +TEST(Counting, TrailingZeroes) { +#if ABSL_INTERNAL_HAS_CONSTEXPR_CTZ + static_assert(countr_zero(uint8_t{}) == 8, ""); + static_assert(countr_zero(static_cast<uint8_t>(-1)) == 0, ""); + static_assert(countr_zero(uint16_t{}) == 16, ""); + static_assert(countr_zero(static_cast<uint16_t>(-1)) == 0, ""); + static_assert(countr_zero(uint32_t{}) == 32, ""); + static_assert(countr_zero(~uint32_t{}) == 0, ""); + static_assert(countr_zero(uint64_t{}) == 64, ""); + static_assert(countr_zero(~uint64_t{}) == 0, ""); +#endif + + EXPECT_EQ(countr_zero(uint8_t{}), 8); + EXPECT_EQ(countr_zero(static_cast<uint8_t>(-1)), 0); + EXPECT_EQ(countr_zero(uint16_t{}), 16); + EXPECT_EQ(countr_zero(static_cast<uint16_t>(-1)), 0); + EXPECT_EQ(countr_zero(uint32_t{}), 32); + EXPECT_EQ(countr_zero(~uint32_t{}), 0); + EXPECT_EQ(countr_zero(uint64_t{}), 64); + EXPECT_EQ(countr_zero(~uint64_t{}), 0); +} + +TEST(Counting, TrailingOnes) { +#if ABSL_INTERNAL_HAS_CONSTEXPR_CTZ + static_assert(countr_one(uint8_t{}) == 0, ""); + static_assert(countr_one(static_cast<uint8_t>(-1)) == 8, ""); + static_assert(countr_one(uint16_t{}) == 0, ""); + static_assert(countr_one(static_cast<uint16_t>(-1)) == 16, ""); + static_assert(countr_one(uint32_t{}) == 0, ""); + static_assert(countr_one(~uint32_t{}) == 32, ""); + static_assert(countr_one(uint64_t{}) == 0, ""); + static_assert(countr_one(~uint64_t{}) == 64, ""); +#endif + + EXPECT_EQ(countr_one(uint8_t{}), 0); + EXPECT_EQ(countr_one(static_cast<uint8_t>(-1)), 8); + EXPECT_EQ(countr_one(uint16_t{}), 0); + EXPECT_EQ(countr_one(static_cast<uint16_t>(-1)), 16); + EXPECT_EQ(countr_one(uint32_t{}), 0); + EXPECT_EQ(countr_one(~uint32_t{}), 32); + EXPECT_EQ(countr_one(uint64_t{}), 0); + EXPECT_EQ(countr_one(~uint64_t{}), 64); +} + +TEST(Counting, Popcount) { +#if ABSL_INTERNAL_HAS_CONSTEXPR_POPCOUNT + static_assert(popcount(uint8_t{}) == 0, ""); + static_assert(popcount(uint8_t{1}) == 1, ""); + static_assert(popcount(static_cast<uint8_t>(-1)) == 8, ""); + static_assert(popcount(uint16_t{}) == 0, ""); + static_assert(popcount(uint16_t{1}) == 1, ""); + static_assert(popcount(static_cast<uint16_t>(-1)) == 16, ""); + static_assert(popcount(uint32_t{}) == 0, ""); + static_assert(popcount(uint32_t{1}) == 1, ""); + static_assert(popcount(~uint32_t{}) == 32, ""); + static_assert(popcount(uint64_t{}) == 0, ""); + static_assert(popcount(uint64_t{1}) == 1, ""); + static_assert(popcount(~uint64_t{}) == 64, ""); +#endif // ABSL_INTERNAL_HAS_CONSTEXPR_POPCOUNT + + EXPECT_EQ(popcount(uint8_t{}), 0); + EXPECT_EQ(popcount(uint8_t{1}), 1); + EXPECT_EQ(popcount(static_cast<uint8_t>(-1)), 8); + EXPECT_EQ(popcount(uint16_t{}), 0); + EXPECT_EQ(popcount(uint16_t{1}), 1); + EXPECT_EQ(popcount(static_cast<uint16_t>(-1)), 16); + EXPECT_EQ(popcount(uint32_t{}), 0); + EXPECT_EQ(popcount(uint32_t{1}), 1); + EXPECT_EQ(popcount(~uint32_t{}), 32); + EXPECT_EQ(popcount(uint64_t{}), 0); + EXPECT_EQ(popcount(uint64_t{1}), 1); + EXPECT_EQ(popcount(~uint64_t{}), 64); + + for (int i = 0; i < 8; i++) { + EXPECT_EQ(popcount(static_cast<uint8_t>(uint8_t{1} << i)), 1); + EXPECT_EQ(popcount(static_cast<uint8_t>(static_cast<uint8_t>(-1) ^ + (uint8_t{1} << i))), + 7); + } + + for (int i = 0; i < 16; i++) { + EXPECT_EQ(popcount(static_cast<uint16_t>(uint16_t{1} << i)), 1); + EXPECT_EQ(popcount(static_cast<uint16_t>(static_cast<uint16_t>(-1) ^ + (uint16_t{1} << i))), + 15); + } + + for (int i = 0; i < 32; i++) { + EXPECT_EQ(popcount(uint32_t{1} << i), 1); + EXPECT_EQ(popcount(static_cast<uint32_t>(-1) ^ (uint32_t{1} << i)), 31); + } + + for (int i = 0; i < 64; i++) { + EXPECT_EQ(popcount(uint64_t{1} << i), 1); + EXPECT_EQ(popcount(static_cast<uint64_t>(-1) ^ (uint64_t{1} << i)), 63); + } +} + +template <typename T> +struct PopcountInput { + T value = 0; + int expected = 0; +}; + +template <typename T> +PopcountInput<T> GeneratePopcountInput(absl::BitGen& gen) { + PopcountInput<T> ret; + for (int i = 0; i < std::numeric_limits<T>::digits; i++) { + bool coin = absl::Bernoulli(gen, 0.2); + if (coin) { + ret.value |= T{1} << i; + ret.expected++; + } + } + return ret; +} + +TEST(Counting, PopcountFuzz) { + absl::BitGen rng; + constexpr int kTrials = 100; + + for (int i = 0; i < kTrials; ++i) { + auto input = GeneratePopcountInput<uint8_t>(rng); + EXPECT_EQ(popcount(input.value), input.expected); + } + + for (int i = 0; i < kTrials; ++i) { + auto input = GeneratePopcountInput<uint16_t>(rng); + EXPECT_EQ(popcount(input.value), input.expected); + } + + for (int i = 0; i < kTrials; ++i) { + auto input = GeneratePopcountInput<uint32_t>(rng); + EXPECT_EQ(popcount(input.value), input.expected); + } + + for (int i = 0; i < kTrials; ++i) { + auto input = GeneratePopcountInput<uint64_t>(rng); + EXPECT_EQ(popcount(input.value), input.expected); + } +} + +TEST(IntegralPowersOfTwo, SingleBit) { + EXPECT_FALSE(has_single_bit(uint8_t{})); + EXPECT_FALSE(has_single_bit(static_cast<uint8_t>(-1))); + EXPECT_FALSE(has_single_bit(uint16_t{})); + EXPECT_FALSE(has_single_bit(static_cast<uint16_t>(-1))); + EXPECT_FALSE(has_single_bit(uint32_t{})); + EXPECT_FALSE(has_single_bit(~uint32_t{})); + EXPECT_FALSE(has_single_bit(uint64_t{})); + EXPECT_FALSE(has_single_bit(~uint64_t{})); + + static_assert(!has_single_bit(0u), ""); + static_assert(has_single_bit(1u), ""); + static_assert(has_single_bit(2u), ""); + static_assert(!has_single_bit(3u), ""); + static_assert(has_single_bit(4u), ""); + static_assert(!has_single_bit(1337u), ""); + static_assert(has_single_bit(65536u), ""); + static_assert(has_single_bit(uint32_t{1} << 30), ""); + static_assert(has_single_bit(uint64_t{1} << 42), ""); + + EXPECT_FALSE(has_single_bit(0u)); + EXPECT_TRUE(has_single_bit(1u)); + EXPECT_TRUE(has_single_bit(2u)); + EXPECT_FALSE(has_single_bit(3u)); + EXPECT_TRUE(has_single_bit(4u)); + EXPECT_FALSE(has_single_bit(1337u)); + EXPECT_TRUE(has_single_bit(65536u)); + EXPECT_TRUE(has_single_bit(uint32_t{1} << 30)); + EXPECT_TRUE(has_single_bit(uint64_t{1} << 42)); + + EXPECT_TRUE(has_single_bit( + static_cast<uint8_t>(std::numeric_limits<uint8_t>::max() / 2 + 1))); + EXPECT_TRUE(has_single_bit( + static_cast<uint16_t>(std::numeric_limits<uint16_t>::max() / 2 + 1))); + EXPECT_TRUE(has_single_bit( + static_cast<uint32_t>(std::numeric_limits<uint32_t>::max() / 2 + 1))); + EXPECT_TRUE(has_single_bit( + static_cast<uint64_t>(std::numeric_limits<uint64_t>::max() / 2 + 1))); +} + +template <typename T, T arg, T = bit_ceil(arg)> +bool IsBitCeilConstantExpression(int) { + return true; +} +template <typename T, T arg> +bool IsBitCeilConstantExpression(char) { + return false; +} + +TEST(IntegralPowersOfTwo, Ceiling) { +#if ABSL_INTERNAL_HAS_CONSTEXPR_CLZ + static_assert(bit_ceil(0u) == 1, ""); + static_assert(bit_ceil(1u) == 1, ""); + static_assert(bit_ceil(2u) == 2, ""); + static_assert(bit_ceil(3u) == 4, ""); + static_assert(bit_ceil(4u) == 4, ""); + static_assert(bit_ceil(1337u) == 2048, ""); + static_assert(bit_ceil(65536u) == 65536, ""); + static_assert(bit_ceil(65536u - 1337u) == 65536, ""); + static_assert(bit_ceil(uint32_t{0x80000000}) == uint32_t{0x80000000}, ""); + static_assert(bit_ceil(uint64_t{0x40000000000}) == uint64_t{0x40000000000}, + ""); + static_assert( + bit_ceil(uint64_t{0x8000000000000000}) == uint64_t{0x8000000000000000}, + ""); + + EXPECT_TRUE((IsBitCeilConstantExpression<uint8_t, uint8_t{0x0}>(0))); + EXPECT_TRUE((IsBitCeilConstantExpression<uint8_t, uint8_t{0x80}>(0))); + EXPECT_FALSE((IsBitCeilConstantExpression<uint8_t, uint8_t{0x81}>(0))); + EXPECT_FALSE((IsBitCeilConstantExpression<uint8_t, uint8_t{0xff}>(0))); + + EXPECT_TRUE((IsBitCeilConstantExpression<uint16_t, uint16_t{0x0}>(0))); + EXPECT_TRUE((IsBitCeilConstantExpression<uint16_t, uint16_t{0x8000}>(0))); + EXPECT_FALSE((IsBitCeilConstantExpression<uint16_t, uint16_t{0x8001}>(0))); + EXPECT_FALSE((IsBitCeilConstantExpression<uint16_t, uint16_t{0xffff}>(0))); + + EXPECT_TRUE((IsBitCeilConstantExpression<uint32_t, uint32_t{0x0}>(0))); + EXPECT_TRUE((IsBitCeilConstantExpression<uint32_t, uint32_t{0x80000000}>(0))); + EXPECT_FALSE( + (IsBitCeilConstantExpression<uint32_t, uint32_t{0x80000001}>(0))); + EXPECT_FALSE( + (IsBitCeilConstantExpression<uint32_t, uint32_t{0xffffffff}>(0))); + + EXPECT_TRUE((IsBitCeilConstantExpression<uint64_t, uint64_t{0x0}>(0))); + EXPECT_TRUE( + (IsBitCeilConstantExpression<uint64_t, uint64_t{0x8000000000000000}>(0))); + EXPECT_FALSE( + (IsBitCeilConstantExpression<uint64_t, uint64_t{0x8000000000000001}>(0))); + EXPECT_FALSE( + (IsBitCeilConstantExpression<uint64_t, uint64_t{0xffffffffffffffff}>(0))); +#endif + + EXPECT_EQ(bit_ceil(0u), 1); + EXPECT_EQ(bit_ceil(1u), 1); + EXPECT_EQ(bit_ceil(2u), 2); + EXPECT_EQ(bit_ceil(3u), 4); + EXPECT_EQ(bit_ceil(4u), 4); + EXPECT_EQ(bit_ceil(1337u), 2048); + EXPECT_EQ(bit_ceil(65536u), 65536); + EXPECT_EQ(bit_ceil(65536u - 1337u), 65536); + EXPECT_EQ(bit_ceil(uint64_t{0x40000000000}), uint64_t{0x40000000000}); +} + +TEST(IntegralPowersOfTwo, Floor) { +#if ABSL_INTERNAL_HAS_CONSTEXPR_CLZ + static_assert(bit_floor(0u) == 0, ""); + static_assert(bit_floor(1u) == 1, ""); + static_assert(bit_floor(2u) == 2, ""); + static_assert(bit_floor(3u) == 2, ""); + static_assert(bit_floor(4u) == 4, ""); + static_assert(bit_floor(1337u) == 1024, ""); + static_assert(bit_floor(65536u) == 65536, ""); + static_assert(bit_floor(65536u - 1337u) == 32768, ""); + static_assert(bit_floor(uint64_t{0x40000000000}) == uint64_t{0x40000000000}, + ""); +#endif + + EXPECT_EQ(bit_floor(0u), 0); + EXPECT_EQ(bit_floor(1u), 1); + EXPECT_EQ(bit_floor(2u), 2); + EXPECT_EQ(bit_floor(3u), 2); + EXPECT_EQ(bit_floor(4u), 4); + EXPECT_EQ(bit_floor(1337u), 1024); + EXPECT_EQ(bit_floor(65536u), 65536); + EXPECT_EQ(bit_floor(65536u - 1337u), 32768); + EXPECT_EQ(bit_floor(uint64_t{0x40000000000}), uint64_t{0x40000000000}); + + for (int i = 0; i < 8; i++) { + uint8_t input = uint8_t{1} << i; + EXPECT_EQ(bit_floor(input), input); + if (i > 0) { + EXPECT_EQ(bit_floor(static_cast<uint8_t>(input + 1)), input); + } + } + + for (int i = 0; i < 16; i++) { + uint16_t input = uint16_t{1} << i; + EXPECT_EQ(bit_floor(input), input); + if (i > 0) { + EXPECT_EQ(bit_floor(static_cast<uint16_t>(input + 1)), input); + } + } + + for (int i = 0; i < 32; i++) { + uint32_t input = uint32_t{1} << i; + EXPECT_EQ(bit_floor(input), input); + if (i > 0) { + EXPECT_EQ(bit_floor(input + 1), input); + } + } + + for (int i = 0; i < 64; i++) { + uint64_t input = uint64_t{1} << i; + EXPECT_EQ(bit_floor(input), input); + if (i > 0) { + EXPECT_EQ(bit_floor(input + 1), input); + } + } +} + +TEST(IntegralPowersOfTwo, Width) { +#if ABSL_INTERNAL_HAS_CONSTEXPR_CLZ + static_assert(bit_width(uint8_t{}) == 0, ""); + static_assert(bit_width(uint8_t{1}) == 1, ""); + static_assert(bit_width(uint8_t{3}) == 2, ""); + static_assert(bit_width(static_cast<uint8_t>(-1)) == 8, ""); + static_assert(bit_width(uint16_t{}) == 0, ""); + static_assert(bit_width(uint16_t{1}) == 1, ""); + static_assert(bit_width(uint16_t{3}) == 2, ""); + static_assert(bit_width(static_cast<uint16_t>(-1)) == 16, ""); + static_assert(bit_width(uint32_t{}) == 0, ""); + static_assert(bit_width(uint32_t{1}) == 1, ""); + static_assert(bit_width(uint32_t{3}) == 2, ""); + static_assert(bit_width(~uint32_t{}) == 32, ""); + static_assert(bit_width(uint64_t{}) == 0, ""); + static_assert(bit_width(uint64_t{1}) == 1, ""); + static_assert(bit_width(uint64_t{3}) == 2, ""); + static_assert(bit_width(~uint64_t{}) == 64, ""); +#endif + + EXPECT_EQ(bit_width(uint8_t{}), 0); + EXPECT_EQ(bit_width(uint8_t{1}), 1); + EXPECT_EQ(bit_width(uint8_t{3}), 2); + EXPECT_EQ(bit_width(static_cast<uint8_t>(-1)), 8); + EXPECT_EQ(bit_width(uint16_t{}), 0); + EXPECT_EQ(bit_width(uint16_t{1}), 1); + EXPECT_EQ(bit_width(uint16_t{3}), 2); + EXPECT_EQ(bit_width(static_cast<uint16_t>(-1)), 16); + EXPECT_EQ(bit_width(uint32_t{}), 0); + EXPECT_EQ(bit_width(uint32_t{1}), 1); + EXPECT_EQ(bit_width(uint32_t{3}), 2); + EXPECT_EQ(bit_width(~uint32_t{}), 32); + EXPECT_EQ(bit_width(uint64_t{}), 0); + EXPECT_EQ(bit_width(uint64_t{1}), 1); + EXPECT_EQ(bit_width(uint64_t{3}), 2); + EXPECT_EQ(bit_width(~uint64_t{}), 64); + + for (int i = 0; i < 8; i++) { + EXPECT_EQ(bit_width(static_cast<uint8_t>(uint8_t{1} << i)), i + 1); + } + + for (int i = 0; i < 16; i++) { + EXPECT_EQ(bit_width(static_cast<uint16_t>(uint16_t{1} << i)), i + 1); + } + + for (int i = 0; i < 32; i++) { + EXPECT_EQ(bit_width(uint32_t{1} << i), i + 1); + } + + for (int i = 0; i < 64; i++) { + EXPECT_EQ(bit_width(uint64_t{1} << i), i + 1); + } +} + +// On GCC and Clang, anticiapte that implementations will be constexpr +#if defined(__GNUC__) +static_assert(ABSL_INTERNAL_HAS_CONSTEXPR_POPCOUNT, + "popcount should be constexpr"); +static_assert(ABSL_INTERNAL_HAS_CONSTEXPR_CLZ, "clz should be constexpr"); +static_assert(ABSL_INTERNAL_HAS_CONSTEXPR_CTZ, "ctz should be constexpr"); +#endif + +} // namespace +ABSL_NAMESPACE_END +} // namespace absl |